No, the plywood we use is already extremely strong because we use grades that use hardwoods for core and face veneers and do not allow any voids, so the only failure we’ve seen is at corner joints. In order to increase joint strength rather than using polyurethane glue, I spread a slow cure, low viscosity marine epoxy on all joint surfaces, assembled the corner joints with pin nails, and then taped around each joint to make dams and poured more epoxy into the joints to to soak into the wood and fill any voids.
We’ve used angle iron/ L brackets inside our bumpers to resolve the issue of plywood joints breaking or coming loose. Figure 9-6 in the manual shows “optionally use metal brackets…to join bumper segments together”
We build our bumper frames only .030” over the size of the robot frame so there’s no room for brackets without mortising the plywood, and most L brackets will be more flexible than a wooden box joint. As long as you aren’t looking for a particularly rigid joint and are fine with the space taken by the brackets, brackets are by far the easiest option. If you’re looking for strength/rigidity and simplicity of construction use brackets on the inside and outside of each joint and you’ll be able to avoid bending of the brackets.
I have always contemplated using bumpers as a structural member of the robot. Part of me want to try it. We have discussed the loose rules around what constitutes as a frame perimeter before and if you can get away with calling the perimeter of the robot. The rules are pretty open and ripe for abuse, FRC convention is what is being used by everyone.
If we find ourselves in a game that allows for less harsh tipping penalties (see 2010) then I may float some things out there could be fin, but not super game breaking. Definitely novel.
I look at it as using bumpers to take impacts, and allow you to use a lighter thinner robot frame. As long as your robot can function fully without bumpers and the bumpers don’t have significant structural members inside frame perimeter, I’m a happy to call it a bumper, but the rules are a bit too vague for my taste. I think sometime we’ll see someone use their bumpers for more than just side impacts and then we’ll see what the CRIs and GDC think.
Anyone want to volunteer to add a structural belly pan and tube frame to their bumpers next year and see what happens?
Major updates underway on the dart method… Lots of learning
That’s a non-reversible single piece vanity cover. Turns out that you can’t install the dratted thing fully darted. Needs ONE open corner.
I did end up using darts in our bumpers this year and it was stellar! The actual sewing of the covers was hours because we ended up having to individually appliqué all the numbers but once it was sewn the actual assembly was pretty much 20 minutes!
If you’ve got access to a CNC router it’s pretty easy to attach a marker and make the seam marking and number painting much easier. We’ve been doing this since ‘22.
I love seeing teams making nice looking bumpers. Sewing darts looks nice but based on the beating our bumpers take I prefer the mitered corner for how quickly I can assemble a set.
but once it was sewn the actual assembly was pretty much 20 minutes!
