Frame Perimeter Tolerance

[MetalJacket]

Let me start by saying I did search first so I know there is another thread here with a similar topic however since that thread was started prior to the new sizing rules I thought it would be better to just start a new one. My question is what is the tolerance on the frame perimeter at inspection? My team is making our frame 28"x28" - which is the max frame perimeter (we did it last year with no problem so that is not our concern). What we were wondering is if we were to powdercoat the frame, thus adding a few thousandths of an inch to each side, would that be a problem? I wouldn't think it would be but I wanted to see if any other teams had experience with this. Thanks,
Jesse

[sdcantrell56]

Why would you build to the nominal max limit?

[BigJ]

Well, in my experience, the inspector won't pull out a giant 30" caliper to measure your perimeter, but I'd caution against building to the very max. I'd leave at least a quarter-inch, if you still have the chance.

[amesmich]

28" inches is 28" regardless of whats on it, however they do say things that protrude out like nut ans bolts < than 1/4" are ok so I would bet it would be ok, but thats just my bet. I would think that if you asked they would say what I said in my first sentence.

I dont think they measure to the nearest 1/16 - .0625, and I cant imagine your coat being much ticker than that? Ifs its an 1/8 thats a different story. Depend on the inspector.

Last year we used 1/4 coper tube from our compressor because of heat. We were failed even though it was not in the rules. Another team got inspected with coper and passed. We brought this to their attention and they revoked the other teams inspection cert and made them change it.(we felt bad) My point is ruels are interperted differently by different inspectors.

[jee7s]

If the inspection procedure is the same as last year, the inspector will be using a tailor-style measuring tape to check the frame perimeter. They will wrap it around the frame in the bumper zone across features that would define a "frame perimeter" per the rules (see the diagrams about gaps, etc). If that end tab is past the 112" mark, you're no good. So, it's up to you to decide the tolerance of the tape, but I'd say it is well under 1/16".

Regarding your powdercoat, that will be more than just a couple thousandths in thickness. I would put it into the tens of thousandths overall. So, if you gain 0.020 (0.005 per side), you're approaching the point where an inspector's tape will reflect the difference.

[cadandcookies]

All I can really say is good luck. Building up right against the limit in itself is asking for a bad time.

[Madison]

Originally Posted by jee7s

If the inspection procedure is the same as last year, the inspector will be using a tailor-style measuring tape to check the frame perimeter. They will wrap it around the frame in the bumper zone across features that would define a "frame perimeter" per the rules (see the diagrams about gaps, etc). If that end tab is past the 112" mark, you're no good. So, it's up to you to decide the tolerance of the tape, but I'd say it is well under 1/16".

Regarding your powdercoat, that will be more than just a couple thousandths in thickness. I would put it into the tens of thousandths overall. So, if you gain 0.020 (0.005 per side), you're approaching the point where an inspector's tape will reflect the difference.

This procedure is not consistent across events. We were never inspected this way.

[Rick Wagner]

No margin? If you design something to be 28 inches square, there's a 50-50 chance it will be under and a 50-50 chance it will be over after fabrication. If the inspectors see a lot of robots close to the limit they may improve their measurement accuracy, in which case, even a 1/64 inch overage will be out of limits. The rules give no tolerance on the limit.

[jee7s]

Originally Posted by Madison

This procedure is not consistent across events. We were never inspected this way.

Must be a Texas thing then. Lubbock, San Antonio, and Houston used the tailor's measuring tape to check the frame perimeter.

I stand corrected.

[Alan Anderson]

There is no tolerance on the frame perimeter measurement. It is either 112.0 inches or less, or it is out of compliance with the rules.

[magnets]

Please, please, please DO NOT BUILD YOUR FRAME 28 x 28!!!!

Let's assume you get your robot together perfectly, with absolutely no extra width or length, you pass your inspection, and play all your matches. Then, you go to pass inspection, and you robot is suddenly 112.5" in frame perimeter. How? When you got the corner of your frame smushed in because you drove into a wall and were hit by another robot, the frame perimeter changed, and you got too big. It's happened to us before, and the last thing an inspector wants to tell you is that your frame is 0.5" too big, and the last thing you want to do is make your frame smaller. It's really, really hard. Trust me....

[MetalJacket]

Thank you all for the input, most likely will not be powdercoating the frame then. As far as the frame perimeter goes, it's a little late to change now (parts already out for mfg) but we should be fine - last year we built to 28x28 doing our entire frame by hand, this year we are doing sheet metal (lasered and bent), so theoretically much tighter tolerance there. I will keep that advice in mind in the future though.

[Steven Donow]

[quote=amesmich;1331369]28" inches is 28" regardless of whats on it, however they do say things that protrude out like nut ans bolts < than 1/4" are ok so I would bet it would be ok, but thats just my bet. I would think that if you asked they would say what I said in my first sentence.
/QUOTE]

In regards to this, previously, I've had the "issue"(ie. it wasn't really an issue) where the LRI further clarified that that rule is simply there in respect to your own FP-ie. if you're 27.5x27.5, those protrusions are okay, but if you're 28x28, they would NOT be okay, because (as said in other posts) 112 inches is 112 inches, so no matter what you still need to fit under the 112 inches-including protrusions.

Keep in mind, this was just one LRI's interpretation, but I assume it'd be fairly consistent across the board.

[MetalJacket]

Originally Posted by DevenStonow

In regards to this, previously, I've had the "issue"(ie. it wasn't really an issue) where the LRI further clarified that that rule is simply there in respect to your own FP-ie. if you're 27.5x27.5, those protrusions are okay, but if you're 28x28, they would NOT be okay, because (as said in other posts) 112 inches is 112 inches, so no matter what you still need to fit under the 112 inches-including protrusions.

Keep in mind, this was just one LRI's interpretation, but I assume it'd be fairly consistent across the board.

That's an interesting interpretation of the rules. R2 says that minor protrusions (such as bolt heads) less than 1/4" are not considered part of the frame perimeter doesn't mention anything about those allowances being related to the rest of the perimeter. I guess in certain situations the lead robot inspector just has to make a call but that would be a situation when I would definitely want to have a copy of the rules on hand.

[magnets]

[quote=DevenStonow;1331383]

Originally Posted by amesmich

28" inches is 28" regardless of whats on it, however they do say things that protrude out like nut ans bolts < than 1/4" are ok so I would bet it would be ok, but thats just my bet. I would think that if you asked they would say what I said in my first sentence.
/QUOTE]

In regards to this, previously, I've had the "issue"(ie. it wasn't really an issue) where the LRI further clarified that that rule is simply there in respect to your own FP-ie. if you're 27.5x27.5, those protrusions are okay, but if you're 28x28, they would NOT be okay, because (as said in other posts) 112 inches is 112 inches, so no matter what you still need to fit under the 112 inches-including protrusions.

Keep in mind, this was just one LRI's interpretation, but I assume it'd be fairly consistent across the board.

Well, that inspector is wrong. The rule says "Minor protrusions no greater than ¼ in. such as bolt heads, fastener ends, and rivets are not considered part of the FRAME PERIMETER." It's very clear.