Drop-center drivetrains: Why?

[JesseK]

Originally Posted by JamesCH95

... On two robots that DID have bigger arms that needed to be controlled with precision we used omni wheels on the four corners so that the robot was more stable and the arm was easier to control.

Anecdotal evidence would suggest that rocking drive trains still maintain the maximum manipulator control aspect given a proper c.g. As an example from 2005, 254's robot had a rocking 6WD with a very long 2-PID arm. When fully extended the arm would shift the c.g. slightly, yet when it was down the tetras were easy to pick up because the c.g. stayed towards one side or the other when the robot was not accelerating.

Unfortunately it is exceptionally hard to integrate c.g. from scratch ahead of time; rough estimates are the best I've ever seen derived at the early stages of design. Since drive train is one of the three systems that MUST work (drive train, electronics, programming) in order to do anything effective in a game, most teams prototype like crazy on a pre-season prototype drive train. Additionally, finishing the production drive train early in the season is atypical of actuality for most teams.

Ergo a wise suggestion to anyone worried about c.g. shift on a rocking drive train is to have a pre-season prototype ready to go such that manipulators may be directly mounted to it during build season prototyping. This will give earlier estimates on c.g. and should produce constraints on shifting c.g. that may dictate where to put the 'heavy' elements (compressor, battery, drive train gear boxes, etc) on the production robot.