Two pressures?
 

Is it possible to use different pressures for the extend and retract on the pistons? For example, use 60 psi for the retract and regulate the 60 psi down to 30 psi for the extend?

Re: Two pressures?
 

why would you want more pressure on the retract then the extend. In pneumatics like we have there is no real "speed control" or "stroke distance control" that we have by limiting pressure input on different sides.

Re: Two pressures?
 

you could use the 2ndary regulator on one of the pneumatic lines downstream from the solenoid valve.

NOTE: im not entirly sure how this would work thoug, i dont know how air reacts passing backwards through the reg. I am under the impression it gets vented, but it might restrict flow then. try it!

Re: Two pressures?
 

in te kit of parts *not sure what they are called* there are little pressure regulators that attach to either end of the piston. The are whit and orange and have a little turny knob on the top for adjusdments. Put those on and tweak around with that.

Re: Two pressures?
 

Re: Two pressures?
 

THe second regulator would be your best choice. It should work but just test it.

Re: Two pressures?
 

those are not pressure regulators, those things are called "Flow Controls". They allow the flow of the air passing OUT of the piston to be controlled. They can be used as 1 way valves to, because air in is unefected, and air out can be cut off when the valvr is all the way closed.

Re: Two pressures?
 

Well, you're 1/2 right. True, you can not regulate stroke distance with pressure. You CAN regulate the speed at which the piston moves (and it can be different extending and retracting) with the small fittings that have the white knobs.
You also CAN create a very simple multi-positioning setup with parts from the kit. This will allow you to extend a piston part of the way and stop.
You typically do this by using 2 selenoids. One double, and one Single.
We did this last year, I can't entirely remember the setup.
But It's not difficult, or space consuming or anything

The spell check feature has not been readded into the forums yet.

Re: Two pressures?
 

ahh oh well im not too worried about my spelling... i know i can type right but im usually just to lazy to go back and fix my lazy online talk

Re: Two pressures?
 

Well I was trying to think of a way to limit the amount of air we lose when you lift ourselves onto the bar. We would still need the 60 psi (actually would it be better to have the retract only exert 130 lbs of force??) to lift, but do we really need 75 cu In at 60 psi to be lost just to extend the piston?

Re: Two pressures?
 

EDIT: So my guess at your intent was wrong. And four other people replied while I was typing this. However, maybe this post with have intrinsic value to someone else. Consider it a recap.

I'm going to sort of ignore your question, because I've got a feeling you're asking how to dodge the 10ft/sec rule with a piston bar hanger. I assume that what you're trying to do is actually control piston extension and retraction *speed*. If thats the case, using a regulator to restrict pressure for the extension is only indirectly going to solve your problem. NoRemorse's flow controls screw directly onto the pistons, and will allow you to adjust stroke speed without effecting force.

If you really want to restrict *pressure* for whatever reason, and you fully realize that this will have only indirect impact on piston speed, you'll need that second full blown regulator.

Re: Two pressures?
 

As an answer to the original question, if a secondary regulator downstream of the double solenoid doesn't work because of the directionality of the regulator, you could always use two single solenoids and have one supplied by the secondary regulator.

Also note: I recall accidentally hooking a regulator up backwards once, and it completely failed to regulate pressure, so I think the regulator after the double solenoid should work. If you want to have more than one cylinder set up like this, single solenoids would be the way to go since I think you're limited to just the regulators in the kit.

Also, to everyone else, I can think of one good reason to set up a cylinder like this. If you know for certain that you don't need 60psi on the retract and only need 30psi, setting the system up like this could potentially save you a lot of stored air and battery power, depending on how often you cycle the cylinder. It works out to about a 25% savings for every extend-retract cycle. That could potentially be very important.

Edit:
I'm a slow typist, but I swear I thought of that before he posted his intentions. Honest.

Re: Two pressures?
 

Not exactly trying to dodge the 10 ft/sec rule. It was more of a way to reduce the amount of air we exhaust when we extend the piston so we don't need to wait 30 seconds for the system to gain enough pressure to fully retract the piston.

Re: Two pressures?
 

Ahh much thanks.. We are all forum hawks tonight.

Re: Two pressures?
 

Well, this is the info I can give you.

1) The piston has the most force when extended (you probably knew this though)

2) In this situation I don't know what you are trying to do makes sence. Are you regulating down the pressure it uses one way to below 60, or do you want it to be more on one side. I believe that you may only use 60psi on the cylenders.

