Yet another bumper thread

[Kevin Sevcik]

There's another bumper problem with the kit chassis while we're on the subject. In the short and wide configuration, you end up with a gap in either two or four corners of the frame. (See attached image) This leaves you with a ~1.5" diagonal on the bumper perimeter that cannot be protected by a bumper. Which means it's impossible to make the short and wide kit frame legal unless you build it 35.5" wide, or know to ignore the instructions, build it 36.5" wide and cut the outside bars long. Or other complicated things that rookies aren't going to know about.

I've posed this to the GDC, and I'm desperately hoping that they rule it legal to wrap the bumpers around this corner or extend them an extra bit to cover it. If they decide that teams will just have to modify the frames to make it possible to legally mount bumpers... Then I'm going to be somewhat annoyed with them and the prospect of helping 50% of the rookies at our regional get their bumpers legal.

[Joe Ross]

Originally Posted by Kevin Sevcik

There's another bumper problem with the kit chassis while we're on the subject. In the short and wide configuration, you end up with a gap in either two or four corners of the frame. (See attached image) This leaves you with a ~1.5" diagonal on the bumper perimeter that cannot be protected by a bumper. Which means it's impossible to make the short and wide kit frame legal unless you build it 35.5" wide, or know to ignore the instructions, build it 36.5" wide and cut the outside bars long. Or other complicated things that rookies aren't going to know about.

I've posed this to the GDC, and I'm desperately hoping that they rule it legal to wrap the bumpers around this corner or extend them an extra bit to cover it. If they decide that teams will just have to modify the frames to make it possible to legally mount bumpers... Then I'm going to be somewhat annoyed with them and the prospect of helping 50% of the rookies at our regional get their bumpers legal.

Maybe I'm missing something, but isn't it already allowed to extend the soft parts of the bumpers? See <R08-J> and illustrated in figures 8-2 and 8-4.

[EricH]

Originally Posted by Joe Ross

Maybe I'm missing something, but isn't it already allowed to extend the soft parts of the bumpers? See <R08-J> and illustrated in figures 8-2 and 8-4?

And Q&A has clarified that, for the 6"-max robot length requirement, you have to have the backing 6" long, but you can have soft parts extending beyond said length that are part of the bumpers but not counted in the length. http://forums.usfirst.org/showthread.php?t=11316

So you are correct.

[GaryVoshol]

If you want to follow the letter of the law, by building the kit frame as illustrated in the picture, you have actually created a very short 45-degree angled face to your BUMPER PERIMETER - somewhere in the neighborhood of 1.4 inches. This face has no frame backing to attach the BUMPER to. Never mind that you can't attach a 6" bumper to a 1.4" space.

Somebody please ask Q&A how to BUMPERize this corner. Following instructions given with kit parts should not lead you to violating the rules.

[Gdeaver]

The kit frame can be built with out that corner gap. For other reasons we could not have that gap.

[Vikesrock]

Originally Posted by Gdeaver

The kit frame can be built with out that corner gap. For other reasons we could not have that gap.

Yes, it is possible to build the KOP chassis without the corner gap, our frame does not have this gap. However, the directions do specify this gap and I agree with Gary that providing teams with a kit that requires significant modification outside the provided directions in order to be a competition legal frame is not overly helpful to veterans and may even be detrimental to rookies.

The heads of the axle bolts I mentioned in my initial post are also visible in the picture posted by Kevin. These bolt heads are significantly thicker than the angle we would be using to clamp the fabric to the bumpers. My uneducated opinion also says that mounting the bumpers with this frame rail as the "support" and those bolt heads being the only actual contact with the plywood would cause them to be much MORE likely to break not less. A large impact occurring near one of these bolt heads would transfer the force through the small area of the head itself which would likely cause the plywood to crack wouldn't it?

Squirell, that sounds like it could be the easiest solution. Depending on what the GDC says regarding this question we will definitely look into this possible solution.

[EricH]

This year, the GDC has allowed pockets for bolts, etc.
http://forums.usfirst.org/showthread.php?t=11389

[MrForbes]

Thanks for pointing that out, Eric, it'll save us some work.

[Fe_Will]

I don't understand why so many people are complaining about the kitbot. It is not intended to be an end-all-be-all solution but a starting point so teams can get something moving. It is a good way to get programmers started early in the build season and to have a moving base to prototype pieces for game function on, I'll admit.

I feel like some people have forgotten (or don't remember) the time when kitbots didn't exist.

[MrForbes]

Originally Posted by Fe_Will

I feel like some people have forgotten (or don't remember) the time when kitbots didn't exist.

Or they weren't involved with FIRST yet.

[Tristan Lall]

Originally Posted by EricH

This year, the GDC has allowed pockets for bolts, etc.
http://forums.usfirst.org/showthread.php?t=11389

I hate to be the bearer of bad news, but if a team is trying to make their bumpers clear a protrusion on the robot, then by definition, that protrusion forms part of the perimeter. Bumpers have to follow the contours of the perimeter.

I fully support the idea of FIRST issuing a clarification on this subject. It's just that I don't think this is a good interpretation of the rules. It's particularly bad, because although the answer is technically correct (there is no such direct prohibition), the rest of the bumper rule makes this technique at best useless, and in pretty much all cases, illegal (because of the perimeter requirement in combination with the minimum bumper coverage and length).

This could be salvaged, however, by loosening the requirements a little bit: just as they stated (in a Q&A, not an update) that a little gap between the bumper and its supporting structure was (sometimes) legal, they could clarify that bumpers don't always have to follow the perimeter, in cases of small protrusions. Put these two things in an update, and everybody's interests will be satisfied. (Of course, some suitable definition of a small protrusion is necessary here, to avoid neutering the perimeter clause completely.)

I also think that it's interesting to hear that the GDC no longer feels that this will introduce undue weakness into the bumper. (This was their rationale for the 2008 prohibition on this design feature.) Do they believe that requiring a structural element to span the entire bumper alleviates this concern? I never personally felt that this was a structural issue, except in extreme cases, and I would have preferred FIRST to either define a strict requirement in the rules, or conversely, give inspectors latitude to determine what is and is not strong enough. The former has the advantage of maintaining consistency, while the latter is at least forgiving to the teams and the officials.

Incidentally, the rulings last year depended on teams reading the one or two Q&As out of hundreds that dealt with this topic, and noting that for the particular case of the 2008 bumper rule, the Q&A was clarifying an existing requirement (teams must build to the bumper specification), and not making up a new restriction (which would be dubiously valid). That's a fine point, but under last year's rules, the teams were expected to follow it.