Q744
Q. Section R21-G, Figure 4.7, indicates a “1” limit for hard parts”. However, a 1” width limit for hard parts is not explained in the rules. We are considering permanently attaching a 1”X1” angle to the back of the bumper (aluminum angle permanently attached to the wood backing) for the purposes of attaching our bumper to the frame perimeter so that the angle can rest on top of the frame perimeter and provide a place for fastening the bumpers to the frame. In this case, the hard parts of the bumpers would be 1.75” wide (1” angle plus 0.75" wood), but the wood backing of the bumper would be tight against the frame perimeter structure. Is this permitted provided we still follow R20 and R22?
A. The 1" restriction shown in Figure 4-7 is described in R21-B and is measured from the FRAME PERIMETER outwards. There is no explicit restriction on the distance hard parts used as part of the “rigid fastening system” may extend into the FRAME PERIMETER.
It appears that Q744 enables some more ridiculous bumper designs than I have ever seen or thought of. Imagine that the fastener from Figure 4-7: BUMPER Vertical Cross Section extended 25 inches to the FRAME PERIMETER on the opposite side of the robot, potentially acting as a cross brace for the robot.
Do you think a design like this is…
A) Illegal, this is an incorrect interpretation of the rules.
B) Legal but a bad idea, may need to explain the legality to an Inspector.
C) Legal, but likely to cause a change in the rules to prevent it.
D) Legal, and a great idea
And here’s why: Your bumpers must be easily removable for inspection. 2 people in under 5 minutes is the guideline.
Can your two people remove all the fasteners from your robot and get the bumpers off in 5 minutes if you put them all the way across? Particularly if they’re also being used for cross-bracing, and aren’t just running through clearance holes? Right.
Now, I know what you’re thinking: “I only have to remove my bumpers once, and I’m good! I can live with that!” Wrong. All robots at the event are subject to reinspection at any time. More particularly if they’re in decent range of a chance at eliminations, and it’s Saturday morning, or if they’ve made changes. And as part of that reinspection, the weighing of the robot may be required. Just as a note, bumpers don’t count towards robot weight. Guess what you now have to take off and put back on, and maybe you have a match in 10 minutes and are being called to queue up?
tl;dr: legal, sure, but it could bite you pretty good.
I mean there are some easy ways that your bumpers could provide your robot with rigidity using this method that don’t require hella fasteners.
I think this is an interesting catch, and I’d love to see teams exploit it. There could be some really cool bumper designs using cross-bracing in the bumpers to make the frame stronger for no weight cost on the main bot.
I don’t think FIRST would change this to make it illegal, but I could be wrong.
I don’t know how they do elims reinspection (or any reinspection for that matter), at your event, but at mine I try not to hassle the team’s by making them take their bumpers off again, unless we really, really have to. The only situation it’s really needed is if their robot weighed in close to the limit, and their new weight (subtracting out the recorded weight of the bumpers, I know, subtraction is hard!) indicates they might have gone over during the event.
All that said, sticking to the guideline outlined in the rules is important, because the odd situation does come up where you need to take off your bumpers and are pressed for time. But relatively few teams really fall within the guideline, unfortunately.
I’m glad to see this Q&A give the response I expected. Believe it or not, this exact same topic came up on Friday when I was working with a rookie team. We went over the rules and came to the same conclusion - there’s nothing wrong with having a bumper support span the entire robot, right down the middle. For their plans it’s fairly easy, and can be slipped on and bolted quickly.
I see the cross-brace bumper as legal if they are also used to attach the bumper to the robot, but likely to generate a rule change, as bumpers are supposed to protect the robot, not add to its functionality. Also, watch the 20 pound weight limit for bumpers (R20).
Says who? Teams have been using bumpers to increase the structural integrity of their robots for years. Please point out where this is even indicated, don’t just throw out what you think.
I have observed “similar” strategies in the past. Just remember, it hinges on how your team answers:
Is this part of the Robot, or a bumper bracket/attachment?
Then makes sure the team going through inspection has it weighed that way as well. I have observed some very elaborate brackets in the past.
There are definitely ways to think about bumpers in the non-mainstream way. Just Think PINK (233).
PINK had a hard time convincing inspectors their bumpers were legit in 2014. It was easily one of the best and most robust bumper setups I’ve ever seen: 1x1" thin wall welded as a rectangle around the inside of their bumpers. The outer edge of the 1x1 tubing defined their frame perimeter, and attached to sturdy 2x1 mounts in their WCD setup. It was very robust, and very easy to change bumpers. Yet the tubing was, more or less, permanently mounted to the bumpers.
