I really should have read the instuction manual ( a warning)

[Peter Beeney]

I have to admit that I’m not quite sure why the manufacturer of an electric motor would state that it should not be run without a propeller on. It would seem to me that he does not have too much faith in the quality of his product. Very little indeed, perhaps. Or, conversely perhaps, the performance figures are considerably optimistic, and it’s hoped that no one will notice this minor discrepancy with the propeller on.

Because these are now universally used by modellers I’m assuming that this is always referring to permanent magnet brushless motors, and the same principle also applies to permanent magnet brushed motors anyway, but provided the voltage applied to the motor is always within the specification it’s difficult, perhaps impossible, to see how the motor can run too fast, and exceed it’s design revs per minute in an unloaded state. Or at least as far as I’m concerned it is; but as always, I do stand to be corrected; I’d be very interested in any explanation of how this can happen.

If this manufacturer’s instruction relates to other types of electric motors, then of course other conditions apply, and it’s possible the motor should not be run unloaded. But I can honestly say that I don’t think that modellers use these motors in any form of modelling, anyhow.

I’d say this has all the makings of eventually becoming another of those little myths and foibles that aeromodellers seem to be so fond of creating. They crop up from time to time, and are invariably quite tenacious, even when they are seen to be exposed they still linger on. But perhaps that’s all part of the spice of aeromodelling; plus in some very back to front sort of way it’s just another way of looking for an excuse as to why the model again bit the dust without warning……

And I’m always looking for one of these……

PB

[Aky208]

Had a prop slap my knee before. Luckily just a nasty bruise. Thought I had set the throttle to zero on the tx behind me, while kneeling on the floor. Must have flicked it when turning round. Plugged the battery in, then ouch. Won't do that again. Had a bruise the size of a fist.