Brushless motors, like regular motors, have different parts (commutator, stater, etc).
What do these various parts weigh?
I took apart a Turnigy D2836 brushless DC motor. Despite the weight listed on the website, the actual weight of the motor without the mounting equipment is 54 Grams.
Here is the breakdown
- Magnets: 9 grams, 16.7%
- Bottom Can: 6 grams, 11.1%
- Top Can: 4.5 grams, 8.33%
- Main Axle: 1.5 grams, 2.78%
- Middle can: 9 grams, 16.7%
- Coils: 6 grams, 11.1%
- Leads & plugs: 4 grams, 7.41%
- Ferrite core: 14 grams, 25.93%
This motor is an out-runner, so the bottom can and the ferrite core have a ball bearing that is included in the weight, but I did not measure it separately. This can be used as a guide for other motors.