# Can two motors be better than one?



## pengyou (Nov 21, 2012)

Thanks for the answers to my last post. In addition to being very informative in and of themselves, I use the new words in your responses to search and learn even more.

I have seen conversion plans that use two motors but they are usually attached at the same point, or attached one in front of the other - is that serial?

Has anyone tried attaching one motor to each differential in a 4wd or awd vehicle? I was wondering, if this were done, and the gearing was changed so that the front wheels had 2.x gears and the rear had 4.x gears...would it help give the vehicle better performance at low speeds and at high speeds?
While still allowing it to be a 4x4, still allowing it to tow, etc.


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## RIPPERTON (Jan 26, 2010)

We did 2 motors on a quad bike.
Not a good idea, the front wheels can get out of control wheelspin.
off road you need to link the front and rear mechanically with a slightly shorter ratio in the front diff so it never gets away from the rear so basically you only need 1 motor. You want the rear to break traction before the front comes in to help.
A road car might be different, assuming the tires are the same diameter you could get away with identical ratios in front and rear diffs but would need sprags or 1 way clutches in the front half shafts. Still only one motor needed here.


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## rantes87 (Dec 27, 2013)

I'm also very interested in using two motors. Can anyone give anymore insight on why this would or wouldn't work? I'm considering having one motor hooked to a fwd trans while another motor is hooked directly to the rear diff. The speed would be limited to the rear motor rpm and reverse might be a bit of a project. Overall I think this would be a great idea.


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## Duncan (Dec 8, 2008)

Look up the old Twini Minis or Mokes,

Two motors would work quite well for AWD - no fancy control strategies needed


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## DavidDymaxion (Dec 1, 2008)

These guys did twin motors, one to the front diff and one to the rear:

http://www.proev.com


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## pengyou (Nov 21, 2012)

Thanks! I am not looking to race but it is nice to know that ev's have come thus far. 2 motors will work...I am assuming that they must be identical and have identical controllers and identical gearing in the diffy? Are there controllers that can control 2 electric motors?


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## Duncan (Dec 8, 2008)

pengyou said:


> Thanks! I am not looking to race but it is nice to know that ev's have come thus far. 2 motors will work...I am assuming that they must be identical and have identical controllers?


No - 
no good reason, there used to be a mini with different sized engines front and rear

If you think about it if you only have one motor/engine driving one end that is equivalent to having a big engine at one end and a tiny one at the other

If you think about how a diff works - essentially it is uncontrolled right to left (or front to back in AWD) 
The road surface effectively makes the two wheels work together, two motors - or four motors 
would work the same way


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## YeahPete (Feb 23, 2012)

Why stop at 2 motors when you can direct drive 4 motors?

http://www.draysonracingtechnologies.com/home.html


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## Duncan (Dec 8, 2008)

YeahPete said:


> Why stop at 2 motors when you can direct drive 4 motors?
> 
> http://www.draysonracingtechnologies.com/home.html



True direct drive is a pain - 
motor torque is roughly related to motor weight,
so enough torque to directly drive the wheel means either a very heavy motor or a reduction gearbox

so you can have

2WD - two motors, two gearboxes - or one motor one diff

4WD - four motors, four gearboxes - or two motors two diffs - or one motor three diffs

for 2WD two motors is definitely NOT the best way

for 4WD four motors is definitely NOT the best way 

To make matters worse - the diffs and gearboxes are cheap and readily available


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## pengyou (Nov 21, 2012)

I like this discussion 

If torque is related to motor weight... torque of (4 x50 pound motors) = torque of (1 x 200 pound motor) ...give or take???

I thought that torque was additive...meaning that if the rear differential of a car gets 80 ft lbs, then each wheel gets 40 ft. lbs.

So what is the difference - whether you have 4 x 10kw motors or 1 x 40 kw motor?


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## samwichse (Jan 28, 2012)

pengyou said:


> I thought that torque was additive...meaning that if the rear differential of a car gets 80 ft lbs, then each wheel gets 40 ft. lbs.
> 
> So what is the difference - whether you have 4 x 10kw motors or 1 x 40 kw motor?


I think you missed the part where he said reduction gearboxes.

Coming from a diff, there's already a 4x (depending on your diff  ) gear ratio. Direct drive, you've got 1:1.

For going direct drive, you would need 4x the motor for the same torque, or individual gearboxes for each wheel... and how is two motors and two gearboxes that better than one motor and a differential?


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