Can Gearing Prevent Cogging of Sensorless System?
 

I have a 60 amp EZRUN sensorless brushless system and was thinking of using it in a 10th scale crawler. I know it will probably cog pretty bad because it is sensorless and was wondering if I could do anything with gearing or anything else to help prevent that or do I need to just buy a sensored esc and motor?

As a very wise man once said, "gear down and volt up."
Use a low KV motor (under 1200kv), the highest voltage batteries the esc is capable of and then gear is down as low as you can go.
Also run low timing.

This will minimize cogging. You can never get rid of it, but it will minimize it.

i ran an outrunner wit no coggging. may have been 850kv

back in the day I ran a Holmes O.G Revolver with a sidewinder on a TLT 2.2 truck. 9.6v and no cogging. Man I miss that little outrunner!

An outrunner would be your only hope to have low cogging while sensorless. I still have some revolver motors, they are 1000 kv. An inrunner just can't make the torque to start up reliably.

Volt up, gear down. Indeed!

I'm just getting started on an experiment very much related to this. I mentioned it briefly in the Newbie thread I started a few days ago, and I've been trying to get more insight from the folks at RCGroups.

Basically, my thinking goes like this: Kv doesn't really have an impact on smoothness. It does effect torque, but so does gearing. What really matters for smoothness is the number of stator teeth and magnet poles - a higher count should mean the ESC switches more times per motor rotation, so any jerking and lurching causes smaller movements of the motor. So, once I get the cash rounded up, I'm going to try the novel and seemingly ridiculous approach of intentionally using a much faster motor. By going with a motor which still has the typical 12 teeth and 14 poles, but is wound for the highest Kv possible, I can gear back to the same torque and wheelspeed, but have more ESC switches per tire rotation, minimizing the effects of any cogging.

Unless I've missed some detail (I really don't know all that much about brushless motor design), this should have the same effect as "volt up, gear down," but allow me to take the same concept even further once I've hit the 3s voltage limit on my ESC.

I'll be sure to let everyone know how it turns out.

You have the right idea. Maximize commutation frequency, minimize wheelspeed. Doesn't roll of the tongue like volt up, gear down does :D

I've got this motor on my scaler, running on 4S. For a scaler the torgue is
just rediculous. And it gets up and goes.

An update to my outrunner experiment can be found here.