Robot frame/bumper question

I’m totally new to the forum here so if I overlooked some rule, please let me know!

My team came up with a design, however we’re not sure if/how bumpers would have to apply. Basically the frame would be the traditional rectangle, however about 1/4 of it at the corner would be cut out (like taking a corner piece from a cake). In the manual they diagram a rectangular frame with a section cut out in the middle, but not an entire corner.
Seeing as the bumpers need to cover all outside corners, would we need 8 in. bumper lengths for the inside of the cut out portion?

I might not be that good at articulating the question, so here’s a quick MSpaint illustration!

On the other hand I’m very pleased with the new rule on being able to split up your team number on the bumpers, as long as it’s identifiable. If only they had changed that for last year’s game…
Also, if anyone is willing to divulge their secrets-- are y’all focusing on climbing the pyramid or scoring frisbee points?

The definition of the bumper mounting and Frame Perimeter are inter linked. Since the Frame Perimeter is determined by wrapping a string around your frame. Bumpers are required on all exterior corners of the Frame Perimeter. Using the string to visualize, the ??? are not on exterior corners of the Frame Perimeter so no bumpers are needed. See also Fig 4-2 for a visual drawing of this.

Wouldn’t that perimeter require bumpers along the diagonal segment of the perimeter string? – 8" from each vertex of the frame perimeter ?

I am of course working from a GDC interpretation from 2012 so the GDC response for 2013 will the deciding factor. I can see many teams thinking along these lines though.

yes, bumpers are required on exterior corners of the frame perimeter as measured by the ‘string test’. I would be shocked if the rules were different than previous years that had the same language.

I’ve modified your original image to show the frame perimeter. Exterior corners do need bumpers, and I would regard your question marked corners as exterior, as they are common to the frame perimeter vertices. Figure 4-2 shows two corners that are not common to the frame perimeter, so do not require bumpers. However, please do regard a ruling from the GDC as kosher, and not mine.



It would. The 2013 rules state “at least 8 in. of BUMPER must be placed on each side of each outside corner” (R22).

However, the redefinition of the bumper rule (which is on balance a very good thing) apparently allows for an unconventional interpretation. The corner protection requirement specifies 8 in of bumper on each side of an outside corner, but does not specify that this 8 in must be measured along the bumper backing. (See attached.)

In fact, because the definition of frame perimeter continues to permit a skew polygon, multiple corners’ 8 in dimensions need not even be coplanar, nor parallel to the floor in any given orientation.



If a diagonal bumper is required, that’d really throw a wrench into our plan… We were hoping to use a mechanism inside the cutout that would allow us to climb. :mad:

One other thing: R04: In the STARTING CONFIGURATION, no part of the ROBOT may extend outside the vertical projection of the FRAME
PERIMETER, with the exception of minor protrusions such as bolt heads, fastener ends, rivets, etc.
If a ROBOT is designed as intended and pushed up against a vertical wall (in STARTING
CONFIGURATION and with BUMPERS removed), only the FRAME PERIMETER (or
minor protrusions) will be in contact with the wall.

Tristan et al,
I am restating the 2012 interpretation of what defines the opening. If you use the string method then the indent is not on nor does it define the Frame Perimeter. Therefore the indent is not an exterior corner. As Bill Miller explained last year, should a team add something to the indent that is made the same as a bumper, it will not be a bumper and we were not to inspect anything that covered that area. By definition in 2012, only bumpers on the Frame Perimeter are in fact “bumpers”. The GDC is the final response in the matter and they of course can change the interpretation for this year. This question needs to be asked in the Q&A.

Your theoretical string defines the perimeter, not the actual frame. So the string stretched diagonally between the two corners- See Nathan’s picture- define the perimeter that needs a bumper at least 8" from each corner. Like Tristian’s picture So you will need a physical frame to back it up.

R22, Fig 4-2 shows an indention with no exterior corners. Not the case here.

Rule seems pretty clear to me. Hopefully Q&A will respond with something that clarifies this.

So, if you took a rectangular frame, but put a birdsmouth cut at each of the four vertices, there would be no exterior corners, and thus no corner protection requirement? I don’t recall an official ruling to that effect.

I’ve always interpreted “exterior corner” (and “exterior vertex”) to mean any vertex on the frame perimeter.1 The vertex defines it, not the adjacent legs of the frame perimeter (if any).

1 Or, in years where the frame perimeter is not a projection onto a 2-D plane, any vertex on the convex hull of the projection of the frame perimeter onto a horizontal plane.

After thinking about it for a minute more, I see which clause you’re getting at—in 2012’s Fig. 4-3, FIRST implicitly interpreted frame openings along the side of a robot as not being exterior corners by showing them as permissible despite not having an 8 in leg of protected frame perimeter on one side of the vertex. (This was convenient, because it allowed robots to have unprotected openings.)

That works for case of a 180° frame perimeter vertex—which can plausibly be said to be not a corner—but doesn’t actually make sense in the general case, as we’re finding in this thread. The lack of generality didn’t occur to me last year.

I agree FIRST needs to issue a ruling on this one.

What I remember from last year was that we assembled the KOP frame and we fitted the corners so the inside corners touched leaving a 1 inch gap looking like the OP’s picture. We were told that the perimeter effectively had a diagonal in there and that it wasn’t going to work. So we had a couple of kids spend three hours cutting and fitting pieces into each corner so we had a square corner.

This year the rules have been changed to allow up to 1 inch of bumper at a bumper end not having to be backed by the robot.

It will be interesting to see what the GDC rules. Hopefully it won’t just be a blanket statement saying the GDC does not make robot design decisions.

Not only is it not a bumper, it also loses the bumper exemption to the weight limit.

So you are saying that you used the standard kitbot frame with the extrusions in the corners but your C channel did not extend to the corner? Then the inspector was correct in the decision. The desire of the GDC (as I understand it) is that bumper ends be backed by robot frame so that collisions do not damage the bumper or the mounting.
This was of more importance last year with teams trying to satisfy all of the bumper rules yet leave as large an opening for picking up balls as possible. An eight inch bumper segment on each side of the front of the robot only allowed a certain width of opening. Teams designed the robot for the larger opening and then made their bumpers only to find out that the bumper hung out over the opening.

It wouldn’t be build season without at least one interesting bumper question!

But I still say this year’s bumper rules are awesome.:slight_smile:


I see that there’s a lot of debate over this question now! One thing I noticed is that someone asked this question in the 2013 Q and A, located here:
Of course, a more specific answer would’ve been lovely… but it is an official response. Thoughts?

Someone in Q&A is thinking like a politician - answering questions without saying anything. See post #6 for a frame perimeter drawing. #7 for more info. 42

The updated drawing for R22 shows the appropriate way to put bumpers on an L-shaped robot.