Bumper Wood

Is it legal to cut off a piece of the bumper wood since it is hitting our robot’s intake when the intake comes down? or is it illegal? I need some clarification on this. Thank you.

Specifics? Drawings? Anything?

It depends where you’re cutting from.

You need at least 8 inches of bumper from the corners of your robot, if the part hits the bumper after that point, you are okay to not have bumper for that area.

It is just a v shape cut on the top on the wood, measure about like an inch width, so like a triangle. There’s two of them so when our intake comes down to take in the ball it doesn’t hit the bumper. The bumper wood interferes with our intake and how it is supposed to take in the ball.

Based on your description, it is very likely that modification is illegal. Additional details, measurements, pictures, etc would be helpful to give better advice.

XX,
A legal bumper is one in which…
R21
BUMPERS must be constructed as follows (see Figure 4-8):
A. be backed by ¾ in. (nominal) thick by 5 in. (± ½ in) tall plywood or solid, robust wood.

Al the full rule reads:

So the question is: If it is a small access hole (for the intake) and does not affect structural integrity, is it legal?

No. The access holes are for bolt heads so that the bumper will fit against the frame.

Steve’s interpretation is the one used in inspection. A notch does not meet that criteria.

Is that anywhere in the rules, or just interpretation?

Realize that you are saying that a 5" wide piece of wood reduced to 4" at one (or two) locations doesn’t affect structural integrity. How does that work?

The access holes for fasteners do effect structural integrity of the wood, but overall enhance the robutsness of the bumper system by getting more backing contact with the frame.

See the 2014 FRC Game Manual, Section 5 The Tournament, part 5.5.2: At each event, the Lead Robot Inspector (LRI) has final authority on the legality of any …

LRIs do not invent rules interpretations on the fly, they base them on training. That training comes from FIRST HQ, through the Chief Robot Inspector – that would be Al.

Daniel,
That is the standard interpretation based on past practice. It has always been used to allow a tight fit to the robot frame. (although in some years it was not allowed)

There was a team at Arkansas who asked the very same question. They wanted to make a notch in the bumper to accommodate their intake mechanism because their intake was designed without the bumpers. Andy, our LRI, said “Absolutely not.” Their intake was unfortunately too wide to just “not have bumpers” where the intake and robot body met; they didn’t have the 8" on each corner clearance.

You aren’t REQUIRED to have bumpers that cover EVERY inch of the perimeter of your robot - depending on the design of your intake along with the rest of your frame perimeter, would it be possible to just NOT have bumpers at your intake point? Is there enough space for bumpers 8" on each side of the corners of your robot?

-Danny

R21.

Based on LRI training, the provisions in part A (allowing small clearance pockets and/or access holes) are there to facilitate meeting part F (rigid fastening system to form a tight, robust connection to the main structure/frame).

We’re looking for something that matches the provided bumper cross section (figure 4-8) as closely as possible for its entire length, with exceptions made to allow for tight, robust mounting. The bumper rules don’t take into account robot mechanisms - your mechanisms need to be designed to take into account bumpers.

A lot of teams (most teams, probably) leave bumpers until the very end. They spend 6 weeks working on a beautiful robot, then give a freshman a single night to come up with suitable bumpers. Some years, it doesn’t matter as it’s relatively easy to manipulate a game piece over, under, or around the bumpers. Other years, like this year, the bumpers really play a big role in game piece manipulation for a lot of teams. Having the bumpers in place changes the geometry and motion required for the ball to enter the robot. Personally, I’m a big fan of making some bumpers as soon as you have a frame and strapping them in place. It’ll help you remember to include all of the constraints when designing your manipulators.

https://mail.google.com/mail/u/0/?ui=2&ik=ab0b6598f4&view=fimg&th=144b71e2bc7f7322&attid=0.1&disp=inline&safe=1&attbid=ANGjdJ-G99sHQY6Yt2L4jvvChkB_OeENpqrxRWZjCrMCGHn5yt5RRMelGjME9wkRUV83AUeKS2g5qvvpA--JrEniHwW9zPgkYeENJNyrPxIfZRkb1qZizr2mzCAhrUg&ats=1394641662857&rm=144b71e2bc7f7322&zw&sz=w1254-h520

So is this legal if there is this small clearance is on the top?

From your link:

…Forbidden That’s all we know.

But probably not. Remember Q&A initially said that since tape is not in the profile for bumpers, you could not use tape. Notches are definitely not there. You might get it through your inspectors. But if they say no & get pushed, it is eventually go to Al & you know his answer

I really hate to discourage you but I agree with most the other comments. Even not doing things like this we have occasionally had variations in some details of interpretation. Before my time involved with FIRST, the team got through an entire regional and then qualifications at another regional only to be asked to change something for finals when re-inspected.

I have always interpreted the spirit of the rule to provide for some minimum standard protection for your robot that is wholly independent of aiding function of the robot. In this case, not a true “aide” but certainly an accommodation.

Having said that, read the rules carefully. Maybe you can design around the 8" constraint or maybe consider the tolerances on cutting the wood.

One other clarification that I don’t think has come up in this discussion.

If you have more than 8" of bumper (say 12" ) from the corner, the 8" minimum rule still does not allow you to notch between the 8" and 12" locations.

A bumper may cover only the minimum 8", but if its longer, all of it still has to fit the bumper rules and match the bumper cross section specifications.

The rules are pretty clear that you must use wood that is 5" x 3/4 thick. A notch that brings the wood to <5" violates the rule.

That being said, remember that the bumpers can be as low as 2" off the ground, so if the top of your bumper is > 7" from the ground perhaps you can lower it/them.

Regretfully, if your design will not function when a legal bumper is in place, you are somewhat out-of-luck, and it becomes a lesson-learned for next year: Read the rules carefully.