Layout of off-board compressor (featuring sweet pics)

[tkbletsc]

Our team is doing an off-season build competition that may involve pneumatics, but we don't have a compressor for every team. This means doing an off-board compressor design, but I can't find much info on how to actually do that.

Here's the standard pneumatic layout:
http://i.imgur.com/v9QESu2.jpg

If I charge the system and simply remove the compressor, the air just escapes.
http://i.imgur.com/JdWpKAW.jpg

So what if I put a valve after the compressor?
http://i.imgur.com/M14kPjn.jpg

That way when the system is charged, I close it, then remove the compressor.
http://i.imgur.com/EfHt8pz.jpg

Only one problem: if I accidentally leave the valve closed when I charge, I'm going to be charging just 6" of tube, and I'm going to have a bad time.
http://i.imgur.com/2w9x319.jpg

We have the emergency relief valve on the compressor, but I'd rather not rely on that. How are you "supposed" to do it?

[Jon Stratis]

See images 4-16 and 4-17 in the Robot Rules, R85/86.

You need to have the pressure relief valve (the blow off valve set to 125PSI) attached directly to the compressor, and a second relief valve on the robot (R87)

You can have the regulator, pressure switch, and pressure gauge (for stored pressure) either on board or off board, so long as they are all together - either all on or all off. If they are off board, then you only have 60 PSI available for storage on the robot.

Most teams will plug it into the manual pressure vent valve in order to charge their system. If you do this, make sure there is a second manual valve somewhere so there is a way to relieve the pressure manually even while charging the robot.

[tkbletsc]

I'm sorry, I still don't understand. In the pictures you referred to, what prevents all the pressurized air from escaping when you remove the compressor?

http://i.imgur.com/o9A5qo4.jpg

Whoosh:
http://i.imgur.com/OH9GLWI.jpg

[Jon Stratis]

The pictures don't show it, but you need to have a manual valve in place on the robot side that you can close to prevent the air from escaping.

[Jared Russell]

We have the emergency relief valve on the compressor, but I'd rather not rely on that. How are you "supposed" to do it?

That's what the emergency relief valve is there for.

[cbale2000]

What you need to do is get one of these (similar ones can be found in assorted pneumatics parts that come in old kits or from FIRST Choice):

http://cdn3.volusion.com/vyfsn.knvgw/v/vspfiles/photos/am-2023-2T.jpg

and connect one of these to it:

http://cdn3.volusion.com/vyfsn.knvgw/v/vspfiles/photos/am-2011-2T.jpg

[Nate Laverdure]

Schematically, your legal options look like this:

Standard "on-board" compression
http://i.imgur.com/HrPhDipl.png

"Off-board" compression
http://i.imgur.com/w9uhHysl.png

"Seriously off-board" compression
http://i.imgur.com/y6x7VGOl.png

[Chris is me]

For our robot this year, we would plug the offboard compressor into a fitting attached to a manual valve. The other end of the manual valve was attached to a T, which itself was attached to an additional manual valve and our stored pressure regulator / automatic relief valve. After this collection of brass and hardware, we ran a tube to the first storage tank and the rest is the same as an on-board setup. I can post a picture if needed.

[CENTURION]

You could also hook up a quick-disconnect fitting like this one:
http://www.hydraulic-supply.com/imagesorg/aqpfd41.jpg

Instead of having a manual valve at the point the compressor attaches.

It solves your problem of accidentally trying to charge only a 6" section of tubing, instead of the whole system.

It's also designed to be connected and disconnected many times, whereas the standard kind of tubing fittings used in FRC are really not meant to be used that way (Though they do hold pretty up well under that sort of use).

You can put the male connectors on each pneumatic system, and just one male connector on the hose/tubing coming from your compressor.

Another bonus: These can often be found at local hardware stores, they'll probably be with the air tools (Nail guns and the like).

As far as I know, these connectors are legal for FRC use (Though as you said this is an off-season project, that may not matter).

As others have said, you do need to have a pressure relief valve on the compressor. It's not just the rules; it's so that you don't blow anything up :D

[Chris is me]

The quick disconnects don't seal themselves when not in use? You still need a manual valve between the quick connect and the rest of the system.

[BBray_T1296]

The quick disconnects don't seal themselves when not in use? You still need a manual valve between the quick connect and the rest of the system.


The female quick disconnects automatically seal. I think he made a typo

[rich2202]

As far as I know, these connectors are legal for FRC use (Though as you said this is an off-season project, that may not matter).


It is an R77-f part. Make sure it is COTS, and bring the pressure rating.

R75 - Must be rated for at least 125 psi. If rated for less, at a regional, we will let you use it if your switch and pressure relief valve are set for the lower rating (robot compliant with the spirit of the rule). At the championship, I am guessing they will not let you compete with the under rated component (robot fully compliant).

[m1506m]

Or use a Schrader valve

[JamesCH95]

+1 to the quick disconnect idea. They come in very small sizes if weight is a concern. This is a standard in multiple industries for repeatedly connecting and disconnecting air lines. IMO this is how one is "supposed to do it."

[CENTURION]

The quick disconnects don't seal themselves when not in use? You still need a manual valve between the quick connect and the rest of the system.

The female quick disconnects automatically seal. I think he made a typo

Oops! Yes, I meant to say that the female connectors should be on the pneumatic system, and the male connector on the compressor.