Motor RPM's

[Evinrude150]

Out of curiosity I was wondering how many RPM's the motor on my stock B400 turns. Do you just multiply the 3800KV by 11.1? That would be around 40,000 RPM's. Do they really spin that fast? Thanks

[dontrinko]

I think the "K" x volts is with no load. Also the motor is geared down so the rotor speed is not near that fast. Don

[Evinrude150]

Thanks for the info. I was asking about the actual motor speed and not the rotor.

[Harbormaster]

The main gear has 140 teeth. The stock pinion gear has 10, so the gear ratio is 14:1.
If you have a headspeed of 2500 RPM, 2500*14=35000 RPM. Yes, the motor on helis turns really fast!

[Evinrude150]

Wow that is really screaming. The reason I am asking is the top of the motor on the used B400 I bought has some metal missing for some reason on the top of the motor. It is like tool marks or something that broke a piece off. I have a vibration that shows up when it is turning enough to lift off and in the air.

I have checked everything and I am suspect that with the motor turning that fast it could be coming from that. I am getting ready to upgrade it with a new motor and better servo's anyway. Thank you

[Harbormaster]

Originally Posted by Evinrude150

Wow that is really screaming. The reason I am asking is the top of the motor on the used B400 I bought has some metal missing for some reason on the top of the motor. It is like tool marks or something that broke a piece off. I have a vibration that shows up when it is turning enough to lift off and in the air.

I have checked everything and I am suspect that with the motor turning that fast it could be coming from that. I am getting ready to upgrade it with a new motor and better servo's anyway. Thank you

I would suggest checking for more likely suspects first, such as a bent main shaft, blades out of balance, main bearings loose in their mounts, chipped teeth, etc. etc.

Better (than stock) servos are always a big step forward with the B400.

Happy flying!
HM

[Evinrude150]

Originally Posted by Harbormaster

I would suggest checking for more likely suspects first, such as a bent main shaft, blades out of balance, main bearings loose in their mounts, chipped teeth, etc. etc.

Better (than stock) servos are always a big step forward with the B400.

Happy flying!
HM

Thanks for the advice. I have a 450X coming and when it gets here I am going to disassemble the 400 and go over it really well