dynamics of motor drive and speed

[richard]

I am interested in what is actually happening when you reach cut out speed.
When I go over 13.5 mph on the Ezee chopper with the throttle still open I can hear a gentle rattle from the motor, when I shut the throttle down it stops. I assumed that when you reached terminal speed for the cut out to operate that all pwer would be cut to the motor. so why can I detect this noise ? would welcome an explanation.
Richard

 

[flecc]

There is no cut out Richard, the Sprint motor in that 20" wheel reaches it's maximum revs at between 12.5 and 13.5 mph depending on the state of charge of the battery, since it's voltage that determines the maximum motor revs.

The rattling might be the orbital gear teeth at the point of no further revs coming from the motor, and therefore free to vibrate between leading and trailing edges of the orbital ring teeth as the wheel spins. I doubt if you'd hear that on a very slight upslope where the fall back in speed maintained the back pressure on the gear teeth, the same effect as shutting off the throttle.

The noise shouldn't be very obtrusive though.

P.S. At maximum revs with the throttle wide open, the motor is very close to it's point of maximum efficiency so current wastage is minimal.
.

 

[richard]

Thanks Flecc, your right the noise is very slight and I only hear it when coasting on a slight down slope. cheers