Bumper Frames - Are They Legal?

Obviously this comes with the caveat that of course we don’t officially know next years rules, but this is assuming robots will be required to have bumpers, and the rules will be generally the same as the past few seasons.

Are bumper frames legal? I have had conversations with numerous people over the years about this and have heard both sides argued. Despite the pages of bumper rules in the robot section every year, it is obviously still not clear enough what is and isn’t legal for bumpers, and specifically their frames or their mounting methods for some.

I have created some basic graphics below to show some different examples of bumper frames, just to cover some of the most common debated parts. I have numbered 1, 2, 3, and ask you to say whether you think each picture is legal or illegal, and explain why.

In the pictures below, the grey area represents a generic WCD frame jsut for an example. For the sake of this conversation, all of the frame parts of the bumper rules are legal (no gaps bigger than 8", blah blah blah, the robot frame is not the focus of this post.)

The blue area represents the bumpers itself (the 3/4" wood, the pool noodles, and the fabric).

The transparent red areas represent the hypothetical bumper frame possibilities. This is what this discussion is about.

If you have any actual examples that are similar to any of the pictures below, I would love to see them and hear whether they were considered legal or not at the events it was competed at with. I have seen real versions of all three of the below examples before and seen them be decided legal and illegal in the past.

LRI’s opinions and feedback would also be super welcome of course, as you all are generally the one’s deciding what is and is not legal to play with.

If you have other bumper frame setups that you are unsure about the legality of, make a similar drawing to the one posted and we can all discuss yours as well.

Let the debate commence!

1: Legal
2: Not legal
3: Maybe legal, depends on the tabs and my memory of the rules

I think this is something that is heavily dependent on the LRI.

Two LRIs had zero issue with our bumpers being backed with a 1/8th of aluminum since it was a two piece set, and the wood would not be strong enough to hold it together.
Another LRI nearly failed us for the exact same setup, with zero changes citing “unnecessary weight additions”.

We also use a frame/bracket system to hold our bumpers on, similar to the first image but with tabs, and not all the way around. (See this image: https://i.imgur.com/3WpSARR.png)

Wait, why isn’t 2 legal? The only rules for bumper frames that I see are 1) that they don’t extend more than 1" across the plywood towards the fabric, and 2) the total bumper assembly doesn’t weigh more than whatever.

I agree with RoboChair and pretty sure we’ve done both 1 & 3 or at least something similar to 3 with no issues.

Edit: If 2 is legal I feel like it’s not in the “spirit of the rules” kind of thing and I doubt any LRI we’ve dealt with would let that pass.

Can you expand on your reasoning why the first is legal but the second is not?

Assume all widths of the red areas are ~1". Height does not matter for this discussion (everything is within the 5" bumper height range).

Often times with the game rules and referees, people are upset about how subjective some rules referees have to judge are, and often times many people (myself included) stress that the less subjective calls referee’s have to make the better. Of course, with the game rules there will always have to be some subjective calls.

Aren’t these same type of subjective decisions LRI’s seem to (have to?) make something that is not ideal and should be avoided? is there a reason some of the robot rules (bumper specifically) are [treated] as ambiguous as they are?

I think the question should be how are they illegal, not are they legal.

In my opinion none of these are illegal based on 2018 bumper rules. The relevant rule is R30B and provided none of these extend more then 1" beyond the frame perimeter, which they do not appear to, then they are not illegal.


Assuming I’m understanding the drawings correctly, I would say yes, yes and maybe.

  1. This is a very common practice. A piece of angle (or sometimes C channel) is bolted to the bumper top and bottom, allowing it to sandwich your frame member and a bolt or pin be dropped through to secure it.

  2. Similar to 1. There is no rule I’ve seen that restricts how far into the robot your attachment system can extend. Note, however, that at the extreme pictured, such internal supports may introduce difficulties with putting the bumpers on and off (2018 rule R26).

  3. I could be convinced, but it’s hard to tell from the picture how much support is really there to prevent vertical movement of the bumpers. That’s really my only caveat with this picture - I would want to make sure that the bumpers aren’t going to come off when your drive team is in a rush and tries to lift the robot by the bumper plywood instead of the frame (regardless of any other robot lifting aids… even teams with great handles or removable lifting hooks sometimes don’t use them). In this case, the red parts act as fabric clamps (2018 rule R30-E) in addition to the mounting structure.

Note that none of these pictures adequately shows the full mounting system (bolts, pins, etc) that ensures the bumpers won’t move during game play. We also can’t determine the bumper weight (which includes the mounting hardware!). The more elaborate the mounting system, the heavier the bumpers are going to be. The picture is not the implementation, and it’s quite possible that something in the specific implementation would cause concern for an inspector and need to be fixed.

I would say the following figure from last year’s manual (and several years prior) is the main root of this conversation.

I’m really surprised by that. Bumpers need to have 2.5" of padding (of specified construction), a strong connection to the frame, and not be too heavy to convey an advantage. What spirit do the rules intend more than that?

