Interpretation of R77-D

[Hawktobot]

Does R77-D also apply to pneumatic cylinders rated less than 120 PSI? Last year we were given special permission during inspection to use two rodless cylinders that were rated for only 100 PSI. The rules state that solenoids rated for less than 120 PSI are allowed as long as a second release valve is installed. Is there any reason that a cylinder would not qualify for the same consideration?

[EricH]

I would wait for your Q&A to be answered. CD is not an official source for rulings.

With the speed the GDC has been responding, that should be sometime tomorrow.

[Hawktobot]

Thanks. Knowing the time frame for responses relieves a lot of the anxiety.

[FrankJ]

Were you given permission by an event robot inspector or the GDC last year? Without something from the GDC (Q&A) you are taking a big chance. The literal reading of the rule is no. One event might accept your logic & another not.

[rich2202]

My guess is that the Q&A will say "no". The rules are the rules, and you are asking for an exception.

That said, the RI's at events have some latitude, which is the "special permission" you received last year. RI's want robots to compete. They are there to help robots compete "safely", not to find reasons to disqualify a robot. Note that I said "safely", which is not the same as "legal".

For example, if you had an illegal motor, they would make you disconnect it, not necessarily remove it, which is what the rules would require. Your "special permission" was the RI's acknowledging that the additional pressure relief valve would keep your robot safe in most circumstances.

"Special Permission" is reasonable when you make a mistake, not knowing any better. If you purposely build a robot that violates the rules, don't be surprised if they make you disconnect it. Once is a mistake. Two years in a row, and the LRI may not be as accommodating. Especially if you ask the Q&A, and the Q&A says "no".

[Jon Stratis]

Personally, I would say no - R75 is very explicit. It's especially a no if you know ahead of time that the cylinders your using are breaking the rules. Accidental use (especially for very young teams, generally rookie or second year) may merit special considerations (so long as it can be made safe AND shown that it gives the team no competitive advantage), at the discretion of the LRI at your event, but then you could easily get a different ruling at your next event.

Your best bet is the Q&A... and once answered on there, you're stuck with that answer - and you'd better bet your LRI will have read your question and your answer. I know I go through them all, with special attention to ones made by teams at my events (I try to get an idea of what crazy stuff I can expect to see, and I want to make sure I know the proper rulings for what they're trying to do!).

[JesseK]

It is such a shame the limit is 120 psi. So many metric cylinders are rated for 8 bars, which is 116 psi. Surely the engineers of the metric cylinders rounded down to 8 bars after they added in a margin for safety.

[Jon Stratis]

Originally Posted by JesseK

It is such a shame the limit is 120 psi. So many metric cylinders are rated for 8 bars, which is 116 psi. Surely the engineers of the metric cylinders rounded down to 8 bars after they added in a margin for safety.

From the bottom of page 4 in the Robot Rules:

Some of these rules make use of English unit requirements for parts. If your team has a question about a metric-equivalent part’s legality, please e-mail your question to frcparts@firstinspires.org for an official ruling. To seek approval for alternate devices for inclusion in future FIRST Robotics Competition seasons, please contact frcparts@firstinspires.org with item specifications.

I would call an 8 bar pneumatic device to be a "metric equivalent", given how close it is to 120 psi. I know, bars and psi aren't really English/metric, but the same principle applies, I think.

I've also seen teams contact a parts manufacturer to get more details on the ratings. Often, once explaining the situation, they can get the manufacturer to provide them with some sort of documentation that says "yeah, 120 psi is perfectly safe".

[Nate Laverdure]

Originally Posted by JesseK

It is such a shame the limit is 120 psi. So many metric cylinders are rated for 8 bars, which is 116 psi. Surely the engineers of the metric cylinders rounded down to 8 bars after they added in a margin for safety.

Jesse, bar is an absolute unit of pressure. 8 bar is about 7 bar gauge (barg), which is about 100 psi gauge (psig).