Re: Pre-charing pneumatic air tank
 

Do you have any idea how many relief valves I've had to help teams set at competition? The above setups would not have had that protection in their shops at home, as most often these relief valves come from the factory set well above 150 psi.

The rules are pretty clear...

Re: Pre-charing pneumatic air tank
 

I think it's important to specify the situation. Teams cannot be expected to maintain their robot in a perpetual state of rules compliance (for example, during maintenance, robots often are in no state to pass inspection or play). Instead, they must demonstrate compliance at inspection and during gameplay. There is a different set of rules (and guidelines) that are in effect throughout an event, largely due to safety considerations.

Re: Pre-charing pneumatic air tank
 

I'm sorry folks, but which part of "One and only one" is not perfectly clear to you?

Aside from the other reasons mentioned, having two compressors gives a team an unfair advantage, since the on-board compressor is not being run as much. This keeps it cooler, allowing it to be more efficient and effective.

Seriously: Follow the rules or don't, but if you don't, stop trying to rationalize your cheating.

:mad:

Re: Pre-charing pneumatic air tank
 

Thanks for pointing out the 5V signal. I was about to check it out. So we would have to either use a resistor/Zener diode to step down to 5V or use a 12V relay instead. Just to reiterate, we are not using this at the competition. We are thinking of using it in the shop for testing and prototyping. The rake will have all the safety and relief valves in place. In my opinion, it is safer than the students trying to pressurize it with a battery and a switch box. I will get together with our pneumatic expert to make sure all the safeties are in place (i.e. safety relief valves, pressure gauges, emergency stop button etc). This is mainly used for testing a prototype that is not a complete robot, so there is no other electronics and certainly no cRIO.

Re: Pre-charing pneumatic air tank
 

This.
Seriously this conversation should be over. What else is there to talk about?

Re: Pre-charing pneumatic air tank
 

Yes, it should.

But we should talk more about this:

First, the relief valve must be properly installed in order to do its job.

Second, relief valves bleed, they don't gush--it's entirely possible to overpressurize a system by adding air faster than the relief valve can relieve it.

Third, I'm 100% positive that you don't have personal knowledge of all the "incidents" mentioned, and so cannot speak authoritatively on what did or did not cause them.

Fourth, rationalizing unsafe or disallowed practices with shoddy handwavium arguments and invented "facts" is not useful. So please stop.

Re: Pre-charing pneumatic air tank
 

Why are you using FIRST components if you are just prototyping? What is the point of going through all this hassle when you can just use a shop compressor with a regulator? If you want to make this be as safe as possible and use FIRST legal components, then get another cRIO and complete the test robot.

When we test we use a small pancake compressor that shuts off at 110 PSI and we use the regulator to limit working pressure to 60 PSI. If we want a real cordless option we run an old 8 slot cRIO on our testing chassis. I just don't get why you would want to over work a small 12V compressor for shop testing.

For competition use see nearly every post above, especially DonRotolo's. It is hard to agree more with someone...

Re: Pre-charing pneumatic air tank
 

Which includes calibration. The one and only time I'd actually recommend shorting the pressure sensor is to calibrate the relief valve--and I can think of a way to test that without even involving the sensor. The idea, of course, is to run the relief valve up to about 130 psi and see if it vents before then (if not, immediately vent the system using a dump valve and readajust).

Re: Pre-charing pneumatic air tank
 

I've surmised that the basis for this restriction is the limited things the inspectors get to see. All sorts of support equipment comes into the pits that is not subject to direct inspection. Some of the more obvious things, like welding and compressed gas cylinders, will be detected by walking through the pits. Other things are not so obvious, so outright bans are in place for them, which the diligent will respect.

Re: Pre-charing pneumatic air tank
 

I posted this elsewhere but here goes...

From the Robot Rules Preamble
"In addition, another intent of these rules is to have all energy sources and active actuation systems on the
ROBOT (e.g. batteries, compressors, motors, servos, cylinders, and their controllers) drawn from a
well-defined set of options. This is to ensure that all Teams have access to the same actuation resources,
and to ensure that the Inspectors are able to accurately assess the legality of a given part."

Many of the same statements are said of the 12 volt battery. i.e.How bad can it get, it's only 12 volts? 12 volts won't kill you! A small battery can't possibly be an issue, it's not like a car battery?!?! The truth is what you don't know can hurt you in both of these cases. Above all we want to provide information that is both useful and safe for our students. Run the numbers for yourself. What force will a 2" cylinder produce at 60 psi, at 90, at 120 at 150?

Re: Pre-charing pneumatic air tank
 

I didn't get a chance to tell Al this at CIR, but it's worth adding to this thread. Al told his inspectors about the possibility of the FRC batteries having enough current to weld a tool to the terminals. I didn't doubt him in the slightest -- I suspect Al's personally seen about 95% of the problems that have happened to a FRC robot -- so I filed that info away for future use. One of the teams I inspected had several batteries that needed to have insulation added to the terminals. I told them about the possibility of the weld & they said "we know; we've done that." ::ouch::

Re: Pre-charing pneumatic air tank
 

And yet they still didn't insulate their terminals.

Re: Pre-charing pneumatic air tank
 

Actually, they weren't that bad. They only had one where the insulation had slipped a little, and one where they hadn't put on the insulation yet. I was probably a bit quick with my "Al told me about a weld" speech; they knew they needed to insulate and had it in the plan. But it was a good thing; now I have a personal 2nd-hand weld reference to use in the future, instead of a 3rd hand from you. :)

Re: Pre-charing pneumatic air tank
 

I nearly had the opportunity to demonstrate how the Anderson battery connector could be sequentially and safely disassembled to allow the installation of these heat shrink insulators for the terminals. Unbolting the battery terminal would not be required and this pair of shrinkers can cover the usual terminal lugs and bolts even if they are wrapped in electrical tape. Other urgent matters came up to interfere with the educational session. Perhaps I will get a tripod and make a video after CMP sometime. Use of this thick insulator will reduce the "welding" risk substantially.

Re: Pre-charing pneumatic air tank
 

I see where you're coming from, since for stored pneumatic energy—in contrast to stored electrical energy—the relevant rules refer to the the legality of the air itself, rather than to the device storing it.

However, for purposes of other rules, a spare part tends to be considered equivalent to the original—for example, your number of motors used does not increment by 1 when you replace a motor with a spare. It's not an unreasonable interpretation to postulate that the "one and only one" compressor treats the original and/or any replacements as the same (as it would be for motor usage, cost accounting, etc.).

In other words, is "one and only one" intended to be equivalently restrictive to R29's "Max Qty Allowed", or is it intended to be more restrictive? If more restrictive, why? Is it FIRST's desire to prevent the advantage gained through this process, when the advantages referred to in Q209 and Q88 are specifically permissible? I suggest referring it to the Q&A, so that they can sort it out.