We are a team of multiple years, but we have always lacked on the bumper side of things. Every competition we attend, we notice that that is what judgement falls upon on many teams. Additionally, we don’t like taking bumpers with us to showcases (though we should for safety’s sake) because of the lack of crispness. This year, we have made strides on the appearance of our bumpers. Unfortunately, we still have not found a good option for bumper attachment that is fast for removal, dependable, and holds bumpers tightly. Any help or ideas would be much appreciated.
Tons of posts on CD on this very topic, have a look around, I’ll link one of the discussions here.
Also teams like triple helix have videos on how to make bumpers well. Our team personally favors the reversible kind, so they don’t have to come off and on quite as fast, as they only get removed for inspection.
This year, we borrowed some ideas from 1305 to come up with a really nice way attach the bumpers to our KOP chassis. It should be possible to adapt it to a custom chassis.
We are using two U-shaped bumper sections that go almost completely around the chassis. The “bottoms” of the U’s are along the two sides of our chassis. On each of the bottoms of the U’s we have a 1/4" x 20 x 2 1/2" bolt inserted from the outside surface of the bumper wood and retained using T-nuts on the inside surface. We drilled the holes in the bumper wood and the sides of the chassis at the same time so they match.
On each of the two legs of each U, we installed one of these steel angles (4 total for the whole robot) so they rested on the top surface of the chassis as shown in the PDF linked below. We then clamped a piece of 1/2" thick plywood under the top of the chassis and the steel angle. Next, we drilled a 1/4" hole through the steel angle, the top of the chassis and the plywood. We drilled the bottom of the plywood out to 5/16" and inserted another T-nut. We ended up using double sided tape instead of glue to attach the plywood to the bottom of the chassis. Four 1/4" x 20 bolt are used to hold the brackets down on the chassis.
end bumper mounts.pdf (167.1 KB)
The bumper sections slip on with the protruding bolts going into the chassis first. We then install the 4 bolts into the steel angles. This arrangement is strong enough that we can lift one end of the robot by lifting the bumper section.
For the past 4+ years we’ve used top side brackets and wing-nuts or wing-bolts with great success.
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Can confirm, takes seconds to remove using the McMaster latches. Usually our robot is narrow enough that with bumpers it still fits through doors… not this year.
Highly recommend the latches.
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Standard construction U shaped bumpers. Angle brackets mounted on back face of bumper. Drilled/tapped pins mounted on frame. Bumper brackets drop down on pins, R Clip goes through pin to secure. Fast, secure, quick change and very solid. Also is easier to fit the bumpers to multiple robots, if you build a practice bot, than some of the systems that require precision fabrication or tolerances.
Can be made in very low tech build environment as all you need is a hacksaw or chop saw to cut the brackets and pin material, a drill press to drill the holes, and a tap set to tap the pins.
We implemented Dzus fasteners for our bumper attachment this year. It requires a bit of know-how and a little bit of money, but it works NICELY as it is our first year not using bolts (that take FOREVER to change).
The ones that I suggest can be found here (and a ton of other places): https://www.dansperformanceparts.com/sand/sand-fabrication-accessories/dzus-fasteners/latest-rage-823140w-dzus-fastener-self-ejecting-wing-nut-each.html
Going with this approach means you will never drop or lose the nut, and it can be very quickly and securely put on or taken off.
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At WC in Detroit I was talking with a team from Israel (sorry, forgot your number!) and they use ‘draw latches’ to hold their bumpers on. They said they work great, and it looked really sweet!
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I saw 254’s bumpers at worlds and they definitely changed their bumper attachment from latches. I didn’t get a good look, but I really want to know what they do now for attachment.
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Tried those McMaster slide latches this year, but really didn’t like them. We found they tended to catch on the way on and off, and the thin sheet metal frame bent easily under load.
Next year we’re going back to the old stand by. 1/4-20 clip nuts and bolts. Fast enough with a cordless driver, and as strong as you can get.
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1895 used these this year to some pretty good success for our first time. Would recommend.
Yeah, the latches work great as long as the bumper mounts are rock solid. At OCR, in quarterfinals, some heavy defense actually bend our bumper mounts, causing the latches to bend as well.
I still like them, but we would need to do a better job of strengthening our mounts in the future
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After seeing 3244’s robot at SpecCheck, we went with Dzuz’s slide mechanism found here.
There was a little trial and error to get them right, but once we got the hang of it, these things were awesome.
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We use 1/2" - 3/4" inch plywood, the size you want the bumper to be. Then, drill and countersink 4 holes for 1/4-20 bolts somewhere on each end. Epoxy the bolts in place (make sure your countersink is wider than you need so you get a good adhesion. Build the rest of your bumper, using solid core noodles and staple on some durable fabric (basically your standard bumper, FIRST has recommendations on fabric type, it works great). Use wingnuts to hold your bumpers in place through a spot on the frame.
Pros:
super strong, we’ve never had an issue.
Cons:
they aren’t single piece, so allow about 2 minutes for a decent pit crew to swap colors
We have used wingnuts, student hand tight, with 1/4-20 bolts epoxied through a plywood backing. no issues.
We’ve used these for a number of years now, and this summer we’re looking at options to replace them. They’re really sensitive to alignment between the bumper and frame, and attaching them requires either very small bolts or very small rivets. We also attach them using this “modular frame perimeter” idea that we have to lawyer our way through every year with inspectors, which is tiring.
We used this method our first year in 2017, if I understand what you’re saying correctly. The problem was it was hard to line up 4 different connection points for each segment correct. We ended up getting rid of some of the bolts because as the matches went on it was becoming harder to get both colors on. Did you address this in any way?
I just want to echo this point. We poorly implemented the latches this year. I think the two problems were we didn’t use thick enough wood screws, and the latches and posts were not positioned with enough precision. What ended up happening was when we came off hab level 2, the bottom of the hab would peel the small metal arms right off the post. I think this also had to do with the fact that this part was a single segment, not a wraparound.
Triple Helix photo of latches for references.
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Can confirm, use of these latches is not advisable with single segment bumpers. For the most part they were okay, but due to variation in construction, our front blue bumper segment had a tendency to fall off during match play. The inspectors were not very happy with how far away you could pull the bottoms of the bumpers.
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