[ausev] Dual electric motor questions

[tomsmail at wtez.net]

Transmissionless DIY EV?  Just don't do it!  (there, how's that for
getting a clear answer).

If you were going transmissionless, then the dual motor idea is very
clever and elegant way to make up for lack of torque, but you'll pay in
efficiency (range).  Best left up to the 'motor-heads' who want to race.

Take it from someone who has (tragically) learned this emperically.

Tom

p.s.
Weight of 5-speed tranny from 1987 Fiero=93 lbs.
Weight of 5-speed tranny from 1996 Geo=75 lbs.


> Hi,
>
> I am a new member of EVA - DC and I am preparing for a conversion using
> a donor car (to be found..).
>
> I am looking for improving weight, reliability, and efficiency by
> getting rid of the gearbox and differential: I would install two
> electric motors (one on each front wheel). I would drive both motors in
> parallel from the same DC-DC converter output. I am also looking for
> using cogged belts to connect the motors to the wheels shafts.
>
> However, the following question came up:
>
> 1. How will the motors torque behave in a tight turn? Since the wheel
> which is inside the turn will rotate slower than the outside wheel, the
> inside motor will deliver a higher torque to this wheel while the outer
> wheel will be driven with a lower torque..  I hope that his torque
> difference will not be an issue in normal driving conditions. Is there
> any member of this bulletin board with this type of experience who could
> advise me before I commit to this configuration? I am pretty confident
> that high speed turns will not be a problem (very low relative speed
> difference between the wheels) but I have not been able to confirm this
> SWAG.. Any recommendation would be VERY appreciated.
>
> 2. How will the DC to DC converter react to a dual motor load? Hopefully
> it should not mind if I am not exceeding its rated amperes, but again I
> do not have any confirmation.
>
> 3. Is there any member who could advise me on the cogged belt idea? I
> think that it is lightweight, relatively inexpensive, very simple,
> reliable, and allows a 3:1 or more "gear" ratio. I did some research and
> found that today we have motorcycles and ultra light aircraft using
> cogged belts passing 100 HP at 3000 rpm. This could be very promising..
>
> 4. What is the best "method" to find a donor vehicle with a dead engine?
> I tried E-bay (not interesting, no dead engine to be seen) - and
> CraigsList - a few hits only. The local wreckers claim they "never" see
> a car with a dead engine (Hard to believe!). Any suggestion?
>
>
> Thanks for looking at these questions!
>
> Michael
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