# yet another direct drive thread!



## evmetro (Apr 9, 2012)

I have read a bunch of direct drive threads here and have a general idea of the challenges of building a direct drive EV. I am guilty of plotting and dreaming of a direct drive EV, and wonder what it would take to build a 3800 lb ev with direct drive with a differential only. Been surfing the kostov site, looking at dual 11's and the 13, and also at the zilla 2k... I know this is pretty far out, and there are many good reasons to not do this, but what would it take to actually do this with 45-55kwh of lithium? I am aware that there will be a challenge getting moving, and getting top speed. 80 mph tops would be nice to see with a big pack, motor, and controller. I don't see much about the series/parallel shifting thing on the zilla, but maybe this could be a help getting this heavy thing moving. You can't offend me if you tell me it can't be done, or if you tell me I have been around here long enough to know better...


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## Matter45 (Jan 2, 2013)

45 - 55kwh of lithium? are you rich?

I am doing a direct drive ute. Ill be taking out the engine and transmission box, and putting a transwarp11 where the transmission was. My biggest fears are, can i fit the transwarp11 and connect it to the driveshaft where the transmission was without major modifications? will the donor car have the correct shaft to wheel turn ratio?

Here is my math. measure the diameter of the wheel. say 60cm as an example.

calculate circumference of wheel

pi * 60cm = 188.5cm

calculate 100kmh (60mph) into cm per minute (because motors are measured in RPM)

100km = 10000000cm

10000000cm / 60 minutes = 166 666cm per minute

Calculate wheel RPM for 100kmh

166 666cm / 188.5cm = 884.17RPM

Optimal efficency for transwarp11 is between 2000RPM - 4000RPM(please correct me if im wrong)

3000rpm / 884.17rpm = 3.39:1 driveshaft to wheel ratio

Basically, direct drive is like permanently sticking a car in 4 gear.

work out the donor cars driveshaft to wheel ratio, then you can work out your top speed. Personally i wouldnt recommend the motor going past 4000rpm. you can go heaps faster then this, but if your after a long term investment then i suggest to keep to this limit. 5000rpm absolute max.

If you are going to use it for street driving, i recommend using this when the motor starts heating up:
http://blog.evtv.me/store/proddetail.php?prod=blowme

EDIT:
if you sacrifice top speed, you gain acceleration + easier management of heat in slow speeds. If direct drive suits your needs over a gear box, then go right ahead. I am doing direct drive because of the limited torque of the clutch/transmission, and if possible after the build, I am going to try and put a small 18hp ICE engine to the other end of the transwarp11 for highway extended range.

As for fitting the motor to the driveshaft, Im a bit iffy there. Not sure if anyone out there can provide info on how hard it is to connect the motor directly to the drive shaft?


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## piotrsko (Dec 9, 2007)

been my experience with my Kostov 11 that it is way happiest with as much voltage as you can give it. a paltry 160 vdc gives you mediocre performance, 120 vdc and it wouldn't get out of its own way. So a 50 KWH pack @ 250 vdc and a Kostov is going to be pricey.


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## mizlplix (May 1, 2011)

Matter's example figures turn out to be 82.8 MPH

I use this gear converter to "play" with my idea cars...

http://www.rocky-road.com/calculator.html

P: Yes, you can do a direct drive heavier car. It just takes a motor(s) and controller(s) suited to the overall mass and a pack(s) to support them, as well as carefully gearing the car to suit the terrain, traffic, weight and motor torque curve.

A hell of a nice set up it would be! 

Miz


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## evmetro (Apr 9, 2012)

Matter45, it should not be a big deal to get a coupler made at a machine shop. Most of the ones I talk to around here are not into limited production runs, and so the prices are higher for a prototype.

Miz, that calculater is pretty cool, and it is bookmarked now. Thanks.

It looks like the dual kostav 11's can can take 348 volts, so about 108 cells. 34 kwh with 100ah cells, 55 kwh with 160ah cells. It would be nice to find some 130 to 140ah cells... 

Does anybody have any good ideas about an independent dif that can take LOTS of torque? I think that taking off would be pretty hard on the dif taking off if the lack of gears is compensated with a lot more torque. The independent dif could be mounted up front on my fwd caddy donor, and the motors in the tunnel. Lotsa fab work, but also my trade...


