Pushing brushless to the max
 

I have not seen a maximum volt or rpm rating on a brushless motor yet, there will be a limit so what is it? Before it flies or burns to pieces:035:

Generally you want to stay around 40000.

Over that you risk blowing the bearings. Theres other stuff too, but I dont remember.

You could have the magnet come off the rotor, fry the windings, etc. Stay around 35 to 40k. It will run cooler, more efficient, etc.

So, based on the previous posts; find the voltage to use by simply dividing the max rpm (35 to 40k) by the kv value of the motor.

Using 35k rpm as the max rpm:
For a motor with a kv of 2000 rpm/v, you'd want to use 17.5v.
For a motor with a kv of 1000 rpm/v, you'd want to use 35v.

Motors with lower kv values will have more windings, therefore will require less current. However, since you are using higher voltage with less current, the total power will be roughly the same as a motor using lower voltage but higher current.

To add to what Brian said, a higher voltage setup will usually have more runtime as well because the motor will pull less amps. It would also be easier on your ESC.

But that's only if you gear down. If you don't change gearing after switching to a higher voltage setup, your runtime will be less (assuming same battery capacity) and it will be harder on the ESC and motor.

I think he's talking about a high voltage setup that also uses a slower motor. In that case you will definately get more runtime.

Yea, I meant if you use a lower kv motor.

65.000 u/min --- I see ratings like these on a lot of the motors... is that a rpm rating or is that something else. Please correct me so I am more knowledgeable.

That is the rating for like the balancing and bearing rating. It is not good to push it that hard. I have pushed some pretty hard with out destruction. You can push more than 40k rpm but just not continously.

Thanks CHC, that's what I figured.. I noticed everyone was saying to hover around 40k continuous RPM to make sure you don't have a premature failure of the motor.

I've got couple brushless motors on there way for use with my new Quark 125... should be interesting.

I see motors with 6500kv that they put small 4 cell lipo in shockflyers, helicopters etc

There must be a limit for warranty issues

Smaller motors have higher rpm limits of course.

Probably because the RPM's will drop drastically under load, correct?

They have less rotor mass so they're less likely to explode.

And the bearings are smaller. Smaller bearings can spin faster than larger ones with fewer problems.