1/2" gap in bumpers, is this acceptable?

[Foster]

We have assembled our robot bumpers on our rectangular robot. The front and back bumpers are as wide as the robot. The left and right side foam extends so that it is flush with the outside edge of the front and rear bumpers. This has created a 1/2" gap between the side bumpers and the front/rear bumpers. (Caused by the plywood backing.)

Do we have a potential problem passing inspection? We think we met the rule for complete coverage, but I don't want to be scrounging pool noodles during our Week 1 competition in Rochester.

[Peter Matteson]

This will not be acceptable at inspection.
You will have to fill that area with pool noodle to meet the rule intent.
I suggest that you cut the noodles at the end of the wood and then add a cut section of noodle there on end as the rules allow. When you re-wrap you should no-longer have gap.

[dtengineering]

Interesting question... my first response was "no way could that be a problem". From the photo the bumpers look sturdy, safe, and fully capable of fulfilling the role of being a bumper, and the 1/2" gap is insignificant to their overall purpose.

But R07-L and the related diagram 8-2, specify that the "corners must be filled".

So yeah... you could have a problem. Thanks for asking the question... we haven't built our bumpers yet, so we'll pay attention to this when we put them together this year. I don't think its likely to be a big problem from a practical point of view (I doubt many inspectors would call it... but they could), but given that you've got two weeks to get the bumpers up to spec right now, that's probably more fun than doing it in two hours on a Thursday morning.

Jason

[Chris is me]

That gap seems like the amount of space a somewhat flexible bumper could easily unintentionally leave if slightly jolted or something. Or, to be more clear, I'm pretty sure I've seen robots pass inspection without the two fabrics exactly touching all the time.

That being said, it's not too long of a fix.

[EricH]

That's... not a 1/2" gap. More like a 1"-2" gap.

I'd go with Peter's suggestion: unwrap the end, cut the noodles, and replace with a vertical section of noodle. You've got time now (and presumably some extra noodle sections laying around), so fix it now and fix it right so you don't have to fix it in a big hurry at the competition.

[Foster]

That's... not a 1/2" gap. More like a 1"-2" gap.

It's 1/2" wide gap that is 2" long.

We have oodles of noodles (oh how long have I waited to post that!) around the shop, so we'll do a quick fix and upgrade the plans for the "red" set.

Thanks to all that replied either here or via PM's.

[GaryVoshol]

You didn't follow the instructions exactly, and this is the result. (And I don't mean that to sound condescending, I'm just stating a fact.)

Originally Posted by <R07>

L. Joints between BUMPER segments and the radial projections of corners must be filled with “soft” BUMPER materials. This may be done with short pieces of vertically oriented pool noodle, by wrapping the pool noodles around the corners, or by beveling the ends between adjacent segments so they form a tight and complete protective surface (see Figure 8 – 2).

Notice the corner labeled "Not OK" in Figure 8-2. Also notice the word "filled" in the rules. I never stopped to think about this before, because the last year I actually worked with the bumpers was before the filled corner rule came into effect. My first reaction would have been, easy, just make the noodles longer and it will work. I guess you've inadvertently proved I would have been wrong. Using a 5" vertical noodle works because it naturally moves around the end of the backer board, whereas an extended horizontal noodle ends up sticking out straight.

Unfortunately I think you'll have to fix it.

Edit: You might also be able to get away with lengthening the noodles on the "butted" end to achieve full corner protection, but you take a risk of that not passing because it doesn't match one of the three ways mentioned in the rules. I think I recall a Q&A last year that said it was OK. If this is your solution, you might ask Q&A, because last year's rules don't apply to this year's game.

[Al Skierkiewicz]

Foster,
As much as I hate to go against Gary, the intent of the the bumper rule is to have no hard parts in the corners that can contact another robot. At first it would seem like this picture is a violation but I think if you hit the upper right corner of the bumpers, you would not be able to hit the hard parts of the two bumper sections nor the corner of the frame. Of particular note are these paragraphs in R07...
A. BUMPERS must provide complete protection of the entire FRAME PERIMETER of the ROBOT (i.e. BUMPERS must wrap entirely around the ROBOT). The BUMPERS must be located entirely within the BUMPER ZONE when the ROBOT is standing normally on a flat floor, and must remain there (i.e. the BUMPERS must not be articulated or designed to move outside of the BUMPER ZONE).
and
N. “Hard” parts of the BUMPER (i.e. plywood backing, fastening system, and clamping angles) may extend up to a maximum of one inch beyond the FRAME PERIMETER. “Soft” parts of the BUMPERS (i.e. pool noodles and cloth covering) may extend up to 3½ inches beyond the FRAME PERIMETER.

The only thing that appears to be a little long is the top bumper section. The hard part cannot extend past the corner of the frame by more than an inch. In this view I cannot tell whether the wrap of cloth is over a hard part or not. Touch would be the only way I could tell.

[WGRAY]

Does your plywood overlap the corner and butt your other corner, if it does you are also in violation.

[GaryVoshol]

I agree with Al, I believe the bumpers meet the intention of the rule. If you were at his event, he'd pass you (subject to the hard parts, which to me looks like you might be OK, but like Al I'd have to feel it). But what will the inspector at your event say? Do you want to risk it?

[sanddrag]

What I'm concerned about is there is a segment of bumper left flapping in the breeze. This could potentially become snagged on something. I hate to say it, but legal or not, I would not want to compete with a bumper quite like this. You have time, go ahead and redo it a bit.

[Foster]

What I'm concerned about is there is a segment of bumper left flapping in the breeze.

There isn't a segment "flapping". The part that is sticking out is the two 2" pool noodles wrapped in fabric.

We have noodle bits cut to fill in the gap and our Master Bumper Builder will do the quick fix this weekend.

Thanks again for all the input!

[mac]

Good evening, As an inspector. No. You must over lap with noodles. Picture in
rules is good.

Mentor Mac
Inspecting at DC and Baltimore
Thomas(just give me a crabcake)
McCubbin

[travis]

Sit around the inspector area and find the guy that is using sound judgement, letting stuff like that slide, and then take your robot to him. If you can kick a bumper in all locations with a size 12 hiking boot, it should pass. That's the idear behind all those rules anyhoo.

Back in the flag pole days I sent our poor overworked teacher out for some 1/2" PVC. She came back with CPVC. Well I said, any body with 1E11 brain cells to rub together knows that in every conceiveable way, CPVC is better than PVC and it would take a draconian, kitten-kicking, monster to tell these little puppy dog eyed kids, at 7:59pm on thursday, that he would not approve their robot with a CVPC pipe. If I was not so gracious, I would have let my feelings be known in no uncertain terms.

[vivek16]

Travis, while I couldn't agree with your opinion more, I think that the stickler inspectors are pretty representative of the "real world" of engineering where constraints must be followed to the defined tolerance. Since FIRST doesn't allow in the rules for the bumpers to be spaced apart a little, aren't we cheating our kids out of part of this competition which is meant to be a microcosm of the real world?

I've reffed lego league before and while it sucks to have to be the one to tell a kid that their creation isn't legal (even if the rule is poorly stated), it's part of the program. There's some pretty brilliant minds at work in the GDC and while they do slip up every now and then, they usually have a pretty good reason for some of the more annoying rules.

thanks, Vivek