# Electric Go Kart - Epic FAIL! :-(



## Tesseract (Sep 27, 2008)

That looks like a SepEx or compound wound motor/generator. Totally unsuitable for the application. About the right size, though.


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## Jimdear2 (Oct 12, 2008)

For starters you are *way overgeared* with those 16.5 inch tires.

With your current sprocket gearing and tire size the motor is only turning 1500 to 2000 rpm at 10 to 15 MPH. Way too slow. The motor is overheating because you are pulling a lot of amps to move that much weight at that slow of an rpm. 

You either need to go to the 72 tooth gear with a 10 inch tire, or if you want to keep the 16.5 inch tires you need to go to 12 or 13 to 1 overall ratio. The least expensive way to accomplish this kind of ratio is with a jack shaft set up.

The motor and voltage is probably not the best choice but properly geared it should give you decent performance. 

I don't recognize the motor but it sure looks like an old radial engine starter.

Does it just have only the two large connections that go to the controller. It looks like a series motor with internal field connections. Take some pictures of the drive train and electrical connections so we can look at them and see if there are any other problems.

Hope this helps
Jim


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## major (Apr 4, 2008)

kevinwil said:


> 1. Looking at the link above, it's hard to tell, but there are actually 4 posts on the motor. Although, I'm not sure if this is series-wound or not. Also, the rotation listed on the page above says CCW, but I'm rotating mine clockwise by reversing the poles. I'm guessing it's not series-wound, as it did not go into run-away when I only hook up the two poles, however, does anyone have familiarity with a setup like this? BTW, the two main poles have a 3/8" bolt, but the 2 smaller poles are about 1/4" or smaller. Clearly lower current, but what are they!?


Hey Kevin,

I'd venture to say you have the motor improperly wired  

major


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## Jimdear2 (Oct 12, 2008)

Kevin,

OOPS!! I totally missed your comment about the number and size of of terminals. Sucks to get old. I got fixated on the oversized tires and skimmed over that.

Listen to major he knows motors. 

Major,

Thanks for not calling me the idiot I was being.


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## kevinwil (May 12, 2010)

Hi Everyone, 

I really appreciate your responses, and I feel like I should have done way more research before just assuming too much. I'm still not clear on the torque/hp ratings on electric motors vs gas motors, so I just assumed electric motors would be happy at high-torque/low RPM movement. 

Also, I thought a series motor would have equal-sized poles, so I assumed the smaller terminals were for an ammeter, or maybe accessories, etc. I did hook it up and watched for 'run-away' and it never seemed to go into terminal spin without the field hooked up. It also looks like it might be a perm mag motor, as it seems to have two huge magnets screwed into the side. (I never did pop this motor apart, as I figured I would never the commutator out, or, back in for that matter, put it back, without completely destroying it.) I thought I would do more damage hooking it up wrong, than just using the two poles.

My wife has a photobucket account, so I took some photos last night and posted them. Here are the links:

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6493.jpg

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6492.jpg

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6490.jpg

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6487.jpg

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6486.jpg

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6484.jpg

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6482.jpg

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6481.jpg

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6480.jpg

http://i43.photobucket.com/albums/e385/sarajwil/gokart/DSC_6477.jpg

So it seems I need to do the following at least:

1. Gear it down more. I was heading this way, and that's why I put 16.5 trailer tires on this guy. I'm using 4x4 bolt wheels, so I really can't put anything smaller on it. I need a jackshaft, which is lame, because I have no welding equipment, or experience with welding for that matter.

2. The motor may simply be the wrong choice. I knew better when I bought it, but I think I only paid $75 or so for it. However, I would never just buy a motor again without knowing all of the specs, and having a wiring diagram! 

3. 24volts was a mistake. I found the batteries for $50 each. They're huge, heavy, and probably should have shot for higher voltage and less amp hours. I figured I would get about an hour of runtime out of this guy, but maybe I should have shot for 30 mins @ 48v. I've built custom battery mounts, and my controller maxes @ 32 volts, so I'd pretty much be starting over if I pushed anymore than 24. Speed was never a concern for me, but it seems the torque is still too low on most motors at 24v. I would also just use a 12v system for the relays/contact switches, etc instead of 24v next time as well. Then, if you do change the voltage, you may only be increasing heatsinks on your voltage regulators, and not redesigning all of the circuits!

If anyone know how to wire this motor, I'd be willing to give that a shot. I can't find any info on it, and the link I posted above was the first time I've even seen anything close. The specs on that page are ok, other than it says it's a CCW motor. Odd, if it is series, would that mean it's unidirectional? I probably have it hook up backwards too, which means I would need a jackshaft to make it spin the right way. Of course, this may be a different motor than what I have as well.

