Legal Bumpers

Technical Technical Discussion
1

Our team decided to build a mecanum drive this year however when it comes to bumpers we are struggling to find something that would legally work at competition. The main problem is around our wheels since they are technically our frame perimeter. Our wheels are 2 inches thick and 6 inches wide so if we tried to put bumpers on the top we would exceed the 10 in bumper zone and if we went around the outside of the wheels it would exceed the 8 in support. If anyone has any ideas they would be greatly appreciated.

Sincerely,
K. O’Neil
FIRST Team 3512

mecanum Drive.jpg
mecanum Drive.jpg1280×960 177 KB



mecanum Drive.jpg
mecanum Drive.jpg1280×960 177 KB

2

You will need to add a frame perimeter around the outside of your wheels that is less than 112" in total length. Don’t know the rules number but that is what you need to do.

3

Think three-dimensionally.

Put your bumpers around the outside of the wheels. Add several supports not more than 8 in apart, including one in each corner that passes over the wheel. They become the vertices of the frame perimeter. You may want to attach these to both the top and outer surfaces of your frame rail (or at least attach it to one and brace it off of the other).

R29 has the pertinent design specifications (but read all of the rules, and especially all of the bumper rules).

On another note, next time, think about these things when you’re choosing a drivetrain. This time, you’re lucky that an easy solution is available.

4

Some relevant rules:

*R02: The ROBOT must have a FRAME PERIMETER, contained within the BUMPER ZONE, that is comprised of fixed, non-articulated structural elements of the ROBOT. Minor protrusions no greater than ¼ in. such as bolt heads, fastener ends, and rivets are not considered part of the FRAME PERIMETER.

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.*

R29 A: a minimum of 1 in. at each end of the BUMPER must be backed by the FRAME PERIMETER

So regardless of your bumper rules, the configuration shown in your photo is illegal based upon R02 and R04.

You must enclose the wheels within a frame perimeter. Once you have done that, hooking up the bumpers should become trivial.

Sorry… you’d probably figured all that out already and were hoping for a different alternative, but this isn’t a bumper issue, it is a frame perimeter issue. Once you meet R02 and R04, the bumper rules will no longer present a problem, I think.

And yeah, I get it… you’re probably already at the existing size limits for frame perimeter. If so, you’ll have to make some changes to shrink your existing chassis.

Jason

Edit: If you’ve got the space, however, Tristan has presented a way to meet R02 and R04