[JesseK]

Ether, the problem with your logic is that Mecanum wheel rollers are not effectively locked when pushing against a hard object. Properly designed rollers still 'roll' at the off angle due to a good bushing that allows the roller to free-roll anyway. The underlying issue isn't that Mecanums can't push; even 70% torque of 4 CIMs is enough to push an object to get out of most situations. It's even good enough to play defense in most situations since defense can usually be done just by turning another robot or getting in the way of another robot.

Conventional wisdom says Mecanums can't push; this is due to software control and a driver's lack of understanding of how a Mecanum design works holistically, OR that the drive train was designed with speed in mind and no high-speed drive train can push worth a durn. We've found that with 4 CIMs a good balance is 10-11 fps before losses. Under the covers, when on a diagonal, software tells 2 motors to drive the diagonal while the other two motors sit idle. This allows the diagonal strafe. Yet when pushing while on this diagonal, the bot effectively has 70% * 1/2 (due to 2 motors out of 4) = 35% of the original torque of the 4 CIM setup. Ergo, Mecanum drive trains with true holonomic control only ever apply 35% to 70% of 4CIMs to any direction. Thus 'Mecanums can't push' should be turned into 'Mecanum drivers don't know how to drive' or 'the whole holonomic idea of Mecanums is terrible for competition robots'.

Teams who try to do a full field-centric Mecanum holonomic drive can probably anecdotally attest to this. This year 1885 did Mecanum, yet we only did standard tank/skid steer with the ability to strafe 90 degree from forward -- nowhere in between. Rarely did we get into a situation where we needed to push, yet we also didn't have a problem since it wasn't setup for true holonomics.