3)If you want one side at 60psi, and the other at a lower, you may need 2 seperate solenoids to accomplish this.......

[tanks]=====['T']===[reg at 60psi]===[solenoid]===[r]
....................||............................ .....................||
.....................\====[reg at 30psi]===[solenoid]===[e]

DISREGAURD the dots!


r and e are 'extened' and 'retract'

I don't know if ths what your shooting for though

Re: Two pressures?
 

I was shooting for something like this

edit:
bah stupid formating

edit 2x:
this doesn't look right at all... must mean it's time for sleep

Re: Two pressures?
 

I understand your intent now... your clarification got sandwiched in between my read and my write. I don't know what your mechanism actually looks like, but would it be possible to leave one side of your pneumatic vented and just use a bit of surgical tubing for the extension?
I'm not sure what the technical term is, but I know I've played with cylinders that had a spring loaded extension and a pneumatic retraction. I couldn't tell you if those components are FIRST-legal, but you might be able to cobble a reasonable facimile together. Then again it might not be worth the added complexity.

Re: Two pressures?
 

that should work, but i dont know how fast the regs bleed off pressure when the air flows backward thriygh them. by puuting them before a solenoid (which requires 2 soleniods) you get a quick dump of rpessure and a MUCh quicker acting piston

But i have never tested this, the flow of air back through the reg may be suffecient for your applicatrion!

Re: Two pressures?
 

There is a way to retract the cylinder using no air at all - leave the other end of the cylinder open - no connection, and use a small spring or the surgical tubing to retract the cylinder

then you only need a single valve to pressurize the business end, and when you close the valve it will vent the air, and the surgical tubing will retract the cylinder.

Re: Two pressures?
 

I think using the single solenoid off a secondary regulator would work best. Just shorten all your tubing so it will regenerate pressure quicker. You don't need to worry about flow controls all that will do will slow down your cyclinder and not reduce amount of air used.

I think he wants to extend and then retract Ken.

edit: But I imagine it would work the other way too

Re: Two pressures?
 

GREAT POINT!!

this might be exactly what your are looking for because one way uses no gas consumption.

Re: Two pressures?
 

Yes, but unfortunately the surgical tubing doesn't provide the retracting force we need. We are trying to save air on the extend. If you look at the picture you may see more clearly why we want to save air

http://www.chiefdelphi.com/forums/sh...ad.php?t=25130

24 '' stroke if I remember right

Re: Two pressures?
 

[quote=KenWittlief]There is a way to retract the cylinder using no air at all - leave the other end of the cylinder open - no connection, and use a small spring or the surgical tubing to retract the cylinder [\QUOTE]

Gentlemen, I think we should all take a big step back from this forum for the night. I've never seen a room full of guys who were all to tightly on the same wavelength!

That or we all need to learn to type faster.

Looking at your robot, getting an elastic extension does look like a pretty hairy engineering problem. It could be done... but I'd hate to tac anything onto such a simple mechanism.

Re: Two pressures?
 

Yeah you can switch ken's model to extend with no air and then retract.
It's hard to explain well though.

Yeah tough, how does your mechanism set when it is extended or is the 24"cyclinder the bulk of the extension.

Re: Two pressures?
 

The bottom piston retracts to lift the bulk of the arm vertical. Then the 24'' piston extends to hook on. Then retracts to lift off the ground, currently this takes about 1 - 1.5 min with one accumulator.

Re: Two pressures?
 

If you can find a place that the latex tubing will pull enough that it will extend the cyclinder when it is pointing down and using the non-pneumatic air extension you can make Ken's spring way work. If not, route all exhaust from you cyclinder to a single solenoid with a stop on one of the output and block so you can control the stroke length of the cyclinder. You look like you could have the cyclinder partially extended to begin with and a least cut down on the wait for it to lift. Or you could lengthen your arm and purchase a shorter cyclinder. A 16" would do the job or even a 12" or 8" and would reduce the air needed. You lose height gained but an inch or 2 feet both get you 50 points. The one just works faster. I would add the second accumulator and make sure to reduce all tubing lengths. PM me and I'll give you more info about the single solenoid.

Re: Two pressures?
 

how about another idea. i can't see exactly how well this'll fit, but how about starting with your cylinder half extended. (use the double w/t single solenoid) from the angle of your photo, it seems like you may be able to do this. maybe.