Bumper fully supported?

[Bob Holmstrom]

Clarification is needed for the meaning of "fully supported".

Our robot frame is 1 inch thick and is located with its top
edge 7" from the floor. Our plan is to fasten the bumper assembly
(with aluminum angles on each edge and corner reinforcement) to the frame with its top edge in the same plane as the top of the frame. The top edge (1") of the bumper would be "fully supported" but a major portion of the bumper
would not have frame behind it. Does this meet the intent of the rule?

Bob

Sorry to post this here but our team is unable to post to the First Q&A forum for some reason. We are logged in but do not have permission to post.

[MrForbes]

It sounds to me like it could meet the intent of the rule, which specifies that there not be any horizontal gaps in support, and seems not to address vertical support issues like yours. I think you'll see that most robots will have the bumpers lower, and it's possible that your bumpers could be broken by robots running into them and pushing in the bottom part of the backing far enough to break the attachments.

[Teched3]

In addition, you might be able to use standoffs in the gap areas to lend support to the lower edge of your bumper backing. This would help to provide greater resistance to impact from bumpers on other robots bumpers located in the lower bumper dimension range.

[Jared Russell]

The entire LENGTH of the bumper must be supported. The GDC said nothing about the entire HEIGHT of the bumper being supported.

The design that you described meets the criteria in my unofficial (and oft uninformed) opinion.

[GaryVoshol]

IMO it meets the letter of the rule. Maybe not what they expected to see, but there is no rule (yet) against it.

I question the wisdom of the design. Mount your bumper. Now kick it down near the bottom. Repeat several times. Does the hardware pull from the wood? Do the mounting brackets break? Does the wood splinter near the top?

If you've got the weight allowance, I'd try to attach several vertical standoffs to the bottom of your frame to give the bumper some additional backup.

[Bob Holmstrom]

Thanks for the responses - they appear inline with our thinking. We understand that the lower edges of our bumpers probably need additional support. We needed to understand the intent of "fully supported" better before we complete the design. The 1/8" aluminum on standoffs answer created more questions than answers - clearly bumper strength depends on quantity/placement of standoffs.

Bumper corners remain problematic. R08-N clearly states: "“Hard” parts of the BUMPER (i.e. plywood backing, fastening system, and clamping angles) may extend up to a maximum of one inch beyond the BUMPER PERIMETER." and then the figure 8.4 shows a ~3/4" extension as not ok!!

R08 does not seem to include any words that state that corner reinforcement of bumpers is allowed or disallowed on the inside surface. I guess the safe thing is to attach the corner reinforcement to the robot frame.

re posting to the First Q&A forum - yes, I was trying to post to the response forum - I will go back and try again.

Bob

[MrForbes]

Originally Posted by Bob Holmstrom

Bumper corners remain problematic. R08-N clearly states: "“Hard” parts of the BUMPER (i.e. plywood backing, fastening system, and clamping angles) may extend up to a maximum of one inch beyond the BUMPER PERIMETER." and then the figure 8.4 shows a ~3/4" extension as not ok!!

The N and O part of R08 refer to different directions...the hard part of the bumper may extend up to an inch out from the side the bumper is on, but may not extend past the end of that side past the corner at all.

http://www.chiefdelphi.com/forums/sh...ad.php?t=72260

[Bob Holmstrom]

Rules N & O are confusing.

One posting said the bumper perimeter can be found by wrapping a string around the robot frame - which seems to define an object in the horizontal plane. The 1" extension would seem to be in the same plane not a perpendicular plane.

Rule O then states that backing cannot extend beyond the edges.

C'est la vie!

Bob

[Tristan Lall]

Originally Posted by Bob Holmstrom

Sorry to post this here but our team is unable to post to the First Q&A forum for some reason. We are logged in but do not have permission to post.

Check that you're posting in the "ask a question" section, not the "responses" section. Also, only team accounts (FRC#) are able to ask questions; your team's username and password are displayed in TIMS.

If that doesn't work, e-mail frcteams@usfirst.org with the problem.

Originally Posted by Bob Holmstrom

Clarification is needed for the meaning of "fully supported".

Our robot frame is 1 inch thick and is located with its top
edge 7" from the floor. Our plan is to fasten the bumper assembly
(with aluminum angles on each edge and corner reinforcement) to the frame with its top edge in the same plane as the top of the frame. The top edge (1") of the bumper would be "fully supported" but a major portion of the bumper
would not have frame behind it. Does this meet the intent of the rule?

I'm not sure I want to hear the answer to that question...unless it's "we're not going to comment on specific designs".

The Q&A has already set something of a precedent with the ruling on one particular design using 0.125 in aluminum, and as a consequence, people are wondering whether their perfectly-reasonable designs are valid.

This is a clause in the bumper rule that needs to be enforced as little as possible (within the rules, of course). Teams that build poor structure will have only themselves to blame, if something breaks—they've been warned; everyone else shouldn't be forced to worry unduly about the ramifications of this nebulously-defined specification. (Closer to the season, a consensus will probably emerge as to how this clause will be enforced; that doesn't really help now, though.)