# ev jr dragster



## jr dragster (Oct 11, 2010)

I am going to build an electric jr. dragster for my daughter who is 10 years old.Last year was her first year racing with a stock 5 hp Briggs with a best run of 15.77 at 40 mph in the 8 th mile.We would like to run in the 10's to 60 mph(she wants to go faster),the car weighs 285 lbs without the driver,I have not yet pulled out the Briggs -thinking it will weigh 240 with out the engine-we must stay under 400 lbs.There is more info at Nedra.com. Now for a newbie question-in knowing weight will be an issue can i get power out of a 24/36volt or 48 or do I need 72. There are some Mars motor on Ebay with controller for under $1000.00-good buy???Do I need a progammable controller? How many runs do you think we would get out of batteries before re-charge?I think I will use a DC motor.I would like to do this for around $1500-$2000 if possible.Will post some pics asap.Thanks for any advice.I own a bodyshop and have a friend who is a machinist and another who is an electrician so we can fabricate most of the parts if needed. Please give me your ideas on motor size,controller and battery.
Thank you!


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## major (Apr 4, 2008)

jr dragster said:


> I am going to build an electric jr. dragster for my daughter....... Please give me your ideas on motor size,controller and battery.


Hi jr dr,

You might be able to find some example systems and build info searching in the bikes forum here. It seems like a lot of kart builds end up there as well. Here is a parts list for a kart kit (just for example). http://store.kta-ev.com/Go Kart Package (Basic).pdf 

I personally would not use a PM motor (like the Mars) (and please call the electric motor a motor, not an engine). The Mars motor may be a good product, but I have seen too many PM motor parts laying on the drag strip and race track to recommend them. Stick with a series wound DC motor for great starting torque and durability. I think you should look at the 6.6 inch diameter motor. A bit heavier, but commonly available, and can provide good performance at low voltage to start and take increased voltage system as you upgrade.

With that in mind, you may wish to find a controller which will accommodate a wide range in battery voltage. WRT the batteries, this application requires power more than a large energy stored. Small Ampere hour (Ah) AGM Pb-Acid 12V batteries will work and not cost an arm & leg. Hawkers or Genesis brand are good. Lithium would be best, high C rate jobs, like A123 or Headway. Maybe even rob some Dewalt tools. You can get into the info forum here and read about energy, watt hours and Ah and such and figure out the number of runs per charge. Most such racers charger inbetween passes. You get the most power from a freshly charged and warm battery.

I think you will benefit from starting modest and working your way up in performance, meaning system voltage and power. Your mistakes will be less costly and you'll get it on the track sooner 

Good luck.

major


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## jr dragster (Oct 11, 2010)

pulled out ice .jr weighs 225 .how do you post pics my pics all say failed when i go to download


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## jr dragster (Oct 11, 2010)

ev drives has a d&d es-10e-33 motor, 500 amp controller 36- 48 volt kit for$ 1091 its kit #5. Kit 9 has a d&d es-15-6 motor 450 amp controller 72 volt kit for $1293.with kit would you recommend to get the jr in the 10s in the 1/8 mile?? could you run the #5 kit at 48 volts then later run it at 72,or would it fry the controller?thanks for your ideas.


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## Harold in CR (Sep 8, 2008)

Where you located ?? There are 2 FREE motors listed in the Classifieds, if YOU or someone you know, could pick them up. See Forklift motors, in Classifieds.


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## jr dragster (Oct 11, 2010)

im in canada a little far to pick up .lol


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## Guest (Dec 6, 2010)

Convert your photos to .jpg format if they are not yet and be sure they are not huge. 100k or so should be just fine. Much larger the server balks. No need to clog up the server with photos that are too large. Use your camera to get nice photos then reduce them in size. Then try again. 

Pete


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## Yabert (Feb 7, 2010)

My D&D ES-15-6 from my motorcycle is to sold: http://www.diyelectriccar.com/forums/showthread.php/suzuki-drz-sm-2005-electric-48239.html
This motor put my 340 lbs DRZ (+160 me) from 0 to 50 mph in 6 sec. But the motor only put watt to the ground.... the power come from headway batteries.

The alltrax 72v 450A controller is really good and greatly configurable.


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## jr dragster (Oct 11, 2010)

does anyone know the weight of alltrax axe 7245 controller?? The d&d weighs 62 pounds,i found 12 volt 22amp hr batteries that weigh 13 pounds each about $60.00 each .car weighs 225 batteries 6 x 13= 78 d&d 62 ,so im at 365 pounds so far have to stay under 400. so will the controller,wiring ,solenoid weigh less than 35 pounds or do i have to lighten the car some how. thanks


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## Jimdear2 (Oct 12, 2008)

jr dragster said:


> does anyone know the weight of alltrax axe 7245 controller?? The d&d weighs 62 pounds,i found 12 volt 22amp hr batteries that weigh 13 pounds each about $60.00 each .car weighs 225 batteries 6 x 13= 78 d&d 62 ,so im at 365 pounds so far have to stay under 400. so will the controller,wiring ,solenoid weigh less than 35 pounds or do i have to lighten the car some how. thanks


Go to the Alltrax site. If the info you need is not on their pages go to to the "Contact Us" page. They answer promptly.

http://www.alltraxinc.com/

Depending on length and guage of cable you are going to be close on the weight. 

I have been running a small pulling tractor. Weight was/is a problem for us as well. Finally went to Headway batteries. We now have a (Edit change this to 99 pound from 65) pound battery that can produce over 100 (EDIT change this to hp from kW) for over 30 seconds. Check with some of the others like Yabert that have gone this route. Slightly more expensive then the lead you are looking at, but you will probably end up there anyway.

Jim


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## Yabert (Feb 7, 2010)

Jimdear2 said:


> Finally went to Headway batteries. We now have a 65 pound battery that can produce over 100kW for over 30 seconds. Check with some of the others like Yabert that have gone this route.


The Headway are rated 909w/Kg (10 Ah) or 1500w/Kg (8 Ah).... so the max power you can produce with 65 lbs of cells will be : 65 / 2.2 = 29.5 x 1.5 = 44 Kw

But 44 Kw is 310 lbs-pi of torque at 1000 rpm or 62 lbs-po of torque at 5000 rpm.

To Jr, the D&D is a great motor, so start with 5 or 6 lead batteries and later if you decide to go with lithium your motor will be good enough...


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## Jimdear2 (Oct 12, 2008)

Yabert said:


> The Headway are rated 909w/Kg (10 Ah) or 1500w/Kg (8 Ah).... so the max power you can produce with 65 lbs of cells will be : 65 / 2.2 = 29.5 x 1.5 = 44 Kw
> 
> But 44 Kw is 310 lbs-pi of torque at 1000 rpm or 62 lbs-po of torque at 5000 rpm.
> 
> To Jr, the D&D is a great motor, so start with 5 or 6 lead batteries and later if you decide to go with lithium your motor will be good enough...


 
I'm not all that good with math, and those of you out there that know this stuff better then me please point out where I'm wrong

The 38120P battery is rated at 8 ah and 25C for at least 30 seconds. That equals 200 amps. I'm hoping that voltage drop at 25 C in a 50S/3P battery will not exceed 2.75 to 2.5 volts per cell. (Still waiting for the batteries to arrive so I can test this volts per cell premise)

So here is what I came up with 

2.5 VPC under 200 amp load times 50 batteries per series string equals 125 volts.
3 parallel strings at 200 amps per string equals 600 amps total.
600 amps times 125 volts equals 75 kW battery output for about 30 seconds.
75 kW equals approx 100 horse power.
150 batteries at 300 grams per cell (I goofed here) is 45 kg equals 99 pounds. 

At approx 100 lbs of battery your math and mine are not too far apart.

Would you please post the formula that you are using to convert kW into torque. It would be a big help.

I also went back and edied my original post.

Thanks,
Jim


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## Yabert (Feb 7, 2010)

Hi

Kw = hp x 0.746 or W = hp x 746

And HP = (Torque x RPM) / 5252.

So 75Kw = 100 hp and 100 hp @ 2500 rpm = (100 x 5252) / 2500 = 210 lbs-pi
If you start from other side, a big 11" motor give 300 lbs-pi of torque @ 3000 rpm, that give 171 hp ((300 x 3000) / 5252).


When you will got your cells please give the result... I'm interested to know the internal resistance difference between Headway 10Ah and 8Ah cells!


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## jr dragster (Oct 11, 2010)

i will go with lead to start with to keep costs down.How would you recommend i buy my kit from ??? ev drives?? or from d&d ?? or any where else? i have read some horror stories on this forum and dont whant to get ripped off. im going to order one in the new year.i emailed alltrax for the weight of cont.


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## Jimdear2 (Oct 12, 2008)

jr dragster,

I bought my ES15-6 and Alltrax 7245 from D&D Motors.

D&D is an Alltrax dealer. They gave me a fair price and good service.

You might shop and get a motor or a Alltrax 7245 on eBay for a better price, but they don't come up often. I've also seen used, prices vary. 

I want to mention that there are other equivalent name brand motors out there as well. ADC, Netgain, Warp and others

If you buy a new motor, plan on spending a lot of time running the motor on 12 volts to seat the brushes. I have run the motor I have for over 6 hours and it just keeps on getting better the more I run it.

Before you read below get used to the fact that good batteries cost a lot and cheap batteries cost more.

If you are going to go with lead I recommend 16 ah Hawker (Enersys) Oddsey batteries, you will probably pay over $100.00 each. They are not cheap but you get what you pay for. They weigh 13 pounds apiece and are about the size of a motorcycle battery. You won't find many, if any, other batteries that will give the kW they will. Look up the specs on the OEM site. you will be imppresed.

You can probably draw twice the amps from the Hawkers, while still maintaining good voltage, then you can from the cheaper lead batteries.

Last gasp on the Headways. 

Yabert has had a set of Headways in service for a while in his bike. He might have a bit of info to throw in here as well. So might Frodus. 

I went through 2 years of pulling with lead, and that experience tells me that high output lithiums are the way to go. At the Power range you need the price difference isn't that bad.

A 72 volt Headway system would be minimum of 20 batteries. You can pull 200 amps (25C) from a single string of 38120P batteries for around 30 seconds and expect it to sag to 50 or so volts at that load. 

At the $19.00 each price that I paid (you might do better) thats $380.00 for a single string and a double string of 40 would be $760.00. 

A 6 battery set of Hawkers would cost a minimum of $600.00.

A double string of 40 Headways weigh 12 kg 26.5 pounds. Six Hawkers weigh 78 pounds.

My 72 volt Hawker pack saged to around 40 volts when I pulled 400 amps. The double string of Headway's (According to Headway) should hold to about 50 volts at 400 amps. As soon as we get our batteries we will put them through some tests to see how they will hold up.

Hope he above helps you decide.

Jim


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## Yabert (Feb 7, 2010)

jr dragster said:


> i will go with lead to start with to keep costs down.How would you recommend i buy my kit from ??? ev drives?? or from d&d ?? or any where else? i have read some horror stories on this forum and dont whant to get ripped off. im going to order one in the new year.i emailed alltrax for the weight of cont.


Lead is the easiest way to learn.... no complex charger and balancing. But it's a fact, many cheap batteries come more costly than few good Headway.

Pay attention to the real price.... that including shipping, custom and taxes! 

Watch your PM.


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## jr dragster (Oct 11, 2010)

i found a d&d model 170-501-001a 48 v for 250 +shipping do you think it would have the power i need to move the 400 pound dragster fast enough? it rated at 13hp is that peak power? what controller would you recomend for this motor.also looking at an advaced dc motor lighter than than the 15-6 d&d by 25 pounds ,but more money. to many decions to make LOL


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## Jimdear2 (Oct 12, 2008)

jr dragster said:


> i found a d&d model 170-501-001a 48 v for 250 +shipping do you think it would have the power i need to move the 400 pound dragster fast enough? it rated at 13hp is that peak power? what controller would you recomend for this motor.also looking at an advaced dc motor lighter than than the 15-6 d&d by 25 pounds ,but more money. to many decions to make LOL


That motor is a made to be used on a golf cart axle and does not have a front bearing and DE cover and has a female output connection. 

I'm afraid it is a very poor choice unless you have access to machine shop equipment.

Probably not a good first time, starting out motor (ask me about the door stop I bought).

I would need to look up the model number of the Advanced DC motor to tell you if it would be good. But a lighter weight then an ES 15 may mean a smaller diameter motor. Get pictures and specs and post them. Many people on the forum will help out.

D&D has a series of motors that start out with the ID code of ES. Like ES 15 and ES 31, those would be good.

Don't buy until you ask. I didn't and paid the price of an unusable motor for my task.

If price is important look for take out and reman lift truck (Hi-Lo) motors. Read through the the Sticky posts about chooseing a good Hi Lo motor in the Motor forum. It's a long read but invaluable.

Hope this helps.
Jim


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## jr dragster (Oct 11, 2010)

can you set up the electric to creep to stage the car ?????


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## jr dragster (Oct 11, 2010)

motor??????????????? amd a000-4009 at kta services for $605 ,50 pounds .or D&D es-15-6, $669 at ev drives 62 pounds with one would you guys recommend?????price is so close that ethier way, 12 pounds in weight is more important .give more your ideas thanks


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## Jimdear2 (Oct 12, 2008)

jr dragster said:


> can you set up the electric to creep to stage the car ?????


jr dragster,

With an Alltrax controller, yes you can, you would add a parllel circuit to your throttle. You would need to find the proper resistor to give the rate of creep you need. Zero ohms is thriottle off, 5000 ohms is full throttle. Somewhere in there at the low end is what you need. A bit of trial and error.

I would operate it with a push button. To use it, foot off throttle and push the button for creep.

Jim


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## Jimdear2 (Oct 12, 2008)

jr dragster said:


> motor??????????????? amd a000-4009 at kta services for $605 ,50 pounds .or D&D es-15-6, $669 at ev drives 62 pounds with one would you guys recommend?????price is so close that ethier way, 12 pounds in weight is more important .give more your ideas thanks


In my opinion (we all know what opinions are worth) both are good motors. I don't know about power and torque differences. If weight is a consideration and power and torque are close go, with the lightest. Since you will only be stressing the motor for a few seconds heat won't be a big consideration.

Ask someone like major to offer an opinion, he knows bunches more then me about motors.

Jim


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## Yabert (Feb 7, 2010)

ADC a000-4009 vs D&D es-15-6!


Isn't exactly the same motor!
Both have same diameter, but the D&D is 12 lbs more heavy because it is 2" longer than the ADC. 

This 2" longer = more torque!

And it's probably why the ADC is rated 6hp continuous/28hp peak and the D&D is rated 10hp continuous/40hp peak.

But don't forget, the 28 and 40 peak HP is only give by the manufacturer, and I'm not sure that will be easily reachable with the Alltrax 72v 450A and lead battery.

My ES-15-6 on my DRZ SM feel like around 35 hp at 83v nominal (62v sag) and 600A.

Well I think you need to forget the 12 lbs in more and appreciate the higher torque!


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## major (Apr 4, 2008)

Yabert said:


> ADC a000-4009 vs D&D es-15-6!
> 
> 
> Isn't exactly the same motor!
> ...


Hi guys,

I recommend jr drag get the motor performance curves and brush size for these 2 motors, then he (we) could make an intelligent decision. Barring that, I'll side with Yabert here 

major


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## Jimdear2 (Oct 12, 2008)

major said:


> Hi guys,
> 
> I recommend jr drag get the motor performance curves and brush size for these 2 motors, then he (we) could make an intelligent decision. Barring that, I'll side with Yabert here
> 
> major


Guys,

I also agree more power is better. 

BUT;

QUOTE_ "If* weight* is a consideration and power and torque* are close* go, with the *lightest*."_ UNQUOTE

I pound over class limits and you're dead.

