Bumper Rules [R33]



The general idea as I understand it is that the structural elements of the frame perimeter cannot move relative to each other, and the bumpers have to be locked in place on the parts of the perimeter they cover.

The one time the non-articulated thing has come up for me as an inspector, the team had built their frame with a joint in it so that they could flex the frame from a flat rectangle to more of an A frame when going over an obstacle on the field. That was not ok, and they had to lock that joint in place to compete. (This was one of those “I’m just going to go ahead and get the LRI right now, because I know you’re going to want to appeal” kind of moments. I felt bad about it because they’d clearly spent a lot of time making that happen, but it was definitely in violation of the requirement.)


The rules say that you can’t articulate the bumpers relative to the Frame Peremiter per R25. However, the question asked here, is how does this relate to the frame, vs the frame peremiter.

My understanding, is that the main frame of your robot, which is supporting you bumpers, cannot be articulated. I think they specifically do not want the bumpers to move relative to themselves (so that they can be used to calculate your frame perimeter. There can be gaps in the frame backing the bumpers, more than 8" wide OR 1/4" deep. per R33. Per the definition provided in the glossary, the FRAME PERIMETER is fixed, non - articulated structural elements of the ROBOT contained within the BUMPER ZONE. When the frame perimeter is used to define the limits on size, it’s size is determined by wrapping a string around it.

For a simple frame, this means that 8" wheels may be off the table. However, it may be possible to avoid the rule by mounting the bumpers above the center of the wheel, where the frame gap can be less than 8" wide (because the wheel is round).

Technically, a string could not be used to “support” the bumpers, because string is not structural. However, a sheet of metal or a polycarb board could be considered structural, but it would likely have to be argued to the judges at each competition.


I’m fairly certain you can’t articulate the bumpers relative to the frame. Is there a Q&A question about this?

Yeah, I’m not talking about bumpers relative to the frame – I’m talking about articulating the frame (with the bumpers attached). Say you make a rigid square outside frame that the bumpers attach to and an inside frame where the wheels are. Can you put a hinge between the two?

Because of Q11 and the way R1 is worded, I think the answer is yes. It doesn’t say that the frame perimeter can’t be articulated, only that the elements of the frame perimeter can’t be articulated.


You’re looking at it wrong. The Frame Perimeter [R1] and bumpers [R26, R31g] must be fixed/rigidly attached and non-articulated. That doesn’t prohibit you from articulating anything else or even everything else relative to the FP on your own side of the field. And if that results in the FP and bumpers moving out of the bumper zone, better make sure they start and stay in the HAB zone.


Yeah. I thought about that. All depends on your frame of reference. But, it’s also the sort of argument that could be described as “too clever by half.”

There’s also the related question of “what does it mean to be structural”? If it’s possible to move the entire thing out of the way, is it really structural?


The problem isn’t that I can prove it as structure, the problem is that with the current wording of the rule you can’t prove that string is not considered structure.


It was a 0.125” piece of polcarb that was 0.5” wide. I will post a picture later. It was not an after the fact thing, we did it intentionally to save weight. All in all we saved about 2lbs doing it that way instead of the way we would have done it in years past. I will post an image later.


The team I am referring to is a different team from the Houston area.


Looks like a yes to me.


I’ve been complaining about this for YEARS!