Chief Delphi - Whats the Best way to do Bumpers?

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Re: Whats the Best way to do Bumpers?

we used aluminum c-channel that fit over the KOP frame c-channel. There were two small (about an inch to inch and a half) pieces on each bumper. We attached the bumpers with cotter pins, so if you pulled directly up, they would come out, but only if you pull directly up. We had 8 pieces, the 4 red, 4 blue, yet it only took about 3 minutes for one person to change all the bumpers (handy when we came directly from one match to the queue, one team member met before the queue, and we pulled off the old bumpers, and put the new bumpers on in the queue.)

Re: Whats the Best way to do Bumpers?

Quote:

Originally Posted by thefro526 (Post 976937)

As far as bumper construction, we made ours according to the guidelines set forth in the manual. (I know, suprise :P)

For attachment we made brackets out of aluminum "U" channel that could slip over our frame without much effort. From there we used 1/4" Push Pins from McMaster similar to part number 92384A036. We found that these worked excellently and almost never came loose during competition. The only drawback is that they're pretty expensive at ~$20 a piece.

We used similar pins at a similar price. Remember they are COTS though so buy them once and reuse them. We've used the same pins for 2 years now. Also the cost doesn't count toward your $3500 limit so build budget shouldn't affect your decision.

Re: Whats the Best way to do Bumpers?

Quote:

Originally Posted by Peter Matteson (Post 976954)

The advantage of them over sprung ball locks is their locking ability. Allows a wider amount of bumper mount variety knowing the pin itself can handle axial load.

Re: Whats the Best way to do Bumpers?

Like most teams- brackets that "sandwhich" the frame. Some holes and these pins for $3 each.

http://www.harborfreight.com/square-...pin-96281.html

One big change I plan for this year is to have handles to lift our robot. The last 3 years the students lift by the bumpers. After a day or two the brackets are bent, holes don't line up, and it becomes a pain to remove and replace the bumpers. Bumpers strong enough for competition are not strong enough to be a lifting point.

Troy

Re: Whats the Best way to do Bumpers?

Quote:

Originally Posted by GaryVoshol (Post 976904)

Even if the rules would allow reuse of the bumpers, you'd be wise to look at making a new set. They get pretty beat up over the course of a year, especially if you go to several events and off-season events. The pool noodles begin to compress, and the wood starts to splinter and even crack. Besides, don't you want a fresh look for your new robot each year?

No problem, the added flexibility of the cracked plywood compensates for the compressed noodles.;)

But in all seriousness, if the inside of the bumpers could slide out of the fabric, then at least the fabric could be reused for probably one extra season.

Re: Whats the Best way to do Bumpers?

So, we had a disasterous bumper year in 2008. Bumpers were an afterthought. In the last 30 minutes of build season. They worked, but could not be removed or installed in my life-time.

Starting 2009 we had a bumper mentor (most serene bumper guru - Mike Rizzo). The bumper mentor did other stuff besides the bumpers, BUT HE OWNED THE BUMPERS. A huge improvement.

In 2010, bumper design was first-of-mind during robot design (the opposite of an afterthought). Bumper change requires about a minute.

Our bumpers have male 5/16" bolts extending from them. They are as symmetric as possible and marked for proper installation. Wing nuts secure the bumpers to the chassis. We bring lots of spare wing nuts.

Key points:
1) we have a responsible mentor w/ students
2) bumpers & mounts are designed robot components from a very early stage

Re: Whats the Best way to do Bumpers?

What type of fabric did everyone use for their bumpers? I don't really know where to get started on this one.

Re: Whats the Best way to do Bumpers?

Quote:

Originally Posted by Colin P (Post 986552)

What type of fabric did everyone use for their bumpers? I don't really know where to get started on this one.

Most teams use 1000 Denier Cordura or a similar ripstop Nylon fabric. In past years a sample of this fabric has been included in the kit.

Here is one source for this fabric:
http://www.seattlefabrics.com/nylons.html#fc1

Re: Whats the Best way to do Bumpers?

Quote:

Originally Posted by BrendanB (Post 976269)

Best or easiest? I'd go with easiest for bumpers any day.

Our team attached our four bumpers together with angle brackets to make one large bumper and then had corner plates that laid horizontal to the top of the robot frame and attached to the robot with wing nuts. Took 2-4 students around 20-30 seconds to install.

Brendan, Marc, et al,

First of all, let me apologize for the length of this post. It is not my intention to rub salt into a wound but rather to give some insight into a process that sometimes appears arbitrary by the field soldiers…

Unfortunately, the one piece bumper design you advocate was ruled illegal last year by the GDC (Official Q&A post: http://forums.usfirst.org/showthread.php?p=39030).

Prior to that post, not only did I consider a one piece bumper legal, but I told many teams to add corner braces to increase support for non-orthogonal bumper impacts during my courtesy inspections at a local pre-ship scrimmage in February (I was Lead Inspector at two Regionals last year).

After that Q&A post this subject was debated by other LRIs on a weekly conference call.

I even made a behind the scenes appeal to the GDC via the Deputy FRC Director. I persuaded him to advocate our (mine and a few other LRIs) position with reasons why corner supports should be considered both desirable and legal along with some illusory drawings (one in attached). His reply was as follows:

Quote:

I spoke to the GDC last night. They have determined this is illegal under the current rules. One element of R07 is that the bumpers must be constructed as illustrated in Figure 8-1 (last sentence of the first paragraph). The only fasteners shown in 8-1 are aluminum angle used in attaching the fabric, and a fastening system allowing attachment to the robot.

R07-N also enumerates the hard parts of the bumper as being the two fasteners above as well as the plywood. No allowance is made for other types of fasteners. I wouldn't say that a team using this corner fastener is violating this element of the rules, because it really deals with something else, but this is additional evidence that only the two types of fasteners were intended to be allowed on the bumper.

This is one of those situations where a reasonable person could make a case that corner fastener approach to connecting bumpers should be allowed, because it strengthens to the bumpers themselves and could make installation and removal easier. However, we must enforce the rules as written, at every regional, to ensure fairness.

The bumper rules are always difficult to write. The GDC looks at lessons learned from prior years when generating rules for the current game. The corner fastener question is an example of the type of information they will often consider when formulating new rules.

I imagine that this design nuance eluded many teams and I imagine that many inspectors missed enforcement as it was pretty far down on our priority list (namely, get the teams on the field fairly and safely).

Regardless, it could be misleading and/or detrimental to teams, looking to his forum for guidance, to advocate corner bracing on bumpers… At least until the 2011 rules come out (I hope).

JMHO.

Mike

Re: Whats the Best way to do Bumpers?

Quote:

Originally Posted by Hawiian Cadder (Post 976239)

our bumpers this year used wing nuts to attach, 2 people could change the colors in less than 45 seconds

Same here. It was quick and did the task extremely well.