Major, glad your here, I'd sure like to see this come out a winner.


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## Jimdear2 (Oct 12, 2008)

Hi,

I just bumped into this motor while looking for something else..

http://cgi.ebay.com/4-HP-DC-Motor-4...643?pt=LH_DefaultDomain_0&hash=item45f8017d73

*I AM NOT RECOMMENDING* it. I just don't know enough. I'm hopeing major would comment on it. It seems reasonably priced and powerful. It might work for jr daragster if they can work with ccw rotation. The low rpm and high torque just means different gearing.

Jim


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## jr dragster (Oct 11, 2010)

ok after 3 months of looking im ready to order my parts so i can get this done in time for racing,or dad will be in trouble. parts list missing ANYTHING??????????
[email protected] es 15-6 motor
axe 7245 72v 450 amp cont w fuse [should i get an extra fuse?]
JCA 400 solenoid
3amp diode [extra?]
1k ohm precharge resistor w 3/8 terminal [extra?]
pb6 throttle
wsb prog cable
deltec 250 amp shunt
10 amp fuse and holder x2
ed 250 emergecy stop x 2
20 feet 2 awg cable
18 wire lugs {some spares for learning lol}
crimper
cable cutters
heat shrink
front rear spockets and chain[wil have to figure gear ratio 4.1??]
lanyard shut off {may get one off a snowmachine}
will make all mounting and brakets.
sound good or will i need anything thanks for your ideas.
priced it all out will come in at $ 2,000 to 2,500 depending on battery prices.
thanks again
6 \12 batteries


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## Yabert (Feb 7, 2010)

http://www.diyelectriccar.com/forums/showthread.php/sale-motor-d-d-es-15-56797.html

I also have fuse and other electrical parts from my motorcycle for you.


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## Ziggythewiz (May 16, 2010)

Jimdear2 said:


> jr dragster,
> 
> With an Alltrax controller, yes you can, you would add a parllel circuit to your throttle. You would need to find the proper resistor to give the rate of creep you need. Zero ohms is thriottle off, 5000 ohms is full throttle. Somewhere in there at the low end is what you need. A bit of trial and error.
> 
> ...


Sorry to revisit an old comment, but wouldn't adding a parllel path decrease the resistance, instead of replacing it as desired? Or did you mean for the added path to be always on and the pushbutton to interrupt the foot throttle circuit?

My throttle cable snapped this morning and I'm considering how to add an easy backup, possibly hand controlled.


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## jr dragster (Oct 11, 2010)

Snow finally melted  got car out of shed.Made some parts from cardboard, motor ,and batteries to see if they will all fit.NO!!!!!!!!!!!!!!!  motor is to big at 6.6 .would have to cut frame and body to make it fit.So new plan will us a Mars 1003 with a alltrax 7245 at 72volts.It may not be the perfect set up, but we will see? Alot of people are using them on bikes and they are working.The weight should not be an issue anymore,car 225 motor 39, batteries 78 ,cont 8 , wires etc 20-30 =370-380.


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## jr dragster (Oct 11, 2010)

finally got pics to load


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## jr dragster (Oct 11, 2010)

got mars 1003 motor kit today.will post build pics asap.what should i build the battery box from steel or alum??


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## jr dragster (Oct 11, 2010)

some fresh paint


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## jr dragster (Oct 11, 2010)

the tear down day one ,removed rear axle,so i can change gear.Made all brackets for mounting mars & controller ,relays ect. Picked up batteries and more alum today,for battery box .Got 18amp hr batteries,will try see how they work. start welding soon first race may 28.


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## jr dragster (Oct 11, 2010)

need some advice on wiring ,went to all trax got wiring diagram,need to put some safety shut offs in, can i put them in where it has the key switch?? need to put lanyard in and one on roll cage.in the rule book it says must shut off all power to motor, will that work as key switch to shut off all power ? I have a ED 250 heavy duty emergeny stop for roll cage ,can it be wired in the same way ?.If you google jr rules it is on page 48.of rule book.Going to weld up battery box and motor plate tommorow,would like to wire it this weekend.worst case if the main contactor was to to arc would holding the brakes blow the battery fuse ? trying to make it as safe as possible.thanks for your help so far


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## Jimdear2 (Oct 12, 2008)

jr dragster said:


> need some advice on wiring ,went to all trax got wiring diagram,need to put some safety shut offs in, can i put them in where it has the key switch?? need to put lanyard in and one on roll cage.in the rule book it says must shut off all power to motor, will that work as key switch to shut off all power ? I have a ED 250 heavy duty emergeny stop for roll cage ,can it be wired in the same way ?.If you google jr rules it is on page 48.of rule book.Going to weld up battery box and motor plate tommorow,would like to wire it this weekend.worst case if the main contactor was to to arc would holding the brakes blow the battery fuse ? trying to make it as safe as possible.thanks for your help so far


I'll put together a copy of the wiring diagram of the system I use on the pulling tractor. You can copy anything you need or is useable. The total system, tether, emergency shut down precharge are all here. You just need to arrange them as you need. I'm having some health issues so it mght be slow.

Jim


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## major (Apr 4, 2008)

jr dragster said:


> need some advice on wiring ,went to all trax got wiring diagram,need to put some safety shut offs in, can i put them in where it has the key switch??


Hi jr d,

I've set up safety disconnects on a number of competition EVs. All rule books which I have seen allow the use of a suitable mainline contactor disconnect opposed to requiring a mechanical separation of the power cable via a high current manual switch or connector. This means you don't have to route the power cables to the rear and/or the dash. It is important to use a suitable contactor. I like the Kilovac EV250. Such contactors will have specifications which include maximum current interrupt. That should be on the order of the short circuit current of your battery. IIRC, the EV250 is like 10,000A, well above most batteries.

Now then, for the rear safety switch, I use a red mushroom push-button. Large and easy to see and operate. I wire it in the negative contactor coil supply line.

The rest of the safety switches I wire into the forward run command switch line. These are usually on the steering wheel (the lanyard would substitute), the throttle pedal box, and elsewhere per the rules. All these switches are in series with the run command. I leave the key switch as a separate circuit, as this will require a precharge sequence to restart.

Extra measures can be taken which could include two power circuit contactors, one in the positive line and one in the negative line (or mid pack). On really high power rigs, often a "oh scheese" bar is used where the driver can pull out a mechanical link in the power circuit, like a copper bar from a fuse holder. This is an all else fails last resort type of thing where guys have a battery capability so high as pushing limits of contactor interrupt capability.

Sorry, no diagrams to post for you. Might be some in the forum wiki.

Good luck and be safe 

major


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## jr dragster (Oct 11, 2010)

batterybox done ,mounts all welded,rear gear changed. ready for wiring.this is a lot more than i thought . 17 days till first race.


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## jr dragster (Oct 11, 2010)

does this look good for the emergency shut offs one in + and one in -,big red shut offs 250,one on roll bar and one operated from a rod that is in the car for the neg. will have switch on wheel for key switch,is the lanyard shut off good where i have it ?? hope to get it running this weekend. thanks for all the help again.


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## nedrapr (Mar 9, 2011)

Cool project. I'm following along. Where do you get one of those Mushroom switches?


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## jr dragster (Oct 11, 2010)

nedrapr said:


> Cool project. I'm following along. Where do you get one of those Mushroom switches?


ev drives.com


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## jr dragster (Oct 11, 2010)

GOT IT RUNNING TODAY. Thanks to carl at evdrives ,had two wires on wrong fixed it over the phone it was awsome he could help me over the phone.Will post some pics a videos later,time for dad to relax and have a few beers.Will try car out tommorow to see how it stages and to get her back in the feel of things.First race next weekend will keep you posted on times and speeds.All shut offs work perfect. THANKS FOR ALL THE HELP AND ADVICE ON THE FORUM!!!!!!!!


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## nedrapr (Mar 9, 2011)

Good luck today! Can't wait to hear how things went. We're building one too. It's challenging getting everything to fit.


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## jr dragster (Oct 11, 2010)

tried car on the grass at 70 feet it was breaking the tires loose, running the alltrax at 60% battery , throttle rate at 10, and throttle at 60 % of full , will let you know on sunday what it ran.


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## jr dragster (Oct 11, 2010)

Left all settings where they were at test and tune sat first run 13.954 at 52.45 did ten min charge second run 13.967 at 52.87,no charge on next run still had 77.6 volts left changed throttle curve ran 13.65 at 53.17, then she lost the breaks at the top end went all the way to floor ,but she just went staight and shut the car down.I was proud of her for knowing what to do for being only 10 years old.Iwas low on brake fluid  dad didnt check that.The car is slow off the start so i may change gear 16 front 32 rear, may change to 13 or 14 ,or do you think i should take the throttle rate up to 10 or change the throttle to 100% KEEP IN MIND I DONT WANT TO FREAK HER OR HER MOM OUT. P.S. rained out on sunday


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## major (Apr 4, 2008)

jr dragster said:


> Left all settings where they were at test and tune sat first run 13.954 at 52.45 did ten min charge second run 13.967 at 52.87,no charge on next run still had 77.6 volts left changed throttle curve ran 13.65 at 53.17, then she lost the breaks at the top end went all the way to floor ,but she just went staight and shut the car down.I was proud of her for knowing what to do for being only 10 years old.Iwas low on brake fluid  dad didnt check that.The car is slow off the start so i may change gear 16 front 32 rear, may change to 13 or 14 ,or do you think i should take the throttle rate up to 10 or change the throttle to 100% KEEP IN MIND I DONT WANT TO FREAK HER OR HER MOM OUT. P.S. rained out on sunday


Hey jr,

Nice job getting it together and to your daughter for getting it down the track I guess I have no idea if this is good performance or not, or how much you'd like to improve. You can get some clues from the guys here on the list, but we're going to need some more info. First off, motor RPM. 52mph = ? RPM. Depending on where that RPM shows on the motor curve will tell you which way to go with the ratio. And it is really helpful to get the current trace versus time for the run. There are some inexpensive instruments which will record this for you, like a cycle analyst. http://www.ebikes.ca/ Or you can just start changing stuff like sprockets and see what happens 

major


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## jr dragster (Oct 11, 2010)

Raced on sat ,changed front gear to 13 ran 12.04 no charge ran 11.85 tried one more run no charge just to see what it would do 12.07.charged batteries eliminations dialed a 11.80 ran 11.85 at 55 miles hr. lost by .03 from other car it was a close race.will keep you posted.


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## toddshotrods (Feb 10, 2009)

Too cool for school!  I'll bet your daughter was smiling, ear-to-ear!  You're edging you way towards the 10s...


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## jr dragster (Oct 11, 2010)

thanks todd, i dont know if she was smiling or me more.we are only running at 80 % of voltage throttle rate at 13 and 75 % of top speed on the controller going to put it up 5% each race hoping when were maxed out to go in 9ss i hope .Just have to give her more seat time to get them lights good, then we will see . everyone at the track is already impressed that we got it in the 11 at 55 miles ,wait till we run it full out .will keep you posted


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## jr dragster (Oct 11, 2010)

Made it to second round  we made my goal for the year at second race. Ran 12.04. 12.06 then no charge ran 12.17. in time trials. First race she ran 11.99 at 53.00 other girl red lighted, dialed it at 12.04,lucky second round ran 12.10 on 12.04 ,other guy ran 9.31 on 9.03 dial , she lost it on the tree, but that will come with more seat time. she put a vid on YOUTUBE, check it out, My first trip down the track in my electric jr dragster. will keep you all posted.


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## toddshotrods (Feb 10, 2009)

Here ya go. Too cool for school! You need a GoPro so we can ride along and see the smile power! 




 
Sweet machine.


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## jr dragster (Oct 11, 2010)

thanks for posting the vids todd you most have read my mind lol


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## jr dragster (Oct 11, 2010)

pumped up the throttle response to 90% left battery at 80% Ran 11.84, charged then ran 11.86 no charge ran 11.99 charged put a 11,74 dial on ran 11.71 at 56.76 mph TO FAST,loaded it up will try some gear changes want to get in the 10s.I have a question if i have 78.7 volts at full charge, and say it sags 30 , will it sag to 42 being a 72 volt cont or will it sag to 48.7 ?? should i go with more amp hr batteries to get more than one run??how many runs will lithum give ?? Ok more than one question.


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## major (Apr 4, 2008)

jr dragster said:


> pumped up the throttle response to 90% left battery at 80% Ran 11.84, charged then ran 11.86 no charge ran 11.99 charged put a 11,74 dial on ran 11.71 at 56.76 mph TO FAST,loaded it up will try some gear changes want to get in the 10s.I have a question if i have 78.7 volts at full charge, and say it sags 30 , will it sag to 42 being a 72 volt cont or will it sag to 48.7 ??


Hi jr drag,

Sag is normally used to refer to the drop in battery terminal voltage when drawing current from the battery. It is due to the internal resistance of the battery. Voltage drop is found by using Ohm's Law, V = I * R. So the higher the current (I), the higher the sag (voltage drop). This voltage drop is subtracted from the open circuit battery voltage (Voc). 

72V is the nominal voltage for 6 twelve volt batteries in series. Your actual measured voltage of 78.7 volts would be used as Voc. But be careful because the battery voltage directly off the charger will settle a little on the way to the starting line, or even more if she does a burnout. 

And I don't think it is really critical to try to calculate this accurately for your application. I'd just use 75V minus 30 = 45V. I don't know where you got the 30V sag. Do you know the internal resistance and battery current?



> should i go with more amp hr batteries to get more than one run??


Higher capacity batteries of the same type (Pb-Acid) will give you more distance or in your case more runs between charges. But those higher capacity batteries (more Ah) will weigh more and tend to slow the acceleration. However the higher capacity batteries will have a lower internal resistance and less sag and possibly a higher voltage under load and make her go faster. The best thing would be to go to a better battery and charge before each run if you're looking for consistency or best performance.



> how many runs will lithum give ?? Ok more than one question.


Between 1 and 1000  It depends on the specific type of Lithium cells and how large (mass) of a battery you make. For the same mass as your Pb-Acid batteries, my guess is you could likely go 5 to 10 passes without noticeable slowing. And sag would likely be much less.

Regards,

major


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## jr dragster (Oct 11, 2010)

Sorry major i just picked a number for the 30 really have no clue. Found this on ebay .how long do you think it will take to charge at 6 amps?? is this a decent buy ??


*72V 20AH LiFePO4 Pack + BMS / 6A Charger For E-bike, item num, 260814666483*


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## major (Apr 4, 2008)

jr dragster said:


> Sorry major i just picked a number for the 30 really have no clue. Found this on ebay .how long do you think it will take to charge at 6 amps?? is this a decent buy ??
> 
> 
> *72V 20AH LiFePO4 Pack + BMS / 6A Charger For E-bike, item num, 260814666483*


You'll sink $800 for that, rated at 1500 Watts  Like 2 hp. Look around. Wise up to Lithium. Maybe start a thread in the battery forum. That eBay deal sounds bad to me, for your application.


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## jr dragster (Oct 11, 2010)

WOOPS i should read better i thought it said 15,000 watts


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## jr dragster (Oct 11, 2010)

FIRE THE CREW CHIEF  changed the gearing to 12 /42 car slowed down to 12.56 at 41 mph, lost chain in first round rear gear came loose.was a bad day. changed gear to 12 /28 hopefully this works. im running ub12180 batteries,i dont think im able to pull the power i need from them ? would the odyssey batteries be better ?? i know i should go with lithium but i think its going to cost to much. what size pack should i look at for lith? some of the ones i found are not saving a lot of weight ,the headways seam to be the lightest, but when i price out batteries any where from $700 to 1100 +bms + charger im in the 2500 range .does that seem right,how fast can they be charged?thanks for now will let you know how it goes with the gear change. what to run in 10s . found one package 24xbms-lfmp cells ,bms system, charger. 40a $2495 ?


