View Full Version : 2013 running 2 - VI air compressors legal?
marccenter
01-02-2013, 12:16
Is it legal to run dual air compressors this year? Would there be any practical plumbing problems to architect around?
Would there be an issue with using the FRC Labview Vi's which are typically design around the use of one compressor and Nason shut-off switch?
Joe Ross
01-02-2013, 12:22
See R80.
While R80 does specify that you can only run one on board compressor, it would be legal to run multiple off board compressors, so long as you include the control and plumbing hardware on the robot. IE 2 spikes, 2 regulators, 2 valves, etc. etc. etc.
Why would you want to? Its not like off-board you gain anything by having two, since the time between matches is so large.
JamesCH95
01-02-2013, 12:49
Why would you want to? Its not like off-board you gain anything by having two, since the time between matches is so large.
Saver wear on the on-board compressor. And faster recharging for those back-to-back elimination matches.
I have yet to see an FRC compressor dead from wear in 10 years of competition. Not saying it doesn't happen, just seems infrequent enough that it shouldn't be a concern sufficient to warrant such an overkill solution.
and unless you have an extraordinarily large quantity of storage tanks on board, I've never seen an FRC bot take more than about 45-60 seconds to fill itself.
JamesCH95
01-02-2013, 13:21
I have yet to see an FRC compressor dead from wear in 10 years of competition. Not saying it doesn't happen, just seems infrequent enough that it shouldn't be a concern sufficient to warrant such an overkill solution.
and unless you have an extraordinarily large quantity of storage tanks on board, I've never seen an FRC bot take more than about 45-60 seconds to fill itself.
You and I have clearly had different experiences in FRC ;)
Not that I've seen a dead compressor, but I've definitely noticed compressors getting weaker after a competition.
R80 applies to the compressor on board or off board. So either way, you only get one. But only your inspector knows for sure.
Al Skierkiewicz
01-02-2013, 14:04
While R80 does specify that you can only run one on board compressor, it would be legal to run multiple off board compressors, so long as you include the control and plumbing hardware on the robot. IE 2 spikes, 2 regulators, 2 valves, etc. etc. etc.
No...
R80
Compressed air on the ROBOT must be provided by one and only one compressor.
This gets everyone every year. You may not, under any circumstances, fill the tanks on the robot with anything other than one and only one FRC legal compressor under cRio control.
The motor on the Thomas compressor is very close to the same internal construction as a CIM motor. We have lost several over the years due to worn bearings, damaged or worn brush assy. or external metallic debris. The surprising thing is we have not lost a piston assy although the seals do dry out with use.
Jimmy Nichols
01-02-2013, 14:07
...and unless you have an extraordinarily large quantity of storage tanks on board, I've never seen an FRC bot take more than about 45-60 seconds to fill itself.
For Logo Motion our robot had 5 Pneuaire storage tanks that took ~5 minutes to fill.
No...
R80
Compressed air on the ROBOT must be provided by one and only one compressor.
This gets everyone every year. You may not, under any circumstances, fill the tanks on the robot with anything other than one and only one FRC legal compressor under cRio control.
The motor on the Thomas compressor is very close to the same internal construction as a CIM motor. We have lost several over the years due to worn bearings, damaged or worn brush assy. or external metallic debris. The surprising thing is we have not lost a piston assy although the seals do dry out with use.
For the record, I'm still of the opinion this is a crappy rule with unclear intent.
1075 built our power wheelchair-gone-forklift cart to have an onboard compressor, which was powered by the 2004 IFI control system that it ran on, controlled by a pressure switch just like an FRC robot, running the older Thomas compressor, just like an FRC robot, but we were not allowed to charge the system at competition with it, because the robot itself wasn't controlling it.
Its no more or less safe, and the argument of it uses battery power from another source is silly because I can change the battery in my robot after I've charged the air system with the dead one from last match.
Al Skierkiewicz
01-02-2013, 16:23
Phil,
You can have your opinion but the rule is the rule. The rule is not presented as a safety issue, it is just a rule. Pneumatics will be inspected according to the pneumatics section. To remind everyone, you need to pass inspection in order to gain points and avoid other penalties. For instance read G5.
Not sure why you think my name is Phil (it's not).
