Pre-charging pneumatic air tank
 

At our last district competition, we routinely pre-charged the air tank while queuing for the match. We were plugging the compressor power directly to a battery with a switch. Once the pressure reaches a certain PSI, we turn off the switch and plug the compressor back to the system.The field staff told us not to do that. If we need to pre-charge the air tank, we must do so via the cRIO. I can see the reason behind it. I can see if the person doing that got distracted and not paying attention to the pressure gauge, that could be dangerous. However, I am thinking we could build a pneumatic charging station by putting together a battery, a master ON/OFF switch, a pressure limiting switch, a spike relay and a compressor such as in this diagram (sorry about the crude diagram, I am at a computer with only mspaint).

Is this allowed?

Re: Pre-charing pneumatic air tank
 

No that is not allowed. All air provided to the system must be provided by the compressor controlled by the CRio.

Re: Pre-charing pneumatic air tank
 

For more info see R80 and R85 (and the rest of the pneumatics rules)

Re: Pre-charing pneumatic air tank
 

You should not bypass the control system. See the following snippet from another post regarding charging pneumatic systems.

*Event though it is in regards to shop compressors, the intent is the same.

Re: Pre-charing pneumatic air tank
 

What I'm going to be doing is keeping the battery used in the previous match in the robot until queue and use it to precharge the tanks before the match is over. Then I'm going to throw a fresh battery in and have someone take the used one back to the pit to charge. Slightly annoying, but we've got to do what we've got to do. Hope this helps :)

Re: Pre-charing pneumatic air tank
 

I still don't understand the intention of the rule. We are thinking of using the same model compressor as the one used in competition. So it is not a more powerful shop compressor. Also, we will be wiring in the same pressure limiting switch and the same Spike as used in the system. The only difference is there is no cRIO. The limit switch directly controls the FWD input of the spike so when the pressure is reaching the limit PSI, it opens the circuit and the Spike will shut down the current to the compressor.

Re: Pre-charing pneumatic air tank
 

IF you are using the compressor that is controlled by the robot using your robot's power supply and running it through the robot, I am not sure why they would ask you to not use it.

The reason for this rule is to keep all components regulated and all people in the area safe. If you were doing this correctly, I am not certain why they would ask you to stop. Maybe to stem the tide of other teams charging in a questionable manner?

Re: Pre-charing pneumatic air tank
 

The INTENT of the rule is SAFETY.
I guess you missed the Ka-BOOM at GTRW when an air tank was turned into little flying pieces of sharp plastic. Even the crickets went silent.

Do what other teams do and have two compressors, one on the bot and then a standalone. BUT only use ONE compressor at a time that is controlled by the cRIO.

Re: Pre-charing pneumatic air tank
 

I'll remind you of R79 - "Compressed air on the ROBOT must be provided by one and only one compressor." That does not say "use only one compressor at a time". It says all air must come from only one compressor - if you precharge with an off board compressor then use an on board one during the match, you are violating this rule.

Mikets - The intent of the rule is safety. Any time you use a compressor at competition, it needs to happen under the control of the robot. In your proposed setup here, you're missing the ability to stop the compressor via the e-stop (something that is pretty important and found in all sorts of industrial applications) or to control it via enable/disable. R78 lays out the required pneumatic components for a minimal system, R80 clearly states that the compressor must be powered and controlled by the robot, and R88 clearly states that the cRio must respond to the pressure switch appropriately. There is no wiggle room here.

Re: Pre-charing pneumatic air tank
 

The reason for the rule is really unimportant. It is a rule. There are a lot of ways to charge the air system safely. All but one them are against the rules so you can't do it that way.

Re: Pre-charing pneumatic air tank
 

The posters are correct. You can only use one compressor. On board or off board is up to you. There are rules that govern what must be used with an on board compressor and other rules for the off board compressor. Working with compressed air can be very dangerous. FIRST has allowed the use on the robots with many safety requirements that must be met. I agree that some may not seem necessary but it is better to err on the way of safety.