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## DanGT86 (Jan 1, 2011)

Some of the strongest independent diffs I can think of are the ford 8.8 from the cobra mustangs and the lincoln mark 8. John metric runs high 9 sec quarter miles on a mark 8 diff in dc plasma. I think the chevy trailblazer also uses a decent irs diff but I trust the ford more. There are 1000hp mustangs using it with slicks.


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## dougingraham (Jul 26, 2011)

evmetro said:


> Does anybody have any good ideas about an independent dif that can take LOTS of torque?


Stock differentials can take a lot of torque. Remember the transmission is a torque amplifier. Your electric motor will put out maybe 400 ft-lbs if you feed it enough current but the original ICE even a small one would have been able to do maybe 100 to 150 ft-lbs into the transmission and in first gear it might be a 3.5 amplification of torque so 350 to 525 ft-lbs into the differential. Unless you are racing this is probably not something you need to worry too much about. If you find out the torque peak of the ICE and the first gear reduction of the transmission that will tell you what the differential could have seen. Find out what current the motor needs to produce that torque and set the motor controller to limit at that current.


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## piotrsko (Dec 9, 2007)

Could be wrong but I think landrovers have a floating axle diff like you want.

A junker vette also might work if they are tough enough.


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## palmer_md (Jul 22, 2011)

the problem will be finding the gear ratio and at what cost. For example the Ford 8.8 comes in 5.14:1 and that is the highest I've found, and an EV will likely need 8:1 I've heard numbers from 7:1 to 9:1 with most around 8:1

http://www.moserengineering.com/gea...gears/8-8-ford-5-14-p-s-gear-motive-gear.html


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## Siwastaja (Aug 1, 2012)

palmer_md said:


> t For example the Ford 8.8 comes in 5.14:1 and that is the highest I've found, and an EV will likely need 8:1 I've heard numbers from 7:1 to 9:1 with most around 8:1


I'd say 5.14:1 is near optimal for a DIYer; I'd definitely go for it. Around 8:1 is optimal for a manufacturer who will use a modern high-rpm high-frequency AC motor that can go up to 10 000 RPM, to save weight and space. 

5:1 reduction might be optimal for a brushed DC or standard industrial AC motor, as you have the limit somewhere around 5000 rpm.

OTOH, some rear differentials are below 3:1, and that is clearly too low. It may be usable, but requires a large and heavy motor, and some common motors used by diyers have poor efficiency at low rpms. Cooling may also be a problem.


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## evmetro (Apr 9, 2012)

I will check out the mustang dif. It would not be too big a problem to experiment with a few ratios. I have a press and shop set up for this kind of stuff. The math can be a pretty nice guide, but experimenting can fine tune things even more.


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## mizlplix (May 1, 2011)

My Ford 8.8 has a 6.14 ratio. I am running 32" tires also. It gives me 80MPH at 5200RPM. In the future I can go shorter on tires to reduce my top speed and pick up on some bottom end torque, but not if I had not planned before hand.
I am running an AC system. This works out perfect.


Know what tires you intend to run before hand. The good low rolling resistance tires are not made in just every size.....If you want to run them, pick them out to fit your wheels, then use their Diameter to calc. your necessary rear gear ratio.

This helps: http://www.rocky-road.com/calculator.html

Miz


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## palmer_md (Jul 22, 2011)

well if 5:1 is good for a DC motor, that solves one problem, but then you still have the problem of no reverse gear. Reversing contactors are real messy. I'd stick with AC for a direct drive system so you can electrically reverse the car.


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## DanGT86 (Jan 1, 2011)

I may be getting my direct drive threads mixed up but is this a fwd or rwd application that evmetro is planning? Depending on budget, the new corvettes run a rear transaxle and may offer some parts that could help. The corvette diff is bassically the tailshaft of the transmission. This could make bolting a motor straight to the diff easier because of the big mounting flange at the input of the diff. 

Also if you are talking dual 11" and a zilla 2k then you would probably have enough torque to overdrive the output of the motor before the diff. This would get your top speed up and take advantage of the big dc motors powerband but keeping them cool at low speed would be an issue. 

I have seen some rear/mid engine vehicles where the diff has been flipped upside down to change the direction the wheels rotate with respect to the chassis. This allows the motor to be placed in front of the transmission rather than behind it. You could look around at sandrail buggies with porsche or vw style transaxles to maybe get some ideas of what is out there for less common diff options. I bring that up because i cant remember if it was fwd or rwd that is in question here.


