I wasn’t aware of Mecanum wheels until I saw the DJI Robomaster, and I was just mesmerized by the way it moves, seemingly floating over the floor in every direction. To me, it was the wheeled version of a quad, with four motors and no other moving parts controlling the vehicle’s direction. A quick Google led me to this video:
It just so happens I have a broken printer sitting on my floor, so I already have the stepper motors for that. But I know nothing about Arduino, so I started thinking about making a brushless motor version instead. I also know nothing about brushless motors for cars, so I just started drawing a wheel that would wrap around the 28mm bell of a drone motor.
I wondered why the rollers aren’t straight cylinders, which would maximize the contact patch. I found out soon enough: the edges of the rollers adjacent to the bottom would project below the bottom roller and lift it off the ground. So THAT’s why the rollers are curved.
I eyeballed the curves of the rollers and marveled at how it resulted in a near perfect circle.
I sent Control.fpv my progress and had an epiphany.
I started over, with a surface that represented the outer diameter of the wheel, and cut it at 45 degrees.
Then I took that cut edge and revolved it to create the roller.
Pattern it and you end up with a perfect circle. Amazing!
Next, the hubs. The Robomaster has beautiful rims, and since I’m doing this partly as Solidworks practice, I decided to draw something nicer than a flat disk. This turned out to be really really hard – the logic of the part was hard enough to figure out, much less model. I ended up with a two piece design, with axles projecting from the rim to hold TPU rollers.
Quick Word on Motors
I knew there was no existing motor made for this, so I ordered a gimbal motor, hoping its low kv would be good (yes I know they have low torque). The motor has a flat top with no axle so I drew up the hub accordingly. The