Drive base isn't leveled

[aonarcan]

We are trying to put the drive base together but we realised that it isn't leveled meaning that all of the wheels don't touch the ground at the same time. Only 4 out of 6 wheels in total touch the ground. Is this a problem or is it supposed to happen? If it is a problem how can we fix it?

[Kevin O'Connor]

Welcome to the FIRST Forums! The center wheel of the AM14U drive base kit is intentionally lowered. This is a technique commonly used in FRC to get the stability benefits of the longer wheel base while maintaining the ability to turn of a shorter wider wheel base.

A "tank" style drive requires the wheels to slip sideways in order to turn and the forces required to turn depend on the length and width of the wheel base. The math for the 4WD case can be found in the paper linked below. A flat 6WD case does alter the math a bit, but long story short, the force required to turn is still pretty high with a long flat 6WD. Lowering the center wheel does one or more (depending on the mass distribution on the robot) of: concentrating more weight on the center wheels when turning (these wheels need to slide sideways less or not at all depending on the center of rotation when turning), or shortening the effective wheelbase (robot balances on 4 wheels when turning and turns around a point centered between them).