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## Rob A (Feb 7, 2010)

I went direct drive on my 64 ranchero. I changed the gear ratio to 4.62:1 the tires are 24"
I have test driven it with 24V and it seems to run good, it only does about 12MPH with 24V. I had a driveline shop make a carbon fiber driveline, they gave me a shrink disk to mount the flange to the motor shaft. Then the driveline mounts to the flange. Here is a pic


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## evmetro (Apr 9, 2012)

The setup that I am considering is a front wheel drive caddy, and I am contemplating the upside down dif up front, and the dual kostav 11's in the tunnel. The tunnel does not have room for this, but I can make room. I fabricate anything as my trade. I have considered the "evglide" powerglide transmission setup, but I stay awake at night thinking about how slick an EV would be without a tranny, and a Cadillac just seems wrong with a manual tranny. I am also found of Hpevs products, and have been waiting for the siamese ac35s to come out with the 144v controllers, but it seems like in a direct drive environment, the dual kostov 11"s would be more to the point than the siamese ac35's. The ac35/7601 combo is rated at 110 lbs of torque, so two of these would only be up to 220 lbs of torque. The kostovs look like they can give over 500 lbs at 348 volts... If there is something that I am missing, I would love to know. This build would see a mile+ of 8% grade on a regular basis, and alot of northern CA foothills, so a Hpevs setup with regen would be more desirable. If it comes to which one provides the nicest performance, I can live without the regen. I would prefer to beat an ICE caddy performance all around.


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## DanGT86 (Jan 1, 2011)

I see. Keep in mind that a high torque setup like that with a clutch less manual wouldn't require constant shifting like an ice. It would be like direct drive but with an in town gear and a freeway gear. Many of the things you dont like about a manual caddy may be gone simply because its electric and requires less/no shifting. And you get a free reverse without contactor mess.


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## evmetro (Apr 9, 2012)

I am about ready to order parts for this caddy, but am now eyeing the powerglide and soliton. I am ready to order the calb 180's for a 60 kwh pack. Is anybody familiar with the soliton idle function? I like the idea of using all the oem pulley drive accessories, but not sure if idling the 11s to run all this stuff will be too big of a drain vs converting the powerglide to an ev glide and converting the pulley accessories to electric.


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## evmetro (Apr 9, 2012)

I will probably sit down in the next day or two and start a build thread since this ev is going to happen. When I started this thread it was more of a hypothetical build so I posted in this section to get educated. Any input ideas in the meantime would be welcome. I am after an ev caddy where I don't need to shift, have tons of power, have "lotsa" range, and all the original bells and whistles work like they should; ac, power brakes and steering, etc. I am fully prepared to heavily modify the chassis and suspension as needed. The one thing I want to avoid is a manual transmission or manual shifting.


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## evmetro (Apr 9, 2012)

I transitioned this topic into the build thread for this cadillac eldorado. Please feel free to pick my proposed build apart! The new build thread is titled "Cadillac Eldorado".


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## piotrsko (Dec 9, 2007)

evmetro said:


> I am about ready to order parts for this caddy, but am now eyeing the powerglide and soliton. I am ready to order the calb 180's for a 60 kwh pack. Is anybody familiar with the soliton idle function? I like the idea of using all the oem pulley drive accessories, but not sure if idling the 11s to run all this stuff will be too big of a drain vs converting the powerglide to an ev glide and converting the pulley accessories to electric.


I'm running about 3-6 battery amps at 192v idling my ranger with a sol 1 and KOSTOV 11" 192 (alternator, gearbox and ps pump) I keep turning idle on and off trying to decide which I like better. YMMV


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## Bowser330 (Jun 15, 2008)

piotrsko said:


> I'm running about 3-6 battery amps at 192v idling my ranger with a sol 1 and KOSTOV 11" 192 (alternator, gearbox and ps pump) I keep turning idle on and off trying to decide which I like better. YMMV


So 6A x 192V = 1,152watts to idle your Ranger....So if you idle for 5 minutes at a stop light, 5 min is 1/12 of an hour, so 1,152/12 = 96 watt hours used for every 5 min of idling. 

Am I understanding that correctly?


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