# Dual rear motor gear reducer?



## joetemus (Jun 29, 2016)

I am starting to design an all electric "exo-car" for autocross and messing around in town. I am wanting to put two warp 9 motors in the rear of the car and use some sort of reducer to get a 4:1 or 6:1 ratio from the motor to a half-shaft then to the wheels. Besides using a chain/belt drive system would anyone know of a way to do this? Is there a powerful enough motorcycle final drive? Planetary gear system? I want to be able to put all the power down straight off the line.

Attached is a picture of the very early stages of the design. Just trying to get an idea as to how wide the rear of the car is going to need to be.


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## samwichse (Jan 28, 2012)

Easier solution:

Turn them 90 degrees so the shafts are facing rear and chain drive them to a beefed-up VW tranny.


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## joetemus (Jun 29, 2016)

I was planning on making them independent. Someday i would like to add two motors to the front and make all 4 independent so I can power one side or the other when autocrossing to help push the car around the track!


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## dcb (Dec 5, 2009)

yah, chain drive, like a motorcycle, kind of like dual swingarms, where the pivot is basically at the motor output shaft.

the front will be a bit trickier, i.e. inboard sprockets or something on halfshafts.

you will need a hell of a lot of battery to do 4 9" motors justice...


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## joetemus (Jun 29, 2016)

dcb said:


> yah, chain drive, like a motorcycle, kind of like dual swingarms, where the pivot is basically at the motor output shaft.
> 
> the front will be a bit trickier, i.e. inboard sprockets or something on halfshafts.
> 
> you will need a hell of a lot of battery to do 4 9" motors justice...


I was thinking something along the lines of this
https://www.youtube.com/watch?v=Yd4YxLunazU
with two motors facing each other and 2 or 3 separate heavy duty chains going down to half shafts. This way I Can have the motors up higher and out of the way of the suspension!


I only need enough battery for a few 1-2 minute autocross runs. That's the only time I plan on running all 4 motors. Basically I need to find the highest C rating pack I can possibly find. 

Right now I am starting with two motors and someday I might bump it up to 4, but if two is fast enough then I will leave it at that!


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## dcb (Dec 5, 2009)

yah just like that, only in my mind the outboard chain would be easier to maintain, but inboard looks easier to make some shielding for to reduce maintenance.


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## joetemus (Jun 29, 2016)

dcb said:


> yah just like that, only in my mind the outboard chain would be easier to maintain, but inboard looks easier to make some shielding for to reduce maintenance.


Thats what I was thinking too. I have been looking around and it looks like a belt drive might be more efficient and quieter than chain. Since I'd have to use probably 3 beefy chains would it be better to use one beefy belt?


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## dcb (Dec 5, 2009)

I've had a challenging time sourcing cogged belts and pulleys, but there are places that can do custom pulleys with cad/cam. A big benefit is they can handle high rpm better than a chain, but that would lend itself to 10k rpm induction/impmac motors and controllers and all that, the brushed motors don't do high rpm so well.


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## joetemus (Jun 29, 2016)

dcb said:


> I've had a challenging time sourcing cogged belts and pulleys, but there are places that can do custom pulleys with cad/cam. A big benefit is they can handle high rpm better than a chain, but that would lend itself to 10k rpm induction/impmac motors and controllers and all that, the brushed motors don't do high rpm so well.


I guess for now I will probably do a design for both and start pricing out different systems. If one is significantly cheaper than the other I will probably go with that. Either way it looks like the simplest solution.


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## itchyback (May 28, 2014)

what about overdrive?
I saw this on a hot rod car show and wondered if it could even be used as a semi-direct drive setup. 
http://www.gearvendors.com
advertise themself as "the strongest" available. not sure if 4:1 or 6:1 is possible but may be more reliable than a belt/ chain. 
also more expensive.


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## dcb (Dec 5, 2009)

sorry, I don't know squat about serious parts like that. Maybe someone else has used it and can weigh in or done their homework on it.


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