A question about 8in Bumpers...

So, our team is having a debate, because the rules listed in the game manual and the updates don’t cover the bumper rule we need for our robot. The entire front of our robot is open, holding a shooting mechanism.

The only “perimeter” is the 3 in total of the end of the chassis. Do each of the 1.5 in count as a whole side that has to be covered, or do we have to have 8 in of bumped extending off of each 1.5 in part of the chassis in the front?

The latter, AND you have to have that 8" of bumper backed by the frame perimeter at both ends.

Frame Perimeter is a convex polygon defined by the outermost vertices of the robot, and does not necessarily follow the frame itself. The side of the frame perimeter you show is as long as the robot is wide. 8" from the corners has to be covered.

Looks like you’ve got a late night and some Thursday at regional work to do.

…hate to be the bearer of bad news, particularly today of all days, but your current configuration appears to be illegal. By

and by

Edit: Sniped by one EricH.

Short answer YES! (and the rules do directly address your situation)

The common confusion is that the rules refer to the “frame perimeter”. They should have called it something else like robot perimeter. The frame perimeter is defined as the convex shape formed by rapping a string around your robot at the widest point within the bumper zone (4->12in off ground). Every vertex of the string (which goes straight across your shooter throat) must have bumpers for 8" on both sides of the vertex. The outside corner of your 1x2 frame must have bumpers - fully supported by the frame, extending 8" from the outside corner towards your shooter throat. Very hard to do on bag+tag night.

In R19 it also says “If a side is shorter than 8 in., the entire side must be protected by BUMPER (see Figure 4-4).” Because the center is open, are they each a “side”?

It won’t be a huge deal, we are prepared to make the a very fun angular front end to make sure it’s covered by the 8 in, it’s just a little more bumper than we had planned on building.

No. The front is one side, it just has a hole in the middle.

Get a piece of string and wrap it around your robot. Any section of string that is straight represents a side.

Out of curiosity, what is the length from the outer edges of those two outer rails?

Our robot is 22 inches wide.

Alright. So, after subtracting two 8 inch sections of bumper on each side, that means you’ll have a bumper opening of 6 inches. Unfortunately, I don’t think you’ll be able to intake a ball through there.

It should be named something that actually says what it is - the minimum bounding convex curve in a horizontal plane. If they’d just add convex, calling it the CONVEX FRAME PERIMETER (or even just CONVEX PERIMETER) everywhere the term is used, they’d probably cut the bumper Q&A volume by 75%.

Your frame perimeter is widest and longest side in bumper zone…I think you need to create a wider side using an outer frame.

So with 22" depending on how long your bot is as longer as its under 120" you could add bumpers to the side to “outer frame” to get 8" per corner and an intake area for your shooter.

So do the math:

120"> = 44+ LL+ EXTRA WIDTH to create a wider frame side so you can intake the boulder in between

8" -----11" Gap ------8" (Like this on front) so front has to be about 27" wide or more

If it is not create an outer frame -OR- widen your existing bot -OR- narrow your shooter

Our bot for instance is similar its 31" long and 27.5" wide (117" FP) with shooter wheels 11" extended past the actual bumpers attached to our starting config frame perimeter.

One thing I could recommend if possible is to cut the corners at the opposite side of your robot. This will allow you to add metal to either side of the frame thus making the gap between your 8 in. bumpers widen. I also would say to do some math before you do any cutting if you were to go with this method. Hope this helps! Good luck

You are going to have to make an artificial Frame with some 2x1 or 1x1. Put a 7 inch piece on both sides and maybe a 45 degree angled piece going back to the frame. It will be make bumpers a little more difficult but you gotta do what you gotta do. You may also just extend your frame 8" going to both sides either way its a similar perimeter value.

FIRST needs to make it a point to reiterate the bumper rules in every update next season.
I would hate to see this come Thursday at a regional event from any robot.:o
No matter how many times its stated, there are always teams that miss this and threads that come up.

Someone was showing me a video of the Frame Perimeter and how to determine that. That video, or one like it, needs to be played at Kickoff, before the Field Tour videos, and be linked in the Manual.

So many teams at the local scrimmage needed some bumper work… mostly, it was support. A few needed help on the Frame Perimeter (like the team who had one that was really complicated to explain just what was wrong with it–as I recall, it was that their treads were in the Bumper Zone, and defining their Frame Perimeter, while their Bumpers were secured up higher, but not quite fully backed. I suggested that they fully back their bumpers–corner-type bumpers here–and that would prevent their treads from illegally defining their Frame Perimeter. That was a fun explanation…)

Just a couple of ideas here to help make the most of the situation:

  1. If your frame perimeter, as defined by <R2>, is smaller than the maximum 120 inches, you could try and make your robot wider, effectively moving the corner further out, and preventing the 8" of bumper from blocking the ball.
  2. Another Thing you could try is to mount the bumpers as high as possible, so that only the top of the ball would have to pass through the gap. the bumper zone is 4"-12" from the ground, and since the bumpers are 5" high, you could have the lowest part of the bumper at 7". with a ball 9.5" in a diameter - it might be able to pass through!

According to this sketch, looks like you need to widen your robot by about 3" in order to intake a boulder.

Another radical notion is to modify it to receive boulder from the embrasure.
Good luck, and feel free to ask for further explanation if needed.


Two more cents:
If you decide to widen your bumpers, you can widen the front side of your bot and keep the back width the same. Your frame shape does not have to be a rectangle.

I would vote for Convex Perimeter - or maybe String Perimeter.

Bumpers must cover at least 8" on either side of the Convex Perimeter and be hard mounted to “frame” within 1" of the Convex Perimeter. Any Convex Perimeter side with Vertexes less than 8" apart must be completely covered by bumper, but this short side does not affect the 8" requirement for the other adjacent sides of these Convex Vertexes.

Thanks for the advice! Last night we just ended up extending the frame out about another 6 inches on either side, so we maintained the opening and didn’t have to change much else. It was a way quicker fix than what we thought it would be, and kept our little robot intact. We will definitely be reading the manual a little closer next year.

That’s not the embrasure, that’s the brattice! (brought to you by Mr. Persnickety)

Just to circle back and make sure, your frame perimeter ended up <=120", correct? You say “little robot” so I’m guessing that is the case, just don’t want you to have fixed for one part of the rule and run afoul of the other half of it in the process.

Happy to know it was a quick fix. Good Luck!