The ‘quick replacement’ method had them replace the frame and bumpers together, so there were two sets of frames (1 per bumper set). They weren’t able to demonstrate the frame could be detached from the bumper though, so it was deemed illegal at the MD regional since the frame itself defined the robot frame perimeter (and the bumper parts are not what define that perimeter). They ‘fixed’ it using zip ties to define something or other.
The 2016 legal way to do this setup would be to detach the 1x1 tubing from the bumpers and attach one of the rectangles to the robot to define the frame perimeter. Then for inspection the other frame would also be weighed with the robot as ‘multiple configurations’. Then the kids demonstrate attachment of the bumpers to the frame rectangle during inspection in 5 minutes. After that it doesn’t matter how the team decides to switch bumpers.
It was a great setup that I wished we could have replicated this year, but for the very large wheels…
Just to clarify, the problem with PINK’s setup was not that they used substantial structural members on their bumpers, but that their frame perimeter was determined by structure permanently attached to the bumpers rather than the frame. If you do frames the way 33 does, and have flanges that define the frame perimeter (meet flush against the plywood more or less) but structure that sticks out from the bumpers but goes within the frame perimeter, you’re completely legal.
This year is a tough year for structural bumpers though, since they sit mostly above the driveline.
In general, the bumper rules (and the Q&A clarifications) fall into two categories: those that ensure the bumpers protect the robot (and other robots, field elements, etc), and those that restrict the geometry and composition of the bumper so that it is not used to increase the robot functionality.
And OBTW, I posted this in response to (emphasis mine):
The quote you just supplied only supports the first half of your statement. The second half of your statement isn’t really supported by the rules anywhere (other than overall bumper weight restrictions, restrictions on the functional outer part of the bumper, etc). It is imperative that we do not read intent into rules where nothing written into the rule supports that interpretation - nothing in the rules prohibits bumpers from being any particular amount of structural.
Why is the presumed intent that bumpers shouldn’t increase robot functionality. That’s just good planning. Ex: 2014 our intake flat-out didn’t work without bumpers. It was planned that way. We also used the bumpers to align the robot to it’s shooting spot. In both cases that robot would have worked differently without the bumpers and they enhanced the functionality. Should they have been illegal?
I did not say that the rules prohibit the bumpers from being structural. I said that the cross-brace was legal but that I thought it would be likely to cause a rule change. The only way to make the call on whether a rules change would result is to read intent into the rules.
Despite the last paragraph of 1.4 of the game rules, I find that when we try to understand the intent of the rules, we are less likely to run afoul of them. When we read them too literally, we are more likely to be disappointed. Edit: If someone hadn’t tried to read intent into the rules, cheese caking would be illegal.
By your interpretation of the intent of the rules all over the bumper intakes in 2012 and this year would be breaking the intent of the bumper rules because they are increasing the functionality of the robot.
Also, by increasing the structural integrity of the bumpers am I not also increasing the protection that they provide to my robot? Therefor the additions still fall into your definition of the intent of bumpers “the bumpers protect the robot (and other robots, field elements, etc)”
If the bumpers as built to protect also assist a function, that’s certainly OK. If there’s a part of the bumper that does not protect or attach, but ONLY serves another function, there are no rules against it, but its use may generate a rule change. It’s similar to G11 this year: if you’re playing the game and a by-product is a violation of a rule on your opponent’s part, foul on him (her); if your action is (judged to have been) performed solely to draw the foul, foul on you.
This kind of structural bumper has been legal for years, and it would be very difficult to make this illegal as it would require an inspector to judge intent. You would essentially be saying there is a limit to how strong or rigid a bumper assembly could be, which is a pretty terrible precedent to set.
Take a look at 118’s 2010 robot or 33’s 2013 robot for examples of how the bumper is built “extra-robust” and then that robustness is taken advantage of by requiring less in the drivetrain. We certainly don’t want to write rules demanding teams build drive frames to a certain robustness, and we don’t want rules saying “if your bumper is too strong, you have to weaken it”, so these rules are likely here to stay. The 20 pound bumper weight limit, along with practicality concerns with being able to remove the entire bumper assembly, will constrain these designs to a reasonable level.
