Question About Bumpers


Hello, I have a question about the FIRST manual, R26 “Bumpers must not be articulated (relative to the frame perimeter)” could somebody explain this to me or illustrate?


It just means that the bumpers must be solidly attached to the outer most frame of the robot.


Articulated is essentially jointed, so they don’t allow adjustable joints = fixed mounting. Frame perimiter is taking a string stretching it aroud largest/widest height in bumper zone. Bumper attatchments attach to that area. Nothing else can exist outside that defined area in starting position.


R1 requires a FRAME PERIMETER comprised of fixed, no-articulated elements. R26 requires fixed mounting points between the BUMPER segments and the FRAME PERIMETER. R25 defines where the BUMPERS must be located.

The end result is rigid BUMPER segments, that cannot move once they are mounted on the ROBOT. Neither the FRAME PERIMETER or the mounted BUMPERS can move/change shape during the MATCH.

What is interesting this year, is that there is no rule requiring you to maintain BUMPERS in the BUMPER ZONE in the HAB ZONE, which opens up lots of interesting climbing mechanisms. Read and understand G23 & R25.


My belief is that the no articulation relative to the frame perimeter limits the bumpers from being moved is such a way as to break the vertical plane set by the frame perimeter. The bumper zone max height effectively sets the max height outside the hab zone. Inside the hab zone, the bumpers still cannot violate the frame perimeter, but no longer have the bumper zone restriction, and can be moved/articulated in the vertical plane.

This allows for climbing, but I believe also vertical movement of the bumpers relative the the robot in the hab zone.

Would love to hear thoughts on the second part of my statement above.


I would suggest taking a really good look at the definition of the Frame Perimeter. I think you’ll find it difficult to justify having the ability to move bumpers relative to the rest of the robot at all, given that the Frame Perimeter cannot be articulated per R1, and the bumpers have to be mounted on the Frame Perimeter per R31-G and R33.


Yes, I am concerned with the second part of my statement being an issue.

My confusion comes from the thought of separating the drive system from the frame perimeter which defines the bumper attachment area. If you were to drop the drive train, or portions at different times relative to the frame perimeter, as in the 2004 Wild Stang solution for climbing (where I dont believe we had such a rule back then), would such a design be legal according to this years rules? If not the actual drive train, does employing a drop down wheel to push up one end, or multiple wheels to pick up the entire bot, articulate the frame perimeter?

R26, states bumpers must not be articulated relative to the frame perimeter, and R1 states the frame perimeter itself must consist of non-articulated structural elements, but still not 100% that the frame used to define frame perimeter holding the bumpers cannot be articulated. I don’t ever want to be in a situation where we have an issue at an event with such a rule interpretation, so while we considered such a design, we have gone a different route.


What I understand the exception in G23 to be allowing is for the robot to extend downward past its wheels, which would typically define the bottom of the bumper zone. This would technically lower the bottom of your robot’s bumper zone and, if extended far enough, put your bumpers outside the bumper zone. Rules requiring that the bumpers be mounted solidly to your non articulating frame perimeter still stand.


Lowering anything on the bot which articulates the frame perimeter would then violate?

Perhaps the frame perimeter is the constraint in the x-y (floor) plane. There can be no articulation of parts that make up this frame perimeter (which means articulation in the x-y).

The bumper zone is the constraint in the z (vertical) direction. It is removed in the hab zone, allowing for bumper movement in the z as long as it is connected to the original frame perimeter structure (per R26).

I stayed away from law for a reason, as I’m not inclined to parse words, but I do believe such an arguement can be made.


I see where you’re confused.
As a parallel-ish scenario: Stingers, in 2012, dropped below the chassis for bridge manipulation while on it, without violating the rules of that year. I’m not 100% on those rules so we’ll kind of ignore the details.

I would generally rule that the frame cannot be articulated, BUT the rest of the robot can be. In other words, let the Frame Perimeter be the “reference frame” and articulate other parts of the robot. It’s confusing…


This is the key point.

The FRAME PERIMETER need to be fixed and the BUMPERS must be fixed relative to the FRAME PERIMETER. Outside of the FAB ZONE the BUMPERS must stay in the BUMPER ZONE, which is defined by R25, with the “normal” projecting rule (the virtual plane and transpose bit).

However, in the FAB ZONE, there is no BUMPER ZONE, and you can have mechanisms that allow you to raise your BUMPERS out of the BUMPER ZONE. For example you could design a chassis that allowed to you lower the drivetrain, or extend down a secondary drive system. Nothing requires the wheels to be fixed relative to the FRAME PERIMETER (the normal KITBOT frame has them fixed, but the rules do not require you to use this chassis). Picture a secondary system that lifts the ROBOT such that the primary drive wheels are at the L2 or L3 height, such that you could just drive on. This is legal this year.


Q104 on the Q&A specifically addresses this question.

The answer restates R26, followed by…
“This does not prevent them from moving relative to what a team may consider “chassis” if that element does not actually make up the frame perimeter.”

The “them” is the bumper - frame perimeter assembly.

Suggest reading the actual Q&A for 100% assurance.


I read “them” as the frame perimeter/bumper combination. As the two are rigidly connected per R31g, the two interpretations are functionally equivalent.

The bottom line is that the frame perimeter/bumper union does not have to stay in the same spot relative to the bulk of the robot; it just can’t articulate within itself. For example, if (as many teams do), you build a west coast drive chassis, and put a “ring” of 1" square tubing above the wheels to support the bumpers, that ring of tubing is the frame perimeter. You are not legally required to rigidly mount that ring to the chassis; when in the HAB zone, it could swing up on a hinge or even get launched and be attached by a piece of string if the whole robot stays within a 30" umbrella around the frame perimeter as it is oriented throughout the launch and landing.


Sorry, yes, the bumper frame perimeter unit. I have edited my post.

As a public service announcement… please always go to the source. Do not read forums for rule interpretations!