Let's Make Robots!

A few questions about brushless motors (and motor scaling)

Hi all !


I am currently working on a new robot that will involve tracks. The electronic prototype is under progress and I start thinking about the mechanic part and many questions keep popping into my head, maybe you can enlighten me ;)
  • First of all, I keep reading how great brushless motors are. Does it make sense to use that kind of motor with a tracks/wheels robot ?
  • When I choose a standard DC motor, finding one with a fine gear reduction that suits my needs (torque, speed) is not too difficult. Same with servos. When it comes to brushless motors, I get lost ! I can't find anything about reduction :( It is not an issue when it is about moving something light (like a propeller), but for a wheels/tracks robot, it becomes a prbl. Any idea, or am I missing something ? :)
  • Last question, more generally, about motor scaling. How do you choose the best motor for your project ? For instance, you know the approximate weight of your robot, the maximum speed you want it to reach and the number of wheels/tracks. How do you determine which motor is required ? Do you apply some physics or just choose a motor with the highest torque ?

Sorry, quite a lot of questions ;)
Thx for reading !

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Hi Lord, (salut)

Good to see that you have a track project coming up,wish I could help you with this. Good luck an I will be looking for your next project my friend :)


Hi Arba,

Thanks for your reply and the links ! Access' posts are very interresting.

I keep looking for info about reduction/gearing. It seems that with planes or helicopters, brushless motors have enough torque, so no reduction is needed. But when you want to move a robot (or RC car, tank or whatever heavier), you need much more torque (and much less speed). Unfortunately, I can't find much about it (while standard geared motors can be easily found everywhere :( )

I'll keep searching :)

Thx again !



Here is a discussion I found pretty enlightening (especially the 2 posts by "Access"):


This next page is from a vendor explaining why they believe what they do is best, so there is some bias, but I think it is mostly good info:


What I get out of that is that choosing a really good brushless ESC is probably more of a factor than the motor itself. The quality of ESCs seems to vary more than the quality of motors. Maybe that's just because a bad motor will quickly burn up or otherwise fail and quickly become a memory while a bad ESC may haunt you forever...