I was going through the checklist and found that our bot was in violation of R31 (my bad ::rtm: but was unsure of a legal solution.
The specific part we are in violation of is:
“Additionally, any gap
between the backing material and the frame:
A. must not be greater than ¼ in. (~6 mm) deep, or
B. not more than 8 in. (~20 cm) wide”
So it’s greater than 8 inches, which means we have to move our support pieces inwards. The distance from the support to either end of the robot is fine, it is only the middle that is too wide.
However, knowhere in the rules did I see a statement on how much the bumpers need to be supported by the frame. In particular, would the following solution be legal?
As you can see, the minimum distance is now less than 8 inches, but the maximum distance:
is still over 8 inches. Would this solution be legal during inspection or does the “minimum” distance have to be <8in?
Maybe it’s just the way the drawing looks to me. But are your wheels OUTSIDE your frame?
If so you’ve got a far bigger problem, because now your wheels form your FRAME PERIMETER, and the BUMPERS have to be attached to them.
If that’s not the case, and your wheels are set back inside, then you may not need to change anything. You don’t need a BUMPER along the whole side of your ROBOT. You only need at least 6 inches from each corner. If you’re willing to leave the center wheel exposed, you don’t need to have a BUMPER there at all.
Your solution appears to be legal. You your only allowed 8 in gap without no support. The rules don’t detail how robust the support needs to be. But keep in mind that defense is likely to be rigorous.
This has been something literally hundreds of robots have done every season since 2010, and is completely legal. This is probably the most common style of drivetrain in FRC apart from the kitbot. Having cantilevered wheels does NOT require your bumpers be attached directly to the wheels. The rectangle tubing members on either side of the wheels are intended to be the frame support. They stick out farther than the wheels do.
OP: The sideways configuration you showed is totally fine. Basically the bumpers have to touch a frame member every 8 inches. It doesn’t matter how MUCH of the frame they are touching - they can touch just a 1" tall section like the sideways tubes show. It’s no problem. As long as the “gap” between each tube is less than 8 inches it’s fine.
I couldn’t tell from the side-on view whether the wheels were the closest thing to me or not. Thus my concern. It would be far easier to fix it now than when they showed up for inspections.
You could always just rivet a small piece of aluminum plate onto the 2x1 in the upright position to make it have more bumper contact. It would fulfill the rule. I have seen teams that even just run some 36" long tube axle spacer from vexpro down the entire length of their frame above their wheels to fulfill the rule as well.
but was unsure of a legal solution.
