Fasteners extending outside the FRAME PERIMETER

[artdutra04]

Well this make sheet metal designs a bit more difficult... back to the old flat head bolts with PEM nut option.


For those which cannot change their fasteners to flat head bolts, here's the McMaster part number that I think will save a lot of teams this year: 8782K12

1" wide x 1/4" thick polypropylene strips at $0.53/foot. Polypropylene is among the lightest and cheapest commonly available plastics, but even still, installing this strip around the outside of your robot perimeter will add just over a pound.

For comparison, using a 1/4" x 1" strip of Lexan will add over 1.3 pounds.

[Rick TYler]

Originally Posted by artdutra04

For those which cannot change their fasteners to flat head bolts, here's the McMaster part number that I think will save a lot of teams this year: 8782K12

1" wide x 1/4" thick polypropylene strips (...) will add just over a pound.
(...) 1/4" x 1" strip of Lexan will add over 1.3 pounds.

6mm Okoume plywood in a 1" wide strip around the robot would add about .6 pounds. Double-layer corrugated cardboard might even be lighter than that.

[GaryVoshol]

Originally Posted by Joe Johnson

As to the rivets below the bumper zone, unless they were lined up with ones in the bumper zone then they would have always been illegal. Am I right on this?

Not precisely. Previously if you had a row of rivets along your FRAME PERIMETER, they would have extended the PERIMETER along that side. Any rivet above or below the BUMPER ZONE, but still within the horizontal limits of that row, would have been protected.

Originally Posted by EricH

You could also try getting some balsa wood. That's pretty light--in fact, a lot of R/C airplanes are made from it.

Originally Posted by Rick TYler

6mm Okoume plywood in a 1" wide strip around the robot would add about .6 pounds. Double-layer corrugated cardboard might even be lighter than that.

Can you say "Squish!" Both of these materials would negate the whole intent of the reason for exempting protrusions in the first place, which was to ensure that bumpers were firmly attached to a solid frame member. I don't see anything that would prohibit the use of the materials. It's just that by using them, you make the bumpers less stable, not more robust as was noted for the reason it was changed in Team Update 6.

Next question, how are inspectors going to measure this for compliance? The old see-what-touches-a-vertical-wall-first test doesn't work. How can an inspector tell that your lower frame is or isn't really 1/8" smaller than your frame in the BUMPER ZONE which defines the FRAME PERIMETER?

[Rob]

I am with the group that rates this change to the design rules as unacceptable when presented at this time in the build season.

I hope that there is a misinterpretation here and that whatt appeared to be a previously acceptable condition will prevail.

While we have the ability to extend the size of the bumper zone by 1/4" in each direction it will require the purchase of some new material as well as the cutting of new bumper wood. This is simply a shuffling of words that created a great deal of waste.

A ruling like this creates the appearnace that the author of this update does not understand what teams go through during the build season. I hope that sanity prevails over misunderstanding and we do not see any other game changing updates during the season.

Rob

[Mike Betts]

Originally Posted by GaryVoshol

...Next question, how are inspectors going to measure this for compliance? The old see-what-touches-a-vertical-wall-first test doesn't work. How can an inspector tell that your lower frame is or isn't really 1/8" smaller than your frame in the BUMPER ZONE which defines the FRAME PERIMETER?

I can not answer for other inspectors, but I always bring a 6 foot level with me... I have only had to use it a few times...

[johnr]

I will admit that after the last couple of years that i read the rules with an eye towards,"What does the gdc want all the robots to look like this year?" For some reason a flat top upside down pyramid came to mind. Now i know why. I feel bad for the inspectors that are going to have to tell a team that their rivet heads are out of perimeter.

[Rick TYler]

Originally Posted by Mike Betts

I can not answer for other inspectors, but I always bring a 6 foot level with me... I have only had to use it a few times...

Whacking team captains with a 6-foot level might be satisfying, but it probably violates some rule or another. Sorry.

[MrForbes]

Originally Posted by GaryVoshol

Can you say "Squish!" Both of these materials would negate the whole intent of the reason for exempting protrusions in the first place, which was to ensure that bumpers were firmly attached to a solid frame member.

You can easily poke your finger into balsa wood or corrugated cardboard. But if you lay a piece of either on the floor, then place a piece of 3/4" plywood on it, and stand on it, what happens?

If there is sufficient surface area behind it for support, these soft materials will probably work very well as bumper shims, to bring the FRAME PERIMETER out past the fastener heads in the lower part of your robot.