The rules for what is allowed and not allowed are quite clear. Please read and follow them to the word. For teams that have been competing for a while, read the rules as they have changed a bit this year.

Re: Pre-charing pneumatic air tank
 

Welcome to the legions of FRC participants that believe this rule unnecessarily excludes a number of perfectly safe ways to charge tanks that give no competitive advantage.

Re: Pre-charing pneumatic air tank
 

As long as you were only using one otherwise legal compressor at a time, I don't really see that you'd be breaking the rules to disconnect the on-board one and use an off-board one instead -- though I'm not sure what you'd hope to gain except a bunch of extra work (and perhaps save a couple minutes of run time on the on-board one). We're allowed to replace a compressor with a different one (the one and only one compressor rule doesn't intend to forbid us from replacing a failed compressor, but merely to limit us to exactly one compressor pressurizing the system), so I don't see that this sequence really violates the intent of that rule:

1. Build ROBOT with on-board compressor
2. Disconnect on-board compressor (as though to remove it and replace with a spare)
3. Connect spare compressor
4. Power-on test, let charge tanks.
5. Disconnect spare compressor
6. Reconnect on-board compressor.

As I said though, I'm really not sure why you would want to do this. Seems like a whole lot of extra work for no benefit.

Re: Pre-charing pneumatic air tank
 

[quote=Jon Stratis;1356359]I'll remind you of R79 - "Compressed air on the ROBOT must be provided by one and only one compressor." That does not say "use only one compressor at a time". It says all air must come from only one compressor - if you precharge with an off board compressor then use an on board one during the match, you are violating this rule.


Mikets, at least he both agree on safety but I stand by my original comment as it was done at GTRW under the watchful eyes of Steve W.

Since I don't have posting rights to the Q&A for an official answer, may be someone could ask FIRST the question as we all know answers here are not official.

Re: Pre-charing pneumatic air tank
 

There was a thread that discussed this topic.

Although, I'm not sure a Q&A was ever submitted; at least I never saw one in my reading and searching the Q&A system.

Re: Pre-charing pneumatic air tank
 

Do yo really believe that this is legal? ONE and only ONE compressor is allowed to be used on the robot. If you charge with one then connect another you MUST discharge all of the air in the tanks or you would have used 2, count them, 2 compressors.

It must be that many people are using compressors for the first time and just skimmed over the rules. Some however just want to cause controversy so they are shaking the cage to see what happens.

Re: Pre-charing pneumatic air tank
 

Guys,
While this often gets into a safety discussion, that is only part of the issue. In the preamble of the robot rules you will find this reference...
"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."

Re: Pre-charing pneumatic air tank
 

As Al says, safety is only one of the reasons behind it--but to be honest, it would be unreasonable of the FRC community to expect the GDC to explain the reasoning behind every rule they make. (Especially but not limited to the fact that people will then use that reasoning as a starting point for an argument.)

What matters here is that there is an unambiguous and clear rule that teams need to follow, and that attempts to end-around that (or any other) rule is unacceptable.

Re: Pre-charing pneumatic air tank
 

The rule has to be there for the safety of all. It is the most accessible way for all teams to store this form of energy safely. whether you/I agree with the rule is irrelevant.

Re: Pre-charing pneumatic air tank
 

Just a note that is legal to replace the battery used to charge with a fully charged one after precharging per Q88.

Re: Pre-charing pneumatic air tank
 

Okay, I am convinced it's not worth doing at the competition. However, in the spirit of learning the intention behind the rules, I would still like to understand why. I understand it's about safety. But would somebody tell me why is my proposed setup not equivalent to the onboard setup? It has the same model pressure switch that will cut off compressor power. It's using the same compressor model and spike as the onboard system. The only difference is the missing cRIO. Regarding the Emergency stop feature, there is a master power switch. We can using a giant red button for it. Again, I will not do this for the competition but at the shop when we are building the robot, there is always a need for the build team to test the pneumatic system while the electronics is being worked on in parallel. We have a modular design so each subsystem can be built and tested separately. This setup will benefit that scenario. The students have been just powering an external compressor with a battery and I always don't like it. If I understand the safety concern, we will be able to build a safe testing setup.
We have many test setup in our shop to make life easier for the build team. For example, we have a PWM generator feeding a Talon so we can test motors without the cRIO. So the pneumatic test setup is equivalent to that.

