Last season we attached our bumpers to the robot by putting grenade pins through L-brackets, but after having them jarred loose and finally having them fall off of the robot in our first match of competition, we were forced to make the switch to nuts and bolts. However, even those fell loose in our second match, forcing us to use nylock nuts. This was less than ideal, as all 12 nuts had to be held from the underside while being attached or detached by a vice grip, pliers, or socket wrench, which in turn forced us to tilt the robot up on end and stop work on any mods or fixes for the five or six minutes it took to change bumpers.
Simply put, there has to be a better way.
How do you and your team usually attach bumpers, and does anyone have ideas for quick and secure bumper changes?
I know that a lot of teams just use Velcro to change colors, but in an intense physical game like stronghold we were concerned about its integrity.
My team uses Velcro to change colors and have never had a problem with the Velcro not working any more or anything like that. It is a super nice system overall because it makes the transition in the pit so much faster (or even in the queue if you forget).
We use a similar system with grenade pins, but with c-channel. This past year we also used “hook and loop fastener” where the bumpers ended (creating a gap) to prevent them from being bent.
This last season, we built 1-piece bumpers, then put an L-angle along the sides. On the robot, we welded some toggle clamps. Pop the clamps, pull the bumper off, put the other one on, lock the clamps down. Didn’t lose a bumper all season (though we did do a rebuild for Champs). I want to say we “borrowed” the idea from Citrus or Poofs or someone up that way.
Another good method is to embed T-nuts in the bumper plywood, on the noodle side. (Glue 'em in thoroughly, though–you do NOT want them coming out!) Then all you need is long enough bolts, strategically placed for easy access.
We have a mentor that does a decent amount of sewing and have had the students do reversible bumpers in house the last few years, similar to the RoboPromo kit:
The video at the bottom of the page does a decent job of walking through the process. Words of caution, make sure they are centered vertically on the board, as tight on the board as possible and that the Velcro on top and bottom has several staples through it. That keeps the Velcro from loosening due to movement of the cloth on the wood backing. Also we use full strips of Velcro at on the top and bottom.
The key to easy bumper switching is use as few bumper pieces as possible. The past few times we have had to use bumpers we have built one piece bumpers where a single bumper wraps around the entire robot. I think most bots I have seen could be build with one or two piece bumpers.
With one piece bumpers we have had success using four mounting bolts (one on each corner). The bolts will go through our frame vertically with the head at the bottom and the threads pointing upward. They are held in place with a nylock nut. A long enough bolt is used that there is thread protruding from the nylock nut. The bumpers have angle aluminum brackets attached that have holes drilled through them that allow the bumper to drop onto the bolts. A second nylock nut is used to secure the bumper to the frame.
This makes a very secure connection and with only four nuts designed for easy access allows for quick changes. Two students can easily change bumpers in less than a min.
In the past we have tried pins, clips, t-nuts, and velcro reversing bumpers, but simply using nylock nuts and bolts and as few bumpers as possible has been the best solution.
Last year 2471 used home made plastic latches, and bolts that fell into slots. This was by far the best attachment method we have ever used. It was very secure and could be put on or taken off in about 15 seconds. Just push down on the bumper to attach, or pull the plastic tabs and lift to remove.
We use some button latches. They are super nice to just drop the bumpers on and clip the latches into place. Also check out these photos of us making bumpers with one of our super amazing alumni mentors that came to Iowa from Chicago to help us make them (We used to have a page on bumper stuff, but apparently it got taken down). Let me know if you have any questions and I can get them answered.
We have used velcro covers, the “four captive bolts” similar to chadr03, and tee nuts (behind a noodle, with a stud at the other for alignment). The four captive bolts was best, with wing nuts to secure the bumper - fastest and more reliable. When you have an interruption in the bumper for an intake (as most teams did in 2016), the bolts should be moved away from the corner and closer to the gap. A few extra bolts without wing nuts will help alignment and provide a backup if you strip threads or otherwise lose use of the main bolts and don’t have time to swap out the extended bolt through nylock.
We used the standard bumper mounting kit this past year. To switch colors is a pain with the thumb screws so a few years ago we came up with a concept. We always have the blue bumpers on and when we need red we just pull the slipcover we made over the blue bumpers. The red cover is just one piece that wraps around all of the bumpers with elastic along the top and bottom. To make sure it says we put a staple in at the ends and one along the top on each side. We have never had a bumper come off using this method.
We used these latches last year for our first time and had problems with them latching by the end of the season. The bumper had shifted size a little, so it was hard to get the latches over the latching pegs. Also, the little metal pieces got bent and so they didn’t stay latched well. Part of what contributed to that was if you put the bumper down on accident with the latches in the closed position, it would bend the metal.
They worked great for the first 2 competitions, it wasn’t until the tail of the off-season that we could no longer get the bumpers on or off. Have you seen any of these issues with these latches? Perhaps you were using them in a way that was better for the latches.
It looks like we played around half as many matches overall (season and offseason) in 2016, so we probably don’t see as much wear as you do. That being said, we build pretty rigid (one piece) bumpers out of bent 1/8 6061 T6 aluminum sheetmetal. They really don’t change shape at all during the season. This probably helps the latches avoid some problems.
When putting the bumpers on, we always have two people, one for every two latches. We are pretty careful to set them on the peg without bending the latch.
Even with these precautions, we still do experience some wear, but nothing that renders them unusable. Our 2014 bumpers lasted 4 competitions and several years of outreach and we never had to do any maintenance on the bumpers that I know of.
In the past my team has used C channel with pins, as it sounds like most people have done. This year we tried to do the same thing but we didn’t make our robot out of C channel (first in team history I believe), and we realized the way we wanted to mount it did not meet the rules. Our solution was angle iron on the bumper, and a flange on the frame perimeter. We drill and taped holes into the frame perimeter bumper mounts and drill matching holes on the bumper- bumper mounts. In the end, we had I believe 3/8" bolts6 10-32 (or 10-24, too long ago :eek: ) holding our bumpers in. There were 2 on the left and right sides of the robot, and 2 on the front (one on each side of the opening). These were one piece bumpers we used. Throughout the season the holes started stripping out so we used flanged nuts on the end of our bumper bolts. Just turn them finger tight and we never had an issue, easy to get off too. With 2 guys, we could get the bumpers are within about 30 seconds. These mounts were strong enough where we could carry the robot by the bumpers, and not cause any harm to the robot.
I really like the design of these bumpers. I don’t suppose you have any resources on how you went about making these? Templates, photos of construction, general tips etc.
(We used to have a page on bumper stuff, but apparently it got taken down). Let me know if you have any questions and I can get them answered.