I don't challenge that it IS a rule, nor that inspectors shouldn't enforce it. Of course you need to pass inspection (presumably by complying with the rules) in order to compete. I think you're taking the argument a bit far.
I do think that inspectors *could* have a hard time enforcing it though. For example, some of the robots that we had on that cart HAD their own on-board compressors, it was simply convenient to use the cart-mounted one.
We've been told not to use it to pressurize the robot before and complied, and the volunteers at the event(s) it was mentioned at seemed to indicate that it was somehow a safety concern because the robot wasn't controlling it, and that was the logic behind the rule.
I further believe though, that questioning the reasoning behind a rule is VALID, and IMPORTANT, because often, even though a rule may have made sense for one reason or another in the past, doesn't mean it still makes sense now. Intent is important. This is a rule that has been around for years, for what appears to be no reason at all.
To be sure, this is the specific portion of the rule I don't understand the reasoning behind.
R80
<snip>... Off-board compressors must be controlled and powered by the ROBOT.
The only reasoning I can come up with, is that they want you to be under software control so the pressure switch will shut things off appropriately. There are lots of ways to solve that without requiring the robot to be the one controlling it.
A better rule might read:
"Compressed air on the ROBOT must be provided by one and only one compressor. Compressor specifications may not exceed nominal 12VDC, 1.05 cfm flow rate. Off-board compressors must still be controlled by a pressure switch to ensure a maximum pressure of 120psi."
I apologize if my preference for a rulebook which promotes maximum freedom of configuration to the teams, while still achieving its goals doesn't sit well with you. The way the bumper and other pneumatics rules keep getting simplified and loosened, and the way HQ has expressed a desire to simplify the rulebook seems to agree with me. "That's the way we've always done it." just isn't a good reason to continue doing something a particular way.
Al Skierkiewicz
01-02-2013, 21:16
Sorry,
I thought Phil was your name. Sorry. There is no mystery to the reason behind this rule. It is in the first paragraph of Section 4...
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.
Emphasis mine. Think about this rule as being as hard and fast as the robot battery, the PD, the legal motor list and cRio. The penalties show how serious the GDC is about enforcement. For instance...
G05
When placed on the FIELD, each ROBOT must be:
A. in compliance with all ROBOT rules (i.e. have passed Inspection),
If it is not a quick remedy: the ROBOT will be DISABLED and must be re-Inspected.
G03
ROBOTS whose operation or design is unsafe are not permitted.
Violation: FOUL & DISABLED. If the issue is due to design: Re-Inspection.
T06
A TEAM is only allowed to participate in a MATCH and receive Qualification Points if their ROBOT has passed
Inspection. If it is discovered after the start of the MATCH that a ROBOT did not pass Inspection, the entire ALLIANCE will receive a RED CARD for that MATCH.
T08
At the time of Inspection, the ROBOT must be presented with all MECHANISMS (including all COMPONENTS of each MECHANISM), configurations...
To use a second compressor of any type means that the robot has not passed inspection. I think that covers it...
We clearly don't see this as an issue of the same, or even similar magnitude. You continue to argue about how it constitutes a violation worthy of claiming a ROBOT wasn't inspected simply because its air system was pressurized by some other source, regardless of whether that source is substantially the same as the presently prescribed system or not.
You just made the argument I've heard so many times, that it needs to be supplied by the ROBOT's battery, because everyone has those, and they have a limited supply of power, so that makes it the same for everyone.
The source of the 12VDC power that powers the compressor is irrelevant in any substantial way, since I can change my battery AFTER I've pressurized the system and before the MATCH. Whether I use a robot battery, a deep cycle marine battery, or a solar fusion reactor to power it changes nothing about the ROBOT as it sits in the ARENA at the start of a MATCH, with a fresh battery and a pressurized air system.
As for the rules you cited:
G03 doesn't apply, its not an unsafe design or operation.
G05 may apply, but it IS a quick remedy, opening the air valve remedies any perceived problem that charging from an external source created, so no DISABLED ROBOT or Re-inspection necessary.
And I suggest that T06 or T08 aren't even relevant to the discussion, as I never suggested more than one compressor.
For sake of argument, though, I don't believe that the intent of the "one and only one compressor" rule is to prevent me from having equally functional, and equally legal on their own off-board compressor panels (controlled and powered by the ROBOT, in accordance with R80), but rather, its intent is to say that you are only to have one compressor provide the air at any one time. Whether this time I use compressor A and next time I use compressor B doesn't particularly matter, otherwise, what happens when one breaks during a competition?
