Metal backed bumpers

[bhughes]

Per R24-A, is it legal to also have a metal backing along with wood, so long as it abides by R24-A and R29-B?

Waiting to be able to ask question on Q&A, maybe someone who does robot inspections can give some insight.

[dtengineering]

Do you see a metal backing in figure 4-4?

Neither do I. Bumpers MUST be constructed using the cross-section shown in figure 4-4.

The structure referred to in R29 is the robot structure. So you can put whatever kind of “metal backing” behind the bumper you want… but that metal backing is part of the robot, is included in the robot frame perimeter measurement, and in the robot weight. It’s NOT part of the bumper.

Jason

[Tristan_Lall]

The structure referred to in R29 is the robot structure. So you can put whatever kind of “metal backing” behind the bumper you want… but that metal backing is part of the robot, is included in the robot frame perimeter measurement, and in the robot weight. It’s NOT part of the bumper.

There’s a potential loophole if the backing is part of the fastening system.

[Bumpers] must attach to the FRAME PERIMETER of the ROBOT with a rigid fastening system to form a tight, robust connection to the main structure/frame (e.g. not attached with hook-and-loop or tie-wraps). The attachment system must be designed to withstand vigorous game play. All removable fasteners (e.g. bolts, locking pins, pip-pins, etc.) will be considered part of the BUMPERS.

I don’t know if the proposed metal pieces satisfy this definition (and all of the other rules dealing with bumpers).

[45Auto]

Inspectors are being pretty strict on the bumpers and Fig 4-4, apparently someone tried to add extra weight by sticking some steel rod down the middle of their pool noodles. See post #37 on the inspection thread:

Al's Annual Inspection Thread 2013

They’ll be looking pretty close at your “metal backing”.

[IKE]

As others have said, it really depends on it is used. You are allowed to use metal to help capture the fabric. You are allowed to use metal “brackets”. As inspectors, we do not have stringent guidelines on what consitutes a “bracket”. If you would like me to take a look at something, send me an email with a picture and I can give you a better assessment.

[lemiant]

I have asked a Q & A about this:
https://frc-qa.usfirst.org/Question/595/are-there-any-limits-to-the-weight-of-the-rigid-fastening-system-as-long-as-the-total-20lb-weight-limit-per-r23-and-the-1-hard-parts-limit-per-r24-e-are-obeyed-in-short-can-large-steel-compon

[androb4]

We have a sheet metal bent in a “C” that is the backing for wood and fabric. It fits inside the the limit for hard/solid materials.

So as long as it fits inside that limit and the entire bumper assembly does not exceed 20lbs, you should be fine.

[thefro526]

As others have said, it really depends on it is used. You are allowed to use metal to help capture the fabric. You are allowed to use metal “brackets”. As inspectors, we do not have stringent guidelines on what consitutes a “bracket”. If you would like me to take a look at something, send me an email with a picture and I can give you a better assessment.

Just to elaborate on what IKE was saying, here’s R23:

Each set of BUMPERS (including any fasteners and/or structures that attach them to the ROBOT) must weigh no more than 20 lbs.

If a multi-part attachment system is utilized (e.g. interlocking brackets on the ROBOT and the BUMPER), then the elements permanently attached to the ROBOT will be considered part of the ROBOT, and the elements attached to the BUMPERS will be considered part of the BUMPER. Each element must satisfy all applicable rules for the relevant system.

As I see it, there’s no reason that you couldn’t run a steel bracket the length of the bumper. Think something like a steel angle, connected to the bumpers on one leg, with holes to connect to the chassis on the other. It’s a legitimate attachment method, just a bit (a lot) overkill. I doubt anyone will hassle you about it if your bumpers are under 20lbs and don’t violate any other rules.