Motor Specs? - RC Groups
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Sep 04, 2013, 11:42 AM
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Motor Specs?

I posted the following questions in the Beginners Training Area but maybe it's better here. If a moderator sees this would you please delete my post from the Beginners forum?

I want to use some of the sizing tools but don't have complete motor specs. How can RM and Io be determined if they're not specified by the motor manufacturer? Is there a way to estimate them?
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Sep 04, 2013, 01:32 PM
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Dr Kiwi's Avatar
If the motor is in the DriveCalc database you can get those figures from there. You can't estimate but if you have the motor on hand you can measure and calculate. No-load current and RPM at two different voltages then amps and RPM from 4-5 props at the same voltage.. plug the numbers into DriveCalc and you'll get what you need.
Sep 04, 2013, 02:58 PM
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Originally Posted by Dr Kiwi
No-load current
Thanks for the response, Dr Kiwi. Can I get the no-load current with a watt meter or is there a better way?
Sep 04, 2013, 04:49 PM
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Dr Kiwi's Avatar
Yep! Just run at WOT without the prop for the shortest time you can, to get a reading [long no-load runs simply generate heat with no cooling available!]. Obviously, to use the Io any further in computations of Kv/Rm etc you'd need RPM without the prop, then amps/RPM with various props.

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