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## jr dragster (Oct 11, 2010)

set the controller to 100% we will see. RUN WHAT YA BRUNG AND HOPE YA BROUGHT ENOUGH  Racing tommorow.


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## jr dragster (Oct 11, 2010)

HAD AWSOME RACE Car ran good driver was on her game. First pass 11.40 , 58 mph second pass 11.43 58 mph. Dialed car at 11.40, first race ran 11.44 .036 light ,second round ran 11.43 58.5 mph .043 light beat a 16 year old with a better light ,i was so proud of her, 3 rd round ran 11.44 at 58.75 .056 reaction . semi finals ran 11.44 at 58.89 fastest pass yet, .185 light lost by .018, was an awsome race day.May change gear to 13 on front ?? 2 more races left


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## jr dragster (Oct 11, 2010)

Raced saturday made third round car slowed down with new gear, changed gear back for sunday ran 11.40s again made it to 3rd round again , finished the season 11 in points out of 28 cars , was an awsome year .We put them on notice of electric power, will post some vids when i find my cord .Where going to put lithium in over the winter and kick some ##s next year. will keep you all posted.


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## toddshotrods (Feb 10, 2009)

Congrats on a good year! Can't wait to see your results next year with Li.


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## Wicked Carts (Nov 1, 2011)

pretty cool we are thinking about building a electric jr.....

we use Odyssey pc925 in our drag cart 

they have great power....

i was reading your post and was wondering why you had a maximun weight limit at 400 pounds thought there was a min weight limit????


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## jr dragster (Oct 11, 2010)

The min weight is 225 pounds , you can be over 400 but then you you have to go to sfi 2.7 i think,car has to be made with heavier material.bigger bars and so on. what kind of amps are you pulling out of them batteries? I am thinking of putting headways in but i dont know if we can swing the cost this year , batteries are not bad at 900-1000 then charger 500-600 . already have chargers for agms ?? so we will see what happens ,i was looking at the odysseys if we dont do lithium. If you have any questions when you start just ask.


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## Wicked Carts (Nov 1, 2011)

i havent seen in the rule book about the bigger bars for weight.... just if its faster than 8.89 it needs to be moly tubing and rack for steering.....

sfi 2.7 is rear engine dragster this i know cause we are building a pro mod golf cart chassis to these specs...

the Odyssey is the best power to weight battery on the market for AGM

the pc 925 is 925 amps... and 25 pounds

you can run 72 parellel with pc 680 and that 1360 amps for 27 pounds for a pair of batts


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## Wicked Carts (Nov 1, 2011)

we have a customer that uses his mini bike to pull the jr dragster in the pits
se we built him atrailer/dolly that will hold the jr dragster and the starter
heres a few pics


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## jr dragster (Oct 11, 2010)

thats cool. Its sfi 2.7B page 47 of the rule book for weight over 400 pounds for electric jr.


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## tropes (Jul 24, 2011)

This new kid on the block is collecting parts for his little brother's jr. dragster.
Just purchased a used K91 motor which weighs 55 lb. The first problem is balancing it on the narrow frame. I've decided to use a jackshaft but not sure where to start with gear ratio without knowing the average R.P.M.. I've also decided to go with a belt drive rather than chain.
Lots to learn for this old man!!!
Any help is welcome
http://www.theowlnest.com/lights7sm.jpg


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## major (Apr 4, 2008)

tropes said:


> This new kid on the block is collecting parts for his little brother's jr. dragster.
> Just purchased a used K71 motor which weighs 55 lb. The first problem is balancing it on the narrow frame. I've decided to use a jackshaft but not sure where to start with gear ratio without knowing the average R.P.M.. I've also decided to go with a belt drive rather than chain.
> Lots to learn for this old man!!!
> Any help is welcome
> http://www.theowlnest.com/lights7sm.jpg


Hi tropes,

My friend Chip built a jr for his son. http://www.facebook.com/media/set/?set=a.2315679524412.126787.1022173811&type=1&l=28728ff98f Chip goes by nedrapr on this forum, but doesn't post much here. You might send him a PM. I think he'd help you.

I haven't heard of a K71 motor. Can you post a spec or photo? Photos and build plans are a good way to get feedback here 

Regards,

major


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## tropes (Jul 24, 2011)

major said:


> Hi tropes,
> 
> My friend Chip built a jr for his son. http://www.facebook.com/media/set/?set=a.2315679524412.126787.1022173811&type=1&l=28728ff98f Chip goes by nedrapr on this forum, but doesn't post much here. You might send him a PM. I think he'd help you.
> 
> ...


Thanks. I went to Chip's Facebook page and will send him a friend request. 
Sorry for the K91 glitch. The motor is an K91-4003 Advanced Motors 72 volt http://www.evmotors.com.au/products/download/K91-4003.pdf

Tropes


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## Wicked Carts (Nov 1, 2011)

Chip is a cool dude....

tropes why the jack shaft and belt drive????

with a little fab work you can make a mount for the motor to align up with the sprocket on the axle...



what voltage and battery combo you thuinking of running????

also what controller?????


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## Wicked Carts (Nov 1, 2011)

tropes said:


> This new kid on the block is collecting parts for his little brother's jr. dragster.
> Just purchased a used K91 motor which weighs 55 lb. The first problem is balancing it on the narrow frame. I've decided to use a jackshaft but not sure where to start with gear ratio without knowing the average R.P.M.. I've also decided to go with a belt drive rather than chain.
> Lots to learn for this old man!!!
> Any help is welcome
> http://www.theowlnest.com/lights7sm.jpg


 
nice looking JR to start with.... 

there is front sprocket and rear sprocket to tire height info ill llook for it or email me

[email protected]

the motors i run make peak hp at 8000-9000 rpm but i have spun them over 12000 rpm....


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## Wicked Carts (Nov 1, 2011)

Use the handy calculator on Jr Dragster Plus website
http://www.jrdragsterplus.com/geargrndr.htm 
Jackshaft Axle RPM = (1/ Final Clutch Ratio) x Motor RPM
_Most EPJDs are direct drive and don't use a clutch _

Ratio = Rear Sprocket / Front Sprocket

MPH = (Jackshaft Axle RPM x rollout / 1056) / Ratio
_where 1056 represents the number of inches in a mile (63360) divided by the the number of minutes in an hour (60)_
New Ratio = the inverse of (mph x 1056) / (RPM x New Rollout)
_where 1056 represents the number of inches in a mile (63360) divided by the the number of minutes in an hour (60)_
Rollout = Diameter x pi
_where pi has been estimated to 3.1415962. Note that diameter can be affected by tire pressure._
*Example*
EPJD with an 18.5 inch diameter tire and motor running 5000 rpm. 15 tooth front sprocket and 72 tooth rear sprocket. Direct drive with no clutch.
MPH = (5000 x 58.09/1056)/4.8 = 57.30 mph


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## tropes (Jul 24, 2011)

Wicked Carts said:


> Chip is a cool dude....
> 
> tropes why the jack shaft and belt drive????
> 
> ...


Using 72 volt Lithium Iron Phosphate. 
A jack shaft to distribute the weight. The axle sprocket is centered on the axle with no wiggle room. If I line up the 2 sprockets the weight of the motor is all on one side. The belt is for weight and strength. My friend Peter is building the controller.


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## Wicked Carts (Nov 1, 2011)

the axle sprocket should be able to slide on the axle..... can you send a pic of the rear axle?????


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## tropes (Jul 24, 2011)

Wicked Carts said:


> the axle sprocket should be able to slide on the axle..... can you send a pic of the rear axle?????


no wiggle room
http://www.theowlnest.com/motormount1sm.jpg


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## Wicked Carts (Nov 1, 2011)

wow no kidden maybe to some fab work on the back half of the chassis..and use a wider axle


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## Wicked Carts (Nov 1, 2011)




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## tropes (Jul 24, 2011)

Wicked Carts said:


> wow no kidden maybe to some fab work on the back half of the chassis..and use a wider axle


Defeats the purpose. This car has run under 7.9 @80 plus mph. Rolling chassis weighs 85 lb. I want to keep the frame as is with the exception of some fabricating to make room for the battery. Rear wheel width is 28" so weight balance is critical.


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## Wicked Carts (Nov 1, 2011)

our with with the paddle tires is 36"

and by adding the jack shaft and belt your adding weight and more moving parts... useing 7/8 moly tubing its a .5 pounds per foot getting a lighter motor would help too


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## tropes (Jul 24, 2011)

Wicked Carts said:


> our with with the paddle tires is 36"
> 
> and by adding the jack shaft and belt your adding weight and more moving parts... useing 7/8 moly tubing its a .5 pounds per foot getting a lighter motor would help too


Already have the heavy motor so I'll just have to "run what I brung".
Live and learn.


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## Wicked Carts (Nov 1, 2011)

we do alot of different fab work and you would be supprised with a different design on the rear you most likly will not add weight to the chassis.... then no jack shaft and stuff.... it just a thought 

we were lucky to find the chassis we have for the most part will work great just to cut and few things and ill post pics when we get into it


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## jr dragster (Oct 11, 2010)

I think the direct drive is the best for the electric ,with the instant torque off the line the clutch is just a waste of time. We had to do some work on our frame to make it all fit.


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## jr dragster (Oct 11, 2010)

wicked was looking at the pic of your jr , where running 50 chain and we streched it , i think you have 35 from the pic ,you will have to change to bigger chain and gear. Or i think you will blow the chain off.


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## tropes (Jul 24, 2011)

jr dragster said:


> I think the direct drive is the best for the electric ,with the instant torque off the line the clutch is just a waste of time. We had to do some work on our frame to make it all fit.


Hi Mark
Sorry I haven't explained myself well. I am not using a clutch. I am using a jackshaft to center the motor. The dragster came with #35 chain but I would like to convert to a belt drive.


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## tropes (Jul 24, 2011)

I realize the first year will be a sharp learning curve but since I have already purchased a heavy, slightly used K91- 4003, 72 volt motor for my conversion, I must consider this motor as a starting point. Is anyone here using this motor and if so, what are you using for battery, controller, throttle, contactor?
Tropes


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## Wicked Carts (Nov 1, 2011)

i havent used that motor so i dont know what is in the inside like armercher size and the feilds....or is it timed

for 72 volts you can use alltrax or Logisystems makes a killer race controller.... PB6 for the throttle, albright contactors

we use AGM Odyssey Batterys you could try the pc680 amp but your motor might be a pig so more amps is always better so the PC 925

or you could parellel the pc680 then you would have 1360 amps great power...in fact best power to weight to $$ ..... might be what you need to put the jr in the 7's

after you get the chassis running good then you could send us your motor and we can make it a race motor....

we have a new motor we need to test but we test on heavy golf carts but our green cart is a good test model pretty consistent so we test new stuff all the time to compare notes.... 


i didnt think you where going to use a cluthch but the weight of a jack shaft and the power going throught a belt in my opion is not good... but try it and then we will all know

good luck
we got the jr drag to test stuff too.... power to weight and other goodies 

sooner or later we want to move to a 160" or bigger rail and want to see what its going to take to run big numbers not sure if we wont to use live axle or a 9" rear end


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## tropes (Jul 24, 2011)

Wicked Carts said:


> i havent used that motor so i dont know what is in the inside like armercher size and the feilds....or is it timed
> 
> for 72 volts you can use alltrax or Logisystems makes a killer race controller.... PB6 for the throttle, albright contactors
> 
> ...


Thanks Wicked
The motor specs are here: http://www.evmotors.com.au/products/download/K91-4003.pdf
I have a Curtis Pot box PB6 and a used Curtis/Albright contactor SW200-505. I would like to use 3.3 V Lithium cells; 12 cells parelled and in series to make a 12volt battery x 6 = 72volt. How would you make this motor into a race motor?
I will start with the belts because I have a friend who owns a NAPA store and will donate them.
Tropes


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## tropes (Jul 24, 2011)

When the car is being towed or the power is turned off and the motor continues to turn the motor becomes a generator. Where is this generated power being spent and is there any harm to the motor?


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## Yabert (Feb 7, 2010)

tropes said:


> When the car is being towed or the power is turned off and the motor continues to turn the motor becomes a generator.


No! 
It is simply became a 20 lbs cylinder turning inside an housing.
Some motors can regen, but they need a proper controller and this controller will put back the energy to battery.


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## tropes (Jul 24, 2011)

Yabert said:


> No!
> It is simply became a 20 lbs cylinder turning inside an housing.
> Some motors can regen, but they need a proper controller and this controller will put back the energy to battery.


Why is it then when I turn the motor by hand my volt meter attached to the terminals reads up to 0.1 volt?


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## major (Apr 4, 2008)

tropes said:


> No! Why is it then when I turn the motor by hand my volt meter attached to the terminals reads up to 0.1 volt?


When you turn a PM motor it will generate a voltage. There is always a magnetic field inside the motor. If there is no circuit connecting the terminals, there will be no current and therefore no power. I think you said you have a series motor. Ideally there is no excitation (magnetism) however there is what is called residual magnetism due to hysteresis in the core steel. So you may see a small voltage at the terminals. But the residual is weak and would fade quickly if you were to connect a load circuit.


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## tropes (Jul 24, 2011)

major said:


> When you turn a PM motor it will generate a voltage. There is always a magnetic field inside the motor. If there is no circuit connecting the terminals, there will be no current and therefore no power. I think you said you have a series motor. Ideally there is no excitation (magnetism) however there is what is called residual magnetism due to hysteresis in the core steel. So you may see a small voltage at the terminals. But the residual is weak and would fade quickly if you were to connect a load circuit.


Good. My concern was turning off the power at 60 mph with direct drive from motor to axle the motor will be turning 4500 rpm.


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## jr dragster (Oct 11, 2010)

WE WON BEST ENGINEERED JR DRAGSTER at the year end banquet in saskatoon this weekend.thanks for all your help on this site. I got a thanks dad from my girl made all the money and hours of work all worth it.  Going to build the trophy case .lol


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## Wicked Carts (Nov 1, 2011)

very nice


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## major (Apr 4, 2008)

jr dragster said:


> WE WON BEST ENGINEERED JR DRAGSTER at the year end banquet in saskatoon this weekend.thanks for all your help on this site. I got a thanks dad from my girl made all the money and hours of work all worth it.  Going to build the trophy case .lol


Congratulations dad


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## tropes (Jul 24, 2011)

Congratulations Mark! I realize now how much work goes into building an electric dragster.


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## madmike8 (Jun 16, 2011)

Too Cool. Congrats!!!


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## tropes (Jul 24, 2011)

Wicked Carts said:


>


what motor and battery are you using?


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## Wicked Carts (Nov 1, 2011)

that motor in the pic is a custom built motor in a advance dc can for our golf carts... for batteries we will use the Odyssey PC 680 AGM battery maybe start at 48volts for testing them go up from there....


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## tropes (Jul 24, 2011)

Wicked Carts said:


> that motor in the pic is a custom built motor in a advance dc can for our golf carts... for batteries we will use the Odyssey PC 680 AGM battery maybe start at 48volts for testing them go up from there....


I notice no cooling fan. Is that just temporary?


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## toddshotrods (Feb 10, 2009)

Congrats to you and your daughter!


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## Wicked Carts (Nov 1, 2011)

tropes said:


> I notice no cooling fan. Is that just temporary?


 
no dont need cooling fan for drag racing


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## tropes (Jul 24, 2011)

Wicked Carts said:


> no dont need cooling fan for drag racing


Good point Wicked. 
I have been trying to calculate a gear ratio needed to achieve 50 mph useing the chart http://www.jrdragsterplus.com/geargrndr.htm
but unless you know the motor rpm at the end of the 1/8 mile you can't.
My guess is about 4500 which means I need a 4.8:1 ratio.
Converting to electric is challenging!


