pic: Offseason Drive and Test Bed

This is a CAD of the drive we made in the offseason, and are going to use as our test bed in build season. Some things in the CAD never made it to the real robot (like how the pneumatics are laid out and the bellypan), but overall it’s pretty similar. This frame was also made for us to try driving a WCD with gearboxes in the back.

When we ran it on the ground it drove at 22 feet per second (according to encoders). This test frame is a WCD with 6 cims, 6 4" diameter 2" wide colsons, and uses the 3 cim VexPro ball shifters with 3rd WCD stage. Gearing is 4.17:1 in high gear, 9.01:1 in low gear.

Looks good! I particularly like what you’ve done with the side rails :D.

I am curious how the actual speed can be so close to the theoretical speed?

Also, did you get the memo that MiniCIMs are ‘in’ now?

Since there’s no weight on the test frame, it’s basically traction limited in both gears. When we add weight and bumpers it will probably slow down quite a bit.

They’re ‘in’ our parts order form :wink:

In addition to what Rafi said, there’s probably also some significant wheel slip, these are brand new Colsons on a super-light frame.

It would be cool to see an experiment to determine the impact of weight on rolling resistance. I’d also like to see the difference between a school cafeteria floor and FRC carpet.

Maybe I’ll pencil that in for next Fall.

I’m partially concerned about the placement of your main breaker. Word of warning: I’m always really concerned about the placement of our breaker and then the inspectors never bring it up, so take the following with a grain of salt. Assuming you have some sort of mechanism inside the robot, in the case of an emergency, you would have to reach inside the robot to emergency stop the robot. A simple fix would just to place this breaker on the other side of that plate, and just run the main wire over the top of the plate. Also the bend radius on that 6 AWG (or even worse if you’re planning for 4) might be a bit of an issue.

Also, are those handles 3D printed? That’s an awesome use, assuming your print can hold the weight. I’ve always designed McMaster handles to put in robots, and it never happens, and if your prints turn out well, I may do that this year.

On another note, what’s with the split bumper in the back there? Those gaps seem like odd choices to have, and I’d love to hear if there’s some reasoning I’m missing.

These boards are meant to be easily movable (including to the bellypan), so having the circuit breaker move with the PDP was part of the plan, but I’ll talk to our electronics person to see if we could put it on a more easily accessible part of the frame.

Those handles are placeholder CADs for some other handles that we’re going to order for the frame.

The split bumper is an optional bumper for test-frame use, since sometimes we need a bumper there to test a mechanism (like an over-bumper intake), while other times we need there to be a gap (like for a gear handler).

Battery placement?

The battery is centered opposite of the gearboxes, placed vertically with a box mounted on some peanut stock extruding out from the frame. This helps with the center of mass and keeps the battery pretty close to the circuit breaker and PDP.