We’ve suffered from difficult-to-mount bumpers for the past two years and wanted some input.
How does your team do it? Are there great ways to do it?
ALSO, what’s the best way of making bumpers - IE, make each side a separate piece? Make the whole thing somehow 1 unit? Make a U-shape that’s 3 sides to slide on, and then finish off by mounting the last side? What has the best balance of aesthetic appeal and ease-of-mounting?
As for mounting, I keep seeing something like a shallow aluminum c shape onto which bumpers slide onto, which I can’t for the life of me understand!
What we’ve done the past few years is bolted some small pieces of c-channel with a hole onto the back of our bumpers, and then put the small pieces of c-channel on top of our frame, line up the c-channel holes with holes on our frame, and put a pin through them. As for amount of sides with separate bumpers, two years ago we used one for each for each side, and this year we made one set to fit on all sides. There really wasn’t too much of a noticeable difference between the two, other than it took more time to make the singular bumper than the separate ones.
We take our bumpers off and bolt them on once per competition for inspection. After that we use reverseable bumpers that many do with Velcro, but this year we sewed in a bungee cord to allow us to flip quickly without having to secure anything.
Our mounting is simply a piece of 20ga aluminum sheet that is bent at 90 degrees and screwed to the bumper with 1/2" wood screws. We then drill holes in the aluminum and run bolts through every 8" or as rules require to attach to our frame. Bolts may not be quick, but we’ve never had loose bumpers and since we rarely remove them we could care less about speed.
We usually have bolts sticking up from the frame of the robot and then holes in the bumper mounts so we basically just drop the bumpers down over the robot and secure it with wingnuts. Combined with the reversible fabric colors, it takes about 30 seconds to switch/take-off the bumpers.
It also takes no tools at all to remove or put on.
We always mount our bumpers on 90º angle brackets directly to the top of the c-channel using quick release pins. When we use this system, we can change bumpers in around thirty seconds by simply pulling the pins out, kicking the robot to make the bumpers fall off, line up the other set, and slide the pins back in. The pins are strong enough to keep the bumpers on the robot even when it’s upside down (we use the variety with a ball bearing at the bottom of the pin), but easy enough to remove that they’re not too much of a hassle for us to hate changing them.
For this year’s game, our original plan was to have 1 wrap-around bumper fall into place and snap on, making a secure fit. However, the quick release system didn’t end up working as the pins we ordered at the time were too short.
For simplicity’s sake, we decided to use just add two pieces of L-angle aluminum to the back of the bumper, mounted such that when the bumper came down on the robot, the bumper would be resting on top of the drivetrain rails. We then used wing screws and some 8020 drop-in nuts to secure the bumper in place.
For the last few seasons 1983 has recessed our bumper backing into the frame and then pop riveted through the top and bottom to secure it. We think that the end result is not only aesthetically clean, but it adds to the structure of the frame. The recess is created by extending the upper and lower sheer panels past the vertical walls of the frame. If you look closely you can see the thru holes for the rivets in the attached picture.
80/20 angle brackets (the small type) attached directly to the frame have always been the standard method on 449, with the bumpers mounting directly through them via. wing nuts. Easy to set up, and it works well.
Last year, 4464 mounted our bumpers through holes in the c-base using washers and wing nuts, but this was a pain and I hope we don’t do it again.
Both teams used separate bumpers for each straight run on the frame perimeter, and that’s worked well enough that I don’t see any reason why we’d change it. Corner bumpers just seem harder to make.
I am proud to report that I have never, ever seen a bumper on one of our robots fall off during a match.
I still like the added structure of having a solid full wrap bumper with no gaps. Here is our take on the quick change color set up. Just sew a loop in and fish 8 feet of elastic through, a few hog rings later and never look back.
We usually have had a C-Channel chassis so we mount vertical 80/20 channel pieces periodically around the perimeter. These pieces are only several inches high and have a thumb screw with the part you would grasp facing the inside of the robot. The bumpers have 14-20 buttonhead bolts screwed into them that stick out just enough to drop them into the 80/20 sections. Usually works pretty well, sometimes we have to use a hammer to give the bumper a little motivation.
As for our actual bumpers, we usually make 2 sets of 2 bumpers. Usually right/left or front/back depending on our robot dimensions or if we have to have a gap in our bumpers that year.
We drilled holes through the backing plywood and glued pins in to it. The pins line up with holes in the robot chassis and are fastened with small wire pins.
Our only problem was reaching the pins in the middle on our shooter side. It’s super quick but only if you can reach your hand in the right spaces.
Use long bolts with spacers (made from air hose) as mounting pins. You can use wing nuts to secure them, but we had no problems just inserting the pins.
We generally use a 1x1 square tube (with radiused edges) to rim the chassis and provide bumper support. The kit channel nests very nicely over the square tube. We fab/weld support clips from 2 short pieces of the kit channel and use a quick release pin at each mounting point. Making the bumpers in L-shaped sections will make them even more secure when mounted. See a model in this thread:
Team 3574 designs their bumpers so there is no “Changing bumpers” during a competition. The bumpers are created so there is a “Flap” with Velcro so you just pull them down or up depending on the color you want.
The bumpers themselves are mounted to the frame with hitch pins for easy removal if we have to work on something in the heat of the competition.
Email us at [email protected] and I can show you a pic of our quick release one.
We even had one of NASA’s Team 118’s engineer complement us on ours, as it sat in their shop for a couple of days this past summer.
Here is a concept drive base/ bumper mount system that I designed a few months ago. It uses two plates, one on top, one on the bottom, and the bumpers are attached by a piece of 2x1 box tubing which is bolted between the plates. This probably isn’t practical without significant prototyping, but I will put it out there anyway. https://drive.google.com/folderview?id=0BxrM5TU8rVcOYnVNaEZYczlCcjQ&usp=sharing
In that design, I was using the bumper attachment brackets as a structrual element, and I was trying to make the bumpers work with my chain tensioning system. 2x1 is probably a bit overkill, but it’s part of the bumpers, so it doesn’t matter a tremendous amount.