Kevin Kolodziej
02-02-2013, 01:12
A proper Q/A is probably in order, but let me test the waters here first:
The offboard compressor must be controlled by the robot as if it is on the robot. The benefit of it being offboard is that its weight is not part of the robot. I.E. it is NOT part of the robot.
Here is my question: Can you have the newer, smaller compressor, on your robot (used during matches to keep your air supply topped off) but use the older, larger compressor offboard to fill your tanks between matches? This would be accomplished by disconnecting the leads from the onboard compressor and connecting them to the offboard compressor and using the existing sensors and power supply. The robot is always receiving air from one and only one compressor.
There are three reasons for this:
1. As Jimmy already pointed out, a robot with a substantial amount of stored air can take a long time to refill. While this shouldn't be an issue in qualifying, as you go deeper into elims, time is less between matches. There is a significant difference between the time it takes the two types of compressors to fill large quantities of storage tanks.
2. The smaller compressors get REALLY HOT quite quickly. Even the larger ones get pretty darn hot after a few minutes of continuous run time. The ability to use two compressors saves wear and tear on both.
3. I've been near a robot that had a brass fitting burst because it was connected to the compressor which got so hot the brass softened and couldn't handle the pressure. Not a catastrophic failure like the plastic tanks, but still quite dangerous.
Kev
Tristan Lall
02-02-2013, 04:59
Whether this time I use compressor A and next time I use compressor B doesn't particularly matter, otherwise, what happens when one breaks during a competition?
Can you have the newer, smaller compressor, on your robot (used during matches to keep your air supply topped off) but use the older, larger compressor offboard to fill your tanks between matches?
The issue of spares is what really drives my disdain for this rule.
If I can switch compressors and batteries because spare parts are allowed, then apart from annoying everyone unnecessarily, all this rule accomplishes is to mandate that the cRIO controls and robot's power distribution system be used. That is unnecessary from a practical point of view, because there are plenty of simple mechanical devices (fuses, pressure switches, regulators, etc.) that can control the system without human or computer intervention—and the pneumatic ones are required anyway! Mandate a proper fuse/breaker on the compressor, and that failure mode is mitigated, without resorting to full robot control.
This rule should not exist in its current form, but it does—and with great regret, will be enforced vigourously.
I've been near a robot that had a brass fitting burst because it was connected to the compressor which got so hot the brass softened and couldn't handle the pressure.
Are you sure that was the failure mode?
There are three reasons for this:
1. As Jimmy already pointed out, a robot with a substantial amount of stored air can take a long time to refill. While this shouldn't be an issue in qualifying, as you go deeper into elims, time is less between matches. There is a significant difference between the time it takes the two types of compressors to fill large quantities of storage tanks.
For every design decision we make, we have to weigh the trade-offs. Why is "our tanks have so much capacity that we may not be able to fill them between elimination matches; is that worth the risk?" any different than "we can't figure out how to make room for both floor pickup & climbing on the bot; which is more important?" Whether we like any particular rule or not, some (most? all?) of them are there (at least in part) to help level the playing field.
Al Skierkiewicz
04-02-2013, 08:04
We clearly don't see this as an issue of the same, or even similar magnitude. You continue to argue about how it constitutes a violation worthy of claiming a ROBOT wasn't inspected simply because its air system was pressurized by some other source, regardless of whether that source is substantially the same as the presently prescribed system or not.
Of course we don't agree, but every other team at your event expects, no demands, that every robot be inspected to the same standard so that they can be sure they are not competing against a team that has an advantage, of any kind.
You just made the argument I've heard so many times, that it needs to be supplied by the ROBOT's battery, because everyone has those, and they have a limited supply of power, so that makes it the same for everyone.
I did not make that argument. The rules state the compressor must be controlled by the cRio and robot battery.
The source of the 12VDC power that powers the compressor is irrelevant in any substantial way, since I can change my battery AFTER I've pressurized the system and before the MATCH. Whether I use a robot battery, a deep cycle marine battery, or a solar fusion reactor to power it changes nothing about the ROBOT as it sits in the ARENA at the start of a MATCH, with a fresh battery and a pressurized air system.