I've posted enough, in my long winded fashion, but I, and my kids thank you! I haven't let them drive it yet, because I'm still working out the bugs. They're going to be disappointed when I start taking this thing apart again! 

Take care,
-Kevin


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## DavidDymaxion (Dec 1, 2008)

I liked the pics, that looks clean and fun.

I trust you run with a floorboard? It would be really dangerous to have a foot slip down off the pedals without one.

The solid axle thing has some benefits. It is light and strong. It also makes the kart more stable at higher speeds (tends to straighten it out). My kids' racing kart is designed to lift the inside rear wheel a bit when the steering is turned to help with low speed turns. Short of radical rear axle redesign, you can do a couple of things that will help a bit: Make the rear wheel track narrower (that's an adjustment on my kids' racing kart), or go with harder rubber kart tires (they have traction ratings, so ask for the ones with the lowest traction). Another thing some karts do is to power just one rear wheel.


kevinwil said:


> Hi Everyone,
> I really appreciate your responses, and I feel like I should have done way more research before just assuming too much. I'm still not clear on the torque/hp ratings on electric motors vs gas motors, so I just assumed electric motors would be happy at high-torque/low RPM movement.
> 
> Also, I thought a series motor would have equal-sized poles, so I assumed the smaller terminals were for an ammeter, or maybe accessories, etc. I did hook it up and watched for 'run-away' and it never seemed to go into terminal spin without the field hooked up. It also looks like it might be a perm mag motor, as it seems to have two huge magnets screwed into the side. (I never did pop this motor apart, as I figured I would never the commutator out, or, back in for that matter, put it back, without completely destroying it.) I thought I would do more damage hooking it up wrong, than just using the two poles.
> ...


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## kevinwil (May 12, 2010)

Yes, I just haven't installed the floorboard, or the two bars on the back that protect the rear sprocket. I got it this far along, and started test driving. (Plus, I don't have the right sized rivets to put the floor on yet.) 

It's still in it's prototype phase. 

Interesting note on the solid axle. I'm guessing I have too much weight on the back too. 80% of the weight is over the rear axle. It probably balances out pretty well when I'm on it, but my 8 year old, not so much.

Thanks!
-Kevin


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## major (Apr 4, 2008)

kevinwil said:


> If anyone know how to wire this motor, I'd be willing to give that a shot. I can't find any info on it, and the link I posted above was the first time I've even seen anything close. The specs on that page are ok, other than it says it's a CCW motor. Odd, if it is series, would that mean it's unidirectional? I probably have it hook up backwards too, which means I would need a jackshaft to make it spin the right way. Of course, this may be a different motor than what I have as well.


Hi Kevin,

I am not 100% sure about this particular machine, but I have helped other guys out with these old aircraft generators. IIRC, they are unidirectional compensated shunt generators. They actually can do very well run as motors, but it takes some know-how to get them properly wired and controlled. There is info out there. May be hard to find. I know I posted several times on EVDL. You might try a search there. I am on a road trip and can't get to my files, not that I am sure I can find the stuff in that mess anyway. Maybe search EValbum and contact somebody there for wiring info.

Or just get a series motor and make life simple  BTW, nothing wrong with a 24V system for a little slow cart. Can be a good starter. Better to make cheap safe mistakes 

major


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## Georgia Tech (Dec 5, 2008)

I have ahd several of these motors..They can make REALLY good power if you hook them up right...that motor should be PERFECT for what you are wanting to do.....
Tell me have you tried hooking the field straight to 24 volts and then controlling the Armature with the controller? This might hel ALOT!!


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## Jimdear2 (Oct 12, 2008)

Kevinwil,

It looks like you will be able to get what you already have there up and running right.

If you just give major a bit of time to get his feet back under him after a trip, I'm sure he can point you to the right place to find what you need.

I wouldn't worry about regearing until you get the motor wired correctly. 

Or maybe Georgia Tech can get you going. 

I guess that the only problem you may have is finding out how the field was wired by the original manufacturer. I gues some were grounded internally on other were grounded externally. The web research I saw shows after that it's just experimenting to find the best field current.

Keep on, don't get discouraged.

Jim


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## kevinwil (May 12, 2010)

Hi Jim,

Thanks for your words of encouragement, and I haven't given up yet. I fully intended this to be my "training model" for a real electric car someday.  

Just for an update, I did look through the forum as Major suggested, and was unable to find one like my motor. I may need to dig more, but I'm actually out of the country myself at the time. (And it seems Swiss internet access is WAY too slow on some sites to be worth digging through right now.)

