Cat5 Bumper Mounts

[HumblePie]

Last year, FRC Team 3489 (Category 5) used a quick change bumper system at the Orlando Regional. We had a few inquiries about it, so I thought I'd share. Pictured is a revised system which should be easier to assemble than last year's. The clips are made from the kit channel, and welded together (epoxy might work, also). They nest nicely over an 80/20 quickframe attached to the top surface of our nanotubes. Drilling a 1/4 hole through the quickframe allows a 1-1/2" long PIP pin (aka Ball Lock Pin, McMaster Carr has them) to hold the bumper securely. Screwing the clips to the bumper backing in place makes sure everything is lined up correctly (this was an issue for us). We screwed 2 sections of bumper backing together at a 90 degree angle to provide additional security and allows for a clean, rounded corner when the noodles are installed.

Would like to hear your feedback.

[nnfuller]

So this is something I have been thinking about for a while now. Our team has never had easily removable bumpers, they have always been the more classic wing nutted on approach. I used to think this was a problem, but at our last regional I had a judge come up to me and say that I should be proud of the way so many students were in the pit working on our robot. At the time I felt guilty because all they were doing was changing our bumpers, but the more I thought about it, the more I realized that it didn't matter what they were doing. Competitions have a way of making many team members who were vital to the build effort feel as if they don't have a purpose,and once scouting is taken care of and spirit is in the bag, they can feel as if their role is to sit in the stands and cheer, or man the pit and talk to people. I loved walking the robot back to our pit after a match and one of our young builders yells "We're blue for the next match!" next thing you know four team members descend on the robot like flies and are working before the cart even comes to a stop. To me this is a small thing that makes a huge difference. Again, I love the engineering behind all these quick change bumpers, just wanted to share my thoughts.

[HumblePie]

Last year was our first try at building a second robot for competition. The unfortunate result was that the students had plenty of troubleshooting work to do at Orlando. Lots of learning moments in that process. Thankfully, the bumper changes didn't take a lot of valuable time.

[Littleboy]

Those bumper mounts look almost too close to the bumper itself. To me, it appears it will be hard to put the clips (thats what they look like at least) into the frame. Most people would have trouble reaching strait down easily to put them on. I would advise 1)adding 2 more Cims and 2) moving the bumper mounts into the frame about an inch or so. This will make bumpers easier to install.

That is one of the reasons I love offseason events. During the normal season, people usually do a specific job or two during each competition they attend. Some get sick of it after a while. Many scouts don't care for scouting. But during offseason events, at least for us, there isn't as much emphasis on scouting. People are working in the pits more and helping out. People also get to try out driving. It makes it a lot more fun for everyone.

[Al Skierkiewicz]

Doug,
From what I can tell from the picture, this is very good way to attach bumpers. Simple, easy for one person to remove and if the design is as it appears, legal. If you are sure that the bumpers cannot be dislodged or change attitude with aggressive play, then I can say "nice design".

[HumblePie]

[quote=Littleboy;1191819]Those bumper mounts look almost too close to the bumper itself. To me, it appears it will be hard to put the clips (thats what they look like at least) into the frame. Most people would have trouble reaching strait down easily to put them on. I would advise 1)adding 2 more Cims and 2) moving the bumper mounts into the frame about an inch or so. This will make bumpers easier to install.

I'm unclear on what you're suggesting, but maybe my OP could have been clearer. The clip assembly (shown in green/light green) is welded together and remains screwed to the bumper. At installation, the clips are horizontally placed over the 1" frame that is bolted across the tops of the Nanotubes, and the ball lock pin is inserted vertically through the entire assembly. The ball lock pins are available in different handle styles if access is tight, but we used a similar system with good result (we did occasionally misplace pins, which is why we considered tethers).

I'm unclear on the Cim reference. Can you elaborate?

[HumblePie]

Originally Posted by Al Skierkiewicz

Doug,
From what I can tell from the picture, this is very good way to attach bumpers. Simple, easy for one person to remove and if the design is as it appears, legal. If you are sure that the bumpers cannot be dislodged or change attitude with aggressive play, then I can say "nice design".

Al,

Thanks for the input. The bumper backing board is only the clip thickness (1/8") from the support structure of the robot, and nowhere is there a span over 7" that is unsupported, so based on the most recent rules, I believe it to be legal. We used a similar system last year at 2 regionals with no security issues (and, sad to say we were flipped over more than once). I do think that constructing the bumper sections in an "L" configuration helps with security, since the bumper mounting points are no longer in a straight line.

[cbale2000]

Not gonna lie, when I read the name of this thread, I thought someone had used Cat5 (ethernet) connectors as bumper mounts...

