motor draw...

[burgie]

is there a recommended amp draw for a modified motor? Obviously, (i think) if a motor is drawing, say, 13 amps, then it's going to burn the comm and/or the batteries are going to dump, I presume.

But if it's set to draw around 5amps, say, then i presume damage to the comm will be limited.

The reason for asking, is that I have just purchased a new comm to put into the can of the worn-out comm. The comm is a 10 double, replacing a 12 double.

Usually, I measure the amp draw of the new motor, (complete) and always when re-building the motor, set it to the same amp draw.

Any advice would be greatly appreciated.

[mrbigger]

i guess you are talking about armatures and comms.
also the low currents you are talking about must be no load draw with you reving the nuts out of you motor.

on load currents will be much higher.

don't suppose this has helped.

[burgie]

The low amp draws are with no load on the motor, as i appreciate the amp draw will increase when the motor is "under load", hence asking what a reasonable amp draw would be for a motor that is indeed not under load.

[PDW]

The no-load current draw on a motor is no indication of on-load performance, so you can only really use it to check that you have put the thing back together properly.

It's a bit like saying that you can judge car engine performance by the fuel consumption on tickover - it's a guide (F1 engine will gulp it, VW Diesel will sip it) but nothing more. An F1 engine is useless for the trip to Sainsburys from home!! (Wouldn't fit in my 306 anyway!)

The current draw is also not related to comm burn. A 14-turn motor will draw less current than a 10-turn. If the timing on the 14-turn is way beyond the optimum, the comm will burn. If the 10-turn is set at the optimum timing, it won't burn.

When replacing your 12-turn (I assume you mean armature, not comm) with the 10-turn, set the timing to about 5 or 10 degrees, gear appropriately, and try it. You may find a little more ooomph with 15 degrees and a smaller pinion, or with 5 degrees and a larger pinion - depends on the track and the car. Check the current draw when you build it, check it when you have found a good track setting, and check it again after you have rebuilt it - the numbers will give you some guide to how well you rebuilt it, but nothing else!! HTH :)

[burgie]

thanks peter - i did mean the armature, and not the comm, obviously struggling with the old thought process today - now i know i was going up the wrong path, I'll stop! :p