While the choice of power source is debatable, the cRio still needs to be powered by the robot battery and so does the control for the compressor.
As for the rules you cited:
G03 doesn't apply, its not an unsafe design or operation.
G05 may apply, but it IS a quick remedy, opening the air valve remedies any perceived problem that charging from an external source created, so no DISABLED ROBOT or Re-inspection necessary.
And I suggest that T06 or T08 aren't even relevant to the discussion, as I never suggested more than one compressor.
Your telling me it is safe does not make it safe. I can assure you that inspectors find unsafe conditions on robots regularly at every event. While opening the relief valve can be a quick fix, why should the event staff, the refs or other teams be forced to endure this match after match.
T06 & T08 are extremely relevant and provide the basis for inspection and the remedy. If you use something on your robot during the competition, it must be inspected. If you use it without it being inspected, you are in fact, not inspected. The remedy is no points for each match you are scheduled for and a Red Card for the entire alliance if you enter the field and the match starts.
For sake of argument, though, I don't believe that the intent of the "one and only one compressor" rule is to prevent me from having equally functional, and equally legal on their own off-board compressor panels (controlled and powered by the ROBOT, in accordance with R80), but rather, its intent is to say that you are only to have one compressor provide the air at any one time. Whether this time I use compressor A and next time I use compressor B doesn't particularly matter, otherwise, what happens when one breaks during a competition?
The intent of "one and only one" in no way can be interpreted to mean more than one. If your one compressor should fail, a spare may be installed and that also should be inspected. It is the reason the inspection staff is on duty all weekend.
To reiterate the procedures for everyone to understand, the LRI, Head Ref and FTA act as a group when something that will affect a team occurs. If the LRI finds that a team has an issue, he brings it to the Head Ref and FTA for discussion. If the Head Ref sees an unsafe or questionable part on a robot, he calls in the LRI and FTA if needed, for discussion. If the three key volunteers still cannot reach consensus, each of us has the phone contact info for higher authority. Each one of the key volunteers is tasked with keeping the event safe, operating within the rules of the tournament, for the enjoyment of all. We take that task very seriously.
The incident that Kevin related above occurred at the Midwest Regional in 2011. A team trying to find an air leak had bypassed the compressor control to keep the compressor running. The heat buildup caused a failure of the tubing and fitting at a brass junction. The failure sounded like a gunshot and any pieces were contained within the robot.
If I can switch compressors and batteries because spare parts are allowed, then apart from annoying everyone unnecessarily, all this rule accomplishes is to mandate that the cRIO controls and robot's power distribution system be used.
Precisely what my point has been all along. At least some LRIs are capable of understanding reasonable thought. I have never argued that the rule somehow isn't the rule and that I don't need to follow it. I'm arguing that the rule is baseless and silly, and achieves nothing in terms of increasing safety or levelling the playing field.
Of course we don't agree, but every other team at your event expects, no demands, that every robot be inspected to the same standard so that they can be sure they are not competing against a team that has an advantage, of any kind.
Again, show me how this provides me a tangible advantage of any kind, and I will concede this point. Of course we should all be inspected to the same standard.
While the choice of power source is debatable, the cRio still needs to be powered by the robot battery and so does the control for the compressor.
So, you're using the rule to justify its own existence? My argument is that there is no need to require the cRIO to be the one controlling or powering the compressor.
Your telling me it is safe does not make it safe. I can assure you that inspectors find unsafe conditions on robots regularly at every event. While opening the relief valve can be a quick fix, why should the event staff, the refs or other teams be forced to endure this match after match.
T06 & T08 are extremely relevant and provide the basis for inspection and the remedy. If you use something on your robot during the competition, it must be inspected. If you use it without it being inspected, you are in fact, not inspected. The remedy is no points for each match you are scheduled for and a Red Card for the entire alliance if you enter the field and the match starts.
What have I said that suggests I don't want my compressor setup inspected? It SHOULD be inspected, the rules are currently needlessly restrictive is all. IIRC the inspection checklist has an item for inspectors to check which reads something to the effect of "turn on compressor; does it shut off automatically at 120psi?". I'm certainly NOT championing for the removal of such an IMPORTANT safety check.
