### Identifying motors and choosing motors

I have four mototrs that I know are Exceed Optima motors, but since they have no labels or other outer markings, I have no idea what the specs are. Does anyone have any tips on how I could narrow down which they might be?

Second, I am looking for the right motors to use for a quad - the total all in weight with everything should be around 1.6KG. I have enough space for up to 11" props. Prefer to run 3S batteries if possible since I have a pile of those already.

I know about the various calculators out there, but I am new enough at this (and a poor enough engineer) that I can't really make heads or tales of all the different numbering systems and specs.

Anyone want to educate me?

#### Replies

• Hi,

Take an AC voltmeter and connect it to any 2 phases of a motor with a known speed kv1.

Put the known motor into an electric drill that rotates with about constant (full) speed. Measure the voltage v1 on the meter.

Now make the same measurement v2 with the unknown motor.

RPM = v1*kv1 = v2*kv2

kv2 = (v1*kv1)/v2

Regards

Soren

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