Pneumatic Restrictions & Improvments

[Jon Stratis]

Originally Posted by DampRobot

I've seen people on these forums and elsewhere explicitly say that you can only have one compressor charging the robot's tanks, which means no off board compressors if you have an onboard one. Not that you're incorrect, but there's definitely a lot of misinformation out there about this.

Yes, that's what I mean. Having to enable your robot with the DS just to charge the tanks is a huge PITA. As long as you can demonstrate that your off board control system will shut off automatically at 120 PSI, and had an emergency pressure relief valve, I don't see how it's a safety concern. In any case, it's exactly how the inspectors determine that the regular onboard pneumatic compressor is safe.

The issue with home-spun pneumatic systems like you describe is that they require a certain amount of knowledge and experience for someone to determine if they're safe... and unfortunately many of our inspectors don't have that knowledge or experience. By requiring specific parts, that it's hooked up in a specific way, that it runs from the robot control system, and specific observable operational behaviors, we can ensure a system is safe without requiring inspectors to be experts. It's the combination of known components with known behaviors and the observable behavior of the system that tells us it was hooked up correctly. With a home-spun system we don't have known components with known behaviors controlling it, so our observations from a single run don't tell us enough to ensure it's safe.

I know a number of years ago my team was working on an off-season project and a couple of the mechanical members decided to "safely" power the compressor by running one of the power leads through the pressure switch and plugging it into a battery. It worked a couple of times before the pressure switch stopped working, as the switch wasn't designed to handle that much current. Given a similar situation, a team could demonstrate proper behavior, only to have that behavior go out the window a few charges later!

[JohnFogarty]

Don't you just love the English language and how it can be vague and very specific at the same time?

I don't understand the whole issue of using an off-board compressor to store air into the robot's system if the off board compressor can easily be connected to the robot's control system (temporarily in place of the on-board compressor) so the the robot can control the air input for a pre-match charge. This way the on-board compressor won't heat up because it isn't being used pre-match.

What I'm seeing a lot of people say is that people used multiple compressors at one time to charge a system. I can see this being a bit of an isssue, but not the situation I mentioned above, because in the senario I provided there is only one compressor/air source connected to the robot's system at any given moment.

[Mk.32]

Originally Posted by Jon Stratis

I just checked, it wasn't specifically asked on the Q&A this past year. Regardless, R79 is very clear - your robot can only have one source of compressed air. Filling it with an off board compressor then using a different on board compressor during the match is two sources. If you dump pressure before the match, your fine... And as an LRI, that's what I'll do if I see a team charging with an off board compressor while having one on board.

My apologies for mis-understanding and not being clear.
What I meant was was switching between two off board compressors, to make sure none of the over heated but only using one actively at a time. While having no on board. My team had to do this due to the enormous (5gal) tank we had and we had deliberate over the "one and only one" rule.

But if a team were to have a on board and then disconnect it, and use an off board properly wired into the robot to pre-fill before a match so the on board stays cool during the match; I would think this is legal? Since air is only being provided by one compressor at a time that is wired legally.

[Tungrus]

Originally Posted by Mk.32

But if a team were to have a on board and then disconnect it, and use an off board properly wired into the robot to pre-fill before a match so the on board stays cool during the match; I would think this is legal? Since air is only being provided by one compressor at a time that is wired legally.

This is legal, there was a clarification early this season, if I remember it correctly the requirement is that the compressor must be operated using robot control system.

Couple of years back I have seen teams using a off-board compressor directly plugged into battery and charging.. this is illegal.

The key thing is there are only so many safety inspectors who can check all on-board and off-board pneumatic systems. It isn't easy for these inspectors to twist and bend in every direction to access the on-board system. If teams are allowed for off-board control system (or worse no control system) and off-board compressor, now the inspectors will have to inspect these systems that may be on the cart or somewhere else. God bless them, they do a good job to keep everyone safe.

[Mark McLeod]

Originally Posted by Mk.32

But if a team were to have a on board and then disconnect it, and use an off board properly wired into the robot to pre-fill before a match so the on board stays cool during the match; I would think this is legal? Since air is only being provided by one compressor at a time that is wired legally.

That would still be an obvious violation of R79.
If the compressed air is generated and mixed from more than a single compressor, then rule R79 is violated.

[Jon Stratis]

Originally Posted by Mk.32

My apologies for mis-understanding and not being clear.
What I meant was was switching between two off board compressors, to make sure none of the over heated but only using one actively at a time. While having no on board. My team had to do this due to the enormous (5gal) tank we had and we had deliberate over the "one and only one" rule.

