pic: Compressor Backpack

[Foster]

Originally Posted by ice.berg

Our team made one of these off-board compressor/air pack deals a few years ago. We used a 5 gal. steel tank rated for 250psi and then a FRC legal compressor. We considered all rules and believed it to be legal. We had pressure blow-off's and dump valves on both robot and pack. Big Al promptly ruled it unsafe for numerous reasons.

Not to push this, but Al is pretty reasonable, he knows the rules and has helped lots of teams to come into compliance. He really wants you to excel safely. I'm sure he quoted the rules and pointed the way to compliance.

What couldn't you do to fall within the rules?

[Foster]

I've gotten sideways in this thread.

Let me start over. Lets turn to be a "how can I" vs "you fail" thread. You are smart, how would you make this work?

I want to have a backpack to charge my robot. Assume, metal tanks. Do I need a cable to the robot to control the initial air load? Once the air load is complete, can / how do I load a remote robot?

[rich2202]

Are you talking:

1) in the pit/que right before a match?
2) At a FRC event, other than right before a match?
3) Outside of an event?

#1 is not possible.
#3 anything goes.
#2 is the tricky question.

For #2, I would make a removable air tank pack that can fit into/onto your robot. It should have 2 connections:
1) Connection to robot vent valve
2) Its own vent valve

During practice, you can run with however much weight you want. While you are in que, you can tether and charge all the tanks you want. Or, even bring the robot charged to the practice field.

For competition, you can remove the extra air tanks.

IF you can get the LRI to allow you to run 2 compressors off field, the removable air tank pack could have a 2nd compressor mounted to it (with all the safety stuff). You would then need a connection to a second PCM, to power the 2nd compressor.

Note: At the championship, I forgot if you had to pass inspection in order to use the practice fields. If so, then you can only run on the championship practice fields in competition configuration (without the spare air tanks). However, there were practice areas where I think you don't need to have passed inspection.

[Jon Stratis]

Originally Posted by Foster

I've gotten sideways in this thread.

Let me start over. Lets turn to be a "how can I" vs "you fail" thread. You are smart, how would you make this work?

I want to have a backpack to charge my robot. Assume, metal tanks. Do I need a cable to the robot to control the initial air load? Once the air load is complete, can / how do I load a remote robot?

Originally Posted by Foster

I've gotten sideways in this thread.

Let me start over. Lets turn to be a "how can I" vs "you fail" thread. You are smart, how would you make this work?

I want to have a backpack to charge my robot. Assume, metal tanks. Do I need a cable to the robot to control the initial air load? Once the air load is complete, can / how do I load a remote robot?

R70 clearly states no off-board air storage. The most you could legally do with this backpack is have a compressor on it that hooks up to the robot to be controlled and to supply air there. And that's only if you don't have a compressor on board.

Even then, I would have some questions about a potentially hot compressor being strapped to someone's back. It would be very easy in that situation to back up, bump into someone, and give them a nice burn to the arm, chest, back, or even face (of the individual was shorter than the one wearing the back pack).

A better solution for carrying around an off board compressor would be something similar to a small toolbox. Put the compressor, gauges, relief valve and everything else in that and it's easily portable and provides some additional Safety from contact with hot parts. You could even get creative, cut a couple of holes for ventilation and power a few fans from a small battery to help keep things cool. Arrange things properly and you won't even have to open the toolbox.

This is, of course, assuming a legal off board compressor set up, with one compressor, no onboard compressor, no storage, and everything controlled from the robot. I don't think using multiple compressors or having off board storage would be legal in any way at an event, even if it was just for pit and Practice field use.

[Alan Anderson]

Originally Posted by Jon Stratis

A better solution for carrying around an off board compressor would be something similar to a small toolbox. Put the compressor, gauges, relief valve and everything else in that and it's easily portable and provides some additional Safety from contact with hot parts. You could even get creative, cut a couple of holes for ventilation and power a few fans from a small battery to help keep things cool. Arrange things properly and you won't even have to open the toolbox.

