On Sat, Oct 4, 2014 at 10:42 PM, Lawrence Rhodes via EV <[email protected]> wrote:
> When I saw the Stella it made growling ticking noises that stopped after > the vehicle made some speed. They said these motors were 98 % efficient. > I thought the run of the mill ADC motor with a Curtis controller was 90 % > and brushless were a bit more efficient. Are these motors worth the 10's > of thousands they cost? Are there motorcycle/bicycle hub motors we can > buy that are very efficient? Each of the Stella motors are 20kw. Some > bicycle hub motors are very powerful. 10 or more kw. Is there a loss of > efficiency with these new powerful motors? What do I need to compliment a > very aerodynamic body/go freeway speeds & not suck the life out of my > batteries? I'm certainly no motor expert, but my understanding is that PM motors only get that high efficiency at max power. The cogging effect (the field is always there) hurts efficiency everywhere else, and a road vehicle spends virtually all of its time NOT at max power. Other attractions of PM motors are their relatively light weight and ease of implementing regen. Those who have converted motorcycles have used these advantages, but some have come to realize they come at a cost. Light weight also means a greater tendency to overheat. Startup torque can be underwhelming. Series motors solve these issues nicely, and also coast freely. I don't want to re-start the coasting vs. regen debate, but coasting with no regen can be a pretty effective range enhancement. The other issue is hub motors. To my knowledge, no-one has made these work on an everyday on-road vehicle. The main concern is unsprung weight, which will be even more of an issue in a hyperlight car. If you want to give a try anyway I'd suggest scooter hub motors, because they have presumably been designed to survive the pounding an unsprung component gets. But the ones I've seen have been designed more for cost than efficiency. If it was me doing this, I'd probably go the Tropica route. Use small series motors near the drive wheels. Use trailing arm suspension and mount the motors at or near the trailing arm pivot, with belt or chain drive to the wheels. That should get you a solution close to what you're looking for with low risk. You're going to have your hands more than full with all the other aspects of this vehicle. Getting hub motors to work well is a whole 'nother project by itself. Chris -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20141005/25aa2bb2/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
