2024 rules state that the ends of each bumper wood segment must be backed by some solid portion of the frame perimeter, with an allowed 1/4" gap. I believe that makes this design illegal:
In this design, there are a few 1/4" aluminum Citrus Mounts attached to the driverails, but most of the 1/4" gap is filled with 6mm polycarbonate pieces attached to the bumper wood (not the driverails).
Am I correct that this is currently illegal? Should this be legal in 2025? That is, is there a structural reason this is a problem? Attaching gap-fillers to the bumper wood would solve some of the bumper attachment problems weâve had in the past.
Thereâs also a length requirement for any gap over 1/4" wide, specifically <8" (if I correctly recall the most current number).
But yeah, adding gap fillers is not uncommon, particularly if you have frame perimeter to spare. Most teams will add them to the robot frame rather than the bumpers, though.
As far as the rules are concerned, your bumpers are fully a part of your robot (just one that may be switched out in between matches and has some extra rules significance), so as long as everything is fastened together I see no reason why it wouldnât count as part of your frame perimeter. You may have a bit of trouble at inspection though, and I personally wouldnât run the risk of having an overly strict inspector and losing out on valuable practice match time.
Fundamental misunderstanding of Frame Perimeter on your part, Iâm afraid.
Frame Perimeter is, by definition, part of the Robot, not the Bumpers. If youâd like to debate that, you can show me from the rules where Frame Perimeter is defined by the Bumpers.
As such, having that shim on the back of the bumpers cannot count for Frame Perimeter in any way, shape, or form. See previous paragraph. What it CAN count for is mounting hardware. (Now, do I agree that it should be âmounting hardwareâ? No. My team mounted our shims on the frame, because a) we had Frame Perimeter length available and b) we didnât want to take gambles with the bumper rules. But I can see the argument for it being mounting hardware.)
And I think thatâs how this one would have gotten through inspectionâthe shims are being defined as mounting hardware for the bumpers. Itâs a bit of a out-of-the-box application of the rule, to be sure, and I wouldnât try to make that argument if I had enough Frame Perimeter length available, but it does count. Doesnât mean that I wouldnât be asking the LRI (or, better yet, Q&A) right up front if it would be an issue, though.
My concern per the old rules with this design is that between 3/4" of wood, and 1/4" of planned gap/filler, youâve left yourself exactly zero tolerance for fabrication errors or additional unplanned gap, and will be heavily at the mercy of picky inspectors.
There is no structural reason that this would be a bad idea, but there are potential rules reasons it could be. Eliminating dumb semantic requirements like treating gap fillers like this as dimensionally problematic only on the bumper, and stopping the rules making fixes like this needlessly difficult and in a grey area that a picky inspector could take issue with, was a prime goal of the bumper task force. Expect to see improvements in these areas when the rules come out. As one example per the blog post, now youâre going to have an inch and a half to work with.
I think Ericâs analysis is right. The relevant sentence in R410 is:
To be considered supported, a minimum of ½ in. (~13 mm) at each end of each BUMPER wood segment must be backed by the FRAME PERIMETER (â¤Âź in. gap, ~6mm).
Based on that, I think you are ok under 2024 rules. Your shims are part of the bumpers so arguably they donât count as filling the gap between the wood segment and the frame, but as long as that gap is actually 1/4", I believe you are legal.
2025 rules are not released and may not be written yet, but they are changing from the 2024 rules including allowing more flexibility in backing material and mounting solutions, so I wouldnât be surprised by less restrictive gap rules.
Let me clear up a few things. Hereâs a top down view. The yellow line in the bottom figure is the FRAME PERIMETER. There is a total of 3/8" between the driverails and the bumper wood. So there is still a 1/8" gap all around for ease of installation. There are only 1-2" inches between any bumper mount or gap filler polycarb, so it is âsupportedâ almost everywhere.
My question is mainly about the polycarb in the corners. Normally this is where our team would add some weak 3D printed swerve-corner that would come out to the FRAME PERIMETER. That seems to be what the 2024 rules require. I think that adding/attaching some material to the bumper itself in this area would be a better solution, though illegal under the current rules.
This design might also run afoul of the 8" gap rule since there is >8" between bumper mounts along the FRAME PERIMETER, even though that gap is filled with polycarb.
I agree with Joe that the rules regarding the FRAME PERIMETER and gap fillers have semantic issues. Iâm hoping the flexibility in the new rules allow gaps to be filled on the bumper side.
Okay, so that is not actually your frame perimeter, and Iâd say that is probably not legal. Those weak 3d prints donât come out to the frame perimeter, they define it. There are no limits on the length of a 1/4" gap, essentially a gap less than 1/4" is not considered a gap. Iâd guess that the shims would be fine under the under 2025 rules but we will see.
Unless there is a weight limit problem, just move the shims to the robot and youâd be clearly fine.
Ah, good point about the swerve-corner 3D prints defining the frame perimeter. They were also necessary to ensure we were âsupportingâ the ends of the bumper wood.
The current rules also mention âbacking material,â which isnât defined. It must include the bumper wood, but it is unclear if it would also include shims attached to the bumper wood.
I really hope this rule is rewritten. That it only specifies a single dimension has always bugged me. If I support 1/2" by 1/8" have I met the rule? Or is attempting to implicitly say 1/2" x X" where X is the full height of the wood segment? (in which case most robots would be in violation). And why is it apparently so critical that it be the last 1/2" of the segment? If the width of the supported area was 0.25"âŚ0.75" (instead of 0"âŚ0.5") from the end of the segment, the change in effectiveness would effectively be zero.