The intent of "one and only one" in no way can be interpreted to mean more than one. If your one compressor should fail, a spare may be installed and that also should be inspected. It is the reason the inspection staff is on duty all weekend.
If "one and only one" can in no way be interpreted to mean more than one, then spares are not allowed. I think we can agree that since that is clearly not the intent of the rule, it must mean that we are not to be using two or more compressors in parallel to speed up the process. This serves the goal of leveling the playing field and I agree that this rule should be continued but have its wording clarified such that its intent is clear.
The incident that Kevin related above occurred at the Midwest Regional in 2011. A team trying to find an air leak had bypassed the compressor control to keep the compressor running. The heat buildup caused a failure of the tubing and fitting at a brass junction. The failure sounded like a gunshot and any pieces were contained within the robot.
So a team testing their robot in a manner that involved purposefully bypassing at least two safety interlocks caused a catastrophic failure of a robot part by overstressing it. THAT seems like a legitimate safety issue, which I'm sure the Safety advisors at Midwest 2011 spoke to the team in question about.
If I can switch compressors and batteries because spare parts are allowed, then apart from annoying everyone unnecessarily, all this rule accomplishes is to mandate that the cRIO controls and robot's power distribution system be used.
Precisely what my point has been all along. At least some LRIs are capable of understanding reasonable thought. I have never argued that the rule somehow isn't the rule and that I don't need to follow it. I'm arguing that the rule is baseless and silly, and achieves nothing in terms of increasing safety or levelling the playing field.
I thought that when we switch batteries we were required to drain the tanks? That way the tank is filled with the battery we compete with and there's no unfair advantage for using large reservoirs.
There's no obvious place I can find this in the rules though. It says robots are inspected before entering the filler line and robots can't be worked on while in the filler line, so maybe that means robots are in inspection state entering the filler line? Inspection state is powered down and tanks empty.
There is no requirement to use the same battery you compete with to fill the tank.
There is also no requirement to show up for queing in "inspection condition" with empty tanks.
It looks like we're arguing for the sake of arguing.
A rule is a rule, no matter what you think of the rule.
If you have a problem, then Q&A is the ONLY LEGAL way to remedy the problem.
Personally, I don't see the big deal in the rule. Sure, it would be nice to have two compressors on board, and sure it would be nice if we didn't have to use the cRIO to control an off-board compressor, but the fact is, the rules tell us what we have to do.
If one compressor cannot achieve what your robot needs, maybe you need to design a better robot. We (364) are also having pneumatic's woes... 10 pistons, 4 air tanks, and 1 itty bitty compressor... but guess what, that's not stopping us. The system works quite well, and we have optimized our control system to only use air when absolutely needed.
We've never had a compressor burn up, and we have used the heck out of the two on our t-shirt shooting robot (not FRC, so that's why we have two). They're 6 years old with hundreds of hours of use and will still happily charge up our 4 gallon tank to shoot t-shirts over 300 feet. Do they get hot? Heck yea they do! But that's the umm... consequence? of compressing air.
Basically, I don't see what the big deal is.
Al Skierkiewicz
04-02-2013, 11:38
Ken,
There currently is no rule that requires you to use the same battery for both purposes. At one time this was the rule and you could only fill tanks after your robot was on the field. I ask teams to not pressurize tanks in the queue as I know that teams regularly are writing code and deploying while waiting to take the field. I have seen on numerous occasions, teams checking new code and having the robot move while in the confined spaces in the queue. In the interest of safety, I will continue to remind teams of the possibility of injury even though no rule yet exists.
guy,
If you don't believe that the cRio could or should be the only control for the compressor, what are you suggesting? If the compressor rules are unduly restrictive, what other rules meet that same criteria in your mind?
Back in post #13, I offered an alternate wording to the rule that would be less restrictive.
In essence, what I'm suggesting is that any method of charging your tanks to 120psi which uses an otherwise legal Thomas or Viair compressor that would meet the 1.05cfm rule, includes a working pressure-based shutoff calibrated for 120psi (ie. the Nason Pressure Switch that we've been using for years) should be legal, regardless of its power source (robot battery or otherwise) and control system. You could even skip the requirement that it be an otherwise legal compressor, but that keeps it easy to inspect.
