[Oblarg]

Originally Posted by efoote868

No, the auxiliary motors would be used in this setup as well. In the picture presented, 8 motors would be driving this robot when it is going full forward. Alternatively, 1 motor could be in gearbox A, which would allow for 6 motors driving full forward in mecanum drive.

In that case, I think you'd almost certainly do better to just plop the extra motors on the gearboxes in a standard configuration.

The gear ratio spread on most shifters (usually ~2.5:1 for a small spread) is such that a mecanum in the low gear will have little use if the high gear is in a reasonable range.

Shifters are useful for tank drives because they allow the same drive train to have high mobility and high pushing power. A mecanum drive will never have the latter to begin with. I've seen many drives set for ~16 f/s without use of a shifter; it's not a requirement to run at that speed effectively. For what it's worth, this thread is the first time I've ever seen any criticisms leveled at mecanum purely regarding mobility - if you build it right, you have a very agile robot.

If you're dissatisfied with mecanum as an omnidirectional solution and are willing to cope with a moderate increase in complexity, octanum and/or nonadrive are the direction to look in; these give you the full benefit of gear shifting, because you do not have low-traction wheels in contact with the ground in your lower gear.