RC-Monster Forums - View Single Post

BrianG · 03.04.2008, 12:54 PM

It seems there are three things to keep in mind when selecting a motor for a vehicle:

1) Motor size. Pick a motor that will have the torque to pull the weight around. For 8th scale MT/truggies, this means a motor with a longer can.

2) Max motor rpm. We all know the Feigaos like to run up to 30-35k max before they start losing efficiency. So, that's a no-brainer.

3) Min motor rpm. This is something we don't usually think about. If you use a motor with a kv that is too low, you have to gear higher for speed. Of course, taller gearing increases current, but it also affects ESC circuit effectiveness. If each motor revolution moves the truck 6", the ESC might have trouble locating rotor position and cog at lower speeds.

So, IMO, you want to pick a motor/voltage combo that will spin up to it's max rpm at the max speed. Spinning the motor at a slower max rpm means you'll have to gear down.

	(#4)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	03.04.2008, 12:54 PM It seems there are three things to keep in mind when selecting a motor for a vehicle: 1) Motor size. Pick a motor that will have the torque to pull the weight around. For 8th scale MT/truggies, this means a motor with a longer can. 2) Max motor rpm. We all know the Feigaos like to run up to 30-35k max before they start losing efficiency. So, that's a no-brainer. 3) Min motor rpm. This is something we don't usually think about. If you use a motor with a kv that is too low, you have to gear higher for speed. Of course, taller gearing increases current, but it also affects ESC circuit effectiveness. If each motor revolution moves the truck 6", the ESC might have trouble locating rotor position and cog at lower speeds. So, IMO, you want to pick a motor/voltage combo that will spin up to it's max rpm at the max speed. Spinning the motor at a slower max rpm means you'll have to gear down.