The simplest such system would be to wire the NC Nason switch in series with the power to the compressor through a fuse from a 12V battery with sufficient current capability. I realize that the reason this is disallowed on our robots is because the startup current of the compressor exceeds the current rating of the Nason switch and so runs the risk of failing the switch in the closed position. I agree that this exact configuration should be outlawed for that reason.
However, there is no reason that a similar pressure switch that DOES have the proper current rating couldn't be used in this way.
Alternately, the system which our cart had, which was:
2x12V Deep Cycle Marine Batteries used to drive the cart->
2004 IFI Control System->
Spike->
Thomas Compressor->
125psi Relief Valve->
120psi Nason Switch feeding the IFI Control System feedback->
Air line to plug into robot.
In essence, using our cart was like charging my robots air tanks using a compressor mounted on another robot that otherwise complied with the pneumatics rules.
We didn't, but you could even take it to the next logical step, and have the cart have more storage tanks on it than the robot, which you could pressurize ahead of time and simply dump into the robot, allowing for a nearly-instant fill (assuming you were smart about how you used release valves in the circuit).
My logic behind all of this is that since we all agree that we can change batteries after charging the tanks, the source of 12V power becomes irrelevant to the equation, provided its safe, and since we all agree that I can put my robot on the field with 120psi in the tanks, the method by which the 120psi gets there, and the time it takes to do it is irrelevant, provided its safe. The 1.05cfm limits how much air I can compress DURING the match to about 2.36ft^3, but the unlimited number of storage tanks and the fact that I can start the match with them pressurized to 120psi makes that 1.05cfm value unimportant to the total cubic volume of air I can use in a match.
Mike Starke
04-02-2013, 20:41
Please stop arguing with Al. He is the lead robot inspector. What he says (and the manual), goes. Bottom line. It doesn't matter if you don't like the rule. You need to follow it.
Justin Montois
04-02-2013, 20:54
Precisely what my point has been all along. At least some LRIs are capable of understanding reasonable thought. I have never argued that the rule somehow isn't the rule and that I don't need to follow it. I'm arguing that the rule is baseless and silly, and achieves nothing in terms of increasing safety or levelling the playing field.
Again, show me how this provides me a tangible advantage of any kind, and I will concede this point. Of course we should all be inspected to the same standard.
Since you asked, Say Rookie Team 9999 doesn't have numerous batteries to bring to competition due to this being their first year. Deep into the elimination rounds batteries are running slim. They have 2 completely charged batteries left. They have a slight pneumatic leak and there is a referee huddle going on at the end of the previous match. The pneumatic system is slowly leaking and the team is concerned they won't have a successful auto mode because their shooter is pneumatic fed and the on board charger won't be able to adequately charge the system enough when the match starts. They can't risk draining their battery either prior to the match to top off their system.
Meanwhile, Veteran team with an off board compressor on their cart doesn't hesitate to recharge their system during the delay because it isn't effecting their match battery at all.
That seems to be a large advantage to me. Just follow the rules.
Tristan Lall
04-02-2013, 21:19
Since you asked, Say Rookie Team 9999 doesn't have numerous batteries to bring to competition due to this being their first year. Deep into the elimination rounds batteries are running slim. They have 2 completely charged batteries left. They have a slight pneumatic leak and there is a referee huddle going on at the end of the previous match. The pneumatic system is slowly leaking and the team is concerned they won't have a successful auto mode because their shooter is pneumatic fed and the on board charger won't be able to adequately charge the system enough when the match starts. They can't risk draining their battery either prior to the match to top off their system.
Meanwhile, Veteran team with an off board compressor on their cart doesn't hesitate to recharge their system during the delay because it isn't effecting their match battery at all.
That seems to be a large advantage to me. Just follow the rules.
If 9999's alliance partner 340 were to hand 9999 a fresh battery from 340's stash, so that they could switch before the match, would someone be breaking the same rule?
More to the point, not every imbalance is a rule violation.
So I guess the high pressure N2 bottle to charge the air tanks is out? :)
Tristan Lall
04-02-2013, 21:57
So I guess the high pressure N2 bottle to charge the air tanks is out? :)
You know, I think that's actually why FIRST doesn't want us using external air supplies—they're (rightfully) afraid of someone mishandling scuba tanks.
(Which brings me to a prior discussion (http://www.chiefdelphi.com/forums/showthread.php?p=1055780#post1055780) on this topic that may be relevant.)
