bobc wrote:Thanks gents,
grindz145 - that was one of the things I wanted to find out - it looks to me as though the ESC is current mode controlled from the way it behaves e.g. slowing down under big load - so it should whack the 40/50A on the label into any motor I wire it to. It was a very cold day so the fact that it didn't get warm is maybe non too surprising!
Hi Bob,bobc wrote:I'm thinking for a "proper job" I'd use a steel spur on the motor onto a big delrin gear on the jack shaft maybe 0.5module - any thoughts?
They give a value for each pitch, that you then multiply or divide, depending on the number of teeth, rpm, size of mating gear, hours/day usage etc.bobc wrote:Miles, torque rating must be a function of diam? (no. of teeth..) I'd not looked at details yet - As it happens a 14krpm motor at 470W is 0.36Nm so quite near, but like you say, it's no big deal to go up to 0.8MOD. Any thoughts on longevity of delrin gears under this kind of loading - anybody run one?
bobc wrote:Interesting - I would have said that puttingthe ESC on a motor that was 4 times too big for it (in current terms) then riding up hills under current limit it would surely have zapped the ESC if it were running "open loop" - I'll have to play some more! And it was the most bargain basement device available... ;^)
bobc wrote:...... Any thoughts on longevity of delrin gears under this kind of loading - anybody run one?
bobc wrote:Good idea Jeremy, I'll do a little exploration (so far as I can without killing it). I would (however) have thought it's easy & cheap enough to get a shunt on the DC- connection - the peak I there would be = phase current (a brushless drive is open circuit on one phase) so I kinda assumed they would use that for current control ('cos it's what I'd do...). I'm going to get me an ATmega BLDC control demo board & learn the job properly :^)
I know if you read up on brushless drive control they always go on about closing the speed loop (with a PID) - for our purposes we don't want to close the speed loop, we want direct control of the torque (& therefore the current). Such a control scheme would work fine for props as well, (though you might want to compensate for the speed squared non-linearity) - you'd end up with a drive that looked after itself and was nearly universally applicable (& my bargain bucket ESC actually gave a damn good impression of it!). I can't believe i've just been outrageously lucky - that doesn't happen to me......
bobc wrote:. The only problem is that the new ESC looses synch if you gas it when it's going slow (loud motor noise and no torque) and it doesn't seem possible to feather the throttle to get round the problem. If others have had this issue, I'd like to know how you got round it!...
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