Brushless Beetle Drive

[Ellis]

Hi Giles. The problem with brushless as drive motors (in any weight class) is the control side. Unsensored motors, which yours will be, need to be in motion for the ESC to have information about how to control it. That basically means that they are awesome once going, but can struggle to get going at all, as the controller has to "guess" what power to send to what phases to make it spin. If the motor is under no load this works fine, it's when it's being held back, say by the inertia of a combat robot, that it may stutter. The generally accepted solution to this is to give the motor plenty of gear reduction, so that it has as much mechanical advantage as possible, ie, so that it doesn't have to fight so hard to spin a wheel. Either that or massively over size it so it doesn't care so much.

The other problem is that brushless motors need to be brought to a total stop before they can change direction. Unlike in brushed where you can just flip polarity and the motor will screech to a halt and go the other way as quickly as it can, a brushless can't do that. This means you need an ESC with the right brain for changing the brushless' direction without a hesitation, and as that's not commonly needed in RC (the world from which what we use originates), those are hard to come by.

Assuming you can get past all that and find a suitable ESC (as Rory/Harry are/have), the benefits are in power density. Brushless RC motors generally blow the socks off brushed motors in power for the same weight. For this reason they can be smaller and lighter for the same grunt. It's just designing a reliable setup to overcome the above that means we're mostly using brushed tech. It's just super simple, super tough, and cheap.

EDIT: I got seriously post-ninjad. Oh well, might still be helpful.

[Giles]

Post ninjad indeed!
Very good info though, thanks a ton. I don't really know much about robotics yet, so finding out the basics is great. It's starting to sound like "you need to know your stuff if this is going to work" In which case, i might be better off buying myself some brushed motors for my first steps into building combat bots