Quote:
Originally Posted by Tristan Lall
That's exactly why it's hazy, though: let's say I use a 0.19 in thick × 1.00 in tall strip of polycarbonate as the backing material, with several screws into the bumper plywood. Will it be strong enough across a 20 in span? My gut feeling is that under most gameplay, it would not break, or even deflect appreciably. But what if the team used (brittle) acrylic instead? Or if they turned the strip 90° to buttress the plywood? I don't think it makes much sense for inspectors to be trying to make that particular determination—it will just be their best guess, and it's ripe for debate that serves no useful purpose.
If your bumper plywood ever breaks, even with no backing (and especially with the aluminum angle depicted in Fig. 8-1), you're probably doing it wrong. And if you use high-quality hardwood marine plywood (as opposed to the regular softwood stuff), you could probably span over 30 in without any backing, and suffer no ill effects.
I just don't think it's valuable to add a specification here, given that it's one more thing for teams to worry about, one more thing that needs to be checked (consistently) at inspection, and is probably superfluous anyway, given moderately-well-constructed bumpers.
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I submit the following two photos into the evidence:
http://www.chiefdelphi.com/media/photos/31159
http://www.chiefdelphi.com/media/photos/23644
A 38" span of bumper isn't likely to survive many of those.
As you say, high quality marine hardwood bumpers with reasonable length spans would be more than fine, and we both know that. But the bumper specifications don't call for high quality plywood, nor maximum span lengths. Instead, they call for the bumpers to be fully supported along their length, which serves a similar function of protecting rookies from underestimating impacts and ending up with snapped bumpers. The rule is, after all, ultimately there to protect less experienced teams from themselves. As are a large number of the rules. Which is why I don't spend time railing against having to electrically isolate everything from the robot frame, the various fusing rules, and other things that I know enough about to do differently and better.