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Unread 30-01-2014, 16:12
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Re: The age old question - bumper mounting

Quote:
Originally Posted by bachster View Post
Thanks for the clarification, Nuttyman54. It still seems to me like this doesn't meet the intent of "backed by the FRAME PERIMETER..." as my definition of "backed" would be surface to surface (or perhaps surface to edge). In this arrangement, there is still no part of the bumper wood directly touching the outside edge that defines the frame perimeter (or within 1/4"). Yes, there are bolts/rivets just interior to the frame perimeter holding a bracket in shear, but in my mind that's not the same thing. If the C of the frame was less than 5" tall, such that the wood directly contacted the outside edge which forms the frame perimeter, that would be more obvious to me that it meets R26. (Or even if the C was just a little bit shorter, and the brackets went to the outside rather than the inside, assuming the brackets are less than 1/4" thick).

If I were to speculate on the intent of R26, it would be that if the robot was hit hard in the bumper zone, the bumper would be prevented from moving relative to the robot (or at worst, would only move 1/4") by the wood surface compressing to the frame perimeter. In this example, the wood is prevented from moving inward by the shear strength of the bolts/rivets, not by the rigid frame perimeter. It is perhaps further prevented from moving by the length of the brackets which closely match the depth of the "C", but you could easily have shorter brackets or a deeper "C" and lose that feature. If I was inspecting this design, I would challenge that it meets the intent of the rules.

Thanks for sharing this example of a different form of implementation and rules interpretation. As a robot inspector, I'm interested in making sure I understand how the rules are and should be interpreted prior to the events. I would be interested in any LRIs' thoughts on this.

Katie
I believe the wood is actually backed the frame perimeter flanges, but that's not captured in my very un-precise powerpoint sketch. Both the frame and angle are made from 1/16" 6061 aluminum.

1983 has run this setup since at least 2011 at regionals and champs and never had an issue with inspections. I believe it also most definitely meets the intent of the rule, which is to provide a robust mounting system for the bumpers to attach to the frame perimeter of the robot and protect our robot, other robots and people from damage. It's one of the most secure bumper attachments I have ever seen.

EDIT: After looking at the robot last night, the top piece of AL angle goes on top of the chassis C, not nested inside, so the angle itself is backed by the frame perimeter. That should clear up any confusion about how it complies the rules.
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Last edited by Nuttyman54 : 31-01-2014 at 13:18.