Originally Posted by Kevin Ainsworth (Post 1408080)

Great design!!!
The more designs someone does the more they learn and the better they get.
Your designs get more compact and innovative every time, keep them coming.

What is shifting the gears? I don't see an air cylinder or servo in there.

I prefer the Vex Versa gearboxes also, due to the fact the output shaft has a flange. The Banebots gearbox doesn't have a flange on the output shaft and that can cause problems if not used correctly. We tried using a round sleeve and a screw/washer to pull the gear up against the Banebots gearbox bearing with bad results last year. We switched to clamp collars and everything ran smooth after that. I agree they're lighter and that's a benefit.

I am a little nervous about retaining the steering balls with a single clip at the top. We went through a discussion about using a clip on our 8WD setup and found they can take about 600lbs of force for a 1/2" shaft so the clip isn't the issue. I am more concerned with the strength of the upper plate that will be seeing that load. I think there are more forces there than you are considering. In normal operations the weight of the robot will bear down on the balls and this will be a non-issue. When the robot is pushed to the side and the balls try to climb out of their grooves you will see vertical load that might cause issues. Again you might be fine.

The other consideration is contamination getting into the steering ball tracks. We had issues with aluminum chips from drilling on the robot, debris from the field and the carpet fibers getting kicked up from the tires getting in the steering grooves. This is the reason that we are switching to sealed ball bearing on our 2nd generation swerves. We disassembled our units and replaced the balls multiple times last year. I would guess Bomb Squad doesn't have this issue because they leave the steering bearing setup above the wheel and not right next to the carpet. I would be interested to hear from them if they have seen this issue also. Maybe consider a labyrinth seal (a winding path to the balls instead of a straight slot between the plates). I was considering using two opposing L-shaped walls instead of two round grooves.

Originally Posted by asid61 (Post 1408043)

That tensioning method could be unreliable. Testing would be paramount, and easier would be to have discrete mounting holes for each tensoning distance.
By "top plate" I mean an upper support. Right now, the only thing keeping the module in place is the weight of the robot. You need to have some kind of way to secure the module from above as well, either by means of a plate on top of the module or by using some kind of loose clamp on the bottom plate.
As for gearboxes, I see what you mean. I'm cadding one like this but shifting right now, and the banebots is considerably lighter than the versaplanetary. However, I hear that they can be unreliable.

Originally Posted by AdamHeard (Post 1408094)

I've seen you rule out the slot tensioning method in a few places. Have you guys had a bad experience with it?

We've done it numerous times, on 550s all the way up to CIMs, without any issue. It's plenty reliable if the fasteners are tight.

You shouldn't use a socket head by itself as it's small head diameter doesn't grab a lot of meat, so we use buttons or a washer in addition.

Originally Posted by asid61 (Post 1408095)

The primary reason reason for out drivetrain failing this year was tension-held bearing blocks on the corners of our WCD. There were two screws going through the bearing blocks on either side of the 2x1 with nuts on the other end. No matter how much we tightened the screws, the bearing blocks would always slip and cause drivetrain failure.After adding some sandpaper-like gripping tape in between the bearing blocks and the 2x1 post-season, we no longer had problems with the drivetrain failing. This is why I always recommend against any kind of friction fits.
Now, the forces are less extreme on the first stage of a transmission, but I still wouldn't do it in the middle of the season.