2024 Crescendo.
the front side (yellow) is 5.5" X .75" (1"x6"). Can the small section on the back, intake side (green), be 4.5" X .75"
Thanks
4.5 is within 5 +/- 0.5 in R408, so long as you meet the other rules, I think it’s OK (but you’re using up all the tolerance, so don’t get even shorter by accident).
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Under 2024 rules, R408-A says the backing must be “5 in. ± ½ in”. Both 5.5" and 4.5" fall into that tolerance, but any small variation risks being outside of it. I’m not sure what your parenthetical reference to 6" relates to, but bumper backing 6" tall would not be legal under 2024 rules.
I know you asked about 2024, but we’re all looking at what’s going to happen next year. We haven’t seen the 2025 rules yet, but from the overview, says that it must cover between 2.5" and 5.5". It is not clear to me that your green bumper comes down to 2.5".
we’re doing off 2024 off season.
6" was the dimensional lumber off Home Depot, 1"X6" is 3/4"X5.5" actual.
This might seem ridiculously petty, but the rules as written say that the backing must be 3/4" nominal. If your backing is 1" nominal but turns out to be 3/4" when measured, then technically it does not comply. I’m not defending the bumper rules here, just pointing out what they say.
This is, of course, incredibly unlikely to come up in inspection (unless your bumpers are overweight), and most off-season competitions do not have (regular) inspection. Obviously, it doesn’t make much material difference, and does not seem to offer significant competitive advantage. And this will all (I hope) be moot in 2025.
Not sure I understand. If the thickness of the plywood is measured at .75" with Caliper, it doesn’t comply?
That plywood is probably sold as (nominally dimensioned as) 3/4" whether it measures 0.75" or 0.72".
Gavin’s point is that a “1 by 6” piece of wood that is actually 0.75" x 5.5" is still nominally 1" x 6" and the rule is worded a little awkwardly, but seems to be explicit that the nominal dimension needs to be 3/4".
That’s almost surely because the rule was written with plywood in mind, not hardwood dimensional lumber. If you make it from 1"x6" dimensional lumber, you’re spectacularly unlikely to fail an off-season inspection (if they even have any) and very unlikely to fail a regular season inspection, even though the nominal size of that lumber does not meet the rule.
(Edit to get Gavin’s name right; sorry!)
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Have you successfully used dimensional lumber for your bumpers before?
I don’t know about the OP, but it has been done many times. I wouldn’t recommend it though. Plywood made from the same species of wood will hold fasteners a lot better and be less prone to cracking, and for 2024 and earlier, you are right on the maximum so if the mill cut the lumber oversized or it absorbs too much moisture it will be illegal (though probably not enough to fail inspection).
I asked because we used non-plywood lumber for our bumper backer. Once.
Give or take what the rules designate, this would be fine. Generally, it’s a safer (and usually easier) option to stay exactly on the preferred measurements (in this case, 5 inches). This border is allowed and can definitely be used, but if you’re unsure on specifics and haven’t fully committed to this model yet, sticking to the outline might be a tad easier. Up to you and your team :]
Bumper is built and done last night with this design. The intake side (green) is 4-5/8" tall just to be safe while still maintaining 7" overall height off the ground. This is just a demo bot for off season, but would like to stay within the spec limits.
For 2024 I did 4.6" tall bumpers, aiming for the limit can be a dangerous game, but no particular reason go for 5" if you can hit a decent tolerance in wood.
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