# Bumper "Overhang"

My team’s system for manipulating the Power Cubes requires a wide open space within the robot and a narrow opening in the front, making what is essentially a U-shaped bot with two “prongs” sticking in towards the center of the opening. I can give specific measurements if necessary.

I cannot find anything in the manual or elsewhere about rules regarding this layout, specifically how the bumpers must be placed. Would the 6 inch rule be all we have to worry about, or are there other restrictions that would apply?

You must have at least 6" of bumper on each side, meaning a total of 12" of cover. For example, if you have a 20" front, you have to have at least 6" of bumper of each side of that front, meaning a 8" opening. I believe that is what you are asking.

So there’s no extra bumper rules considering the interior space? In that case, we’re set. Thanks!

Make sure you understand what this means…it would probably be a good thing for YOU if you post a picture or sketch (with dimensions) of what you have in mind, so we can see if we think it meets the rules. Words don’t work very well to explain this stuff, since words mean different things to different people.

In general the way I would suggest you check… put a string around the widest part of frame at or below 7.5" and that pretty much defines your frame (bumper) perimeter… that is the part that needs bumpers of at least 6" per corner and if any side is less than 6" it needs a bumper.

The only “inside thing” would be height in starting position up to 55". As long as the prongs don’t go outside your frame perimeter the string defined , sounds to me like its probably ok.

Good point- Here’s a general sketch of the layout

If the opening is 20" and you have two 6" bumpers on the comer that side is 32" lets call that X

Is the other Y dimension 28" or less?

Max starting configuration size is 33x28 (x 55 tall)

Yes the other dimension is 27.5

Sounds good. From what you describe IMO of course come to your own conclusion in the rule book.

Remember that the 6" needs to be from the outside corner of the frame, not from the outside corner of the bumper.

Also pay attention to (emphasis mine):

That is, also have some robot frame structure extending 6" from the corner - don’t have the wooden bumper sticking out past the end of the frame structure.

Would B mean that only 8" of opening around the Wheels.

If by this you mean gaps in the frame perimeter due to e.g. cantilevered wheels:

• If you only put bumpers on the corners, you only need 6" from each corner.
• If you have bumpers continue down the full left and right sides of a WCD
style robot, the frame needs to come out and touch the bumpers at least every 8".
• If you have gaps of (for example) 10", you could have a disjoint bumper segment that covers only the structural part of the frame perimeter; a recent Q&A verified that you may have more than two bumper segments on a robot side. I don’t see any minimum length for such a segment.

I would be truly concerned with damage to the frame should you have a high speed collision on the unsupported 6" front pieces.

.

That sketch is not to scale; there is only 1.5" of unsupported bumper on either side.

Reading this thread leads to lots of confusion. I’m not sure the OP has it straight yet.

The diagram should include a clear distinction between the frame perimeter, actual framing members, and the proposed bumpers.

Another way of looking at this: Because 6" of frame must be covered on each side of a corner, a minimum bumper (or pair of bumpers if built as two pieces) at a 90 degree corner will measure 9.25" on each side along the outside of the bumper, because bumpers are approx 3.25" inches thick.

Also, the last .5" of bumper must be backed by solid frame material at each end of the bumper.

unsupported bumper, or unsupported frame? There’s a BIG difference!

Borrowing from my team’s twitter account, see the attached image. The far side of the robot has an opening similar to what’s been described.

Notice that there is 6" of actual frame material on either side of the opening. Not just 6" of bumper (when we get the bumpers made), but 6" of frame. This is due to the wording of R32:

BUMPERS must be supported by the structure/frame of the ROBOT (see Figure 8-8). To be considered supported, a minimum of ½ in. (~12.7 mm) at each end of each BUMPER wood segment must be backed by the FRAME PERIMETER. “Ends” exclude hard BUMPER parts which extend past the FRAME PERIMETER permitted by R30, part B. Additionally, any gap between the backing material and the frame:
A. must not be greater than ¼ in. (~6 mm) deep, or
B. not more than 8 in. (~20 cm) wide

Emphasis mine.

You need some sort of structure/frame of your robot at either end of each bumper segment.

As it is, I’m not going to trust the frame as it’s pictured, we’ll be adding some support brackets to better secure those 6" frame segments.

Sorry I meant unsupported frame. That’s what I get for posting before 1pm.

If that sketch is just the frame then you should be okay.