[ttldomination]

Do these pins hold the bumpers "tight"? With wingnuts you can tighten the bumpers to the frame. I'd suspect there would be some wiggle/play with the bumpers due to the wiggle/play in the pin inserts?

I don't have experience with this, and as much as I like to see rookies "descend" on the robot, I hate to see members struggle to mount bumpers as we are walking to queue.

- Sunny G.

[HumblePie]

Originally Posted by ttldomination

Do these pins hold the bumpers "tight"? With wingnuts you can tighten the bumpers to the frame. I'd suspect there would be some wiggle/play with the bumpers due to the wiggle/play in the pin inserts?

I don't have experience with this, and as much as I like to see rookies "descend" on the robot, I hate to see members struggle to mount bumpers as we are walking to queue.

- Sunny G.

The nesting of the kit channel clip over the 1' square tube takes care of the vertical movement (haven't measured the exact clearance, but it's pretty close) and the ball lock pin takes care of the horizontal plane. If you drill a 1/4" hole through the square tube, the clearance is just that of the 1/4 inch ball lock pin and the 0.257" hole in the kit channel. Connecting 2 bumper backings together at a 90 degree angle (with wood screws and/or glue) makes any wiggle almost negligible. The issue we saw with wingnuts our rookie year is that not every student can get them really tight, and some loosening was possible during the match.

[ttldomination]

Originally Posted by HumblePie

The nesting of the kit channel clip over the 1' square tube takes care of the vertical movement (haven't measured the exact clearance, but it's pretty close) and the ball lock pin takes care of the horizontal plane. If you drill a 1/4" hole through the square tube, the clearance is just that of the 1/4 inch ball lock pin and the 0.257" hole in the kit channel. Connecting 2 bumper backings together at a 90 degree angle (with wood screws and/or glue) makes any wiggle almost negligible. The issue we saw with wingnuts our rookie year is that not every student can get them really tight, and some loosening was possible during the match.

Oh yes, I was advocating the pin/lock mechanism and not the wingnuts. We've had many a times when we were in a rush and we realize that we have the wrong bumpers on.

- Sunny G.

[Phyrxes]

We have used a similar method before, once you find the correct length ball lock pin (from Mcmaster for us) everything goes together nicely. While we have never tethered the pins we trained the students to leave the pins in the robot frame when the bumpers were not on it.

[Jon Stratis]

We've been talking about switching to a pin like that... I really hope we finally do it this year.

Can you expand on the light green bumper mounts? Is it a piece of C channel with an additional L bracket on top? Was this primarily for additional support vertically, as the bumpers are really only supported along the bottom edge by the frame?

We always try to keep our frame in the center of the bumpers, which has allowed us to use some C-channel sized to fit snugly over the kit frame, without any additional supports. Of course, we've always used nuts and bolts, so it's been a pain to take the bumpers on and off. Fortunately, we've used reversible bumpers the past two years, so that hasn't been a problem!

Bonus points: attach the pins to the bumpers through a small cord (many of those quick release pins have holes pre-drilled specifically for this!) so you don't lose a pin!

[HumblePie]

Originally Posted by Jon Stratis

We've been talking about switching to a pin like that... I really hope we finally do it this year.

Can you expand on the light green bumper mounts? Is it a piece of C channel with an additional L bracket on top? Was this primarily for additional support vertically, as the bumpers are really only supported along the bottom edge by the frame?

We always try to keep our frame in the center of the bumpers, which has allowed us to use some C-channel sized to fit snugly over the kit frame, without any additional supports. Of course, we've always used nuts and bolts, so it's been a pain to take the bumpers on and off. Fortunately, we've used reversible bumpers the past two years, so that hasn't been a problem!

Bonus points: attach the pins to the bumpers through a small cord (many of those quick release pins have holes pre-drilled specifically for this!) so you don't lose a pin!

I'll attach a closeup for clarity.

The 2 clip pieces are made from the kit channel (the lower one is just cut to length) and the 2 are welded together. This allows for the bumper backing to be fixtured at the desired height and attached to the bumper clip (in place) via wood screws. Depending on bumper height, the clips could also be mounted "upside down" as shown in second illustration. Connecting 2 perpendicular sections of bumper handles the bending moment so that the clips do not have to be centered on the bumper backing (helps save weight by not having structure dedicated to bumper support). And, yes we are considering tethers (non-conductive for sure!).

[Jon Stratis]

Very nice, thanks for the additional clarity! Depending on robot design, you may find your frame naturally in the middle (ish) of the bumpers instead of along one edge. This year, our frame was in the bottom third of our bumpers, but we had a little weight to spare, and put some vertical frame members in the corner as well. This gave us some additional support AND allowed us to build in handles to carry it with

Again, very nice design, thanks for sharing!