Faster motors, with more torque. Okay, how do we do that?

Well, faster is achievable with bigger wheels. I bought mounts for roller blade wheels last year, and also bought wheels up to 90mm in diameter.

The model is about 25 lbs., or 11.4 kg.

I'd like it to move at a minimum top speed of 3 mph. Preferably 4.5, so it can catch up to people walking.

And that's the end of what I know.

Reading about choosing motors for robots, I found many pages outlining the relationship between acceleration, velocity, wheel size, motor RPM, stall torque, and whatnot. It took me a while to figure out what all of the pieces were that I didn't know, but eventually I came to the conclusion that I wanted a 12v motor, at about 300rpm, with 77kg/cm stall torque (3.77N/m, 33.4 lb-in).

The motors I'm using are 30kg/cm stall torque - less than half what I want. That jives very closely to what I see. The Dalek moves at a calculated 1.8 mph, which is about half of what I want. Great, I'm getting somewhere!

So, much scouring the Internet, I really didn't find motors that fit the bill. I found a pair that were slightly more powerful than what I'm using now, but they're also *longer* - I'd have to build a more elaborate mount system for them, because they won't fit in the current mounts under Bob. Rats.

And this is where Bob sat for about a month.

One of the things I love about Hackaday is the inspiration from other peoples' projects. I obviously have a lot of projects that are running concurrently, all the time; most of them are sitting and waiting for inspiration, money, or time. Sometimes all three.

So when I'm stymied on motors for Dalek Bob, and a post like An Open Electric Wheelchair comes to Hackaday - Eureka! - I'm suddenly thinking about how hoverboard wheels have the power I need, with compact mounts because they're hub motors.

Order one hoverboard just to disassemble it: check.

Organize an 11-year-old family member to "test" the hoverboard before disassembly: also check. :)

If I'm going to use these brushless 36v DC motors to drive Bob, I'm going to need new control circuitry. The old motor controller is out the door. As is the 12v power system. Thinking through the cascading changes, I've got a lot of details to address.

Converting from 12v to 36v also means building a new 12v distribution system for the shoulder motors, and continuing to power the Arduinos as-is. I'll need a new mount for the battery itself; two new brushless motor controllers; a new power relay interface (I really like a hard off switch); a new circuit breaker, as we're talking about potential draws up to 20A, if I push these motors hard. Oh, and I had already hacked the heck out of the power switch the first time around to make it fit, so rewiring the power switch might just mean replacing it.

Lots of parts on order! We'll see what happens this weekend when everything arrives...