Quote:
Originally Posted by Andy A.
My impression was that the new perimeter rule was at least partially driven by a desire to eliminate the sizing box as a choke point in the inspection process. It will be interesting to see how it goes. The cynical part of me thinks the 'string around the 'bot' method has some room for error and ambiguity the sizing box did not.
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Getting rid of the inspection box may well free up a bit of extra pit space in the more tightly-packed venues (the Waterloos of the world), and simplifies inspectors' logistics. But I suspect that the decision was also driven by the design of the boxes themselves.
The tolerancing on the sizing boxes was done incorrectly from the outset. They should have been designed and constructed with a geometric tolerance that inherently passes all legal robots, even given the degree of dimensional uncertainty in manufacturing the box.
Instead, the sizing boxes as delivered to events were occasionally undersized in places. Although FIRST's eventual change from the ratcheting strap on the shipping cart (which caused the front frame of the sizing box to bend like an hourglass), to a locking hard case saved them from wear and tear, in the first few years of those sizing boxes, on more than one occasion, the inspectors had to use brute force and/or fabricate gussets to expand the sizing box to an acceptable plus tolerance. (I believe the worst one I ever dealt with was about 0.15 in undersized in one corner, and 0.20 in undersized right down the middle.) All so that teams that built their robot with an ill-advisedly fine minus tolerance could (correctly) pass inspection with a minimum of delay.
All things being equal, it's better to risk passing a slightly oversized (illegal) robot than to risk failing a slightly undersized (legal) one. After all, the inspection apparatus are the embodiment of FIRST's rules; if the boxes are not designed to ensure that every legal robot will pass, teams will lose confidence in the apparently lackadaisical attention to specifications, and believe that the size restrictions are suggestions rather than hard limits. That makes the job harder for the inspectors, and in the long run, harder for FIRST as well. Next time they need a sizing box (or similar), they should consult with an engineer who works in gauge design for manufacturing.
The point of that anecdote is to illustrate why I suspect that FIRST decided that the sizing boxes were an unsustainable investment. They're probably worth well over $1 000 each, and you need one in good repair for every field set (of which there are probably 15 by now). Even if you realize that some of them are out of spec, it's hard to justify the cost of replacing them all. If you only fix the dimensions on the new ones, then some regionals get differently-enforced rules. This decision saves FIRST money in the long run, and saves them the headache of treating the sizing boxes like precision gauges.