I have a 23t tamiya 540 motor that turns 26,500rpm with no load on 7.2v. I have not found the specified kv of the motor
but i have figured that it would be around 3680kv but the motor only turns 22,000rpm loaded (i assume this is in you average car,it being a car motor) so if i want to calculate the motors kv do i calculate it using the loaded rpm of 22,000 which would give me roughly 3055kv or the unloaded?

unless i am calculating it wrong by just going 26,500/7.2.

thanks,

kv is how a brushless motor is messured.
kv is the rpm per volt the motor turns.
a 2200kv motor spins 2200 times per volt that is applied to this motor.

so at 11 volts( 3 cell lipo) it turns 6600 times a min.

that is what i have been told.

flip

You mentioned RPM per volt but multiplied by number of cells. A 2200Kv motor will spin 22440RPM unloaded on 11.1v

Kajab
You use the unloaded figure. Kv is never determined under load.

Kv is determined by using a known RPM which spins the motor. The voltage generated by the motor spinning is then read and used to calculate Kv. This way efficiency is already included.

Your motor is about 3500Kv nice even number.


Ryan

ok thamx for letting me know that.
now how do you figure out the load on the motor.

flip

Generally reduce unloaded rpm by 20% and that is general load. But this can be affected by a ton o things so just estimate.

Ivan.

Now that is one of the best little gems that I have read in a while.
I do appreciate that there are many variable that affect this estimate, but it is a good ball park figure to work on.
I too use the same motor that was mentioned at the top of this thread.
I can tell you that in 2 of my hulls with an Octura 531 prop on 6 good cells it is spectacular.