Bumpers, snap on/snap off

Hello Cd,

We as a team waited till the last moment to make the bumpers and put them on. I was wondering what material teams used for their bumpers and how they mounted them. I am looking for a fast method, kind of a snap on/snap off method.

Thanks guys

The 2008 rules specified a bolt and nut system, so we used fanged elevator bolts in the bumpers, and long coupling nuts (they’re large and easy to get a wrench on, and easy to find when you drop them) to attach the bumpers to the robot chassis. It worked well.

http://www.mcmaster.com/catalog/114/gfx/small/92221ac1s.gif

Wax on, Wax off… Sorry… I couldn’t resist.

About the bumpers…

We had a frame rail on the left and right side of the robot, so we made bumpers that would slide over the frame rail, then dropped some pins to keep them secured. For the back, we made some pieces that would slide into the frame rail since they were hollow. I believe the back pins also went through these to lock them into place, then we had some diagonal support pieces that attached the back bumper to the side bumpers.

Just looking on our website, we don’t have any good pictures of our frame and bumpers…

Pretty much everyone went with the plywood, pool noodles and fabric bumpers last year, as bumpers were required by the rules.

As for mounting, I think some people used wing nuts + bolts to attach the bumpers. It’s very sturdy, and as long as the wing nuts are easily accessible it’s very fast to remove/attach.

Did you have any problems with the “fangs” coming out of the plywood? We tried fanged nuts and they kept popping out. We ended up using zipties, which did not go so well either… I would NOT recommend that :smiley:

we used those fanged nut things to hold bolts in the side of the bumper. Then cut out a key-hole shape in the frame so that the top of the bolt could slide in and then fall down tightly into place. This proved to be very easy to mount/unmount the bumpers.

For our rear bumper we went with drilling 2 holes in the 1x2 that forms the rear part of our frame. then we mounted 2 small pieces of angle to the bumper and used I-bolts to hold the bumper in place.

EDIT: We used epoxy to hold the fang nuts in the wood and except for one they all held. loosing the 1 was no big deal since we had 3 mounting points and it was the middle one.

We used fanged nuts in the plywood the year before and did have problems, which is why we changed to the fanged bolts. They are pretty darn big! (we used the 5/16" size) and hold just fine. And if they do pop loose, they won’t go far.

We attached delrin blocks to slide into 2x1 pieces off of the chassis. Then dropped clevis pins in to hold them, can get all four sides on and off in a breeze, inspectors like it, and it looked clean.

First of all, with any bumpers… or any part on the robot… make sure you follow the rules. Doing tech inspection in Atlanta we found teams with 1/2" plywood (3/4" was required), improper holes drilled in the plywood, improper corner construction, and even teams that had screwed their bumpers on rather than using the specified “nut an bolt fastener system”. I can only imagine how many violations were caught at regionals if we were still finding violations at the Championships. And yes, even minor violations were sent back to be fixed. The Q&A forums will typically have lots of bumper questions… and lots of very specific bumper answers. Whether or not your tech inspector agrees with the Q&A answer, or whether or not your tech inspector thinks the Q&A answer is “reasonable” doesn’t matter… the rules is the rules and they will be enforced.

Now, as for a couple of other suggestions for connecting bumpers that stay within the rules. We got around the problem of having the fanged nuts come out of the plywood (we had problems with that one year, too) by building our own nuts from a piece of 3/16 (or was it 1/4?) band iron. We just drilled three holes in a 2" long piece, tapped the middle one for a 1/4 20 thread and then used screws through the outside holes to attach the “bolt” to the plywood. Using screws, instead of fangs, was much more secure.

To take that a step further, rather than use a standard bolt to attach the bumper directly to the frame, screw an eye bolt in to the bumper. Then you can have vertical bolts on your frame that you place the eyebolts over. Throw a washer on top of the eyebolt, then a nut to squeeze it down in place and you can get your bumpers on and off in a matter of just a couple minutes.

Yes, this description would be better with a drawing or photos, but I hope you get the idea… if you look around at the thousands of robot photos (and other threads on CD) I’m sure you’ll see something like it as we certainly did not come up with the eyebolt idea ourselves…

Jason

P.S. Just noticed the comment, above,

“We attached delrin blocks to slide into 2x1 pieces off of the chassis. Then dropped clevis pins in to hold them, can get all four sides on and off in a breeze, inspectors like it, and it looked clean.”

This sounds like an excellent system, is a good idea, but… based on my understanding of this description… should not have passed tech as it was not a “nut and bolt fastener system”. The rules are very specific and sometimes exclude “good ideas”.

Please note: there have been rule changes in the bumper section of the robot rules in the past. Don’t dedicate yourself to a bumper design just yet. I know there were many suggestions for the bumpers in the post mortem meetings. Things could change this year.

I agree with Al. Heck their might not even be bumpers next year. :ahh:

This past season had a lot more rules dealing with bumper construction. We were forced to rebuild our bumpers during week 6 once we found the rule about no extra holes in the wood.

Just a word of advice. Dont put off bumper making. Yes the robot it priority #1 (especially if bumpers are not required), but when designing your bot keep in mind how you want to secure the bumpers to the frame and how their placement will affect other parts of your bot. (you dont want a bumper to get in the way of you manipulator)

…or be functionally impossible to put on once you have the whole robot together. (Wonder why 1618 ran without a back bumper at Chesapeake?)

Hope not, we bought a bunch of noodles on clearance.

Turn the students loose and get out of the way. They’ll find a use for 'em!:p:rolleyes::ahh:

Until the bumper rules for next year are released, think about possible methods. Can you: embed something inside the bumper? design the frame so that it’s easy to get to a bolt/nut that’s coming through? come up with something off-the-wall that’s secure? Then see how those methods compare to the rules after Kickoff.