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## major (Apr 4, 2008)

tropes said:


> Good point Wicked.
> I have been trying to calculate a gear ratio needed to achieve 50 mph useing the chart http://www.jrdragsterplus.com/geargrndr.htm
> but unless you know the motor rpm at the end of the 1/8 mile you can't.
> My guess is about 4500 which means I need a 4.8:1 ratio.
> Converting to electric is challenging!


Hi tropes,

I don't remember what motor/controller/battery you have, but 4500 rpm sounds too high for end of run motor RPM. You'd have good launch torque but hit peak power too soon. That is unless you have a low design voltage motor running on a high voltage battery. But not knowing what motor/battery you have, I could be way off base. Anyway, I suggest you leave plenty of wiggle room for ratio adjustment in your build  

Regards,

major


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## tropes (Jul 24, 2011)

major said:


> Hi tropes,
> 
> I don't remember what motor/controller/battery you have, but 4500 rpm sounds too high for end of run motor RPM. You'd have good launch torque but hit peak power too soon. That is unless you have a low design voltage motor running on a high voltage battery. But not knowing what motor/battery you have, I could be way off base. Anyway, I suggest you leave plenty of wiggle room for ratio adjustment in your build
> 
> ...


This is the motor http://www.evmotors.com.au/products/download/K91-4003.pdf
The battery is 72 volt LiPo. How does the controller come into the rpm mix?


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## jr dragster (Oct 11, 2010)

Buy lots of gears and trial and error .we have 10-20 gears some are brand new never tryed yet, and some we never will ,we will end up using them for paper weights. lol Thats racing.


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## tropes (Jul 24, 2011)

jr dragster said:


> Buy lots of gears and trial and error .we have 10-20 gears some are brand new never tryed yet, and some we never will ,we will end up using them for paper weights. lol Thats racing.


You're right, that's racing but I'm stuck on using belt drive and the sprockets sizes are limited. The tallest gear combo I can find is 4.83 which leaves using the motor to jackshaft sprockets to make changes. I will start with what I've got and make changes once I get the car moving.


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## major (Apr 4, 2008)

tropes said:


> This is the motor http://www.evmotors.com.au/products/download/K91-4003.pdf
> The battery is 72 volt LiPo.


4800 RPM is down around 5 hp. 



> How does the controller come into the rpm mix?


It sets the maximum motor current and therefore the maximum torque from the motor and also the peak power. Look at page 3 from the link. It is motor performance at 72V. For example, if the controller has a 300A current limit, you get about 45 lb.ft. from the motor at full throttle launch. It stays at 300A and 45 lb.ft. until 2200 RPM. Then the current and torque decrease as the motor speeds up from there. Peak power is at the 45 lb.ft. 2200 RPM point which is 18.5 hp.

I think you should try to hit the peak power about 3/4 down the track. Also, I used 300A as an example controller limit. I think you should go higher. 

major


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## jr dragster (Oct 11, 2010)

tropes what brand and size of battery did you get??


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## tropes (Jul 24, 2011)

jr dragster said:


> tropes what brand and size of battery did you get??


A friend who owns a Sparrow EV had some extra Headways 16ah and a rebuilt DCP controller. I purchased them in October but he has not yet configured them to 72 volts. I anticipate their arrival shortly but I am still working on the frame and motor mount. First things first.
How about you? Do you have a battery yet?


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## Wicked Carts (Nov 1, 2011)

tropes said:


> Good point Wicked.
> I have been trying to calculate a gear ratio needed to achieve 50 mph useing the chart http://www.jrdragsterplus.com/geargrndr.htm
> but unless you know the motor rpm at the end of the 1/8 mile you can't.
> My guess is about 4500 which means I need a 4.8:1 ratio.
> Converting to electric is challenging!


 
the rpm at th end of track is what your looking for.... 

with our carts with 12:1 gears and 22" tall tires 53 mph is 11500 rpm

8:1 with same 22" tire is 7100 rpm is 58 mph

peak torgue is 8000 to 9000 rpm on motors

the motor voltage the higher the motor will rpm

the bigger the controller the quicker it will get there


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## tropes (Jul 24, 2011)

jr dragster said:


> tropes what brand and size of battery did you get??


I'm trying to figure out where the cable goes from the lever mounted to your frame on the driver's right side.


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## tropes (Jul 24, 2011)

tropes said:


> I'm trying to figure out where the cable goes from the lever mounted to your frame on the driver's right side.


Figured it out. It's a Big Red Button without the red knob.


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## jr dragster (Oct 11, 2010)

We took off the knob and made a rod to thread on to the shut off in the car , that one is on the negative side,the one on top is the pos side cut off.I got the strobe light from a forklift place in toronto its 72-144 volts i think, if you cant find one i can can find the info for you it was like $50.00 or so.


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## tropes (Jul 24, 2011)

jr dragster said:


> We took off the knob and made a rod to thread on to the shut off in the car , that one is on the negative side,the one on top is the pos side cut off.I got the strobe light from a forklift place in toronto its 72-144 volts i think, if you cant find one i can can find the info for you it was like $50.00 or so.


I just got one of those el cheapo switches from Carl at EV Drives. I'd like to use just one and have a cable from the switch to the driver.
I have a cluster of 12 volt amber flashing lights that I'd like to use.
Do you have a red tail light? What do you use for a dial-in board and flag holder?


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## jr dragster (Oct 11, 2010)

tropes said:


> I just got one of those el cheapo switches from Carl at EV Drives. I'd like to use just one and have a cable from the switch to the driver.
> I have a cluster of 12 volt amber flashing lights that I'd like to use.
> Do you have a red tail light? What do you use for a dial-in board and flag holder?


You need a shut off on the roll bar and inside the car. for 12 volt lights 
you will need a dc to dc converter{ more weight} as for the rear light you can buy a battery powered one 9v , you dont need a dial in board just write on the car. flag holder just weld some tabs and drill holes.


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## tropes (Jul 24, 2011)

jr dragster said:


> You need a shut off on the roll bar and inside the car. for 12 volt lights
> you will need a dc to dc converter{ more weight} as for the rear light you can buy a battery powered one 9v , you dont need a dial in board just write on the car. flag holder just weld some tabs and drill holes.


The main contactor is a 12volt solonoid. The same 12 volt source could be used to light the 12 volt flasher. Could you not just use the safety disconnect (BRB) on the positive side of the battery and connect a lanyard to it from the driver's compartment?


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## tropes (Jul 24, 2011)

tropes said:


> The main contactor is a 12volt solonoid. The same 12 volt source could be used to light the 12 volt flasher. Could you not just use the safety disconnect (BRB) on the positive side of the battery and connect a lanyard to it from the driver's compartment?


With this basic setup you can take off 12 volts anywhere between the contactor and the auxiliary battery.
http://www.theowlnest.com/basicwiring.jpg


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## major (Apr 4, 2008)

tropes said:


> With this basic setup you can take off 12 volts anywhere between the contactor and the auxiliary battery.
> http://www.theowlnest.com/basicwiring.jpg


Hey tropes,

That wiring diagram is wrong. A2 on the motor needs to go to M- on the controller and A2 on the controller needs to be left unconnected.

major


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## tropes (Jul 24, 2011)

Thanks major. Good to see you're on the job.


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## jr dragster (Oct 11, 2010)

tropes said:


> With this basic setup you can take off 12 volts anywhere between the contactor and the auxiliary battery.
> http://www.theowlnest.com/basicwiring.jpg


 why do yo want to run an extra 12 volt battery ??more weight , just get a 72 volt contactor. 72 volt light .


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## tropes (Jul 24, 2011)

jr dragster said:


> why do yo want to run an extra 12 volt battery ??more weight , just get a 72 volt contactor. 72 volt light .


The contactor (Curtis/Albright SW200-505) uses a 12 volt solenoid switch. Either you take it off the main battery or you use a 12 volt auxiliary battery. Peter, who is building the Raptor controller says he prefers a 12 volt auxiliary battery so I figure why not use it to light up the 12 volt LED flasher.


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## tropes (Jul 24, 2011)

Your 2 emergency switches could also be 12 volt if they shut off the contactor.


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## Wicked Carts (Nov 1, 2011)

you can also run a contactor on 24 volt less voltage drop.... the guys building drag quad and drag bikes are running a 14v lith screw gun batt... i will find a link of the guy making the billet mount for the batts

for the tail light we just use a LED bicycle light uses it own battery....


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## Wicked Carts (Nov 1, 2011)

here is the style of tail light they are like $9.00


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## tropes (Jul 24, 2011)

Wicked Carts said:


> you can also run a contactor on 24 volt less voltage drop.... the guys building drag quad and drag bikes are running a 14v lith screw gun batt... i will find a link of the guy making the billet mount for the batts
> 
> for the tail light we just use a LED bicycle light uses it own battery....


My contactor has a 12 volt coil. I am concidering using a second contactor as an emergency shut off. I have the red LED bicycle tail light mounted on the frame but the NHRA in their wisdom requires electric cars to have a flashing amber light as well.


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## Wicked Carts (Nov 1, 2011)

tropes said:


> My contactor has a 12 volt coil. I am concidering using a second contactor as an emergency shut off. I have the red LED bicycle tail light mounted on the frame but the NHRA in their wisdom requires electric cars to have a flashing amber light as well.


 
i think there is also an amber light for the bikes....


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## major (Apr 4, 2008)

Wicked Carts said:


> .... the guys building drag quad and drag bikes are running a 14v lith screw gun batt... i will find a link of the guy making the billet mount for the batts....


Hi guys,

I found a nice way to get low power 12V on small EVs.









Just cut a flashlight in half for the socket.










Mount the socket on the kart and charge the battery off-board. It is a nice little 12V lithium battery weighing 0.4lbs. Battery cost is under $20 on sale. Flashlight is under $15. I'd get the drill/driver kit which comes with battery and charger for under $50. Then you have a nice little drill/driver to use when you're not racing or at the track.

I even did this to convert an old dead NiCad tool battery to Li. Cheaper than buying a replacement NiCad.










Regards,

major


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## tropes (Jul 24, 2011)

i have a concave warp in the brake rotor and have not been able to locate a replacement. the rotor is 7" diameter, 1/4" thick, 4 bolt 2.5" diameter mount.


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## Wicked Carts (Nov 1, 2011)

here is the billet mount for the 14.4 dewalt


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## tropes (Jul 24, 2011)

Wicked Carts said:


> here is the billet mount for the 14.4 dewalt


That is a good looking piece of work.


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## Wicked Carts (Nov 1, 2011)

tropes said:


> That is a good looking piece of work.


 
i dont make them a guy makes them for the pro stock drag bikes and alot of the sand drag quad guys use it.... thinking of using it on our drag carts


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## major (Apr 4, 2008)

Wicked Carts said:


> here is the billet mount for the 14.4 dewalt


Yep, that's real pretty. Kind of makes my approach look like a PoS  I wonder where he gets the contact block. Using these tool batteries on smaller or special purpose EVs is a great idea.


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## jr dragster (Oct 11, 2010)

Happy holidays to all best wishes in the new year .


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## tropes (Jul 24, 2011)

jr dragster said:


> Happy holidays to all best wishes in the new year .


 Thanks and a Merry Xmas to you and your family. Hope to see you at the track in 2012.


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## tropes (Jul 24, 2011)

I would like to place a safety switch on the brake as per drawing. Two reasons: 1) the power to the motor can be turned off by the driver with two hands on the steering wheel;
2) the motor has no power when staged so no movement until the brake is released.

Is there a down side to this set-up?


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## major (Apr 4, 2008)

tropes said:


> I would like to place a safety switch on the brake as per drawing. Two reasons: 1) the power to the motor can be turned off by the driver with two hands on the steering wheel;
> 2) the motor has no power when staged so no movement until the brake is released.
> 
> Is there a down side to this set-up?


Controllers almost always have a "run enable" input. B+ usually needs to be present on this pin for any power signal to go to the motor. You showed a Curtis type in this http://www.theowlnest.com/basicwiring.jpg On those types of Curtis, there is pin#1 for this function. Pins #2&3 for the potbox. I recommend using a microswitch on the brake lever to control this signal opposed to opening the contactor supply.

You did not show a pre-charge circuit on your diagram. This is a reason to keep the brake switch out of the contactor supply.

major


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## jr dragster (Oct 11, 2010)

you have to have a tether in the car to shut it down .so no need to put one on the brake, i think if something happened to the car if the brakes where held down and the car was at full throtle the fuse would blow?or that was the way it should work.


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## tropes (Jul 24, 2011)

major said:


> Controllers almost always have a "run enable" input. B+ usually needs to be present on this pin for any power signal to go to the motor. You showed a Curtis type in this http://www.theowlnest.com/basicwiring.jpg On those types of Curtis, there is pin#1 for this function. Pins #2&3 for the potbox. I recommend using a microswitch on the brake lever to control this signal opposed to opening the contactor supply.
> 
> You did not show a pre-charge circuit on your diagram. This is a reason to keep the brake switch out of the contactor supply.
> 
> major


Thanks for the input. It appears the concern is closing the contacts at full throttle. i can see how this surge of power to the controller could cause damage.
The Curtis PB5 does not have a micro-switch (run-disable).

tropes


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## major (Apr 4, 2008)

tropes said:


> Thanks for the input. It appears the concern is closing the contacts at full throttle. i can see how this surge of power to the controller could cause damage.
> The Curtis PB5 does not have a micro-switch (run-disable).
> 
> tropes


There should be other microswitches available for the brake pedal. Often used for brake lights.


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## jr dragster (Oct 11, 2010)

pulled out the lead batteries ,got to get on the lithium ,will get some ordered next week or so.Cant decide headway or r/c batteries?


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## jr dragster (Oct 11, 2010)

Was cleaning out some old emails and ran across this link.Check it out we got mentioned by bob frye here is the link he mentions the electric jr dragster at the end.www.*youtube.com/watch*?*v*=*kiDX5y96*-*58 .*


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## Guest (Feb 19, 2012)

jr dragster said:


> pulled out the lead batteries ,got to get on the lithium ,will get some ordered next week or so.Cant decide headway or r/c batteries?


It the only choice is R/C or Headway? Go with Headway. Have you looked into the A123 Pouch cells. 19AH size and they have more than enough punch for any drag vehicle. Perfect for racing. Good pricing now too. LiFePO4 with nano phosphate. Loads of power for these puppies. You could build a 40AH size cell. Easier to build than headway and more stable than R/C type cells. Power to spare and more than likely better power than some R/C type cells. 

Pete


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## Yabert (Feb 7, 2010)

jr dragster said:


> pulled out the lead batteries ,got to get on the lithium ,will get some ordered next week or so.Cant decide headway or r/c batteries?


Let say 72v pack. 

-A123 20Ah: 24 cells in series, 27 lbs (without connexion), rated around 30 Kw of peak power at 450A. Safe, but a little complexe to build. From 600 to 1000$ for 24 cells.

-Headway 38120HP (8Ah): 24 cells in series and 2 in parralele, 35 lbs, rated around 27 Kw of peak power at 450A. Safe and relatively simple to build. From 800 to 1100$ for 48 cells.

-TURNIGY nano-tech 10s (5Ah): 2 in series and 2 in parralele, 12 lbs, around 30 Kw of peak power at 450A (my guess). Can be dangerous if improperly used, but simple to build. Around 600$ for 4 pack.


Personnaly, A123 20Ah seem the best choise, but you need some skill to build proper battery pack.


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## jr dragster (Oct 11, 2010)

Yabert said:


> Let say 72v pack.
> 
> -A123 20Ah: 24 cells in series, 27 lbs (without connexion), rated around 30 Kw of peak power at 450A. Safe, but a little complexe to build. From 600 to 1000$ for 24 cells.
> 
> ...


