I am working on a project that will use electric motors for vehicle propulsion and energy regeneration. I had hoped to use a direct drive motor, but it would need to be quite large to provide adequate starting and low speed torque. It looks like a two speed transmission with ratios of 4:1 and 1:1 would be a good solution.
I will probably be using a roller chain and sprocket set so I can mount the motor(s) on the frame. One possibility would be two sets of sprockets and two chains, with some way to couple only one at a time to the drive wheel. I'm thinking about magnetic clutches or a mechanically positioned sliding disk on a splined axle with pins to engage holes in either sprocket.
Another idea would be a planetary gear system that would have a 4:1 ratio from the outer ring gear to the sun gear, with the planetary gears held stationary, and then free the planetary gears but lock up the entire assembly together to get a 1:1 ratio.
I would be grateful for any insight any of you may have for a good way to accomplish this. I am an electronics engineer with some mechanical experience, but not enough to make a good choice for this design. The assembly would need to handle about 20 HP at up to 3600 RPM.
There has been some discussion in a hybrid/EV group about efficiency of mechanical speed reducers and transmissions. One member claimed it would have only about 70% efficiency. My initial research and common sense indicate it should be at least 90-95% efficient, and I would think it should be nearly 100% efficient in 1:1 ratio (with only bearing friction and maybe some windage).
I would like to be able to obtain a suitable transmission for something like $200 each in moderate quantity. Any suggestions on sources for this?
Thanks,
Paul E. Schoen