Re: Pre-charing pneumatic air tank
 

Using a system with a pressure switch that will control a relay whether it is a spike or simple 12v relay with a properly calibrated blow off valve would be safe in general, despite not being legal for use at an event.

The safety concern I would have is that if people are working on the rest of the robot while the pneumatics are pressurized there are potential safety issues. Power may inadvertently be applied to a solenoid causing an actuation that could harm someone who's hand or head was in or near a robot. A tool that slips or is dropped could potentially cause one of the plastic tanks to explode ect. It is for that reason that it is highly recommended that work only occurs on the robot when the power is off and the pressure has been relived from the pneumatics.

Re: Pre-charing pneumatic air tank
 

There is one more very large difference. Your onboard pneumatics system (with its compressor and pressure switch and everything else) gets checked by the inspectors for proper operation. Your proposed setup does not. Its design might well be equivalent, but the execution does not get evaluated by people responsible for ensuring that every team plays by the rules.

(The more fundamental difference is that your proposed setup won't work. :p The Spike control input is a 5 volt signal.)

Re: Pre-charing pneumatic air tank
 

I believe the bigger difference is that the off-board compressor even with the same model compressor, and pressure limit switch directly wired to the realy (eve if that would work) and it's own E-stop button is: it is not controlled by the driverstation. So hitting the e-stop, or disable on the driverstation, would allow the compressor to still run. Which is considered an un-safe condiditon and must be avoided. Thus the reason for having air be controlled by the cRIO.

In any system where an E-stop is required you want one which kills all functionality which could cause harm/damage. Having mulitple mutually exclusive E-stop buttons as would be the case in your setup defeats the purpose of the E-stop.


Regards,
Kevin

Re: Pre-charing pneumatic air tank
 

How about posing that to the Q&A? After all, Q88 says you can replace the battery (of which one is permitted); why not the compressor?

I'd rule it legal on that basis, absent a Q&A to the contrary.

Re: Pre-charing pneumatic air tank
 

Here here.

Re: Pre-charing pneumatic air tank
 

Tristan you better read the rules. It says 1 compressor. There are rules about filling tanks. If you have an issue you ask the Q&A. Plain and simple, as an acting LRI and reading the rules and going for training, I deem it illegal.

Re: Pre-charing pneumatic air tank
 

OK. I'll take this one:
1> Are the 2 setups equivalent? No they are not ... then next few answers will demonstrate why.
2> Same model pressure switch --- the pressure switches are set to 120PSI. There is no telling (IE Proof) that the offboard pressure switch is set to the same setpoint as the onboard one. Should it not be set, the pressure could reach almost 150PSI
3> The wiring on the pressure switch is rated for less than 3 amps. The compressor runs at ~ 8 amps with a startup over 20 amps. This alone should suggest you should not do this.

When it comes to pneumatics, I'll err on the side of caution every time (and I've worked with it for ~15 years).

Re: Pre-charing pneumatic air tank
 

I have worked with pneumatics for 26 years and I want to make 2 points.

1) The compressors on the robots will go far higher then 120 psi. That is why FIRST wants the compressor controlled by the cRIO.

2) It would be time consuming to make the inspectors have evaluate each unique none standard control system.

I still have dent in a leg from a broken air line 24 years ago and that was at 110 psi.

Re: Pre-charing pneumatic air tank
 

I think that some of the rules for the pneumatics are a little weird. All the "incidents" mentioned have not been due to over pressurization. The relief valve takes care of that.

