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Old 03-21-2011, 11:41 PM   #1 (permalink)
harlequin2
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Join Date: Mar 2010
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Two Motors - are better than one!

I did mention that I used two motors in my car because I couldn't fit one big one in and someone suggested I start a new thread and put the details in, so I'll give it a go.
My original plan was to use a single, big motor such as a Warp9 or the equivalent from Advanced, but when I stripped the car down, I found I would have to mount it right up where the ic engine was and extend the drive shaft to reach, leaving a whole lot of waste space (where the transmission was) and putting the weight quite a long way forward. I had planned to put most of the batteries up where the radiator used to be and I thought the weight distribution would be front heavy that way.
I looked at the motor specs and decided that two Advanced L91s would give me more power and torque than an FB1 (9") and right up there with a Warp11. And for somewhat less money too. I thought also that perhaps one could have an "economy" mode with one motor and a "power" mode with two!
So I sat down and designed a frame to hold the two motors, longitudinally ie one behind the other, with suitable couplings.
That was the first problem, as a coupling that could connect the two motors together was difficult to find, very expensive and extremely bulky.
The BMW E30 uses a rubber "doughnut" to couple the gearbox output shaft to the first, short, drive shaft section and this can obviously handle the ic engine's power and torque, so I thought to adapt this to make a coupler for my two motors. A trip to the local wrecker provided two couplers from which I could modify the 3-legged "spiders" that hold it all together. A bit of lathe work and some welding produced the first picture, shown loosely assembled on a motor shaft mounted in my customwood frame. The next shot shows the thing mounted in the real Al frame and connecting the two motors together. Number 3 is the actual Al frame made out of 10mm Al plate bent, curved, cut and welded, then a couple of shots of the drive shaft coupling off the rear motor.
The frame is designed to mount on the original rubber engine and gearbox mounts in the BMW, so the whole thing is free of any vibration or harshness.
Anyway, that's the mechanics of it.

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