Mark McLeod
04-02-2013, 21:58
So I guess the high pressure N2 bottle to charge the air tanks is out? :)
Maybe a hyperbaric chamber and the dump valve can just be opened to the ambient atmosphere...
Please stop arguing with Al. He is the lead robot inspector. What he says (and the manual), goes. Bottom line. It doesn't matter if you don't like the rule. You need to follow it.
Why do people seem to think that my disagreement with a rule is tantamount to me saying I don't think I need to follow it? I understand that the rule is what it is, and consequently I have to follow it. Silly rules get thrown away and replaced with better ones because people discuss them and the reasons behind them. It doesn't just happen out of the blue. I don't understand the logic behind this rule, and nobody has been able to explain what it adds to the competition.
The argument of a rookie team deep in the eliminations not having a battery makes no sense to this argument for a whole host of reasons. a) Spare parts has charged batteries for that express purpose. b) Hopefully their veteran alliance-mates would have one to share, and c) your argument isn't even relevant since the scenario you've described is wholly within the rules.
Also, Al is a Lead Robot Inspector, he's not the only one. Tristan is an LRI as well, and he agrees with me.
Mark McLeod
04-02-2013, 22:34
Also, Al is a Lead Robot Inspector, he's not the only one.
Al is the Chief Robot Inspector, and he is the only one, just like Tigger...
Also, Al is a Lead Robot Inspector, he's not the only one. Tristan is an LRI as well, and he agrees with me.
Al is Tristan's lead inspector. If Tristan has a question, he talks to Al. Al is the Lead LRI. That means, that if Tristan agrees with you, but Al does not, Al wins, and you fix your robot.
I don't know what the rule adds to the competition either--now. I would go so far as to say it's a "holdover" rule; it's been on the books in one form or another ever since I can remember, but maybe should be looked at in terms of revision.
Didn't realize Al was the Chief LRI. The remainder of my point stands.
I don't see questioning the logic of a rule as being the heinous crime that he seems to. The rules are not gospel and shouldn't be taken as such. They change with every Team Update and are clarified with every Q&A answer.
I don't see questioning the logic of a rule as being the heinous crime that he seems to. The rules are not gospel and shouldn't be taken as such. They change with every Team Update and are clarified with every Q&A answer.
I suspect that it wasn't the questioning of the logic itself. I suspect it was the tone of the questioning. Effectively calling a number of LRIs incapable of understanding reasonable thought doesn't necessarily go over very well, as I think you'll agree. Al might also have been making a preemptive move in case rookies were reading the thread and thinking the manual was just guidelines (I've actually seen a rookie refer to bumper guidelines this year when referring to the bumper rules).
If I were to question the logic, I would say simply, this doesn't make sense, can anybody explain the logic. And if nobody could, then I would say, can anybody tell me why is the rule on the books in the first place. (I suspect it was initially to prevent teams from using portable shop-type compressors, which can easily go over 120 if you let them.) I would also ask that question of the GDC at the end of the season, to give them time to work out the answers to the questions.
Tristan Lall
04-02-2013, 23:39
Just for disclosure's sake, I'm not currently signed up to be an LRI at any 2013 events. (But I've done it many times in the past.)
Al Skierkiewicz
05-02-2013, 08:13
Guy,
Just to update everyone, the Nasson pressure switch cannot handle the run current (10-12 amps) of the compressor let alone the start current(22-25 amps). It won't fail immediately but it will fail at some point. Teams regularly still make this mistake every year.
So am I reading this correctly? You have a functioning pneumatic system on your robot and you want to pre-charge the robot from a second system you have built for this purpose using a second control system, any battery and second compressor?
Everyone,
To set the record straight, I am the Chief Robot Inspector for FRC. That doesn't mean that I have ultimate power nor does it mean I make the rules. It certainly doesn't mean I can't make mistakes. Just that I have slightly more responsibility than other LRIs and I am the contact person for FRC HQ. I still depend on all robot inspectors to get the job done and the division LRIs (of which I am just one of four) discuss items throughout the year. Tristan, has served as LRI and division LRI with me when Champs were in Atlanta, at which time furthering his education took more precedent. His opinions are his own.
