Bumper Mounts
 

How do you mount your bumpers? 1351 is currently in discussion about the best (and strongest) way to attach them.

thanks,
Sam

Re: Bumper Mounts
 

It would depend on how you would mount your chassie and what material it would be made out of. You could screw them to it or go as simple as zip ties which are really light.

Re: Bumper Mounts
 

The Tips and guidelines has some discussion on this subject. I saw all kinds of attachements last year but the ones that impressed me the most used a piece of aluminum angle drilled for mounting holes with bolts through the bottom of the chassis. The best one used eye bolts on the back of the bumpers which simply dropped over threaded rod on the chassis and attached with butterfly nuts. No tools needed and it only took a minute or so to remove for weigh in.

Re: Bumper Mounts
 

Are we allowed to use zip ties to mount the bumpers?

Could someone please give some examples of "bolt-and-fastner" systems?

Re: Bumper Mounts
 

No. The GDC is very strict on the bumpers this year--it has to be something like a bolt-and-nut system.

Re: Bumper Mounts
 

We use these with 1/4" 20 bolts. You just drill a 1/4" hole into your plywood and smack them in. Note that they need to go on the INSIDE of the bumper so that the bolt pulls them into the wood.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXK019

Re: Bumper Mounts
 

I posted this a while ago and I've learned a lot since then. It is good to have your bumpers secured with big bolts but...

as long as the wooden backing of the bumper sits flush with your chassis, the bumper mounts only have to hold it in place. Any force imparted on the bumper should be translated to the chassis, not to the mount.

We use 1/4 inch aluminum angle. We may even downgrade that to save on weight.

Sam

Re: Bumper Mounts
 

Team 1726 has used either t-nuts (which can be hammered into a wooden board) or t-bolts to mount their bumpers. A quick McMaster search will show the various hardware. Considering the directions in which force will be applied to your bumpers you shouldn't need an incredibly tough mounting system as most of the force will be transmitted right on through as noted above.

You should be more worried if your bumpers are unsupported in the center as they may shatter.

Re: Bumper Mounts
 

We used 1/4-20 carriage bolts hammered in the spec-size plywood through a 1/4" thru-hole. Typically, only 2 bolts per bumper are needed. The square shank under the head bites into the plywood and keeps the bolt from turning while being tightened. The bolts ran through holes drilled into the side frame members (1.5"x1.5" welded aluminum tubing frame) and fastened by wing nuts that are hand tightened (i.e. no tools).

That is a very clever idea. Do you recall which team used that method?

We might look into using that ourselves--thank you!! :D

Re: Bumper Mounts
 

Last year, a member of another team told us that we shouldn't leave any mounting hardware on the bumpers apart from the bolts and/or nuts. I am beginning to doubt whether we would've failed inspection had we left our angles on the bumpers.

Is it legal to leave some light mounting hardware on the bumpers for inspection?

Re: Bumper Mounts
 

No. The only mounting hardware that is legal to be on the bumpers at inspection is the nut/bolt fastener as described in <R08>. Any other mounting hardware must be attached to the robot and be included in the robot size and weight restrictions.

Re: Bumper Mounts
 

Our team uses HDPE spacers to keep our bumpers offset the correct distance from our wheels. I understand these are most likely not legal bumper parts, and so will need to be included with the robot weight, but would it be acceptable to, after weighing in, reattach these spacers to the bumper, rather than the frame? For simplicity's sake, and just owing to the general design of our robot, this would be preferable.

Re: Bumper Mounts
 

That sounds like a good Q&A. Just remember that if you make finals, you'll have to take them off the bumpers again.

Re: Bumper Mounts
 

Calle,
What you describe sounds like the spacers should stay with the robot for weight and size. The inspector at your events will make the final decision once he or she examines your robot construction. Please plan accordingly.

Re: Bumper Mounts
 

This is our bumper mount system. The hex shaped standoffs are bolted to the chassis, and touch the bumper, but do not attach to it. The long coupling nuts in the corners are threaded onto the "fanged elevator bolts" that are mounted inside the bumpers. We used the long nuts to make it easier to handle the nuts without dropping them into mysterious crevices, and to have a lot more area to put the wrench on them.