Bumper requirement.

We have a chassis configuration that would look like the picture. The corner to the angled in part is 4.5 - 5 ". As per R19 …If a side is shorter than 8 in., the entire side must be protected by BUMPER…] So then we only need to cover the said part correct and not the angled part inside the opening?

The side isn’t only 8 inches though. The side is, if I understand correctly, 9-10 inches plus whatever that opening is. Ergo, you need 8 in on each side.

I have uploaded an edited version of your image below. The line highlighted in green is defined as a side of your frame perimeter. Because the frame perimeter is defined as the polygon formed by all exterior convex angles on your robot, the side continues through the gap in your robot’s frame. Your bumpers as currently configured are illegal unless rectified to match the configuration shown in blue.

Yes I seen the >=8 but doesn’t the rule say

“If a side is shorter than 8 in., the entire side must be protected by BUMPER”

This is our debate.

The side of the Frame Perimeter.

Here is how to settle the debate: Take a string, stretch it around your frame. That string is your Frame Perimeter. Any point where that string forms a corner must have 8" of bumper on either side, plus a fill-in piece to fill the corner. If the string forms a curve, the entire curve gets a bumper.

I’ve attached a full-robot sample image–one side of the opening is legal, one is not. Your design is currently on the “not” side of that.

Its sinking in… I don’t have to like it. We are going to have to rework a few things.

Technically isn’t the 8" measures from the corner of the robot, not the corner of the bumpers? This would require it to extend an additional ~3.25" in to the gap on each side.


This is correct. I should have clarified that in the drawing, but that is why the arrows didn’t extend all the way to the end of the bumper.

R26 then states BUMPERS must be supported by the structure/frame of the ROBOT

This would mean the front C-channel must extend in from the corner >=8" correct?

How much of the vertical 5" bumper backup board must be supported by the structure/frame?

There are many ways to support it, but the simple version is to have the channel be 8" long. There is no specific amount in the vertical direction that needs to be supported. The main point of the rule is that you can’t have the end of the bumper floating in free space. A flat sheet of thin metal that covers the entire back of the bumper also wouldn’t count as supported for most inspectors.

My guideline is that if the bumper was not present, you wouldn’t be able to bend the frame behind it easily by hand. If you are counting on the bumper to be a structural element of your frame, then it won’t pass inspection.

No we would cut the regular c-channel to 8". Seems though we might only have the bottom 1 to 2" in contact with the frame. We will see, just wanted to know if there was a rule we had to pay attention to.

Thanks you all been a huge help