Attaching Bumpers

So we finished and bagged the robot… sans bumpers. We Have built them (pool noodles and plywood). My question is: What is the best way to attach these to the robot when we open the bag after competition? We will have to remove them periodically, but have them remain firmly affixed. How do we do this?

Most teams use a quick release pin. Team 3467 uses these pins that go through a bracket on the bumper and then through the bumper frame. We also have re-usable zip-ties that we put through the key chain circle on the pin and around the frame. The bumpers stay on no matter what and with two people, we can take them off in under 30 seconds.

The good news is that you can probably find someone at the Buckeye Regional to help you with attachment of your bumpers. The (potentially) bad news is that many attachment systems work best when the fasteners on the bumper go through it from the outside in. That is, fasteners go on before the fabric covers them over. It’s not a requirement, but wood screws into the backing boards don’t give the same secure feeling as machine screws coming through it. There are many ways to do it, though, so don’t despair.

If you use the kitbot chassis, here’s a quick method I found year’s ago on CD (so I can’t take credit for it) that we have been using for years, although to install the tee nut you should really do it from the back side (inside the fabric); there may be an alternate nutplate you can secure to the face of the plywood or you could use lag eyebolts that thread into the plywood. You will need (per bumper, one for each color) two 1/4-20 Tee nuts and two 1/4-20 eye bolts ~2 inches long, (per bumper) two 1/4-20 x 2 inch bolts, two 1/4 fender washers, and two 1/4-20 wingnuts

  1. Pick 2 holes in the chassis that are clear for attaching the bumper, spaced sufficiently far apart to give you some good wheel base. The holes are on 1 inch centers so I makes it easy to transfer the measurement to the bumper.
  2. Put the bumper next to the chassis and determine the height needed to put the bumper in the correct zone (between 2 and 10 inches from the floor)
  3. Mark on the plywood the center of the 2 support holes, about 1/8th inch above the frame, then drill holes in the plywood to clear the tee nuts (I think they are 5/16, could be 3/8).
  4. Install the tee nuts into the plywood from the back (fabric) side and thread in the eyebolts
  5. Put the bumper against the frame and adjust the eyebolt lengths so they line up with the holes in the frame. Drop in the bolt and fender washer, and secure from the bottom with a wing nut.

Makes for a simple, adequate attachment and pretty quick changeout.

As an FYI our frame is TIG welded 1" square Aluminum tubes that are 5" from top to bottom (3" in between the tubes).

Our method historically has been to include two pieces of C-channel (one at each end) sized to fit over our frame rails, and have a vertical drilled hole in the rail such that a hitch pin can be dropped through to keep them on.

This year, we used aluminum angle (2", I think) set to go over the top of the frame rail, and used a clevis pin and hitch pin clip arrangement.

(Products linked are for shape not size.)

Both methods have nicely met our criteria of tool-free bumper removal and replacement in under 2 minutes and bumper stability during matches. Both methods are also cheap, quick to implement on practice day without disassembling your bumpers, and should work with the frame style you’ve described assuming your rails are at an appropriate height for attachment and you appropriately size the brackets and pins.

Here is a cross section of what you might do. If you bring the angle stock to the tournament not cut to length as you’d be using, then it will not be part of your 30 pounds of fabricated material. Do all cutting and drilling on site to save the poundage.

Orange angle stock segments are screwed to back of bumpers with 4 or 6 10 at least wood screws. Round head will work since they won’t contact the frame. The green are bolts for which you have drilled holes through both the frame and the angle stock segments. Do the drilling only after hitching the angles to the bumper and fitting the bumper into place in the frame. If you get a nice long drill bit, six inches or more, you’ll be able to get both top and bottom in the same pass. You would also be able to use a nice 6" bolt through all four parts of your attachment system.

Do this in at least two spots on each bumper. If you have a set of red and a set of blue bumpers, put the angle segments in slightly different spots on the bumpers and drill different holes in the frame for each of red and blue sets. Of course you can use the same bolts, but I would get some red and blue sharpie marks around the corresponding holes to reduce frustration trying to fit the bumpers on at color changes.

Good luck. Next year, mount the angles on the bumpers before the fabric goes on and you’ll be able to use machine screws or bolts to do it.