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John Minchell

Electric motor ID

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John Minchell

Are there any electric motor guru's out there?

I have an old Aveox brushless inrunner which has no ID info on the label, so I don't know what it is or the input power it can handle.  Its just the right size for one of my airframes and I would like to use it.  I know how I can work out the Kv (revs per volt) with a disc on the shaft, a rev counter and a variable power source.  But how do you work out the max amps and volts it can handle?

I have an old Aveox advert and can establish that it is one of about 3 or 4 posibilities but with Delta and Y winds (which I do not understand) I am stuck.  The sensor ESC it came with was damaged and did not work, but can handle 5 to 16 cells (6v to 19.2v) or 2 to 5 LiPo cells.  However that is not really a definitive answer for the motor itself.

Anyone got a simple test method to work out max amps or volts or watts please?

TIA JohnM

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Mr_SMO

In the absence of an answer after waiting nearly a week, I could suggest you ask again in rcgroups. (Aircraft-electric General, ---power systems.)

A rule of thumb, is that a motor can take about 3 x weight in grams, as watts.

So, if it weighs 100 grams, that's 300 watts, which at 11 volts, will equate to about 27 / 28 amps. Simply put a prop on, the size you could glean from motors of a similar weight from other manufactures, then adjust the size of prop accordingly.

Experiment carefully, and with a watt meter, of course, and see what happens to the temperature.

Hope this helps, even though it isn't scientific.

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John Minchell

Thanks for your suggestion Mr SMO ( your 3x grammes = watts) works out to 750 watts.

I did some digging on RCG and found a couple of obsolete Aveox spec sheets. 

Once I have worked out the Kv by testing, that will tell me which motor I have and the tables have max volts, amps, watts & prop size I can use.

John M

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John Minchell

Tested the Kv by using a drill press running the motor as a generator at known RPM and averaging the voltage reading across the 3 pairs of wires.

Apply    Kv = RPM / (volts x 1.414 x 0.95)  to work it out. 

The Kv told me which wind the motor was, then used the old data sheets to tell me what I could use in prop size and amps & volts.  Job done.

Might be helpful for someone.

John M

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