I don't get why they think that the cRIO control is going to be a super safe solution. They're relying on programming and wiring done by inexperienced high school kids.

This question is for inspectors. Which of the following would be illegal?

-Connecting the compressor to a drill battery
-Connecting the compressor to a robot battery with breaker
-Programming the robot to run the compressor an additional 10 seconds after the pressure switch says its full to fill all the way to 125 psi because the pressure switch stops at 115 psi.
-Programming the robot in auto to run the compressor non stop and let excess pressure vent through the relief valve
-Having a button on the computer that runs the compressor when held, used to charge a system at 95 psi to 115 psi before a match starts
-Having a button on the computer that runs the compressor when held, used to charge the system until the relief valve starts releasing air

-shorting out the pressure switch to run compressor

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.

Re: Pre-charing pneumatic air tank
 

1). Yes, it does require that my relief valve is connected and calibrated. But I've already done that so that I can pass inspection.

2). Please show me an FRC compressor filling faster than the relief valve can bleed.

3). The two incidents mentioned in this thread were at normal operating pressure. Please find me the one that isn't.

4). Please show me the rule that prevents me from running the compressor for an extra couple of seconds after the pressure switch tells the compressor to stop. Also, can you show me my "fact" I invented?

Re: Pre-charing pneumatic air tank
 

I would argue R88 part C prevents that. Since you are choosing to continue running the compressor after the switch tells you to stop, I would say you are over pressuring the system - you're pressuring it past the stop point for the switch, which is the only legal feedback for controlling the compressor.

Re: Pre-charing pneumatic air tank
 

R81 “Stored” air pressure on the ROBOT must be no greater than 120 psi.

My pressure switch stops at 114 psi. So, if I run for 8 extra seconds, I'll get to 119. It's not over the pressure limit.

Re: Pre-charing pneumatic air tank
 

I believe the critical word here is "replacement". If you leave the onboard compressor in place while you use an offboard one, you're not using a replacement. You're using a second compressor.

Re: Pre-charing pneumatic air tank
 

R34 does not list compressed air not generated in compliance with pneumatic rules as an allowable source of energy on the robot.

R88 says the cRIO must be able to control the compressor relay based on the state of the pressure switch. Shorting the pressure switch doesn't change its state.

Re: Pre-charing pneumatic air tank
 

There is a way to calibrate your pressure switch to stop at 120psi.

Re: Pre-charing pneumatic air tank
 

How?

Re: Pre-charing pneumatic air tank
 

I don't know, but see this post:

http://www.chiefdelphi.com/forums/sh...77&postcount=5

Re: Pre-charing pneumatic air tank
 

You can recalibrate your pressure switch. Remember you don't have to use a specific pressure switch. You really don't want to stop at 120 psi because with scatter it might be 121 psi the one time the inspector is watching it. Those little pressure gauges aren't that accurate anyway.

With all the exploding air tanks, regardless of reason, expect the inspectors to be particularly diligent and narrow in their interpretation of the rules. To get the sticker you will have to conform to their interpretation, not yours. That is just is how life works. :)

Re: Pre-charing pneumatic air tank
 

I think I see the problem: when I read "Disconnect on-board compressor (as though to remove it and replace with a spare)", I assumed that meant "take it off the robot (like you would to replace with a spare)", not "unplug its air hose".

As the former, it's essentially two spare part swaps in quick succession. As the latter, I can see why it might be more problematic.

Re: Pre-charing pneumatic air tank
 

Considering that the goal is to end up with a fully-pressurized pneumatic system, I would expect that unplugging air hoses would be problematic. My interpretation of the "disconnect" proposal was that it was talking about the electrical connections, but since it seemed very unlikely to meet the requirements of the rules I didn't pay a lot of attention to the details.

I can't see any benefit in doing (or pretending to do) such a double swap, so I doubt that was the intent.