My wife however, may have changed my plans. She hates that the go kart won't go in reverse, and now I'm pretty sure the motor I have it unidirectional. That being the case, I would need a transaxle, which I'm not really interested in. So, I need a reversible motor either way.

i don't have welding equipment, but a guy I work with does, and I might be able to get him to build something for me.

So, I've been thinking about using this motor:

http://cgi.ebay.com/4-HP-24V-DC-VEH...tem&pt=LH_DefaultDomain_0&hash=item35a8e1d92b

It's 8000 RPM @ 24v, but it seems torquey. It's listed @ 32 in lb, which seems pretty good. With that much RPM, I would definately need the jackshaft to slow it down enough. So I figure I could do a 12:1 reduction with two 10 teeth and two 60 teeth gears. From the go kart calculator, that would give the cart a top speed of 36mph, and keep the RPM's higher on the engine. I have an idea for building a mount for this motor with the jackshaft, and then put a reversible contact switch in to placate my wife. 

So the motor in question is series, and should work fine with my controller. I still don't know if 32lbs of torque (this is what I should get with a 12:1 reduction) will be enough to move the 600lb cart. I'm not looking for earth-shaking acceleration, only a setup which won't damage the motor.

It seems like this is a wench controller motor, and even though it's smaller in HP than my current motor, I think it's going to work.

I appreacite any input, or formula's I could use to help make this calculations. I'm a computer nerd, but not too good at physics. 

I'll still try and wire the motor up properly and see what happens before I order anything, but the wife wants reverse, so either way, this setup would likely only be temporary.

Thanks!
-Kevin


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## major (Apr 4, 2008)

kevinwil said:


> So, I've been thinking about using this motor:
> 
> http://cgi.ebay.com/4-HP-24V-DC-VEH...tem&pt=LH_DefaultDomain_0&hash=item35a8e1d92b


Forgetaboutit!!!!!! 

See post #44 http://www.diyelectriccar.com/forums/showthread.php/finding-motor-my-ev-lawn-tractor-44087p5.html 

major


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## TX_Dj (Jul 25, 2008)

Kev,

Keep in mind- gas powered go-karts don't have a reverse either... but that's no reason not to put one in your electric cart.

Also, welding shouldn't be necessary for a jackshaft installation.

Move your motor forward, drill new holes for your mounts if necessary. Then using two bolt-on bearing/housings and an appropriately sized shaft to fit those bearings and two new sprockets, and possibly some spacers to stand the bearings off the frame enough to keep the sprocket clearances in check for the axle sprocket, just slap it together and be done with it. More noise, more friction losses, but easier to dial in an acceptable ratio that way.

Best of luck!


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## kevinwil (May 12, 2010)

Hey Everyone, 

Update, good and bad news. Well, I decided to give up on my old motor, and after much deliberation, I bought a Manta motor. This is just a brushed briggs rebuilt with higher temp epoxy? I've read these motors may not be too well balanced, but I'm probably never going to exceed 1800 RPM with one, so I suspect this should be fine. I also expected this would work with my 400amp 24v PWM based controller. I built a custom mount out of angle-iron, and got the motor to mount very well. Probably too weak for some's tastes, but the best I can do without welding! I got everything wired up, and took it to the end of the street and back. WOW! That's what I was looking for! Very nice pickup, and pretty good speed. I drove it to the end of my cul-de-sac, and back in my drive way, when suddenly, DEAD! No movement whatsoever. This was tops, a 4-min drive.

I started checking things out with my volt meter, and my worst fears confirmed, the controller was not putting off any voltage. The throttle/enable lines are great, but the motor was not getting any power. :-(

I waited for about 4 hours(praying for an internal-overload to reset), but the controller just won't put anything out now. ARGH!!! I was so close!

My controller is actually a kinetek pump motor controller, and the only thing I can think is that the blocking diodes were not sufficient for the reverse voltage being put off while coasting. Or, I'm not using a pre-charge resistor, so maybe I should? (Can I use one on the neg terminal without issue? I'm actually breaking the neg line with my contactor, not the pos.)

I have already ordered an AXE4834, as I see a lot of folks using this controller on the brushed etek's out there. It seems like it might be fine for my application, but I can't figure out why my 400amp controller died in this setup. 

Well, hopefully my AXE shows up by this weekend, and I'll actually be ready to drive this thing for awhile. This EV stuff is an expensive hobby. 

BTW, anyone interested in buying my old motor? I'm probably going to put it on ebay to help recup some of the extra cost here. I don't think I'll be able to use it for anything else anytime soon.

Thanks!
-Kevin


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