Rod Hower wrote: > From the electrical design standpoint I'll have to agree with > Seth. I have very little mechanical experience (although I did > get A's in my ME classes in school). Anyhow, I would recommend > that you look at torque speed curves for any motor and come to the > conclusion that at least one gear reduction will do wonders for the > motor effeciency for an EV that has to go 0-70MPH.
I think this is exactly the case. All drives are a compromise between many factors. A single-speed drive eliminates the transmission at the expense of requiring a higher-power motor and controller for the same vehicle performance. But... here's an idea we discussed before, but haven't followed up on. Suppose you keep the torque converter, but leave out the transmission? Most torque converters have at least a 2:1 ratio between input/output speed, and many modern ones can be locked. When you start from a dead stop, you have 2x the motor torque for a smooth, more powerful start. As you speed up, the torque converter gradually changes to 1:1. When you get up to speed, lock the torque converter for cruising. There are no gears, and no shifting. Torque converters are lighter and simpler than gearboxes, and (presumably) cheaper. Efficiency is lower, but not enough to matter if you keep it locked most of the time. -- Lee A. Hart Ring the bells that still can ring 814 8th Ave. N. Forget your perfect offering Sartell, MN 56377 USA There is a crack in everything leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