Re: Pre-charing pneumatic air tank
 

The pressure switch is not adjustable. If your switch senses pressure at 114 psi, and you are sure your pressure gauge is accurate then replace the switch. It is likely defective and about to fail. I naturally would assume your gauge is faulty as over the years, this is more often the case with this complaint. Therefore running your system beyond the cutoff sensed by the switch is likely over pressurizing your system. Know when your data is lying to you.

Re: Pre-charing pneumatic air tank
 

I was envisioning a variant of the poor man's tubing plug: bend the tubing over sharply, and zip-tie around both legs of the bend to stop the air. I admit I've never tried that with an already-pressurized tube (and don't particularly recommend it either way).

To charge the tanks right before the match, yet still have a cool compressor for use during the match?

Re: Pre-charing pneumatic air tank
 

Many of the robot construction rules may not make sense to the robot builders. But think not of "rules" but of "specifications". I wish FIRST would call the robot construction "rules" ,"specifications" instead.

When real engineers build products for the customer, it is the customer who gives them the specifications. The engineer doesn't argue with the specifications, but builds the product to meet them, because that's what the customer is PAYING FOR.

The customer may have a very valid reason for the specification, even if the engineer doesn't know what they are. For instance, specifying the model motor to be used on the robot. Say a customer is buying a mail-delivery robot to place in each of its 5000 business locations. They already inventory a particular motor at each of these locations, so it makes sense for them to specify this motor for use on the robot you have been contracted to design. It saves the customer from having to spend thousands to stock a different motor when you can design around their existing motor. Motors go bad, and having the right motor in inventory is nice and saves the customer money.

Another example from the same mail-delivery robot. The specifications may call for dimensions to not exceed 28 in. If you design larger than this, the robot won't go through all the doors in the customer's many locations.

Stop trying to get around FIRST's robot specifications Design your robot to meet them, even if you, in your infinite wisdom, think these specifications are dumb!

Dr. Bob
Chairman's Award is not about building the robot. Every team builds a robot.

Re: Pre-charing pneumatic air tank
 

Theres a guy on our team that really loves to do this, especially when the tube is already pressurized. It leaks a bit while you're folding it over, but holds much better than a push to connect fitting once it's folded over and zip tied.

Re: Pre-charing pneumatic air tank
 

In your real life example above what happens when the customer comes back after you have been building for, lets say three weeks and changes the specifications? Would you, as the design be entitled to some form of compensation?
Just asking.

Re: Pre-charing pneumatic air tank
 

Spec/Requirement changes happen all the time. Part of my job is to actually work with our internal customers to help them figure out what it is they want before I start working on delivering it - and trust me, sometimes what they really want is nothing near what the originally asked for.

When specs/requirements change, sometimes the changes can be incorporated without issue, and other times it results in renegotiating the contract. On some of our bigger projects, we'll have a contract date we're supposed to hit, but if the scope for the project increases due to outside forces (Marketing asking for a new feature, for example) sometimes that contract date will change.

Re: Pre-charging pneumatic air tank
 

A common strategy is to under bid a job knowing that you will make up the difference on change orders. I know of situations that was cheaper to allow a poorly specified job to complete, rip it out & start over.

I am not sure what this has to do with pre-charging your air tank unless you bought the wrong compressor. :)

Re: Pre-charging pneumatic air tank
 

There was only one change to the pneumatics rules all season and it was just a minor language clarification.

All the other pneumatics rules have been the same since kickoff, with most of them being unchanged from previous years. I do not see any "change in specifications".

Re: Pre-charging pneumatic air tank
 

That was sort of my point. But after 3 pages (oops 5) of discussion, I felt the thread needed some levity. There really needs to be a mild sarcasm smilie.

But since we or on the subject of specifications, anybody notice the recommended regulator in rules has a maximum outlet pressure of about 100 psi? You have to adjust it to 60 PSI. Which is how most people interpret this rule, but it is really not what it is saying.

Re: Pre-charging pneumatic air tank
 

R82 - "working " air pressure on the robot must be no greater than 60 PSI and must be provided through one primary adjustable, relieving, pressure regulator.

