On 7/28/07, dale henderson <[EMAIL PROTECTED]> wrote: > what is banding? i've 'upgraded' my motors with an aluminum screen around > them is that what you mean?
No, what I'm suggesting (speculatively, since I've never seen inside one of these motors, never mind used one), is that you wrap a band of Kevlar tape around the rim of the rotor. The same technique used to band the windings or commutator in wound field motors to protect them from coming apart at high speed. Since Etek and PMG motors are used at or near their limits on a typical EM, they tend to run hot. The clips on the rotor have come off on quite a few motors. You've demonstrated when that happens, a clip can seize the motor and lock up your rear wheel. There is also reason to believe that just normal use over a long period of time may have the same effect. Low level heating and cooling cycles are known to weaken solder under load, and those clips are under substantial load from centrifugal force. The fact that some motors have spit their clips while *not* running under heavy load supports this scenario. Banding the rotor means the Kevlar takes the load from centrifugal force, not the solder. A banded rotor won't eject clips, so it can't lock your rear wheel. The only things I don't know are how much Kevlar you need or how much clearance there is between the rotor and the inside of the case. A good motor shop should be able to help there. What I do know is that I would not use an Etek or PMG on an EM without securing those clips. Not doing so presents the very real chance of having it lock solid and pitch me under the bumper of some car on the highway. I see this as just as likely as a controller fail-on situation, and we all protect ourselves from that, right? Chris
