Mechanical Details

In comparison to Holonomic or Swerve drive, Mecanum is quite simple. All you need is four independently driven Mecanum wheels. These can be bought or built. I bought mine from AndyMark (www.andymark.biz), but that doesn't mean you should.

Mecanum is a certain amount heavier than a comparable tank drive system. One probably uses the same number of motors, but two more transmissions (one per wheel total), and the wheels themselves are heavier than usual. My skateboard*, with 4 AndyMark Super Shifters, 4 small CIM motors, a 2005 electronics board, and an aluminum frame, weighs around 70 lbs.

One challenge I did not work on was how to ensure that all four wheels stay in consistent contact with the floor. Usually, the issue comes when the robot runs over an object. A bolt likely wouldn't be an issue, but a small poof ball might be. Sitting the chassis low enough to the ground that such objects get pushed would work. The other option is to include suspension of some sort. Standard bumpers, if placed well, can substitute as the former of those. I do not know how to use suspension in a robot. I personally would recommend considering Swerve drive if active suspension is a likely option (student project opportunity!).

Speed is also supposedly a concern. My mecanum bot is not really a fair case either way; the sprockets from the transmission to the wheel are by far not designed for speed. Changing some things in the transmission and/or the sprockets would help significantly.

In short, there's not too many problems with mecanum drive from a mechanical standpoint. The wheel type and wheel independence are what determine a mecanum bot. The software makes up for the mechanical simplicity, though. The software will be covered in a future post.



*Skateboard in this case is either a technical term or language abuse