Cantilever Wheel Bumpers

[EricH]

Originally Posted by vamfun

"Under the provisions of Rule <R08-M>, the entire length of the BUMPER must be structurally backed by the frame of the ROBOT. Standoffs, stanchions, and spacers used to mount the BUMPERS that result in lengths of the BUMPERS being unsupported will be considered a violation of this rule."

We plan to place aluminum structural plate (say 1/8in) across the Standoffs so to meet the intent of this rule. The plate will be bolted to the frame with pillow blocks. The plate is removable to get access to the wheels.

Does anyone see a R08 violation with this?

I don't, but it never hurts to make sure.

I'd phrase a Q&A question similarly to: "Would structural material running the length or width of a bumper attached to the bumper side of a set of standoffs meet the intent of <R08> if it was removable separately from the bumpers?" (This to cover other similar tricks.)

[Tom Line]

Calling it structural doesn't make it structural.

1/8 aluminum is pretty thin, and I doubt you'll actually be relying on it for any structural support for the robot - especially not in a single thin strip.

Definitely Q&A this, because as I see it, if you had a judge that understands robot design, they'd take one look at that 1/8 inch thick strip of aluminum and tell you it doesn't meet the rule.

[MrForbes]

This rule was a major cause of our decision to go with non-cantilevered dead axles this year. It turns out to have saved us some time and work, too. Plus we have a nice mounting surface (the robot chassis) at the perimeter of the robot to mount our roundish ball handling mechanism.

[Jared Russell]

Good Q&A question.

The wall thickness of the kit frame is only 1/8", so I think that this should suffice (granted the kit frame is C channel).

[Taylor]

"roundish ball handling mechanism". I like that.

[Madison]

Originally Posted by Tom Line

Calling it structural doesn't make it structural.

1/8 aluminum is pretty thin, and I doubt you'll actually be relying on it for any structural support for the robot - especially not in a single thin strip.

Definitely Q&A this, because as I see it, if you had a judge that understands robot design, they'd take one look at that 1/8 inch thick strip of aluminum and tell you it doesn't meet the rule.

Unfortunately, the inspectors are not typically qualified to determine what may or may not be a structural member. A plate, no matter how thin, will in some manner affect a frame's rigidity and strength.

Who is the ultimate arbiter of "structure" and of what represents sufficient contribution to the durability of other structures?

[Jared Russell]

Originally Posted by Madison

Who is the ultimate arbiter of "structure" and of what represents sufficient contribution to the durability of other structures?

Where can I sign up?

[JesseK]

Originally Posted by Madison

Unfortunately, the inspectors are not typically qualified to determine what may or may not be a structural member. A plate, no matter how thin, will in some manner affect a frame's rigidity and strength.

Who is the ultimate arbiter of "structure" and of what represents sufficient contribution to the durability of other structures?

I agree.

To stay in compliance with this rule we're using 1/8" thick honeycombed fiberglass plates, and the gaps themselves are relatively small (7" max). We know that this is structurally sound, but to the typical person "that stuff is too thin".

[Kevin Sevcik]

Ultimately, the teams will probably have the final say in whether something counts as structural support for a bumper. But I think everyone should note the GDC's caution that they implemented this because unsupported bumpers were breaking or splintering under impacts. So teams should probably expect to get away with "structure" that doesn't look too incredibly flimsy.. But they should also expect bumpers to be closely examined for damage and for robots with damaged bumpers to be banned from the field until the problem is fixed.

Originally Posted by Tom Line

Calling it structural doesn't make it structural.

1/8 aluminum is pretty thin, and I doubt you'll actually be relying on it for any structural support for the robot - especially not in a single thin strip.

Definitely Q&A this, because as I see it, if you had a judge that understands robot design, they'd take one look at that 1/8 inch thick strip of aluminum and tell you it doesn't meet the rule.

Sure it does.

Anyone see the plastic coverings on the sides of 254 for 06, the last year before bumpers were required? I recall them only using some (fairly) thin polycarb, and they were fine....

[waialua359]

Lets all not forget that the most sound structure on the perimeter is the bumper themselves. Adding an additional thin sheet as the backing is bonus.
I have yet to see a bumper break completely in half due to impact.
If it happened, I bet rarely.
Mandatory bumpers (in how they should be made and mounted) in itself should be self-sufficient. If not, why make them required (considering the purpose is to protect robots)?
If the new rule implies that the bumper themselves may not hold up during a competition, then the rules for how to make them should be modified to meet its objectives in any situation.

[qwertyuiop[]\]

Does the back have to be completely covered? we are planning just to bolt our bumpers on to the second layer of our 8020 frame.
_________________ second layer
|_______|________| first layer

[EricH]

Originally Posted by qwertyuiop[]\

Does the back have to be completely covered? we are planning just to bolt our bumpers on to the second layer of our 8020 frame.
_________________ second layer
|_______|________| first layer

You should be fine. If you really want to be sure, ask Q&A.

<R08> M says length, not height or back. If they had wanted the entire back covered, they would probably have said so.

[Richard Wallace]

From a related thread:

Originally Posted by dlavery

I hate to "break" it to you, ...

I highly recommend reading Dave's full comments on this topic, in the thread linked above.

[Molten]

1/8 inch is not enough. Look at lavery's math. If I was a ref, I'd tell you to go back to the drawing board. Sorry, just my opinion. Not an actual official.

Why is everyone determined on having cantilevered wheels? Can someone give me a bit of info? Is there really much of an advantage?