But if a team were to have a on board and then disconnect it, and use an off board properly wired into the robot to pre-fill before a match so the on board stays cool during the match; I would think this is legal? Since air is only being provided by one compressor at a time that is wired legally.

R79 did not include any wording indicating "at a time".

R79

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.

The wording of the rule is straight forward and strict - all of the compressed air in use on the robot during a match must come from one and only one compressor. You can't mix sources between on-board and off-board, or charge halfway with one compressor and finish it off with another.

Personally, I think this rule could stand to be expanded a little to allow more variation in how pneumatic systems are charged, but as it's written it's very strict. Thinking about the reasoning behind it, I can see safety being one reason, fair play being another (not every team can afford to buy 2+ compressors just to charge their system), and good design being a third (If you can't charge your system without overheating your compressor, then you may want to re-think the design of the system and the constraints you have to work within, rather than just "throw more compressors at it" - not intended to be directed at you in particular, alternating compressors from one match to the other so they have time to cool down is certainly a valid engineering solution).

[notmattlythgoe]

There are ways of keeping a compressor from over heating. We had some over heating problems on our practice bot prior to going to our first competition, mainly because we had a lot of pneumatic components on our robot this year. What we did was place a fan on the robot blowing across the heat sink and the compressor never got hot to the touch after that.

[nuclearnerd]

Originally Posted by sanddrag

Quick exhaust valves. PLEASE

Seconded.

Look, I get that there need to be restrictions on the pneumatic power available, but think about it this way: When the game requires your robot to through 4lb balls 10 feet in the air, you're going to need a certain amount of power. That power can be either delivered through a sketchy assembly of springs and a latch mechanism that was likely never meant to work under load
*or*
it can be delivered with commercial-off-the-shelf tubes, valves and cylinders that are engineered for the application, can be reliably assembled without machining resources, and have published specifications to govern their use.

Honestly, pneumatics are the safest way to deploy a given amount of power IMHO.

[Oblarg]

Originally Posted by nuclearnerd

Seconded.

Look, I get that there need to be restrictions on the pneumatic power available, but think about it this way: When the game requires your robot to through 4lb balls 10 feet in the air, you're going to need a certain amount of power. That power can be either delivered through a sketchy assembly of springs and a latch mechanism that was likely never meant to work under load
*or*
it can be delivered with commercial-off-the-shelf tubes, valves and cylinders that are engineered for the application, can be reliably assembled without machining resources, and have published specifications to govern their use.

Honestly, pneumatics are the safest way to deploy a given amount of power IMHO.

It's worth noting that allowing quick exhaust valves doesn't really increase the amount of available power, since it's legal to simply leave one of the orifices on a two-stroke cylinder open to the atmosphere. I imagine the motivation for not allowing them is something else (thought I have no idea what that may be).

[AdamHeard]

Originally Posted by Oblarg

It's worth noting that allowing quick exhaust valves doesn't really increase the amount of available power, since it's legal to simply leave one of the orifices on a two-stroke cylinder open to the atmosphere. I imagine the motivation for not allowing them is something else (thought I have no idea what that may be).

Was this unique to this year?

A 2011 Einstein team ran quick exhaust valves (968).

[sanddrag]

Originally Posted by Oblarg

It's worth noting that allowing quick exhaust valves doesn't really increase the amount of available power, since it's legal to simply leave one of the orifices on a two-stroke cylinder open to the atmosphere.

And this is why they should be legal. The only conceivable safety concern I can come up with relating to their use is you can move fast in two directions instead of just one with an open port Anyhow, to the OP, great thread.

[Mk.32]

Originally Posted by AdamHeard

Was this unique to this year?

A 2011 Einstein team ran quick exhaust valves (968).

I believe it was a Q/A:

https://frc-qa.usfirst.org/Question/...-per-rule-77-f

And the tread this year concerning it: http://www.chiefdelphi.com/forums/sh...d.php?t=124806

[JB987]

Originally Posted by Jon Stratis

R79 did not include any wording indicating "at a time".



The wording of the rule is straight forward and strict - all of the compressed air in use on the robot during a match must come from one and only one compressor. You can't mix sources between on-board and off-board, or charge halfway with one compressor and finish it off with another.

Personally, I think this rule could stand to be expanded a little to allow more variation in how pneumatic systems are charged, but as it's written it's very strict. Thinking about the reasoning behind it, I can see safety being one reason, fair play being another (not every team can afford to buy 2+ compressors just to charge their system), and good design being a third (If you can't charge your system without overheating your compressor, then you may want to re-think the design of the system and the constraints you have to work within, rather than just "throw more compressors at it" - not intended to be directed at you in particular, alternating compressors from one match to the other so they have time to cool down is certainly a valid engineering solution).

