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.

[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.

[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.

[gabrielau23]

Originally Posted by jee7s

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.

I think Chesapeake and DC used it as well?

[nathannfm]

Last year at one of the MAR qualifiers the inspector used a metal measuring tape with the bow in it to keep it extended. When he wrapped it around our bot naturally it was way over because of the bow, so I asked him to pull it a bit tighter and jokingly said it was 112 in the CAD. after pulling It tight it was pretty hard to tell the exact size, but the tape still wasn't conforming to the frame properly so he just gave it to us.
My advice (if there is really no way to change it) would be to bring a cloth tape and pull it out if they give you any trouble after trying a metal one, no guaranty they will accept it but but be nice about it and maybe they will pass you.

[Alan Anderson]

Originally Posted by nathannfm

My advice (if there is really no way to change it) would be to bring a cloth tape and pull it out if they give you any trouble after trying a metal one, no guaranty they will accept it but but be nice about it and maybe they will pass you.

At every event I attended last year, a number of cloth measuring tapes were included in the supplies designated for robot inspectors.

If you haven't put your frame together yet, it would be easier to shorten it now rather than wait until it's assembled.

[Michael Hill]

At QCR last year, we had a piece of rope with 2 knots tied in it at 112". Unfortunately, it was rather difficult to measure exactly 112" because it stretched up to .25" or so. I was surprised we didn't use a soft measuring tape.

[Al Skierkiewicz]

When we used the sizing box, the robot had to fit, bolt heads and all. Now that bolt heads are not considered, this should be easier.

[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.

[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.

[artdutra04]

Originally Posted by 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.

There technically is a tolerance but it's asymmetrical; it's 112.0 +0.0 / -112.0