Mechanum Wheel Sizes

[Nemo]

Some people always make mecanum sound harder than it is. Let's assume that a team has already figured out how to build, program, and drive a basic 2WD/4WD/6WD FRC robot. For such a team, I would claim the following:

1) Mecanum drives are not difficult to build. You can get preassembled wheels and gearboxes from AndyMark, and hubs to connect them. All you have to do is find a way to fasten the gearbox to your frame. That is about as easy as a drive can get. No chains required. It is not very heavy, either.

2) Mecanum drives are not difficult to program. You don't even have to program it, because holonomic drive code is included in the libraries with our software. All you have to do to turn an arcade drive into a holonomic drive is add "+ x" or "- x" to the motors for the strafing axis joystick input.
Front left motor: y + z + x
Front right motor: y - z - x
Back left motor: y + z - x
Back right motor: y - z + x

Adding gyro feedback prevents the robot from driving crookedly or rotating when you don't want it to. That admittedly adds a bit of complexity, but only a bit. I am not convinced that encoder feedback is necessary if you have a gyro.

3) Mecanum drives are not difficult to drive. I'd like to know how many of the people claiming otherwise have actually driven one. I thought the whole point of a mecanum drive was to make it EASIER to get where you're trying to go, pointing the direction you want to point. A 6WD is less forgiving to the driver than a mecanum drive, because it's faster and easier to correct your slight driving mistakes when you can strafe.

Mecanum can be a reasonable choice for some teams. It is not going to work well for all games, but it was fine for 2011 (flat field, protected offensive zone, and peg goals that were easier to score on with strafing ability).

Mecanum is also not going to be as good as 6WD at the highest level of competition, because a 6WD robot (which has inherently better traction) with a really good driver does not need strafing to quickly get the robot exactly where it needs to go. However, it is okay to focus on getting more competitive at the regional level. The forgiving nature of a Mecanum drive (item 3 above) might, in fact, make some teams more competitive at that level than they would be with 6WD.