The only way I can think of to improve this would be to include a miniature Driver Station to tether to the robot and enable it.

[JamesCH95]

Relevant thread: consequences of one of those plastic tanks letting go. Other legalities aside I'd not want a bomb (and we are talking about energy levels associated with explosives) strapped to my back or the back of anyone else.

http://www.chiefdelphi.com/forums/sh...d.php?t=127956

Edit: on the topic of failure modes...

Even with metal tanks, what happens if a line bursts near the operators head?

What happens if someone trips and falls and the battery starts leaking/spraying battery acid?

I see a LOT of ways for someone to get hurt in some pretty horrific ways for the advantage of having a snazzy, heavy, backpack to charge a robot with air at practice in shop. This is an application where a light-duty shop compressor plus a long hose and/or hose drop would be the right way to go. I understand the appeal of an air-charging backpack, I/my team made one in 2003 to charge our robot that didn't have a compressor, but in hindsight it was not safe and did not get us any significant advantage.

[Wilcarp]

Turn down for WATT

[ice.berg]

Originally Posted by Foster

Not to push this, but Al is pretty reasonable, he knows the rules and has helped lots of teams to come into compliance. He really wants you to excel safely. I'm sure he quoted the rules and pointed the way to compliance.

What couldn't you do to fall within the rules?

We appreciate all of Al's input on our robot, matter of fact he saved us at Milwaukee last year. So we appreciate all of his efforts.

But anyways if I remember correctly it had to do with the diagram in the rule book showing the off board compressor options. We read it as this is "what you need to have" while the rule was "this is only what you could have" off your robot for pneumatics systems. And since there were no tanks in the off board section of the diagrams, the tank was not allowed.

[Mr V]

I would definitely ask it be removed from an event I am a LRI at and if I saw it as an RI I would immediately get the LRI.

I would not allow it to be used on the practice field because we need to maintain equality. If other teams see you using it on the practice field they could easily assume that you use it to charge the tanks on the robot before taking it to the competition field. A RI or LRI can not check and make sure that you do not use it before every match.

Sometimes it is about perception.

[Nyle]

Not all white plastic air tanks are the clippard ones
If I'm not mistaken, the air tanks in the picture are, in fact, from pneuaire, not clippard. Not that that makes it a good idea.

[Dale]

(deleted)

[GeeTwo]

If the goal is to have a way to charge the tank for practice, it would be much simpler to use a single A/C air compressor than four or more 12V ones.

• Include a tee somewhere in your high-pressure side, just on the tank side of the pressure relief valve so that relief valve will function as a safety.
• For competition, the third branch of the tee will be capped with a solid plug.
• For practice, replace the solid plug with a vent plug, with a quick disconnect on the open end. Keep this vent plug closed except when externally charging.
• To do an external charge:
  • attach the external compressor at the quick disconnect
  • open the extra vent plug
  • turn on the compressor
  • When you reach the desired pressure (or the relief valve vents), turn off the compressor
  • close the extra vent plug
  • disconnect the quick disconnect fitting

[dellagd]

Originally Posted by bEdhEd

I think we may be able to get away with this at some events IF we only use it to compress when testing systems in the pit and practice field. This could actually be useful for the practice field, due to the limited time.

Without commenting on its actual legality, I have personally seen this ruled illegal at events in the past, even for pit use.

Regardless, it is awesome. What are all of the components strapped to? Is that part of one of those auto mechanics creepers or part of a stretcher type thing?

[brianbond]

That is awesome...

[doctorflems]

Originally Posted by Jon Stratis

R70:

Emphasis mine.

Honestly, this backpack scares me from a safety perspective. What happens to the unlucky person wearing it if a tank should explode? As an LRI, I would insist it be removed from the venue, and I bet the UL Safety advisors would agree.

The solution to that safety issue is to put an OPV at every stage of the system, including one at each end of the tank, and set to 65% of the tank's pressure rating. This way, you have a redundant safety mechanism with about a 50% safety margin. With four tanks, you do this to each tank. In the case that a tank does fail, the frame of the pack should be designed to at least somewhat protect the user.