At the moment, our robot has 5.25" sides at the front, and about 0.5" of clearance on both sides to the intake. As I understand it, the robot as is would be impossible to mount legal bumpers onto, since the bumpers must cover 6".
We’ve come up with three possible solutions, and I would like to know which one is the most effective while still being legal.
The first solution is to extend the frame perimeter around where the bumpers are at by putting 0.75" pieces of plywood. This would be the most convenient and effective workaround, but its legality depends on a very liberal interpretation of frame perimeter and bumper rules.
The next solution is to extend the entire frame perimeter by placing a sheet metal plate around the side chassis plates so that the sides become 6". I can’t seem to find a reason for this to be illegal but would like to avoid this solution since it’s timely, costly, and heavy.
Finally, we could rework the intake and put some angle iron towards the inside of the robot to extend it to 6". This I am almost certain is legal, since our team has done this in the past, and theoretically only a minor adjustment to the intake would be needed to squeeze a half inch from it.
For those in dark mode: there ARE pictures there. Switch to light mode temporarily to see them.
First image: Correct! You’d be–at minimum, 1/4" too short. Good spot on yourselves.
Second image: Plausible, except that the Frame Perimeter now has two extra corners and you’d need to run bumpers on the side of the robot now. Not exactly a great option. (This is the “LRI at the regional says to do it this way” option.)
Third image: Yep, that’s legal. I would suggest something other than sheet metal, though–try plastic or angle aluminum, or maybe plywood, just given the weight concerns.
Option 3, rework the intake: Yep, legal.
Option 4: Is there a reason that you can’t widen the entire robot by 1.5"? You’d need to lengthen the crossbraces, sure, just wanting to check that that’s not an option for you as it is.
Option 5: Over-the-bumper intakes rock. At this point in the season, that’s either “steal Everybot/Ri3D” or “next season”, though.
Thanks a ton!
Yeah, sorry for the potato images - had to find a random online sketch tool and use a trackpad.
For the second image, would we need to cover that 3/4" lip with bumper, or can it just sort of hang out?
Option 4 would require a new back plate to be machined, since it’s a sheet metal chassis, along with some mounting things for our indexer. Probably a last-resort option for us.
It’s a lot more complicated than that on the second image. I’ll draw a picture if the words don’t get it across.
Draw a line from the back of that bumper all the way to the back corner of the robot on the same side. That’s your new frame perimeter. Incidentally… the bumpers are supposed to mount to the Frame Perimeter… on both sides of all corners. And there’s a new corner on the perimeter.
Once you’ve done the geometry on that… see if there’s any way to add 3/4" of frame to the front and only the front, and then draw that line straight back to the back corner. This is called “the easy way to do picture 2”, at least once the sheet benders get done making rude comments about the designers.
So that tiny 3/4" corner does need bumper it seems. Booooooo.
Could we do those standoffs all along the side of the robot and just have a full side bumper?
Also, you guys got me excited for dark mode. And then I saw #AllBlackEverything mode and thought it was better dark mode. It was not.
Black is robot frame, red is the Frame Perimeter for your proposed solution, blue is the Frame Perimeter I’m suggesting. Green shows bumpers. (Obviously not to scale, this is a quick-and-dirty sketch.)
The basic problem is that per R401, all corners of the Frame Perimeter (including that one that we’re making by parking the bumper out on that side) require bumpers on both sides, for 6". Putting a bumper on the 3/4" side does nothing for the protection requirement: it’s not on the Frame Perimeter at all. (This is why knowing the definition of Frame Perimeter is so important.) The second image in R401, top side, captures this perfectly.
So, there’s two good options.
Standoffs on the side (or your favorite 3/4" frame thickener, which I think I would suggest, due to the support rules in R410) is one method. You only need to go 6" from the corners, incidentally, as long as you do it on both ends of the robot–the Frame Perimeter follows those standoffs if they aren’t Minor Protrusions. (Which reminds me: R101, note what counts as a minor protrusion.)
Something like this, where the green is the standoff/expansion plate. Build 'em solid-ish (plywood, thick plastic, aluminum boxes), build 'em identical depth, mount 'em on the same line. If you do that, you’ll only need side bumpers on the green parts (which are assumed to be 6" long here), and you’ll be able to put your 6" bumpers on the front/back as well.
Build a new side, at a slight angle, and support it a bit–see the second drawing in the top picture. That’s also legal–there’s no particular rule saying that your robot must be a rectangle, and I’ve seen robots built as trapezoids before. The hazard there is getting the bend right.
Re: #AllBlackEverything: I’ve been bitten by that one too. Once. Welcome to the club.
A number of years ago I helped a team in a similar situation - we found the problem at week-0 and spent the entire time between then and the event emailing about how to fix it.
@EricH ’s suggestion 1 is spot-on as the easiest to implement. His suggestion 2 is what the other team ended up going with. The key difference, and what made them chose option 2, was the frame perimeter measurement. Remember, the frame perimeter cannot be more than 120”. I haven’t seen a measurement mentioned yet, so be sure to check that first! If you don’t have one already, I recommend buying a fabric tape measure. It’s by far the easiest way to check your frame perimeter dimension. Depending on what your number comes out to, you may need additional changes!
Could we do those standoffs all along the side of the robot and just have a full side bumper?
If you did something like this it would be legal under my interpretation of the rules. There are many west coast drive teams that do similar standoffs that support the bumpers. The width of the standoffs need to be >1/2" to be considered supports and the gap between them can be no larger than 8". Of course your final frame perimeter still needs to be less than 120"
Thank you all for the suggestions!
I’ll relay these to my team, but we’ll likely try option 1 first. Our frame’s currently 28" x 30", so it’ll be close but still legal!
