View Single Post
  #42   Spotlight this post!  
Unread 30-03-2013, 02:49
Tristan Lall's Avatar
Tristan Lall Tristan Lall is offline
Registered User
FRC #0188 (Woburn Robotics)
 
Join Date: Aug 2001
Rookie Year: 1999
Location: Toronto, ON
Posts: 2,484
Tristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond reputeTristan Lall has a reputation beyond repute
Re: Are we allowed to use helium?

Quote:
Originally Posted by Al Skierkiewicz View Post
You know all the answers to your questions. There are specific exclusions to air storage as you have pointed out. Everything else is subject to the rules.
The fundamental question concerns the meaning of "pneumatic" in the rules. If they mean to restrict all pressurized gases with it, then this is relatively clear-cut. If they mean to restrict air only, the existing rules on safety, energy storage and parts utilization could be applied to helium, without posing undue risk. An appropriate level of regulation can be achieved in at least two substantially different ways—so why presuppose that FIRST intends one and not the other? (I also eagerly await FIRST's response, if anyone chooses to ask the Q&A for it.)

Also, the 1 atm specification you mention—although reasonable—is not stated in the rules, and to my knowledge has never been articulated by FIRST. As a result, teams may wonder why other indications of FIRST's intent aren't really in harmony with that specification:
  • Is the nitrogen in a gas shock above 1 atm? (Probably—so why does FIRST explicitly exempt it?)
  • What if I had a small, sealed, air-filled container at 1 atm, inserted it into a vessel and used a legal vacuum pump to evacuate the vessel to 0.8 atm? Is the container now subject to the pneumatics rules? (In other words, is the 1 atm gauge or absolute?)
  • Is a nitrogen-filled tire tube an "air-filled (pneumatic) wheel" for the purposes of the rule? (And is that because commercial nitrogen is "air", or because all compressed gases should be subject to the pneumatics rules?)

By the way, since I didn't really explain my rationale earlier: the energy source rule covers forms of energy that are "used" (I presume this means intentional energy release during a match). Every robot can catch fire: that doesn't mean we prohibit every single robot because it's a source of (chemical potential) energy not enumerated in the rules. By the same token, if popping a balloon is an unintended failure mode, there's an equally good case that that energy release is not use, and thus not subject to the energy storage rule. The safety rule covers it adequately.

With regard to the compressed air source rule, it uses the word "air", and so I have a hard time accepting that it covers gases that are not (in any conventional sense) air. As others have noted, calling commercial-grade helium air is as bad as calling it natural gas, uranium or starstuff.

Quote:
Originally Posted by Al Skierkiewicz View Post
Not true. Prior to specific rules, the flow chart for checking the legality of parts would allow pneumatic tires.
The 1999 rules contained (and possibly introduced) many of the pneumatic system principles we use to this day. I'm certain that the use of pneumatic wheels in FRC predates the advent of the parts usage flowchart several years later (unless there was another flowchart prior to 1999).

I distinctly remember a team using the Skyway Ø8 in pneumatic wheelchair wheels in 2001, and many teams using them thereafter. (I suppose they could have been filled with something else, but I kind of doubt it.)

Quote:
Originally Posted by Alan Anderson View Post
Was there ever a year when the flow chart was considered to have the status of an actual rule, rather than being a (possibly incomplete) summary of the rules?
I think the flowchart was called out as enforceable by a numbered rule in some years, but in others it was merely appended to the manual and was ruled advisory (like a Q&A response).
Reply With Quote