While many rules need no logic (they are there merely to add some additional challenge to the design), some rules are born from the mistakes of the past. These are an attempt to make things better and more easier to read/understand/implement. Some rules/penalties are in response to previous issues. The need to be inspected prior to receiving points and the harsh penalty is in direct response to issues that have arisen in the past. The compressor rule we are discussing is partly for this reason. It is easy for teams to deal with competing with a team that has deep pockets and a large mentor and sponsor backing provided all other parts of the competition are equal. Some teams actually revel in the challenge of competition with these large teams knowing that they are able to field a robot with the same limitations as the larger teams. Sponsors, spectators and people off the street marvel at how all teams design a robot using the same motors, batteries, compressor and control system, and have to fit the same weight and size. All participants depend on these factors to level the playing field. The Head Ref and their staff perform that function on the field, and LRIs and their staff perform that off the field. Insuring the level playing field is what makes this competition great!
Mark,
That's spelled T I double GGGGGGGGG E R!
@Al: Your assessment of my statements is essentially correct. At one time, we had a fully functional on-board pneumatics system which could be precharged by this separate fully functional "almost-robot". Other years, we dropped the on board compression (and ended up having to hack together something to abide by this rule at the competition, instead of just being able to charge from the cart's compressor).
While I agree using a second FRC level control system to do this is something not all teams (ie. rookies) could do, I don't believe that a control system is necessarily integral to the setup. Without looking around for COTS replacements for the Nason switch, I don't know if there exists one with sufficient current rating for a series setup. Or perhaps with a little ingenuity it could directly feed a spike a control signal. At the very least, something like an Arduino could certainly do the job.
Al's mention of the pressure switch was a tangent. The pressure switch should be wired to the CRIO digital input per rule & never see the motor current of the compressor. I believes he mentions it has an example of things not to do. Rules aside there are other pressure switches designed to handle motor loads. They abound on small shop compressors.
Al Skierkiewicz
05-02-2013, 11:36
Everyone,
I have been waiting to put this out there, so here goes. One of the reasons for this practice has been to prevent all the teams, every year, who use any of a number of different methods to charge tanks. Yes, everything from shop compressors with no cutoff and no over pressure relief (the team shuts off the pressure relief valve because it "keeps leaking air") to "we watch the gauges and disconnect the air hose when it reaches high enough" to "we just connect the compressor to a battery and disconnect the leads when the compressor gets too hot or we think we have enough". If you can think of all of the possibilities, I can tell you of at least one more you haven't thought of.
Justin Montois
05-02-2013, 11:43
If 9999's alliance partner 340 were to hand 9999 a fresh battery from 340's stash, so that they could switch before the match, would someone be breaking the same rule?
More to the point, not every imbalance is a rule violation.
And if instead of 340, they are also paired with rookies?
More to the point, it's all about keeping a level playing field for everyone.
And you're right, not every imbalance is a rule violation, except in this case of course where it actually is.
ferret_guy
05-02-2013, 11:45
As mentioned in another thread (linked above somewhere) it could directly feed a relay to controller the compressor. I use a scuba tank all the time to fill compressed air of all sorts but if someone were to miss use somthing like that at a competition it could be very dangerous, pharps (just a thought) each robot has a standard 1/4" or 1/2" quick disconnect adapter (like the type found on a air compressor) and events have a large regulated 120psi system. now that i think about it though that could all much cost and complexity to an event.
Al Skierkiewicz
06-02-2013, 09:02
Mark,
Sounds good but many events, MARS more than others, have a hard enough time with power distro. Insurance would then also rise.
Tristan Lall
07-02-2013, 00:47
More to the point, it's all about keeping a level playing field for everyone.
One team does something well, and another does it poorly; you want to level the playing field by making them both do it poorly? They tried that in Harrison Bergeron, and you know how it turned out?
And you're right, not every imbalance is a rule violation, except in this case of course where it actually is.
Let's be specific: which rules are being violated?
One team does something well, and another does it poorly; you want to level the playing field by making them both do it poorly?
Yeeeeah, as a Canadian FRC competitor, I'm tired of consistently being outperformed by the two strongest teams in FRC (if 5yr average OPR is to be trusted as a metric of team strength), but I'd hate to beat them because they were holding back, or had their wings clipped by the rules.
We make the competition better by raising the floor, not lowering the ceiling.
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