Bumper bracket and weight considerations

[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.

[EricH]

According to which year's rules?

By 2008 rules, I would say that it would count with the bumper, assuming the attachment method was legal.

[ajlapp]

Assuming the most current rule set.

I agree, I think the bracket goes with the bumpers.

[kramarczyk]

That is how we did bumpers this year... the bracket stayed with the bumper and was weighed as part of the 15 lbm allowance.

Now if somone would only come up with a universal bumper bracket.

[Jon Jack]

Why do you need to design a bracket?

We just mounted clevis pins on the wood backing on the bumpers and ran the clevis pins inside, through the chassis and captured them using quick release pins. We've been able to attach and detach our bumpers in under a minute the past couple of seasons.

[MrForbes]

The only problem with the clevis pin method is if an inspector takes the "bolt and nut system" rule literally (which they probably should).

Chassis design can incorporate bumper attaching points, if you plan ahead.

[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.

[Cory]

Originally Posted by Jon Jack

Why do you need to design a bracket?

We just mounted clevis pins on the wood backing on the bumpers and ran the clevis pins inside, through the chassis and captured them using quick release pins. We've been able to attach and detach our bumpers in under a minute the past couple of seasons.

Even though a quick release pin is the best way to mount bumpers, it's technically been illegal since bumpers have been around.

I wish the bumper rules were changed a little bit to allow methods of retaining the bumpers that are strong and quick to be released, yet are not strictly bolt and nut interfaces.

[Richard Wallace]

Originally Posted by Cory

... I wish the bumper rules were changed a little bit to allow methods of retaining the bumpers that are strong and quick to be released, yet are not strictly bolt and nut interfaces.

I do, too. It is not fun for robot inspectors to tell a team that has devised a clever solution that it must be changed to match the less-elegant one that is required by the rule book.

However, I have also seen some quick-release bumper mounts that were not-so-elegant, nor very robust. Teams that built them were better served by changing to the standard mounting method shown in the rules. IMO it will be a challenge for FIRST to write a new standard bumper rule that allows cleverness in the mounting scheme, while preserving safety, robustness, and fairness.

The worst kind of specification is "I'll know it when I see it" (IKIWISI). I'd rather enforce a rule that is clear, even if it disallows some solutions that I think are cool.

[Wayne C.]

This discussion misses the point-the bumpers!!!

Who cares how they are mounted as long as it is safe and there is no unfair advantage?

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.

This is a VERY sore subject since I spent most of a day dealing with a x**&*^ inspector at Nationals who seemed to think there is only one right way to do things. Apparently the rumors of the CD community weigh a lot with some inspectors over others. Sometimes enforcing the spirit of the rule book is more important than enforcing the letter of it.


Mark these words- the day is coming when all FIRST robots will be clones of each other with little or no freedom for individual innovation of design.

Lets hope that this year's game will encourage a diverse array of innovative designs and materials uses. Otherwise we might as well eliminate the Xerox Creativity Award.

WC (yeah- this ticks me off)

[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.

[Cory]

Originally Posted by Richard

I do, too. It is not fun for robot inspectors to tell a team that has devised a clever solution that it must be changed to match the less-elegant one that is required by the rule book.

The other problem is that many inspectors are not calling teams on it. We spent a lot of time (wasted a lot of time, really) making sure our bumpers would be legal. We would have very much liked to use a quick release pin, but decided it did not meet the letter of the rules. Once we got to the events we saw many teams who had used non bolt-nut fasteners, and were never told to change their bumper configuration.

[waialua359]

what's even worse is when you have a setup, and told from regional to regional that its legal, its not legal, and then its legal again (in terms of where the fasteners weight count towards).
We had different interpretations on whether the nut/bolt fastener counted either towards the weight of the bumpers or the robot which in situations caused us to not meet the 120 and or 15lb requirements.
The whole issue of using bumpers is to protect bots and some inspectors focus more on the wording than the purpose of having them mounted to your bot.
As just mentioned, I hope the rule(s) are revised. It was a pain taking the bumpers on and off.

Thanks for the idea on the clevis pin. If its allowed next year, we may try that.

[Greg Needel]

I wish we could go back to making bumpers optional. While there are many advantages to having them I can think of just as many not to have them. I wish it was a choice instead of a requirement, then people could attach them legally or not at all and still be fine.