I looked at the a123 they look a little complex for me to tackle at this time, headway cells dont look to complicated , the turnigy would be the easiest to build ._I dont know if i want to use them?_ The chargers would be about the same price. Where would you buy headway cells from ? ,got to get on this first race is may 26.


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## tropes (Jul 24, 2011)

jr dragster said:


> pulled out the lead batteries ,got to get on the lithium ,will get some ordered next week or so.Cant decide headway or r/c batteries?


If you want to go with the Headways, Carl at EV Drives has a friend who builds the Sparrow and has them in packages of 72 volt.

tropes


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## Yabert (Feb 7, 2010)

jr dragster said:


> headway cells dont look to complicated.


Right!
If you take this route, don't forget the cell holder.
Just like that, 38120S (10Ah cells) can do the job if you can live with 16Kw peak (for 2 parralele cells) or 23 Kw (3 parralele cells).



> the turnigy would be the easiest to build .I dont know if i want to use them?


Easy to build, light, powerful....., but potentially dangerous. All is about your trust in your knowledge.



> Where would you buy headway cells from ?


Best price is direct from china. I bought mine from Headway. Search for Laurraine or Michelle + Headway on forum or on net.

Good luck and continue to share video and results!


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## jr dragster (Oct 11, 2010)

I got an email from headway they will not have any 38120hp cells for about two months. They have the 38120p cells in stock .
here is what im going to order 
50 headway 38120p cells
100 2 hole conectors
50 2 peice holders.
Sound good?? Im going to build two packs of 24 cells each try running one pack and changing packs between races or will try with 2 and see which one works better.
Charger ?? headway has a 15a charger, should i get a higher amp charger 30 or 40 ? for quicker charging .Would like to charge pack in 15 minutes max.Any thing we should look for in a charger? I was going to buy a r/c charger/ balancer, to balance the pack at home.Thanks again for all your help on this site, without your help this never would have got done.GIVE YOURSELF A PAT ON THE BACK.


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## Yabert (Feb 7, 2010)

jr dragster said:


> Sound good?? Im going to build two packs of 24 cells each try running one pack and changing packs between races or will try with 2 and see which one works better.


Two 18 lbs battery pack... cool! But limited power around 11-12 Kw. What was your power setting last year?

If I'm not mistaken, your Alltrax controller can't limit battery Amps separatly from the motor Amps.
So, how do you limit battery amps? Low voltage setting?
It isn't a good idea to pull more than 200A from a single 8Ah Headway.


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## toysdoneright (Feb 20, 2012)

jr dragster said:


> does anyone know the weight of alltrax axe 7245 controller?? The d&d weighs 62 pounds,i found 12 volt 22amp hr batteries that weigh 13 pounds each about $60.00 each .car weighs 225 batteries 6 x 13= 78 d&d 62 ,so im at 365 pounds so far have to stay under 400. so will the controller,wiring ,solenoid weigh less than 35 pounds or do i have to lighten the car some how. thanks


 I used the 7245 controller last yr on my kids jr dragster It doesnt weight very much 5#- 10 # at most Its a good controller but it will only handle 90 volts then lock up till the voltage drops. Depending on how fast you want to go & your weight package you need to think more voltage.I used a very light car ,a me 1003 motor approx 35# and 7 -12 voltj 18ah jumper pack gel batterys and a kid that was 120# and my best run was 11.02 Alltrax is suppose to come out with a 144volt controller this fall ? They also told me I was going to have one in January of this yr. I guess my next aption is the kelly controller Not just price but because of contolling the throddle .You will need a soft staging yet fast 60' GOOD LUCK


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## jr dragster (Oct 11, 2010)

What kind of charger can you use for the A123 pouch cells,There priced so good i think i might have to use them.I was thinking buy a small charger balancer for home then a 20 -30 amp for track,just dont know what kind?Most charge higher than 3.3.I was thinking of building 6 seperate packs of 4 cells each ,then if one cell goes bad it will be easy to change it out.I will have prices tommorow on the cells if they are a good price im going to order 50 i think.{some for screw ups}


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## Wicked Carts (Nov 1, 2011)

hey guys its been awhile been busy ....

i hope this weekend we will be testing the 40aph on 72 volts in our drag cart....


might not have the punch of the a123 but the price is fair and with all the safty features....

we think the 20aph is the beter way to go and we could do that weighing 40 pounds...

we are testing the 40aph cuase thats whats coming in and it still weighs less than my Odyssey 72 volt pack....

i have 100 of passes on my 72 volt pack running a 3 different tracks

i will keep you posted and would love to hear what you think of these liths.... here is a link

http://lithiumion-batteries.com/72VoltLithiumBattery.aspx


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## toysdoneright (Feb 20, 2012)

jr dragster said:


> What kind of charger can you use for the A123 pouch cells,There priced so good i think i might have to use them.I was thinking buy a small charger balancer for home then a 20 -30 amp for track,just dont know what kind?Most charge higher than 3.3.I was thinking of building 6 seperate packs of 4 cells each ,then if one cell goes bad it will be easy to change it out.I will have prices tommorow on the cells if they are a good price im going to order 50 i think.{some for screw ups}


 What do you know about the flight power batterys ? that Shawn Lawson is using


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## jr dragster (Oct 11, 2010)

I think they will be the same as the turnigy ,but im no battery expert.They would probably work but you need so many to get the aph up to be safe.I really thought about using some r/c kind of battery but the price is up there and not sure about pulling high amps for 10 sec.Hopefully some one that knows more than me will post.


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## Wicked Carts (Nov 1, 2011)

jr dragster said:


> I think they will be the same as the turnigy ,but im no battery expert.They would probably work but you need so many to get the aph up to be safe.I really thought about using some r/c kind of battery but the price is up there and not sure about pulling high amps for 10 sec.Hopefully some one that knows more than me will post.


 
how fast are you wanting to go???

thge odyssey pc 680's are the best bang for the $$$$ 

72 volt pack weighing 90 pounds.... about $600 bucks

smart lith battery you can run a 20aph batt 72 volt pack is 40 pounds $1600.00 with charger

they can also make them with the power pack cells t have even more power....


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## toysdoneright (Feb 20, 2012)

jr dragster said:


> I think they will be the same as the turnigy ,but im no battery expert.They would probably work but you need so many to get the aph up to be safe.I really thought about using some r/c kind of battery but the price is up there and not sure about pulling high amps for 10 sec.Hopefully some one that knows more than me will post.


 FLIGHTPOWER EVO-PRO Lite 14.8V 2200 mAh 4 Cell LiPo Battery. 25C(55A) Continuous 50C(110A) Bursts (3 sec). Charge rate 2C (Normal) Max 5C Approved Does this mean much to you ? I think its saying that its about the same as the 12 volt 18 ah agm. Can some one tell me the difference ? Other than 2.8 volts and 4 ah's or 400 mAh if I read right


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## Wicked Carts (Nov 1, 2011)

well a 72 volt pack 40aph of the smart batterys lith are on the way should be here friday and i hope to test them at the track sat....


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## jr dragster (Oct 11, 2010)

toysdoneright said:


> FLIGHTPOWER EVO-PRO Lite 14.8V 2200 mAh 4 Cell LiPo Battery. 25C(55A) Continuous 50C(110A) Bursts (3 sec). Charge rate 2C (Normal) Max 5C Approved Does this mean much to you ? I think its saying that its about the same as the 12 volt 18 ah agm. Can some one tell me the difference ? Other than 2.8 volts and 4 ah's or 400 mAh if I read right


The 2200 is 2.2 amp hr so you would need 8 x 6 of them for 17.6 ah gets pretty $$$$ check the a123 20 ah pouch cells i think they will work the best,im dealing on them know will keep you updated


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## jr dragster (Oct 11, 2010)

Wicked Carts said:


> well a 72 volt pack 40aph of the smart batterys lith are on the way should be here friday and i hope to test them at the track sat....


What is the c rate of those batteries? hope they work good a fair bit of money ?


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## Wicked Carts (Nov 1, 2011)

jr dragster said:


> What is the c rate of those batteries? hope they work good a fair bit of money ?


 
they have a 3 c at continuous and a 10c post for 10 sec 


 i know they dont have the punch or power they are for energy they can make them with the power cells but we are going to run these and see what the numbers are...


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## jr dragster (Oct 11, 2010)

What was your best run last year? good luck hope it goes way better let us know. i wish we could get on the track . dam snow. to bad your not closer i need a rear seat kit for my cart , shipping would kill .


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## Wicked Carts (Nov 1, 2011)

72 volts with pc 925 odyssey 22" slick 6:1 gears 1/8 mile 10.46 @ 59.96 mph with me in cart over 900 pounds


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## Wicked Carts (Nov 1, 2011)

on 108 volts same pc 925 6:1 with 18" tall tire 9.84 @ 63.095


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## Wicked Carts (Nov 1, 2011)

jr dragster said:


> What is the c rate of those batteries? hope they work good a fair bit of money ?


 
do you think the price is high????


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## toysdoneright (Feb 20, 2012)

jr dragster said:


> The 2200 is 2.2 amp hr so you would need 8 x 6 of them for 17.6 ah gets pretty $$$$ check the a123 20 ah pouch cells i think they will work the best,im dealing on them know will keep you updated


Boy I rated them wrong I thought 100Mah was 1 ah Thats a difference Thanks for your help Now that I showed how dumb I am I have another question In parrellel you pick up amps but volts stay the same in series volts go up but amps stay the same Example 12 18ah batterys with 400cca . In parrellel you would have 12 volt but 216 ah and 4800 cca? In series you would have 144 volt but 18ah and 400cca ? JUST LEARNED MORE The 18ah battery only has 100 cranking amps. My battery shop just did a load pull on a new one. Now what do I keep my controller and get better batterys or do I have to do both to run 7.90?


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## Wicked Carts (Nov 1, 2011)

toysdoneright said:


> Boy I rated them wrong I thought 100Mah was 1 ah Thats a difference Thanks for your help Now that I showed how dumb I am I have another question In parrellel you pick up amps but volts stay the same in series volts go up but amps stay the same Example 12 18ah batterys with 400cca . In parrellel you would have 12 volt but 216 ah and 4800 cca? In series you would have 144 volt but 18ah and 400cca ?


 
you still have that wrong but on the right track


using 12 volt batts parrellel 72 volt with pc 925 odyssey 28 aph would be

72 volts @ 1850 amps 56 amp or

single pack 144 volt would be 925 amps 28 aph


we are all here earning and want to learn more so your not dumb at all


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## major (Apr 4, 2008)

toysdoneright said:


> Boy I rated them wrong I thought 100Mah was 1 ah Thats a difference Thanks for your help Now that I showed how dumb I am I have another question In parrellel you pick up amps but volts stay the same in series volts go up but amps stay the same Example 12 18ah batterys with 400cca . In parrellel you would have 12 volt but 216 ah and 4800 cca? In series you would have 144 volt but 18ah and 400cca ? JUST LEARNED MORE The 18ah battery only has 100 cranking amps. My battery shop just did a load pull on a new one. Now what do I keep my controller and get better batterys or do I have to do both to run 7.90?


 


Wicked Carts said:


> you still have that wrong but on the right track
> 
> using 12 volt batts parrellel 72 volt with pc 925 odyssey 28 aph would be
> 
> ...


Hi guys,

Looks like some confusion. I hope I can help. Battery charge (or capacity) is measured in Ampere hours. Please use "Ah" for abbreviation. It is the amount of current (Amperes or A) that can be delivered in a specified time. An 18 Ah battery could deliver 18 A for one hour, in a perfect world. In the real world, the battery guys fib about that and you only get 18 Ah if you discharge slowly over a 20 hour period (C/20). Then you could use 0.9 A for 20 hours and get the advertised 18 Ah. With lead acid batteries, at a one hour rate, you can only get about 70% of the charge specified for the 20 h rate. This derating is often referred to as the Peukert effect.

You guys are not so much concerned with the 20 hour discharge or even the one hour. You need a battery which will deliver current for 15 to 20 seconds. But this capability is related to the longer Ah rating. In lead acid cranking batteries, they use the cold cranking amps (CCA) as an indication of the high current discharge capability. This is kind of fuzzy and it is difficult to depend on a spec like that as evidenced by the 400 CCA rated battery only delivering 100 A on test.

With the Lithium batteries or cells they use a C rating. C is equal to the charge (or capacity) at one hour. So an 18 Ah cell has C = 18. The ability to deliver current is called a "C rate". You will see this referred to with Lithium cells in the specifications as this cell is rated at "3C continuous and 10C peak". This means that the cell can be discharged at 3C (3 * 18) or 54 A for 20 minutes (1 hour/3) continuously or discharge at 10C (10 * 18) or 180 A for short durations (usually maybe for 1 minute).

Once you have built a battery pack of a certain voltage, "C" relates to the energy which determines how far you can go and "C rate" relates to the power which determines how fast you can go. C rate specifications always relate to C, obviously, so that is why you're concerned with C.

You often need to consider using parallel connected cells to get the high current (A) needed for drag racing. You need to use series connected cells to get the required voltage (V) for the motors. So battery packs end up being a combination of series and parallel connected cells (or batteries as in the case of the 12V 18Ah batteries). Convention is to use P for parallel and S for series. Then if you have a battery pack consisting of 12 batteries (12V 18Ah each) and wire them for 72V, you would have a 2P6S pack. 2 in parallel, 6 in series. The 6 in series gives you 72V (6 * 12V) and the 2 in parallel gives you 36Ah (2 * 18Ah). If each battery can deliver 100A (100A/18Ah = 5.55C), then the 2P6S pack can deliver 200A (5.55C * 36Ah). This shows that the C rating doesn't change with parallel or series configurations, but the current does. That is the usefulness of C ratings, they are normalized when comparing cells. You can always add more cells to get more current, but the C rate stays the same.

For a dragster you ultimately want a battery with a very high C rating. This will give you high power for low battery mass. Ideally you would want a battery which could deliver all its energy (or charge) in 15 seconds. 15 seconds is 0.00417 hours. So that relates to 240C for a C rate. A 2 Ah battery could deliver 480A for 15 seconds if it were rated at 240C. 

The industry isn't quite there for 240C cells yet. And for what you may be able to afford, let's use 20C. If a cell has a 20C specification then you could use 24Ah of cells and expect to be able to pull 480A. If the 20C cell was available only in 4 Ah units, then you would need to use 6P, six in parallel. If they were 3.3 V/c (volts per cell), then 22 cells would give you 72.6 V nominal. The pack would be 6P22S or 132 cells in series parallel.

You could expect 3 minutes of total discharge time at 20C. The 20C rating more than likely would have been a peak so running for 3 minutes straight at that current isn't an option. But with cooling periods between short duration 20C discharges, that is what is available.

Regards,

major


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## jr dragster (Oct 11, 2010)

Ya what he said LOL. thanks major that really explains it in plain english for us


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## jr dragster (Oct 11, 2010)

We ordered 50 a123 20 ah pouch cells today,paid by wire transfer hope they show up.lol. were going to build 2 packs of 24 cells each, try to run just one string and change out betwwen races ,also ordered 40ah charger.Will have to build the packs so they can be changed easy.I hope this will get use into the low 9s.Should knock off 50pounds and more power?Then start the gearing all over again,gotta love it.Will let you know when 123 show .Wicked did you get a chance to try batteries ????


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## toysdoneright (Feb 20, 2012)

jr dragster said:


> We ordered 50 a123 20 ah pouch cells today,paid by wire transfer hope they show up.lol. were going to build 2 packs of 24 cells each, try to run just one string and change out betwwen races ,also ordered 40ah charger.Will have to build the packs so they can be changed easy.I hope this will get use into the low 9s.Should knock off 50pounds and more power?Then start the gearing all over again,gotta love it.Will let you know when 123 show .Wicked did you get a chance to try batteries ????