Re: Pre-charging pneumatic air tank
 

R77-G Pressure regulators with a maximum outlet pressure of no more than 60 psi.

That says maximum, not working. I am glad that it is interpreted like R82 since I don't think one conforming to the letter of R77-G is generally available.

Re: Pre-charging pneumatic air tank
 

We simply plug our DS directly into our Radio and enable the bot in que, once the system is charged, disconnect and shut off. No need for any fancy external systems.

Re: Pre-charging pneumatic air tank
 

We had a question about the "one and only one" wording so we asked it in Q&A. I think that many people will be surprised with the result.

Game - The Robot
Q209 Q. Rule R79: "compressed air on the ROBOT must be provided by one and only one compressor." 1) We can only use one compressor at a time, but can swap out compressors (e.g. if the one we are using starts to overheat). 2) We can only use one compressor for an entire event. Which reading is correct?
FRC2485 on 2014-01-22 | 2 Followers
A. Situation 1, but also consider T8 and T10.
Published by GDC

I'm not trying to stir the pot but simply point out that it is legal to use multiple compressors (e.g. if one starts to overheat).

Re: Pre-charging pneumatic air tank
 

If you replace the compressor with another that is legal. If you use one compressor to fill the tanks then reconnect the other one for match with air from first compressor in the tanks, without venting tanks, that is not legal. If I saw that being done I would report it to the FTA and Head Ref and would recommend that the air tanks be vented just before match starts.

You would also be playing with an un-inspected robot which would be a DQ for your alliance if they wanted to go that far.

Re: Pre-charging pneumatic air tank
 

If the team is correctly asserting that it's a spare, wouldn't that imply that all spares, once installed, must be re-inspected? (Right now, conventional practice is not to require this—for good reason.)

Or are we not presupposing that it's a legal spare? (And why?)

Re: Pre-charging pneumatic air tank
 

If anything, working on a pressurized system is unsafe, and thus able to be disallowed by the LRI.

Re: Pre-charging pneumatic air tank
 

I do not believe your Q/A covers the specific question of this thread. "Is it allowable to have one compressor installed in the robot, and use another prior to a match start off-board to pre-charge the air system". (Assuming all other safety conditions are met such that the cRIO controls the off-board compressor, only one compressor is running, etc).

For your Q/A post to be helpful in this thread, you must ask that specific question.

That question covers the meaning/intent of "one and only one". Which as it stands is taken to mean a team can only ever use one compressor to charge the air system on the robot and the scenario in the question I provide is considered illegal. Pre-charging before the match is allowed, but it must be done by that one compressor, which is either permanetly installed on the robot, or premanently lives off-board the robot. In either case, the spike and pressure switch used must be controlled by the robot cRIO.

The one compressor, if installed in the robot is allowed to be replaced in the pits, just as any other COTS item is, and follows applicable rules and procedures for doing so. Reading your Q/A, the replacement of the compressor is what is considered "allowed to use multiple" compressors at an event. It is still unclear from your specific Q/A if the GDC approved precharging from another compressor and I would not take thier response to mean that you can.

Hope this helps,
Kevin

I'm laughing out loud right now. How long can this thread go on???

To answer that you need to decide if humans (and by extention, FIRST) will be able to move elsewhere before the sun burns out.

Re: Pre-charging pneumatic air tank
 

In theory, this thread can go as long as the page cap that is provided by the Vbulletin software and server details of chiefdelphi allows.

Re: Pre-charging pneumatic air tank
 

It's like when you see a wreck on the highway. You know you shouldn't, but you just HAVE to slow down and look ... ;)

Re: Pre-charging pneumatic air tank
 

All it will take is for someone with Q&A rights to ask the correct question.

I would have asked a long time ago.

Re: Pre-charging pneumatic air tank
 

....or I can shut it down.

Re: Pre-charging pneumatic air tank
 

Might be a good idea, Steve. As G.B. Shaw famously commented, wrestling with a pig just gets both of you dirty, and the pig likes it.