And this is exactly what we did. There was simply two independently controlled compressors mounted on a small platform off board and in case there was a rapid turn around issue in eliminations (or a broken compressor) we were prepared to use the second one as a backup should the primary one be overheated. Per the reasoning demonstrated in some of these posts, anyone who has a broken compressor and replaces it would be breaking the r79 rule if they used the replacement to add air to the system. Head inspectors at two regionals agreed we were compliant. By the way, as I recall we never had to use the second compressor...and we eventually substituted for a Firestone heavy duty cycle ( also legal) compressor that worked fantastic at Champs.

[DampRobot]

Originally Posted by FrankJ

I would eliminate plastic storage tanks completely. I would consider requiring that storage tanks be mounted to avoid damage by contact with the field or other robots, but that would be a hard rule to word.

Please, no!

Plastic tanks are one of my favorite technical developments for FRC in recent years. They make large volume pneumatic systems much, much lighter, and have raised the overall level of competition. There prevalence in FRC speaks volumes to how useful the average team has found them.

The failures in the white plastic tanks that have occurred have all been the result of user error, not defects in the tanks. All the failures that I have seen reported on CD were the result of overtightening the fittings on the white plastic tanks (and there have been no reported catastrophic failures of the black tanks). This problem has already been solved in two ways. First, the black plastic tanks (with integrated NPT fittings, which cannot be overtightened) are being sold, and can be exchanged for the white tanks for free. Second, there's been a great deal of education in the FRC community about the dangers of overtightening these fittings, both through Bills Blog, and these forums. Another possible way to resolve the issue would be through more rigorous pneumatic inspection, or even possibly a FRC-wide phaseout of the white plastic tanks (but NOT a blanket ban on plastic tanks in general).

We deal with a lot of stuff in FRC that's potentially dangerous. Dropped robots could break toes, batteries can leak, drills and saws can seriously injure students if misused, and any number of high potential energy mechanisms could inflict great injury if they failed catastrophically. Thankfully, our response as a sport isn't just to ban anything that could potentially be a safety risk. Instead, we maintain a safety-orientated culture, educate students and mentors about potential safety issues, and deal with potentially unsafe robot mechanisms on a case by case basis at regionals.

The right way to deal with this safety issue is through updated pneumatic inspections and through education to the community. Blanket bans are unnecessarily blunt, and would deprive teams of a great resource.

[Mk.32]

Originally Posted by DampRobot

Please, no!

Plastic tanks are one of my favorite technical developments for FRC in recent years. They make large volume pneumatic systems much, much lighter, and have raised the overall level of competition. There prevalence in FRC speaks volumes to how useful the average team has found them.

The failures in the white plastic tanks that have occurred have all been the result of user error, not defects in the tanks. All the failures that I have seen reported on CD were the result of overtightening the fittings on the white plastic tanks (and there have been no reported catastrophic failures of the black tanks). This problem has already been solved in two ways. First, the black plastic tanks (with integrated NPT fittings, which cannot be overtightened) are being sold, and can be exchanged for the white tanks for free. Second, there's been a great deal of education in the FRC community about the dangers of overtightening these fittings, both through Bills Blog, and these forums. Another possible way to resolve the issue would be through more rigorous pneumatic inspection, or even possibly a FRC-wide phaseout of the white plastic tanks (but NOT a blanket ban on plastic tanks in general).

We deal with a lot of stuff in FRC that's potentially dangerous. Dropped robots could break toes, batteries can leak, drills and saws can seriously injure students if misused, and any number of high potential energy mechanisms could inflict great injury if they failed catastrophically. Thankfully, our response as a sport isn't just to ban anything that could potentially be a safety risk. Instead, we maintain a safety-orientated culture, educate students and mentors about potential safety issues, and deal with potentially unsafe robot mechanisms on a case by case basis at regionals.

The right way to deal with this safety issue is through updated pneumatic inspections and through education to the community. Blanket bans are unnecessarily blunt, and would deprive teams of a great resource.

Well if you are going for the massive amounts of air might as well get one of these: http://www.ebay.com/itm/5-Gallon-4-1...d00480&vxp=mtr

They are thin sheet metal, and weigh only about 4-5lbs if i can remember correctly and pressure rated for 200psi. To till them we got the 100% duty cycle compressor from vlair and also later upgraded to the Firestone compressor which is much beefier then the KOP vlair.