Quick Bumper question

bumpers

#1

Can the bumpers be mounted such that they DO cover the entire perimeter, but along the perimeter they cover only the top half of the chassis. We are using the 2inch Vex material for the base of our robot, so we want to mount the bumpers so that the bottom 1 inch of the material is not protected by bumpers. Our bumpers still are 6 inches tall, but instead of covering the 2inch Vex + extra 4 inches, they are covering 1 inch of Vex + extra 5 inches.

Hope that makes sense. I can provide a picture if we need clarification, but I just left the shop.

Thanks!


#2

As long as you satisfy R25 (so the entire bumper is contained between the floor and a plane 7.5" off the floor), it doesn’t matter how much of the frame is actually covered vertically.

R25


#3

As well as R3, don’t make the bumper itself more than 5 1/2" tall.

R31. BUMPERS must be constructed as follows (see Figure 10-6):
A. be backed by ¾ in. (nominal) thick (~19mm) by 5 in. ± ½ in. (~127 mm ± 12.7 mm) tall
plywood or solid, robust wood. Small clearance pockets and/or access holes in the plywood
backing are permitted, as long as they do not significantly affect the structural integrity of
the BUMPER.


#4

Provided of course, that it is greater than zero.

R33. BUMPERS must be supported by the structure/frame of the ROBOT (see Figure 10-8). To be considered supported, a minimum of ½ in. (~13 mm) at each end of each BUMPER wood segment must be backed by the FRAME PERIMETER (≤¼ in. gap). “Ends” exclude hard BUMPER parts which extend past the FRAME PERIMETER permitted by R31-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

#5

How actually does this play out. If you had a WCD, using tiny wheels, and wrapped it in 1"x1" tubing to create a FRAME PERIMETER (FP) . Your entire FP could be under your BUMPERs, if you want them as high as possible. R33B defines the horizontal requirements for backing (no gaps larger than 8"). What I don’t see anywhere is the vertical overlap requirements.

How much engagement do you need between FP material and BUMPERS in the vertical dimension?


#6

As much as is necessary to have a “rigid fastening system” to a reasonably astute observer.


#7

I am good with the “rigid fastening system”… The “reasonably astute observer” does not fill me with rainbows and sunshine.

In theory, bumper mounts every 8" with FP backing only in the corners meets the letter of the rules. Not sure if that level of engagement would pass at all events. Curious if anyone has experience with going down that route?


#8

Do you have any photos of exactly what you’re concerned about. There may be a "reasonable observer " or two on here that could chime in with what they think. ;D


#9

The rule is written intentionally vague because it’s hard to regulate things like this because of the many diverse build styles in FRC. You must have at least some verticle part of the frame perimeter backing the bumpers in order to not violate the maximum gap rules but there is no regulation on how much must be in contact as long as there is some.


#10

As per R30, if your BUMPERS have any sort of multipart mounting system, the side that is attached to the ROBOT is considered part of the ROBOT. We use a L bracket & post system, with the brackets mounted on the BUMPERS, and the posts mounted to the frame rails. The posts are drilled and the BUMPER is secured with R clips, making for very quick bumper changes. It is a robust mounting system (you can easily pick up the robot by the BUMPERS and we have not had the system fail, over a number of years of using it. By its very nature, it allows you to mount the BUMPERS at whatever height is most advantageous, while still being rules compliant, which means a variable amount of vertical overlap with the FRAME PERIMETER. Especially with the new KitBot, with the reversed side rails, I can easily see only having FRAME PERIMETER backing on one edge of the frame rail which is a rather small amount.


#11

Thanks for the help, all!


#12