pic: VersaDrop GrassHopper Drive

[Chak]

Originally Posted by Jack S.

Looks great!
2) As an offseason addition to our grasshopper drivetrain, we modified the center module to be able to actuate up and down. This actually reduced the drag and made the whole drivetrain much more smooth.

I have never used omni-wheels in real life, but from a theoretically standpoint it does makes sense to either drop the strafing wheel or actuate it. The friction force you get from each wheel is limited by the traction of each wheel, which is dependent on the weight on each wheel. Left flat, the center wheel only gets 1/5 of the robot weight going sideways compared to the 4/5 of the weight going forwards. If you drop the wheel, actuate it with a piston, or put it on a spring, the center wheel will support more of the weight of the robot and (according to what I've heard) move smoother. Personally, I like the idea of actuating it with a piston or spring since the total weight supported by the center wheel would be easier to calculate. Again, let me emphasize that I have no experience and I am simply repeating what I've read. It sounds reasonable though.

Is there a reason to use the 2 CIM single speed double reduction gearbox when you only have 1 CIM? It looks like a Single Reduction Clamping Gearbox would work just as well, in addition to being smaller, lighter, and simpler (slightly more efficient because less stages! ). The lowest ratio on this gearbox would be 11:72, and Vexpro's chart gives a speed of 11.47 ft/s with a 4'' wheel. That speed is slower than your first post but faster than your second post. I suppose one drawback could be the lack of a ready-made encoder mount.