How comes 20 ah ? wont that just give you max of 200 amps? Remember I'm dumb when it comes to batterys I realy hope this works for you Cause then maybe you can teach me how to build a big set GOOD LUCK


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## Wicked Carts (Nov 1, 2011)

the lith batts did come in yet so wasnt able to test....

we have a sand drag race at the end of the month and the weekend before we are going to test at Barona 144 or 156 or 164 volt PC925 on 8:1 gears

the Barona track give 330 ets and MPH and this will help me pick a gear or tires sizes


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## major (Apr 4, 2008)

toysdoneright said:


> How comes 20 ah ? wont that just give you max of 200 amps?


Hi toys,

This relates to what I talked about in post #168. C rate. These cells can do a "C rate" of 30. That means each cell can put out 30C. C = 20 (from 20 Ah). So 30C means 600 Amps.

Also see discussion of these cells on this thread: http://www.diyelectriccar.com/forums/showthread.php?t=70710

Regards,

major


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## Yabert (Feb 7, 2010)

Effectively Toys, you miss something.

Like you can see below, each cell is rated at 1200-1400w.
So, for 24 cell in série, it's a potential of 33600w (33.6 Kw) of peak power for 10 sec.

24s 1p (76v 20Ah), only 26 lbs and a theoretical potential around 30Kw with a 450A controller.... I like it!


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## toysdoneright (Feb 20, 2012)

major said:


> Hi toys,
> 
> This relates to what I talked about in post #168. C rate. These cells can do a "C rate" of 30. That means each cell can put out 30C. C = 20 (from 20 Ah). So 30C means 600 Amps.
> 
> ...


 Thanks Major thats the number I understand Because my 18ah batterys are only good for 150 to 200 amps


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## Wicked Carts (Nov 1, 2011)

toysdoneright said:


> Thanks Major thats the number I understand Because my 18ah batterys are only good for 150 to 200 amps


 
toys 
some of your numbers are not always true... Odyssey AGM pc 925 is a 28 amp our but with 925 amps


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## toysdoneright (Feb 20, 2012)

Wicked Carts said:


> toys
> some of your numbers are not always true... Odyssey AGM pc 925 is a 28 amp our but with 925 amps


 I had my Power Sonics batterys load tested twice @ two different places 1 first was @ a battery shop they tested with full charge 157 cca They also pulled a brand new one charged it and came back at basicly same cca The second time I took one to Advanced Auto They used a computer tester and it came to 217 cca At the same time I tested a Magna power It tested @ 437 cca


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## Wicked Carts (Nov 1, 2011)

toysdoneright said:


> I had my Power Sonics batterys load tested twice @ two different places 1 first was @ a battery shop they tested with full charge 157 cca They also pulled a brand new one charged it and came back at basicly same cca The second time I took one to Advanced Auto They used a computer tester and it came to 217 cca At the same time I tested a Magna power It tested @ 437 cca


 
im just going off the man. specs im sure if you test each battery they will read different on different test..

the pc925 is a 380 CCA


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## toysdoneright (Feb 20, 2012)

Wicked Carts said:


> im just going off the man. specs im sure if you test each battery they will read different on different test..
> 
> the pc925 is a 380 CCA


 This is why I don't understand batterys Everyone uses different #s Guess I will buy my own load tester and load test them the way I will use them Full load for 10 seconds Then see how many amps they pull and how low the volts sag I would also have to record before and after volts to see if a battery recovers better than the next ? Then repeat 10 times with 30 mins between pulls to duplcate race passes and time between What else should I test or record? As long as I do the same with each battery that should tell me what type of battery should work the best ? Can I buy 1 pouch cell and do the same ? It should give me the info just will have to scale it up if I use them?


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## Wicked Carts (Nov 1, 2011)

toysdoneright said:


> This is why I don't understand batterys Everyone uses different #s Guess I will buy my own load tester and load test them the way I will use them Full load for 10 seconds Then see how many amps they pull and how low the volts sag I would also have to record before and after volts to see if a battery recovers better than the next ? Then repeat 10 times with 30 mins between pulls to duplcate race passes and time between What else should I test or record? As long as I do the same with each battery that should tell me what type of battery should work the best ? Can I buy 1 pouch cell and do the same ? It should give me the info just will have to scale it up if I use them?


 
i could be wrong but i dont think a load tester will do the same test as a drag cart or jr drag

it has been prooven time and time again for the agm side of things the Odyssey is the best on the market

for 30 pounds you can use 2 pc 680 parrelel is 1380 amps for 5 seconds 32ah

the fastest golf cart is running these not sure what voltage but under 7 seconds over 90 mph in the 1/8 

you also have to keep in mind what your controller can handle 

we ran a parrellel pack of pc 925s so a total of 1850 amps and i only have a 1200 amp controller so i wasnt using the full 1850 amps...


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## major (Apr 4, 2008)

toysdoneright said:


> This is why I don't understand batterys Everyone uses different #s Guess I will buy my own load tester and load test them......


Yep. So true with lead acid. And never trust a battery salesman 

I alluded to this in my long post (#168). CCA is not a number to hang your hat on. And quality of lead acid batteries is all over the place. If you want to race and win with lead acid, you need to set up a battery lab (or hire one) and test every battery when you buy it and several times a season. I have personally tested over a thousand, mostly Optimas, but just about everything out there before I switched to Lithium. Now I test Lithium 

And I have tested Genesis, but not so much Odyssey. I don't think the model number relates to the usable current as a PC925 isn't rated at 925 amperes. It may output that much current, but the voltage will sag so low as the actual power will be way down. Short circuit current is an impressive number, but can do no useful work, or in other words, delivers zero power.

When you get into Lithium, the C rating is a much more reliable indicator. Still, I test every one. But most hit or exceed spec. Whereas with lead acid, it was all over the place. And it does take special equipment to test Lithium cells. They will be in the 3.3 to 4 volt range so a 12V lead acid load tester won't sufficiently load them. 

Welcome to electric racing.....Batteries are a bitch.

major


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## toysdoneright (Feb 20, 2012)

major said:


> Yep. So true with lead acid. And never trust a battery salesman
> 
> I alluded to this in my long post (#168). CCA is not a number to hang your hat on. And quality of lead acid batteries is all over the place. If you want to race and win with lead acid, you need to set up a battery lab (or hire one) and test every battery when you buy it and several times a season. I have personally tested over a thousand, mostly Optimas, but just about everything out there before I switched to Lithium. Now I test Lithium
> 
> ...


I GIVE!!! The more I know the dummer I am! I'm going with K.I.S.S. Keep It Simple Stupid I know where I'm at now. So I'm just going to add more lead and try to figure out how many volts and amps it takes to run 7.90 @85.0 We just have to be under 400#sfor the car


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## Wicked Carts (Nov 1, 2011)

toysdoneright said:


> I GIVE!!! The more I know the dummer I am! I'm going with K.I.S.S. Keep It Simple Stupid I know where I'm at now. So I'm just going to add more lead and try to figure out how many volts and amps it takes to run 7.90 @85.0 We just have to be under 400#sfor the car


 
under 400 pounds????

i would start is 6 of the PC 680's 72 volt and then run it a see what the numbers are...

im sure i can get you to run the 7.90 but the mph doesnt really matter...

a buddy has ran 9.80s at 55mph with a heavier cart than mine on a parrellel pack 72 volt 925s

6 of the pc 680 would only be 90 pounds


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## Wicked Carts (Nov 1, 2011)

remember amps is horse power... the same voltage more amps will run better ets


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## major (Apr 4, 2008)

toysdoneright said:


> I GIVE!!!


Sorry to confuse you with facts and science. I race to win. I forget some race for fun. Just remember, good batteries can beat more batteries.

Good luck and have fun 

major


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## toysdoneright (Feb 20, 2012)

Wicked Carts said:


> under 400 pounds????
> 
> i would start is 6 of the PC 680's 72 volt and then run it a see what the numbers are...
> 
> ...


Yes under 400# for the car plus driver The battery's have to be under the top of tires and inside the chassis The main power wires can not go thru the driving compartment


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## toysdoneright (Feb 20, 2012)

major said:


> Sorry to confuse you with facts and science. I race to win. I forget some race for fun. Just remember, good batteries can beat more batteries.
> 
> Good luck and have fun
> 
> major


 Not racing for fun But we need the car to repeat the run This is ET racing not heads up Totally agree good battery's make more sense But I give up going with K.I.S.S. Hopefully I will under stand battery's better later in summer I will try to load some photo's from last yr so you can see where everything has to be and how much room we have NHRA has there rules the problem is no one has legally gone 7.90 that I know of Shawn Lawless has but his car is overweight and the battery is above the tires


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## Wicked Carts (Nov 1, 2011)

toysdoneright said:


> Not racing for fun But we need the car to repeat the run This is ET racing not heads up Totally agree good battery's make more sense But I give up going with K.I.S.S. Hopefully I will under stand battery's better later in summer I will try to load some photo's from last yr so you can see where everything has to be and how much room we have NHRA has there rules the problem is no one has legally gone 7.90 that I know of Shawn Lawless has but his car is overweight and the battery is above the tires


 
beleive me i know about NHRA and there rules and specs... we have been working with them on building our 90" wheel base cart....

we have guys running in the 7's on 144 volt of 680s single pack in a heavier cart than your 400 pounds.... so i should be much trouble with a jr drag.... what controller you using????


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## Wicked Carts (Nov 1, 2011)

a heavier cart has run 7.87 @ 82mph on 144v on a single pack of odyssey pc680.....


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## jr dragster (Oct 11, 2010)

The A123s are here now have to figure out how to make them into a pack will post pics later.


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## EVfun (Mar 14, 2010)

Wicked Carts said:


> remember amps is horse power... the same voltage more amps will run better ets


Watts is horse power (746 watts equals 1 horsepower.) Watts equal volts times amps. The same voltage with more amps will apply more watts. You could also go with more voltage at the same amps to increase horsepower.


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## Wicked Carts (Nov 1, 2011)

EVfun said:


> Watts is horse power (746 watts equals 1 horsepower.) Watts equal volts times amps. The same voltage with more amps will apply more watts. You could also go with more voltage at the same amps to increase horsepower.


 
if thats the case im 179 hp on paper


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## Wicked Carts (Nov 1, 2011)

how are the A123's coming?????????????


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## toysdoneright (Feb 20, 2012)

Wicked Carts said:


> how are the A123's coming?????????????


I gave up the high tec idea Going either Deka etx20l or odyssey pc680 I can't decide I have talked to both sides but ones numbers aren't the same as the other Deka is 310 cca and 17.5 ah odyssey is 220 cca and 16 ah but they say they can do 680 amps for 5 seconds Deka has no numbers like that Deka said to charge slow Odyssey said to charge fast Who would think lead batterys could be so have to understand?


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## toysdoneright (Feb 20, 2012)

toysdoneright said:


> I gave up the high tec idea Going either Deka etx20l or odyssey pc680 I can't decide I have talked to both sides but ones numbers aren't the same as the other Deka is 310 cca and 17.5 ah odyssey is 220 cca and 16 ah but they say they can do 680 amps for 5 seconds Deka has no numbers like that Deka said to charge slow Odyssey said to charge fast Who would think lead batterys could be so have to understand?


I went back and did some older reading you said some one went 7.87 with 144 pc680's any idea what the weight package would have been?


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## jr dragster (Oct 11, 2010)

was a really busy winter at the shop didnt have much time to do anything with the car till last week .Have all my spacers made holes all drilled in battteries ,there all balanced and chargered up ,should get packs made up this weekend.Ihope will post some pics , first race may 25 ,always wait till last minute.lol .


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## Wicked Carts (Nov 1, 2011)

toysdoneright said:


> I went back and did some older reading you said some one went 7.87 with 144 pc680's any idea what the weight package would have been?


it was a golf cart pro mod style.... 6:1 gears golf cart rear end i think 19" tall tires under 500 pounds...with out driver it might have been a parrellell pack of 680 so that makes it 1360 amps....

i can understand your fustration with batts and the sales men... you need to under stand they are just sales men and they all say there stuff is better than the other... i always say proove it let me have a set for a test and if they run the # then yes your are right they are better but im not spending $2000.00 to find out your wrong.....

for a agm batt the Odd.. have been prooven the best for the weight ....

the pc680 is the best batt they have for power weight and costs....
2 of them weight the same as a 925 but now you have 1360 amps 

the cost for 2 is the same a one 925...

my cart on 144 volts pc 925's bypass with 6:1 gears 18" tall tire and spinning the slicks on the lunch 9.34 @ 69.5 mph

cart weighs on 72 volts 625 + 150 (to toal 144 volts) + me 230 pounds =

1005 pounds.... we know on 72volt my cart with a 100 pound lighter driver it went .30 faster and 1 mph faster...


im not affraidright or wrong good or bad what i have done....

the only way to learn is try it


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## Wicked Carts (Nov 1, 2011)

we have some lith batts we will be testing the cart on 48 volts and compare them to our pc925 numbers on the track...


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## jr dragster (Oct 11, 2010)

Got the A123s almost done


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## tropes (Jul 24, 2011)

jr dragster said:


> Got the A123s almost done


Good talking to you tonight. Thanks for the advice. Hope my controller is back this week and I will be almost done too.


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## Wicked Carts (Nov 1, 2011)

my cart with me in it is close to 1000 pounds

144 volts 925 amp

we ran our best pass last night

8.92 @ 71.69 mph


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## Wicked Carts (Nov 1, 2011)

ok did some 48 volt agm pc925 and 40ah 3C lith batts the last couple of weeks.....


4 agm pc925 is 100 pound pack

4 of the lith was 60 pounds


agm best out of 5 runs was 11.896 @ 48.64


lith best run 11.704 @ 49.83 mph

this test was on my green drag cart with me driving arounf the 800 pound range....


on a 144volt pack it will save 120 pounds....

now the trick is to find a better lith C rating for more power...


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## toysdoneright (Feb 20, 2012)

Question did PC 925 or the lith"s runs closer to each other as in 11.70 11.72 ect vs 11.89 12.20 12.50 for the other batterys ?


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## Wicked Carts (Nov 1, 2011)

toysdoneright said:


> Question did PC 925 or the lith"s runs closer to each other as in 11.70 11.72 ect vs 11.89 12.20 12.50 for the other batterys ?


 
do you mean did the lith batts run more consistant????


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## toysdoneright (Feb 20, 2012)

Yep thats what I'm looking for Thanks Dan


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## Wicked Carts (Nov 1, 2011)

well these were new batts


first pass was a 

11.95
11.96 dont think it charger was on in between rounds
11.727
11.704
11.715


and we have done about the same on the 3 4 5 pass on agm batts...

i have several 3 pass in a roll with in a tenth on agm...

in fact last weeks pass on 48 volt agm

12.45
12.24
12.20
11.91
11.89
11.93


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## toysdoneright (Feb 20, 2012)

Thanks I was hoping they would be more consistant with the lithiums We run with in 2 tenths all day on agms 100 amp hr batterys But not fast enought I am still waiting for time to get it ready for this yr We leave next friday for our JR Dragster nationals in Denver Ive been working my tail off to make the alcohol version go fast enough Thanks For all your help When I get back for the Nationals after july 4 th Its time to make it run If I dont brake much there Thanks again Dan


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## Wicked Carts (Nov 1, 2011)

toysdoneright said:


> Thanks I was hoping they would be more consistant with the lithiums We run with in 2 tenths all day on agms 100 amp hr batterys But not fast enought I am still waiting for time to get it ready for this yr We leave next friday for our JR Dragster nationals in Denver Ive been working my tail off to make the alcohol version go fast enough Thanks For all your help When I get back for the Nationals after july 4 th Its time to make it run If I dont brake much there Thanks again Dan


 

our useing the wrong agms...

hell the track can make 2 tenths....


