pneumatic cylinder question

[Honga]

I have a solution in mind, but it supposes upon the application. Can you give us more indication of stroke accuracy, stroke length, speed, repeatability etc?

 

[rpoet]

OK, time for some answers to the questions. I never thought I'd get this many responses!

@Honga - The stroke will be 6", which is the travel of the cylinder.

@kamenges - this is for a theatrical special effects application. The piece of scenery that the cylinder is being built into has to be moved and connected by actors. That's why I was really hoping for a single-hose connection.

@jimfun71 - cycles and makeup air will be no problem. They have to run once per show; that's once or twice a day. Stage crew will be checking the pressure as part of pre-show duties.

I hope these make things a little clearer. Thanks for all the responses!!

-rpoet

 

[seaston_65]

I think your best bet would be to run 2 air lines and colour code the lines.
Blue line to blue connector, Black line to black connector (or whatever)

 

[Honga]

I like alarics idea. Kiss approach is good.

 

[kamenges]

If you're worried about correct connection, maybe something like this:

http://www.twintecinc.com/

Keith

 

[shooter]

how about a train brake system it works with only one line and is air operated.
it involves a simple pneumatic valve, and when the pressure in the line is lost the brake will be on.
look for westinghouse brake
yes it uses a kettle on each cylinder.

 

[TConnolly]

I think your best bet would be to run 2 air lines and colour code the lines.
Blue line to blue connector, Black line to black connector (or whatever)

...or two different diameters. That way there is only one way it will hook up.

 

[milldrone]

I think your best bet would be to run 2 air lines and colour code the lines.
Blue line to blue connector, Black line to black connector (or whatever)

...or two different diameters. That way there is only one way it will hook up.

There are some suppliers of "twin" airline tubing. Some have color coding to help with identity.
https://estore.industrialcontrolson...tem+detail&itemcode=ICD1219-1/4T+(1219-440T3)
https://estore.industrialcontrolson...em+detail&itemcode=ICD1219-5/32T+(1219-130T4)
http://rsd.net/search/prod.php?prod_id=797&prod_no=Pneumatic+Tubing&cat=Controls
http://www.legris-pneumatics.com/webcat/Detprod.asp?ProductCode=L120116
http://www.pexsupply.com/Chevron-Tubing-1063636-5-32-Plexco-Pneumatic-Tubing-Twin-Tube-Black-500

 

[ndzied1]

I think the key for the use in this application is the single connection. To that end you could use something like this:
http://www.colder.com/Tabid/72/MaterialID/1/cID/1/sID/68/Products.aspx

The line sizes are pretty small so you may have to double up on them if you need the cylinder to move fast.

<disclaimer - I work for a company that distributes for Colder Products>

 

[Roy Matson]

From the diagram you show a needle valve.
Are you also trying to control the speed?
If so the needle valve goes on the exhaust.

 

[rpoet]

I've redesigned the system to use double acting cylinders, using the valve to admit air to the rod-end of the cylinder. I will use a spring for "retract." I need to stick with one air line for cost reasons, as well as simplicity.

@Roy - I need to control both extend and retract, so I need the needle valve to go in the line to the cylinder, not in the exhaust. We do weird things in theater sometimes.

Thanks again for all the replies!


-rpoet

 

[shawn_75]

Putting the throttle/needle valve on the cylinder exhaust has some significant advantages. Mainly, controlling cylinder speed on the exhaust port causes your cylinder to operate at or near it's fully capable force (air pressure * cylinder area) throughout the entire stroke. If the air inlet is throttled to control speed then your cylinder will operate just above the breakaway force of the mechanicals it is attached to. If the mechanical linkages are smooth and the load fairly constant throughout the stroke, you should have acceptable operation. But, if the linkages are not good and tend to bind or if the load changes over the length of the stroke (ie. you are rotating something from vertical to horizontal) then you will have jerky motion or inconsistent speed.

Using a combination speed control / exhaust muffler like this on your solenoid valve http://www.amazon.com/Norgren-MM001A260-Sintered-Control-Muffler/dp/B002095NGA
will not only provide smooth operation but will attenuate the exhaust noise.

 

[rpoet]

Good advice Shawn. The load should very consistant; I'm lifting something against gravity, but your point is well taken. The nice thing is it will be all QC push fittings, so changing things will be easy.

I am building a special 8-way muffler with inputs for all eight air circuits I'm using. I will post pictures when the system is built. As this is theater, silence is absolutely golden. I have a design based on PVC fittings and (I know this sounds nuts) a large, fluffy paint roller. I've exhausted 3" bore, 60" throw cylinders through my muffler design, and you couldn't hear anything more than a whisper.

-rpoet