# Leaf motor - no gearbox?



## Emyr (Oct 27, 2016)

You might not be able to get a high enough final drive ratio, so you'll end up with poor torque at the wheel, geared for 200mph but without the power to get there.


----------



## doobedoobedo (May 28, 2017)

Yes that kind of confirms what I was afraid of.

The highest ratio diff is 3.91 (slk200) which is about 1/2 the geardown on the leaf if what I've read is correct. So I'd get poor acceleration with a ridiculous theoretical top speed .

I which case if I want a rear drive two seater with no gearbox an MR2 might be better suited then.


----------



## brian_ (Feb 7, 2017)

doobedoobedo said:


> Yes that kind of confirms what I was afraid of.
> 
> The highest ratio diff is 3.91 (slk200) which is about 1/2 the geardown on the leaf if what I've read is correct. So I'd get poor acceleration with a ridiculous theoretical top speed


Right... half the Leaf's torque to the wheels, so half the acceleration with the same mass of vehicle.

Another way to think of this is that the Leaf motor needs to turn about 2800 rpm or higher to produce its maximum power; while that corresponds to a reasonable speed with the correct gearing, with this gearing it would mean that you would have less than 80 kW at anything short of highway speed.



doobedoobedo said:


> I which case if I want a rear drive two seater with no gearbox an MR2 might be better suited then.


Are you thinking of an MR2 with a complete Leaf drive unit (motor plus transaxle, so it has the stock Leaf gearing) replacing the Toyota engine and transaxle? Yes, that would make sense. 

Another alternative would be to put the motor in the SLK's transmission tunnel, but put a compact single-speed reduction box on the output of the motor. The ev-Torquebox is an example (although it is relatively expensive and larger than necessary).


----------



## doobedoobedo (May 28, 2017)

First yes for the MR2 I'd put in the whole transaxle as that would seem to make the most sense.

Nice idea about a single speed reduction box, I hadn't though of that. That EV torquebox is insanely expensive, maybe something like this https://www.ebay.co.uk/itm/Motovari...990372&hash=item260785f31a:g:P~oAAOSwKEFb0dAp would work?


----------



## brian_ (Feb 7, 2017)

doobedoobedo said:


> Nice idea about a single speed reduction box, I hadn't though of that. That EV torquebox is insanely expensive, maybe something like this https://www.ebay.co.uk/itm/Motovari...990372&hash=item260785f31a:g:P~oAAOSwKEFb0dAp would work?


Yes... although I don't know about the torque and speed ratings of that one, or how well the offset would package in the car. Someone else was planning to use a very similar unit (sorry, I can't remember who, so no link to their thread).


----------



## Duncan (Dec 8, 2008)

doobedoobedo said:


> Is this feasible?
> 
> I'm looking to convert a 2 seater (probably an SLK so about 1300Kg) the only gear reduction would be the diff.
> 
> ...


Why a Leaf motor?
That would be an ideal application for a DC series motor


----------



## doobedoobedo (May 28, 2017)

brian_ said:


> Yes... although I don't know about the torque and speed ratings of that one, or how well the offset would package in the car. Someone else was planning to use a very similar unit (sorry, I can't remember who, so no link to their thread).


That was just the first thing I found. I need to do more research.


----------



## doobedoobedo (May 28, 2017)

Duncan said:


> Why a Leaf motor?
> That would be an ideal application for a DC series motor


A DC motor is an alternative, and probably would be cheaper overall. I'd need to find a manual and keep the gearbox, manual SLKs are fairly thin on the ground and it cuts down choice considerably.

Leafs are readily available as scrap now, so for an AC motor it seems the obvious choice.


----------



## Duncan (Dec 8, 2008)

Hi

I didn't bother with a gearbox for my "Device" - just direct drive and an 11 inch Forklift motor

An SLK is a bit heavier so you would not get the performance

https://www.youtube.com/watch?v=LUpyAY2sFWw

https://www.youtube.com/watch?v=c3vOUHN3FeU

the second one starts about 40 seconds in


----------



## doobedoobedo (May 28, 2017)

Haha you win for fun factor . I think I saw your build thread a while ago. Do you have reverse?


----------



## Duncan (Dec 8, 2008)

Reverse is obtained by running the motor backwards - I'm using the reversing contactor out of an old forklift


----------



## doobedoobedo (May 28, 2017)

Thanks Duncan. I'd read elsewhere that reversing contactors weren't great, but I've re-read your device thread and it seems that it's certainly not the weak link. I may have to re-consider my options (in a good way ).


----------