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## jr dragster (Oct 11, 2010)

hows it going ? we have been busy put the a123s in car left the same gearing as last year ,last year ran 11.44 just changed batteries ran 10.55 and run all day at the test and tune with no charge.


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## jr dragster (Oct 11, 2010)

first race last weekend changed the gearing ran best run 10.19 going to change gear see if we can get 9s for next race . car ran a total of 8 runs on sat from 10.19 to 10.25 . we won !!!!!!!!!!!!!!!
we won are first race ever i was so proud of here the car ran good and she cut some .021 lights to take the win .I had perma grin . raced sunday and car ran just as good as sat we won again !!!!!!!!!!!!!!!!!! IT CANT GET ANY BETTER .we have a test and tune july 14 going to give it more gear see what it will do .we ran all day sat on one charge and all day sunday on one .Ran sun 10.22 to 10.25 car is really running good with the a123s .


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## tropes (Jul 24, 2011)

jr dragster said:


> first race last weekend changed the gearing ran best run 10.19 going to change gear see if we can get 9s for next race . car ran a total of 8 runs on sat from 10.19 to 10.25 . we won !!!!!!!!!!!!!!!
> we won are first race ever i was so proud of here the car ran good and she cut some .021 lights to take the win .I had perma grin . raced sunday and car ran just as good as sat we won again !!!!!!!!!!!!!!!!!! I CANT GET ANY BETTER .we have a test and tune july 14 going to give it more gear see what it will do .we ran all day sat on one charge and all day sunday on one .Ran sun 10.22 to 10.25 car is really running good with the a123s .


Congrats. So good to see an electric doing great. We got in two runs in Estevan on Sunday. ran a 10.49 off the trailer on that concrete runway and started bouncing at the end. Found out the second run that the frame had cracked on both support rails just under the motor. Ran the old sprocket so only 53 mph. Pro Metal is doing repairs this week but hope to be in Med.Hat on the 15th. Keep up the good work.
tropes


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## Wicked Carts (Nov 1, 2011)

jr dragster said:


> first race last weekend changed the gearing ran best run 10.19 going to change gear see if we can get 9s for next race . car ran a total of 8 runs on sat from 10.19 to 10.25 . we won !!!!!!!!!!!!!!!
> we won are first race ever i was so proud of here the car ran good and she cut some .021 lights to take the win .I had perma grin . raced sunday and car ran just as good as sat we won again !!!!!!!!!!!!!!!!!! I CANT GET ANY BETTER .we have a test and tune july 14 going to give it more gear see what it will do .we ran all day sat on one charge and all day sunday on one .Ran sun 10.22 to 10.25 car is really running good with the a123s .


What voltage is the battery pack? Glad to hear about the wins


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## jr dragster (Oct 11, 2010)

72 volt pack 24 a123s ,charge to 79.9


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## tropes (Jul 24, 2011)

jr dragster said:


> 72 volt pack 24 a123s ,charge to 79.9


Our 72 volt has 20 Enerdel cells but the Shumacher bulk charger charges to 79.3. Time to get a BMS and a new charger. What is the voltage of each a123 cell?
tropes


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## major (Apr 4, 2008)

tropes said:


> Our 72 volt has 20 Enerdel cells but the Shumacher bulk charger charges to 79.3. Time to get a BMS and a new charger. What is the voltage of each a123 cell?
> tropes


Careful. LiPo (EnerDel) is different than the LiFePO4 (A123). See http://www.diyelectriccar.com/forums/showthread.php/recent-battery-test-kokam-71238p2.html for some tested comparison.


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## tropes (Jul 24, 2011)

I checked each cell before i installed the battery. Each cell was 3.9 volts. Cell voltage has never dropped below 3.6 volt since


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## Wicked Carts (Nov 1, 2011)

what size A123's are you running??? you can PM if you like

also what controller you running????


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## jr dragster (Oct 11, 2010)

were running the A123s 20 ah pouch cells with an alltrax 7245 72 volts 450 amps and a mars 1003.I will post some vids later.


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## jr dragster (Oct 11, 2010)

I balance charged the cells at 3.5 and only charge them to 79.9 or 80 .


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## Wicked Carts (Nov 1, 2011)

thanks for the info... what were you 60ft numbers????

the alltrax controller is not a race controller

we love and use there stuff in all of our custom carts

we have the SPM 72 volt controller coming in soon to test in 100ah lith in a limo cart


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## Wicked Carts (Nov 1, 2011)

by chance do you know what the battery pack weighs????


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## jr dragster (Oct 11, 2010)

I would guess with the alum box 27 to 30 pounds


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## Wicked Carts (Nov 1, 2011)

jr dragster said:


> I would guess with the alum box 27 to 30 pounds


 
crazy lite


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## tropes (Jul 24, 2011)

jr dragster said:


> were running the A123s 20 ah pouch cells with an alltrax 7245 72 volts 450 amps and a mars 1003.I will post some vids later.


What RPM is the Mars 1003 turning? Our K91 seems to hit the wall at 3900. That's why I wanted to advance the brushes.
Tropes


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## major (Apr 4, 2008)

tropes said:


> What RPM is the Mars 1003 turning? Our K91 seems to hit the wall at 3900. That's why I wanted to advance the brushes.
> Tropes


Performance curves are a bit tough to read, but http://evdrives.com/images/Motors/ME1003/Product_Info_ME1003-1.pdf states the Mars turns 3000 RPM at 72V. Both motors look to have similar torque in the 400 to 450A range. Mars being a PM motor has a flatter curve, but I don't see that as a factor. And I am surprised the mars can tolerate the high current.

I did find the K91 curve http://rapidlibrary.com/source.php?...%20Curve%20%2072-96V.pdf&sec=66e36ac057062570 Looks like at 72V the 3900 RPM point is down to 100A. That is way way below peak power. 

I still say it's the gearing  

major


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## tropes (Jul 24, 2011)

major said:


> I did find the K91 curve http://rapidlibrary.com/source.php?...%20Curve%20%2072-96V.pdf&sec=66e36ac057062570 Looks like at 72V the 3900 RPM point is down to 100A. That is way way below peak power.
> 
> I still say it's the gearing
> 
> major


It could well be the gearing. Our 60 ft. times 1.7's are much quicker than the other juniors in our class but our 53 mph is much slower. we will make some modifications before July 14.
tropes


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## major (Apr 4, 2008)

tropes said:


> It could well be the gearing. Our 60 ft. times 1.7's are much quicker than the other juniors in our class but our 53 mph is much slower. we will make some modifications before July 14.
> tropes


Yeah, I think you need a giant step in the ratio. And do you know if you're pulling the full current limit (450A) at the start? That would be motor current, not battery current.


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## tropes (Jul 24, 2011)

major said:


> Yeah, I think you need a giant step in the ratio. And do you know if you're pulling the full current limit (450A) at the start? That would be motor current, not battery current.


No, I don't know if the motor is drawing full current but i am having trouble hooking up even with the 10 inch Hoosiers. the motor definitely has torque.


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## major (Apr 4, 2008)

tropes said:


> No, I don't know if the motor is drawing full current but i am having trouble hooking up even with the 10 inch Hoosiers. the motor definitely has torque.


What about cutting your ratio in half


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## tropes (Jul 24, 2011)

major said:


> What about cutting your ratio in half


Sounds pretty drastic. That would be 2:1.


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## Yabert (Feb 7, 2010)

jr dragster said:


> I would guess with the alum box 27 to 30 pounds


Cool! 27-30 lbs able to output 27-30 hp with your configuration...
Please shared picture of your battery pack..


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## major (Apr 4, 2008)

tropes said:


> Sounds pretty drastic. That would be 2:1.


I think drastic measures are in order here. Probably the best way to go faster is to increase voltage, but you're unable to that in 2 weeks. A brush advance will buy a few % increase in RPM per amp, but decrease torque per amp and likely not gain you much and risk comm damage. So I think gear ratio.

I'm going on little data, so let me know if I got something wrong. You say now you finish at 53 mph which is 3900 RPM, right? Let's use some rounded numbers from the curve. That is about 100A. 100A at 72V is 7.2kW. If, if, and I'd like to have you confirm, if you actually pull 450A, the peak power would be like 32kW. Now the battery will sag and you'll not see 72V at 450A, but let's just use it for now. That means you finish the run at 7.2/32 or 22% of your peak power. I want you to get that ending power way up there. So, let's shoot for 250A. That would be 18kW. Or 56% of peak power.

Using the motor performance curve, at 72V, the RPM would be about 2500 for 250A. How do we get to that point at the end of the pass and be going faster? Decrease the ratio. How much? Well, let's use SWAG  If we cut your present ratio in half, then 2500/3900*53mph*2 = 68mph.

There are a whole bunch of assumptions in what I did. Not accounting for battery voltage sag is a biggie. Also the reduction in torque at the wheel due to ratio change will affect the ability to accelerate possibly causing you to fall short of reaching 2500RPM. And if that reduced wheel torque slows the launch you may see increased ETs even with higher exit speeds.

Hey, that's my thinking.

major


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## Wicked Carts (Nov 1, 2011)

i look at this info a little different..... 
first your not going to get good numbers from that alltrax controller .... even with good A123 .... thats a production controller on a race controller....

i havenet played much with sprocket gear ratios but i have played with gears in a golf cart....

on 72 volts on a race 1200 amp race controller PC 925 batts and a heavy 800 pound cart have ran 10.42 @59 mph 

8:1 gears with a 22" tall tires 7400 rpms is 60 mph

even with those numbers our best 60ft is 1.90

we now run 6:1 with a 18" tall tires but have not tested on 72 volt yet....

the more amps you can run will get you better et's and less voltage drop and the alltrax will like you better for that....


this link might help you on gears and rpms... nerdra i think has a sprocket gear rpm formula 

http://www.4qd.co.uk/faq/roadspd.html


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## tropes (Jul 24, 2011)

Wicked Carts said:


> i look at this info a little different.....
> first your not going to get good numbers from that alltrax controller .... even with good A123 .... thats a production controller on a race controller....
> 
> i havenet played much with sprocket gear ratios but i have played with gears in a golf cart....


First let's get things straight. You might have me mixed up with Jr Dragster. I am using a Raptor 1200 controller. I am using a 72 volt Lipo battery built by Enerdel. My motor is a K92-4003 built by Kinetek.
Major has given me a lot to digest but I think he's right about the gear ratio. This is our first year racing junior dragster so the learning curve is steep. I appreciate the input but I must take things slowly and become familiar with the set-up.


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## Wicked Carts (Nov 1, 2011)

tropes said:


> First let's get things straight. You might have me mixed up with Jr Dragster. I am using a Raptor 1200 controller. I am using a 72 volt Lipo battery built by Enerdel. My motor is a K92-4003 built by Kinetek.
> Major has given me a lot to digest but I think he's right about the gear ratio. This is our first year racing junior dragster so the learning curve is steep. I appreciate the input but I must take things slowly and become familiar with the set-up.


 
ok sorry yes i was mistaken... what numbers have you run???


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## tropes (Jul 24, 2011)

Wicked Carts said:


> ok sorry yes i was mistaken... what numbers have you run???


Our numbers and video links are here http://www.theowlnest.com/jrdrag.html


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## Wicked Carts (Nov 1, 2011)

my thought would be gearing....

when we ran 22" tall tire with stock gears 12:1 we went 52 mph with me and then with a 100 pound lighter drivier it went 53 mph


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## jr dragster (Oct 11, 2010)

Some battery pics [/ATTACH][/ATTACH]


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## jr dragster (Oct 11, 2010)

We had 60 foot times best was 2.88 worst was 2.34 thats from 16 runs 330 times were 6.321 to 6.387. This is bracket racing you dont need the fastest car to win {dragging rights are nice } you just need to be consistant every race and cut good lights.I will gear my car at the next test and tune and try to run 9s but if it losses the consistance i will change back, its a fine line to run, we ran 66 miles hr then changed gearing and only ran 59mph but car is quicker ,but not faster.Spinning is not winning,the gearing is hard to get we played with it last year with the lead ,and will do it this year with the lithium.So you want something that you can change the gearing easy and not to expensive.Im sure i could gear the car to run 70mph but it would be in the 13s,im trying to get in the 9s i dont really care what the mph is its not important to me ,more worried about running the same time every run .And having fun with my kids at the track.


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## Wicked Carts (Nov 1, 2011)

in our cart each taller gear we went to the better the et's where...

good luck


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## jr dragster (Oct 11, 2010)

major said:


> Performance curves are a bit tough to read, but http://evdrives.com/images/Motors/ME1003/Product_Info_ME1003-1.pdf states the Mars turns 3000 RPM at 72V. Both motors look to have similar torque in the 400 to 450A range. Mars being a PM motor has a flatter curve, but I don't see that as a factor. And I am surprised the mars can tolerate the high current.
> 
> I did find the K91 curve http://rapidlibrary.com/source.php?...%20Curve%20%2072-96V.pdf&sec=66e36ac057062570 Looks like at 72V the 3900 RPM point is down to 100A. That is way way below peak power.
> 
> ...


 you sure dont like the mars ?? its only running for 10 secs have had no problems its a light motor and a light car .


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## jr dragster (Oct 11, 2010)

Wicked Carts said:


> in our cart each taller gear we went to the better the et's where...
> 
> good luck


 to a point then it will slow down thats what we had last year


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## tropes (Jul 24, 2011)

jr dragster said:


> We had 60 foot times best was 2.88 worst was 2.34 thats from 16 runs 330 times were 6.321 to 6.387. This is bracket racing you dont need the fastest car to win {dragging rights are nice } you just need to be consistant every race and cut good lights.I will gear my car at the next test and tune and try to run 9s but if it losses the consistance i will change back, its a fine line to run, we ran 66 miles hr then changed gearing and only ran 59mph but car is quicker ,but not faster.Spinning is not winning,the gearing is hard to get we played with it last year with the lead ,and will do it this year with the lithium.So you want something that you can change the gearing easy and not to expensive.Im sure i could gear the car to run 70mph but it would be in the 13s,im trying to get in the 9s i dont really care what the mph is its not important to me ,more worried about running the same time every run .And having fun with my kids at the track.


This is a good example: when we ran our electrics together during time trials your mph was 62.14 and ours was 52.35 but our E.T. was quicker.
http://www.youtube.com/watch?v=2akGsAKoZ1E&feature=related
I think the 60 ft. times are important but to run a 9 second, mph must be at least 60. That is my unscientific WAG.


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## tropes (Jul 24, 2011)

jr dragster said:


> you sure dont like the mars ?? its only running for 10 secs have had no problems its a light motor and a light car .


I'm not sure what the best motor is for a junior but that ME1003 seems to be doing the job for you. My K91 was something I got used and cheap. It's hard to compare with so few electrics. 
BTW, what is the weight of the car without driver?


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## major (Apr 4, 2008)

jr dragster said:


> you sure dont like the mars ??


Leftover feelings from a bad experience years ago  Hey, I'm glad it is working well for you. And I'm glad you're winning


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## jr dragster (Oct 11, 2010)

Didnt do to good this weekend went out first round she had a good light the car just didnt run good .ran 10.35 on 10.20 dial in. I charged the batts on friday and we only got one test run on sat then went racing usally get three runs then race i think the batts were cold ??will try again in a couple weeks charge them in the morning and get some heat in them.I hope that was the problem, cant lose on week cant make it past first round the next , thats racing. were rained out on sunday.


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## tropes (Jul 24, 2011)

jr dragster said:


> Didnt do to good this weekend went out first round she had a good light the car just didnt run good .ran 10.35 on 10.20 dial in. I charged the batts on friday and we only got one test run on sat then went racing usally get three runs then race i think the batts were cold ??will try again in a couple weeks charge them in the morning and get some heat in them.I hope that was the problem, cant lose on week cant make it past first round the next , thats racing. were rained out on sunday.