Re: Pre-charing pneumatic air tank
 

I know, I know. But I haven't seen anyone address this yet, so.....
A large part of the point is to restrict teams to only the power and air provided by the battery and legal compressor. If you have a system with 20 Clippard tanks, you have precious little chance of keeping it fully charged with the on-board compressor and battery. You could perfectly safely charge it with any number of other methods, including a separate 120V compressor, a separate 12V compressor constantly running in your pits, etc. But you'd be gaining an advantage. The simplest way for the GDC to ensure no one gains this advantage is to constrain teams to only using the specified charging system.

Re: Pre-charing pneumatic air tank
 

That's certainly the effect, but to what extent is eliminating that advantage really the intention, and does that continue to be a useful restriction to impose?

As an arbitrary constraint, I suppose it's acceptable. As a solution to the problem of teams using unsafe filling methods or excess pressure, it's terrible.

Re: Pre-charging pneumatic air tank
 

I thought that was wrestling with a referee, not a pig. :yikes:

Re: Pre-charging pneumatic air tank
 

At Tech Valley this weekend, I talked to a team that had a seven-gallon(!!!) aluminum tank on their robot. It takes a legal compressor almost 30 minutes to fill it, which they figured "wouldn't be a big deal" because they never drop below 100 psi through a match.... (Last year, lack of air bit them, so IMO they overcompensated).

They were "scrambling" (mentally, because what they were really doing was waiting and hoping for field delays) in the pit, because they got reinspected after a modification, and had to dump their air. I asked them what would happen if, during the tournament, they popped a fitting or somesuch--and their eyes got wide in the manner of suddenly-realized unintended consequences.

They did make the tournament, acquitted themselves well, and had no problems with their air system, by the way.

Point being that, were they able to fill this tank with an off-board compressor of their choice, it could be a huge advantage in stored energy over other teams, and just like other types of stored energy it's entirely fitting that it's restricted in some manner or another.

Re: Pre-charging pneumatic air tank
 

Does this mean you have an eight-gallon tank being drop-shipped to the Finger Lakes Regional next week? I bet you could pimp out your octanum drive an have it jump off the floor when you switch wheels!!! Might help get some distance on your truss shots.

Over-done is indeed under-rated.

Re: Pre-charging pneumatic air tank
 

That is a good way to fry the common Viair compressor as it has a 9% duty cycle with a max recommended on time of 3 minutes. There is a 100% duty cycle version though. I haven't seen a duty cycle rating on the old Thomas compressors.

Re: Pre-charging pneumatic air tank
 

This is an interesting question. If you read the allowable parts you will see that A says "Items available in the 2014 Kit of Parts"
This would include items available from First Choice.

In First Choice there is a regulator that goes to 100 psi but can be turned down to 60 psi.

KOP regulators:

http://firstchoicebyandymark.com/en/fc14-010 (up to 60psi only)
and
http://firstchoicebyandymark.com/en/fc14-125 (up to 100 psi)

This second one can be adjusted down from its 100 to the working pressure of 60. I believe that it is the ONLY adjustable regulator that is allowed under the rules.


If there are other such regulators in the 2014KOP they can also be used in the pneumatics system... I have not found them but perhaps they are there.

Any OTHER regulators that are NOT in the KOP fall under
G which says "Pressure regulators with a maximum outlet pressure of no more than 60 psi"

The rules are explicit and do not call out "functional equivalent pressure regulators" they say they must have a maximum outlet pressure of 60 psi

I think that this is pretty clear There are no QA findings to the contrary.

If you want to have a regulator that has an adjustable rating above 100 psi at any time... you would be required to use the one mentioned above from the KOP. The rule says you may not have a maximum output rating above 60PSI for any non KOP regulators.

Re: Pre-charging pneumatic air tank
 

As a reminder to all, that is one primary regulator. You may not have multiple primary regulators. You may have additional regulators downstream from the main.