Bumper bracket and weight considerations

[MrForbes]

Interesting point Wayne...I don't quite agree that the bumpers will be overweight if built to the specs, since one of the specs is that they will not weigh more than 15 lbs (please pardon they lawyerspeak). Ours weighed about 12 lbs and went all the way around the robot, which was only 26 x 36", and we used heavy attaching nuts/bolts, and no aluminum angle. I did not find a size specification for the aluminum angle, but I think that if we had used 1/2" x 1/16" angle it might have met weight. I can imagine that it would be very easy to make the bumpers overweight if you were to make them as large as possible and use the angle, or if they were a bit smaller but used more substantial angle.

Overall I think there is a lot of room for creative use of materials and design...the bumpers, motors, electronics, and pneumatics seem to be areas that are limited, but there is good reason for most of the limits.

[Jeff Pahl]

Originally Posted by Wayne C.

Consider this more- if you built the bumpers exactly to the specs in the rule book last year they could not make the specified weight.

I had the interesting experience last year of inspecting at events on opposite sides of the US (Peachtree [GA] and Minnesota) and also at the Championship.

I observed that plywood does not have the same density, depending on the source. Different parts of the country, it is made from different woods which affect the weight. Of course, the moisture content can make a difference, too.

One of my least favorite parts of inspecting last year was having to try to explain to teams that fact. You would have one team with a set of bumpers that fully wrapped the bot that would just make the 15 lbs, and the next team would be at 15 lbs with only three sides. I had teams tell me that it was impossible to build 4 sides of bumpers that met the rules and the weight, but I also saw many teams that managed to do just that.

And I had a discussion with Russ Bevis, the Chief Inspector for FIRST, about this very subject at the Championship.

I'm not going to touch the attachment discussion, that subject still makes my blood pressure rise...

[MrForbes]

Originally Posted by Jeff Pahl

I observed that plywood does not have the same density, depending on the source. Different parts of the country, it is made from different woods which affect the weight. Of course, the moisture content can make a difference, too.

That is something I had not considered...we seem to get the dry, light stuff!

[Richard Wallace]

The only place to look for an authoritative interpretation of FRC rules is the official FIRST Q&A forum. The pertinent section of that forum for 2008 can be found here.

The attachment method described by the OP would comply with <R08> as written and officially interpreted on the forum linked above; however, the bracket(s) would have to be attached to the standard bumper using strong stiff (threaded) fasteners, and be removed from the bumpers when they are weighed during inspection. The weight of the bracket(s) would count as part of robot weight, not bumper weight. See this Q&A response, among others.

[IndySam]

Originally Posted by ajlapp

If I design and employ a bracket for attaching bumpers to my robot such that the bracket is always attached to the bumper, is that bracket then considered part of the weight of the bumper?

i.e. you remove the bumpers by removing the bracket.

We did brackets the two out of the last thee years and the inspectors always required them to be weighed with the robot.