  1. Legal
  2. Is complicated (see below)
  3. Legal

I feel like 2 is complicated because it has extra material that doesnt appear necessary. 1 and 3 primarily go around the general frame, but 2 reaches the same area and adds unnecessary addition I feel like. If you had strictly the angled parts and not the part going around the entire perimeter, I feel like you could justify that as mounting if that makes sense.
That’s the impression I’ve gotten atleast just from previous discussions, events, Q & A, etc.

Judging from the GDCs Q&A responses, they read the rules pretty literally. For example aluminum angle in the corners and to capture the fabric is legal. Steel doing the same thing is not. If your frame is part of an “robust bumper attachment” and doesn’t violate other robot rules, I would argue all the way to Al that is legal. A frame by itself is not because frames are not listed as a bumper component.

Why does the red angled structure in my second example not count towards the 1" limit of “hard parts”? Also is this 1" limit fixed to where it is shown in the figure? Or is it free to float horizontally from overlapping the plywood to not at all?

Again, I think everyone can probably start to tell my point is about the horizontal area limitations of bumper structure, this conversation is assuming weight is legal, the robot frame support is legal, the fastening is secure, etc. etc.

Worst case IMHO is that the frames would count to the weight of the robot.

What about this photo? I assume it is there to clarify and visually represent all the rules in R30.

Once again I will reiterate that I think people should be operating with a mentality of tell me how it is illegal not is it legal.

The image is clarification of the rules. R30-B states:

hard BUMPER parts allowed per R30-A, R30-E, R30-F, and R30-G must not extend more than 1 in. (~25 mm) beyond the FRAME PERIMETER with the exception of minor protrusions such as bolt heads, fastener ends, rivets, etc. (Figure 8-4 and Figure 8-6).

The red portion is not extending beyond the frame perimeter - it is contained entirely within it. So that rule doesn’t come into play at all. the rule does matter for #3, but my assumption on that one, based on the relative dimensions in the image, is that the red portion does not extend more than 1" past the frame perimeter in any direction.

1 Like

The 1" stops once you’ve hit the frame perimeter that backs the bumper. This disallows from attaching a 2" spacer to the bumper between the backing and the frame perimeter making your robot artificially large as that would be included in the 1".

I will happily accept this explanation.

Can we at least agree that the way the image went about showing the 1" restriction for going past the frame perimeter is possibly misleading? I mean if that is what the picture is supposed to be demonstrating, then it is a little odd that it does not even define what/where the frame perimeter is in the picture.

To me, it looks like that 1" range displayed is partially inside and outside the frame perimeter, which then makes you wonder if the 1" range applies to any “hard parts” used on the bumper, especially considering it says “1” limit for hard parts."

If what you are saying is the true correct interpretation of how FIRST wants the rules to be, I propose they at least modify this image to demonstrate their point better, and I would personally like to see an extra clarification that there is no limit to how far within the frame perimeter and “hard parts” on the bumper can extend.

I’m only driving this point home, because I have specifically seen bumpers in the past that look like #2 a number of times, with emphatic rulings of both legal and illegal, with this specific rule and figure cited. If LRI’s are not agreeing on how to rule on this, and there are different long time mentors from quality teams who differ on their interpretations of this rule, then clearly the manual is not doing a good enough job.

Figure 8-4 provides specific guidance on R30-B, and includes the robot frame in the picture. Figure 8-6 shows how items like the attachment system and clamping angle can impact the 1" determination.

If that picture is being used to say that your image #2 is illegal, then I would point out that the attachment system in that picture extends into the robot beyond the indicated 1" limit, and shows no dimensional limit for that attachment system.

oh boy! My chance to be the Q&A answer provider! Here’s my thoughts:

  1. We cannot rule absolutely on hypothetical ROBOT designs, and the final decision as to legality of a particular ROBOT lies with the Lead ROBOT Inspector (LRI) at each event.

  2. We cannot rule absolutely on hypothetical ROBOT designs, and the final decision as to legality of a particular ROBOT lies with the Lead ROBOT Inspector (LRI) at each event.

  3. We cannot rule absolutely on hypothetical ROBOT designs, and the final decision as to legality of a particular ROBOT lies with the Lead ROBOT Inspector (LRI) at each event.

More seriously, in my opinion:

  1. Legal
  2. Illegal
  3. Legal

I think that your interpretation of the three scenarios depends on your interpretation of the word “beyond” in the context of 2018’s R30-B (anyone have a dictionary?):

hard BUMPER parts must not extend more than 1 in. (~25 mm) beyond the FRAME PERIMETER

Since the GDC doesn’t specify a direction that “beyond” refers to, I choose to interpret it as referring to both inside & outside the frame perimeter.

I think this interpretation is broad enough not to severely limit teams, without allowing more ridiculous abuses of bumper rules. If R30-B only refers to the space outside of the frame perimeter, it quickly becomes either:

  1. extremely difficult to attach bumpers to a robot
  2. bumpers being used as structural pieces of robots

I’d like to be somewhere between the above two scenarios.