Chris Tromley wrote: Damon Henry wrote:
My Datsun truck weighs in at around 2600 pounds and includes the original transmission. I am using an ADC 6.7 inch motor... it is possible for a smaller motor to get the job done on a smaller car. You do need to be concerned about cooling and you also need the proper gearing to help the little guy out.
I agree. I have a Renault LeCar conversion, and am using the ADC L91 long 6.7" motor with the stock transmission. It has worked fine, and easily does 70+ mph. The key is a) adequate cooling, b) a transmission, or gearing so the motor doesn't "lug" at low RPM, c) proper driving habits (keep motor RPM high; not low as you would for an ICE).
Chris Tromley wrote:
Will a transmission be used? Depending on the battery pack and controller used, you could easily triple or quadruple the torque. BANG goes your transmission...
Good point. Regardless of motor size, the batteries and controller will set the max current, and thus max torque that the motor produces. It can easily be many times more than the Berkeley drive train was built for.
The Corbin Sparrow was around 1500(?) lbs, was direct drive and used an 8" ADC motor, and didn't seem to have any cooling issues.
No, but they had other motor issues due to not setting the brush advance correctly.
The usual problem with direct drive is that folks simply remove the transmission. The stock differential ratio is such that you are now forcing the motor to operate as if you're in 3rd gear all the time. That forces low motor RPM, causing overheating and failures.
To make direct drive work, you need a *bigger* motor and controller to compensate. They have to be happy at high enough currents to get the kind of torque you were getting in 1st gear but *without* the transmission.
Conclusion: If you want to use a small motor and controller, use a transmission. If you have a big motor and controller, you can leave out the transmission; but be sure to include extra cooling.
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