We went out too in the first round but we broke out. Ran a 9.74 on a 9.85 dial in.


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## major (Apr 4, 2008)

tropes said:


> We went out too in the first round but we broke out. Ran a 9.74 on a 9.85 dial in.


In the nines.  What did you do differently? mph?


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## tropes (Jul 24, 2011)

major said:


> In the nines.  What did you do differently? mph?


Yes, 4 passes: 9.94, 9.93, 9.89,and then a dial in of 9.85 and ran a 9.74 @ 57.4 mph. 
60 ft. time of 1.67 was much quicker then the gas cars. 
I attribute the 5 mph to the advanced brushes and the quicker times to the tweeking the Raptor controller.


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## tropes (Jul 24, 2011)

jr dragster said:


> i think the batts were cold ??will try again in a couple weeks charge them in the morning and get some heat in them.I hope that was the problem.


I'm sure temperature has a big affect on the car's performance. We now have a thermometer at the staging area and are logging temp. to E.T.
Our times definitely are related to temperature.
BTW, what does your car weigh?
Tropes


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## jr dragster (Oct 11, 2010)

last year it was 350 pounds so i figure with the battery change 290-310 .somewhere in there


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## tropes (Jul 24, 2011)

jr dragster said:


> last year it was 350 pounds so i figure with the battery change 290-310 .somewhere in there


I was wondering what the weight difference was between our two cars. I am going to weigh our car next weekend in Medicine Hat.


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## jr dragster (Oct 11, 2010)

when i built the car i read that i should have the cables from the controller to motor three feet long , now i read they should be as short as possible which one is better or does it matter?? i could take out probably half .


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## tropes (Jul 24, 2011)

jr dragster said:


> when i built the car i read that i should have the cables from the controller to motor three feet long , now i read they should be as short as possible which one is better or does it matter?? i could take out probably half .


as short as possible. less resistance = less heat.


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## tropes (Jul 24, 2011)

weighed in MH on Friday. car weighs 276 lb.


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## jr dragster (Oct 11, 2010)

were building a new car for next year chrome moly .Want to build a 7.90 car in the 1/8 .Was thinking using D&D es15-6 motor any other sugestions?? controller was looking at alltraxs new controllers but only 72 volts 740 amps dont know if that will run 7.90s,if it wont you cant go up on the voltage . So solution jr can go up to higher voltage ,or the zilla not sure which one to use . The alltrax is the lowest priced at 1,100 dollars the others are around 2,000 give or take.Need to keep it as light as possible ,will have 144 volts of A123s to use{made 2 packs for car now}so going up in voltage would be easy to do would need new charger,{ does anyone make a charger that is adjustable say from 96 volts to 144 ??} more voltage more weight,need light as possible .Car that were using now will go down to 48 volts for the new driver thats turning 8 next year,what have i got myself into?? lol.. having lots of fun planning and building and watching her race.{and spending money} thanks for your info .


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## tropes (Jul 24, 2011)

jr dragster said:


> were building a new car for next year chrome moly .Want to build a 7.90 car in the 1/8 .Was thinking using D&D es15-6 motor any other sugestions?? controller was looking at alltraxs new controllers but only 72 volts 740 amps dont know if that will run 7.90s,if it wont you cant go up on the voltage . So solution jr can go up to higher voltage ,or the zilla not sure which one to use . The alltrax is the lowest priced at 1,100 dollars the others are around 2,000 give or take.Need to keep it as light as possible ,will have 144 volts of A123s to use{made 2 packs for car now}so going up in voltage would be easy to do would need new charger,{ does anyone make a charger that is adjustable say from 96 volts to 144 ??} more voltage more weight,need light as possible .Car that were using now will go down to 48 volts for the new driver thats turning 8 next year,what have i got myself into?? lol.. having lots of fun planning and building and watching her race.{and spending money} thanks for your info .


Sounds like a good plan. The ES-15-6 is basically the same motor as our K91, 1" longer, more torque. The difficult part may be finding a 120VAC charger. Looking forward to seeing a 7.90 electric.
Tropes


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## major (Apr 4, 2008)

http://www.engineeringtv.com/video/All-Electric-Dragsters-at-Lawle; 

I thought you guys might find this interesting


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## tropes (Jul 24, 2011)

major said:


> http://www.engineeringtv.com/video/All-Electric-Dragsters-at-Lawle;
> 
> I thought you guys might find this interesting


Chip Gribben pointed this car out to me last week. It is so encouraging to see a 7.9 sec. electric Junior. We are also using a Halfscale chassis and a similar jackshaft setup. Because of the age of our driver we are limited to 8.9 seconds which we should achieve with 96 volts. We have run a 9.53 with 72 volts which is probably the quickest electric in the Thunder class. Consistancy is still a problem but I hope that will come once we get our gear ratio figured out. Thanks for the link.


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## jr dragster (Oct 11, 2010)

Ordered the D&D ES-15-6 today for the new car just trying to figuire out what controller to buy alltrax 72 volt 740 amps or ths solution jr can go higher voltage but only 600 amps ?? just dont know which one there is a big price diff.But want a 7.90 car and dont know if it will do it at 72 volts ?? will do more reading.any thoughts ????


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## major (Apr 4, 2008)

jr dragster said:


> Ordered the D&D ES-15-6 today for the new car just trying to figuire out what controller to buy alltrax 72 volt 740 amps or ths solution jr can go higher voltage but only 600 amps ?? just dont know which one there is a big price diff.But want a 7.90 car and dont know if it will do it at 72 volts ?? will do more reading.any thoughts ????


Since you've chosen the motor, the 740A will get you 23% more torque than 600A on the motor shaft. But you can get that back at the wheels with ratio. But with the higher voltage controller you can go a lot higher than 23% in voltage above the 72V controller to realize increased power.


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## toysdoneright (Feb 20, 2012)

my thought is high volts because volts = rpm amps = torque you can gear it low to get quick 60' and still get mph have you checked with altraz they where going to build a 144 volt controller


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## jr dragster (Oct 11, 2010)

major said:


> Since you've chosen the motor, the 740A will get you 23% more torque than 600A on the motor shaft. But you can get that back at the wheels with ratio. But with the higher voltage controller you can go a lot higher than 23% in voltage above the 72V controller to realize increased power.


so the more voltage the more rpm i will get?so i need a controller that will do over 72 volts say 96 volts or more .more reading


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## tropes (Jul 24, 2011)

jr dragster said:


> Ordered the D&D ES-15-6 today for the new car just trying to figuire out what controller to buy alltrax 72 volt 740 amps or ths solution jr can go higher voltage but only 600 amps ?? just dont know which one there is a big price diff.But want a 7.90 car and dont know if it will do it at 72 volts ?? will do more reading.any thoughts ????


If I was building a 7 sec. car I would talk to Rich Rudman at Manzanita Micro about his Zilla controller and would definitely go with 96 volts.


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## major (Apr 4, 2008)

jr dragster said:


> so the more voltage the more rpm i will get?so i need a controller that will do over 72 volts say 96 volts or more .more reading


Yep. If you wanted equal performance, 72V with 740A limit = 600A limit with 89V. Same peak power, but higher voltage gives you higher RPM with lower torque. So if you changed the drive ratio by 23%, the car should behave exactly the same.

With the 72V, 740A controller, you can't go any higher. Get a controller, even if it is a little less current (600A), where you can go higher in voltage (and RPM). 96 Volts sounds good, but you should be able to get a controller which will allow even higher, like up 144V, or beyond.

Don't discount brand Z controllers for 1000A. Get the best of both worlds....more current and higher voltage


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## jr dragster (Oct 11, 2010)

major said:


> Yep. If you wanted equal performance, 72V with 740A limit = 600A limit with 89V. Same peak power, but higher voltage gives you higher RPM with lower torque. So if you changed the drive ratio by 23%, the car should behave exactly the same.
> 
> With the 72V, 740A controller, you can't go any higher. Get a controller, even if it is a little less current (600A), where you can go higher in voltage (and RPM). 96 Volts sounds good, but you should be able to get a controller which will allow even higher, like up 144V, or beyond.
> 
> Don't discount brand Z controllers for 1000A. Get the best of both worlds....more current and higher voltage


thanks major what would you use if you where building,you can pm me if you what dont want to start a war over controllers


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## toysdoneright (Feb 20, 2012)

I was running 72 volt controller @ 90 volt and 400 amp in a half scale car last yr with a total pacage weight of about 400# [car and driver ] we could only go 11.02 et My thought is go too big you can always choke it back to lower volts and amps That way you will have more reserve But I think its going to take 120 volt and 600 amp to do 7.90 with my set up Yours is different than mine Good Luck


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## Yabert (Feb 7, 2010)

Hi JrDragster

Since you have chosen the motor, go for a bit more voltage and less amps.

By experimentation, the four ''little'' brush of the D&D ES-15-6 don't particularly appreciated to pass 700A. They spark a little bit during few hard acceleration at 700A in my motorcycle.
I think that a good 100-120v under load (imply 120-144v battery without load) and 450-600A will be awesome (50-60Kw peak).

Oh!, yes, few problems! An higher voltage battery pack add complexity and it don't exist 144V+ controller at affordable price (forget Kelly). You will need to stick with Zilla, Soliton or Synkromotive (or maybe futur Alltrax model (rumor))!


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## tropes (Jul 24, 2011)

Congratulations Mark on winning Satuday's points race. You and your driver did a great job. Wish we could have been in the finals with you. Two electrics would have been impressive.

Peter


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## jr dragster (Oct 11, 2010)

tropes said:


> Congratulations Mark on winning Satuday's points race. You and your driver did a great job. Wish we could have been in the finals with you. Two electrics would have been impressive.
> 
> Peter


same to you for winning sunday ,would have been good to race you sunday in the final but she was a little slow out of the gate in the semis . thats racing


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## jr dragster (Oct 11, 2010)

Was looking around here what do you guys think of doing an ac drive jr dragster. Was looking at the HPEVS ac 20 ,sure has alot of rpm 7500,less torque but you could probably make it up on gearing,already built a dc car so try something different if it will work to run 7.90 .What do you think good bad ?????


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## jr dragster (Oct 11, 2010)

raced this weekend she won bigbuck shoot out $400.00 CASH she was pumped she also got a minnie wally ,got bullet for new car


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## tropes (Jul 24, 2011)

jr dragster said:


> raced this weekend she won bigbuck shoot out $400.00 CASH she was pumped she also got a minnie wally ,got bullet for new car


Congratulations from the other electric.


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## tropes (Jul 24, 2011)

jr dragster said:


> raced this weekend she won bigbuck shoot out $400.00 CASH she was pumped she also got a minnie wally ,got bullet for new car
> View attachment 14124


What is the motor and what is attached to the end?


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## jr dragster (Oct 11, 2010)

tropes said:


> What is the motor and what is attached to the end?


i got yaberts one from his motorcycle build ,check his build. 
thanks for the mill again yabert


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## tropes (Jul 24, 2011)

jr dragster said:


> i got yaberts one from his motorcycle build ,check his build.
> thanks for the mill again yabert


I see it's a gearbox. Will you then replace the gearbox and replace it with a sprocket?


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## jr dragster (Oct 11, 2010)

tropes said:


> I see it's a gearbox. Will you then replace the gearbox and replace it with a sprocket?


dont know may use it or may use a jackshaft like shawn lawless used with a chain , will see what fits the best


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## tropes (Jul 24, 2011)

jr dragster said:


> dont know may use it or may use a jackshaft like shawn lawless used with a chain , will see what fits the best


The jackshaft seemed like our only option; 1.) to narrow the rear axle, 
2.) to balance the weight of the motor. If you use it with the gearbox you will have some motor torque issues to deal with. I look forward to seeing the progress.


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## jr dragster (Oct 11, 2010)

some pics of the new car now just have to get to work changing to evjr dragster


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## tropes (Jul 24, 2011)

jr dragster said:


> some pics of the new car now just have to get to work changing to evjr dragster
> View attachment 14356


Looks Good. What controller are you planning to use?

Peter


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## jr dragster (Oct 11, 2010)

tropes said:


> Looks Good. What controller are you planning to use?
> 
> Peter


 solution or the zilla are the two im thinking about??


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## tropes (Jul 24, 2011)

jr dragster said:


> solution or the zilla are the two im thinking about??


Soliton1 and the Zilla 1K are both at the top of my wish list of contollers. I wish either would accept an inductive throttle which is much more responsive than the PB6. Maybe the Hall Effect throttles are better.


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## jr dragster (Oct 11, 2010)

Got the D&D set in the car turned the wheels at 12 volts ,was going to put a base plate on the motor.Can it be mounted on the bolts that are there already or do they hold something inside see pics ,or should i drill and tap into the bottom?? I dont think the strap will pass nhra tech .LOL


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## tropes (Jul 24, 2011)

> Can it be mounted on the bolts that are there already or do they hold something inside see pics ,or should i drill and tap into the bottom??


Don't do either. Use the 4 bolts on the face. How was it mounted on the bike?
Peter


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## Yabert (Feb 7, 2010)

Hi Jr

I strongly suggest you to mount the motor vertically instead of horizontally.
I also suggest you to use the six 5/16-18 bolts under and on the side of the gearbox and/or the four 1/4-20 bolts on the motor face (link between motor and gear box) to fix the assembly to the frame.
That will transmit the torque to the frame and you can add a fixation to hold the motor as I done.
Put blue lock-tite on the screw thread to ''seal'' the gear box (I'm not specially proud of this solution...)

By ''transmit torque'', I mean that will fix the assembly to the frame and prevent it to move/turn.


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## jr dragster (Oct 11, 2010)

Hi yabert the motor is sitting at an angle probably up 4inches in the back ( hard to tell in the pics ) I can't set it all the way up just will not work ,I'm going to use the mount on the gear box side to a plate on the bottom,was looking for a mount to hold the rest of the motor and found the mount I wanted at kta will order one , or if Im not to lazy I will build one.


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## Yabert (Feb 7, 2010)

In this case, you can turn the motor and used the existant 5/16-18 hole in the motor cassing to fix all to the frame (pic). Hold on the upper frame tubes or in the bottom frame. Two 5/16 bolt are strong enough to hold the motor.

I just remember than I maybe have dual wafer H49 racing brush for you. They coming from my Warp Impulse 9 and they can increase considerably the capacity of the motor to receive high amps. What was the brush dimension on the D&D?


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## jr dragster (Oct 11, 2010)

[/ATTACH]



Majestics car show in regina on weekend with new driver Ella.


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## jr dragster (Oct 11, 2010)

Got the new car painted (not running yet but sure looks good)
Painted golf cart also


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## major (Apr 4, 2008)

jr dragster said:


> Majestics car show in regina on weekend with new driver Ella.


Where's Megan? She move up to Formula One?


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## jr dragster (Oct 11, 2010)

Finnally got the new car done no rap on yet
View attachment 1
















6311[/ATTACH]


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## casey.mynott (Sep 29, 2011)

Hey jr dragster!

The JR's looking awesome! We have to see if we can get you me and Peter out on the same track. Would be awesome to pit the ev jr's against one another in front of a crowd! 

Casey
http://www.dssev.ca



jr dragster said:


> Finnally got the new car done no rap on yet
> View attachment 1
> 
> 
> ...


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## tropes (Jul 24, 2011)

Sounds like a great idea.
Peter



casey.mynott said:


> Hey jr dragster!
> 
> The JR's looking awesome! We have to see if we can get you me and Peter out on the same track. Would be awesome to pit the ev jr's against one another in front of a crowd!
> 
> ...


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## tropes (Jul 24, 2011)

Hi Mark
are those 19" Hoosiers?
Peter



jr dragster said:


> Finnally got the new car done no rap on yet


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