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Thread: Regulators, flow rates, and pistons.

  1. #1
    Insider new ion?'s Avatar
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    Regulators, flow rates, and pistons.

    So, I've been given a project that is based on pneumatics. Unfortunately, I know nothing about fluids.

    I'm going to be using a Palmer's LP Female reg set to 100 psi (limited, I have some valves that are only rated for this). Through 5/32 ID line connected with push-fittings I will be feeding pistons that need to shift two different loads. The one I'm worried about is a 72 lb-f load, 1/2" stroke.

    I'm worried that the regulator will be choked by the lines or just not able to provide a high enough flow rate to move this 3/4" (or maybe 7/8") piston EDITED - Steve pointed out I'm dumb and this needs to be a 1-1/16" piston. To simplify other integration with other parts, the team is looking at replacing this 3/4" piston with a 1-1/16" piston with position feedback. I am currently unable to find a cylinder with a >1" bore piston with position feedback.

    What I'm asking for, is help. I'm not asking directly for "how fast will this piston move with these constraints" (yet) but what I am asking, is for the guidance and tools to get that answer. I don't really have time to wade through all of fluids, unfortunately.

    If this system won't work as is, I can (not that I'd like to...) implement a post-regulated air cylinder to act as a capacitor.

    I can provide more information if required, but I'd rather not do it out in the open.
    Last edited by new ion?; 01-11-2015 at 01:44 AM.

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    Insider PBSteve's Avatar
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    Forgetting about flow I think your piston has to be >=1" to lift 72 lbs at 100psi, doesn't it?

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    Insider new ion?'s Avatar
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    OMG I'm such a dumb ass. wow that's a brutal error. Ummm... I'm just going to go cry in a hole now.

    I am so embarrased. Area. Not diameter.

    Thank you. I knew I was missing SOMETHING.

  4. #4
    Flow rate through hoses depends on both cross-sectional area and length, right? I don't know any of the math, but shortening all the air lines should improve flow.

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    Insider PBSteve's Avatar
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    I mean, the hoses shouldn't really be a problem. If they become a constriction, use a bigger hose (unless I'm missing something).

    Just have to make sure the reg flows well enough. Why are you using a paintball reg? There are a lot of industrial regulators out there. IMO I'd overdo the flow though the reg, and just do some kind of adjustable flow restrictor to get the speed you want.
    Ever so many citizens of this republic think they ought to believe that the Universe is a monarchy, and therefore they are always at odds with the republic. -Alan Watts

    I work for the company building the Paragon

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    Insider new ion?'s Avatar
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    Simply because its what I know. We're going with a 68SL to store the air. Its the right size for the job.

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    The bigger question is intended cycle rate. How fast are you trying to cycle it? 20cps? Or does it need to switch in say, 20ms?

    It will cycle just fine if you are aiming for 100cycles per minute, for example, and the calculated force is the limiting factor.

    So, what are your fixed and unfixed variables?

    Also for faster cycling, a smaller surface with a higher pressure cycles faster. So that running at 150-200psi with a smaller piston will increase your switching speed and give you the same force. Then you can keep your position sensor.

    Or is the 100psi a limitation? They make some nice 300psi hose, and the reg will recharge faster with a 200psi operation.

    You get faster switching, faster reg recharge, your position sensor and a smaller ram by upping the pressure.

    Also: What are you switching with? Mechanical or solenoidvalve? What model/size?

    Lastly: QEV's - I have added some for emergency valves that are HUGE, for 12" or better pistons. The increase in cycle time was significant (of course, we also had a 3/4" feed line that was 150' long...so) and at the paintball level we know they work good also. So grab some of those to help.
    Josh Coray
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    Insider new ion?'s Avatar
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    I'm looking for effective cycle rates of as fast as possible - however, the system doesn't have to repeatedly cycle quickly, just each time, I'd like each of these pistons to reach the end of their strokes ASAP.

    Fixed more or less at 100 psi. I'm using some MAC 34's and a Clippard EV-P-05-13A0 to control position. These valves are limited to 100psi.

    I should say, these pistons operate independently. One is to provide position feedback and through the Clippard EV-P valve, we will adjust it's position to a target.

    The other piston I just need to reach the end of it's stroke in either direction ASAP. At rest, it sits in the middle of the stroke, held there by what it's moving.

    I can email you some more information to make this less vague, if that helps.

  9. #9
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    You can get Mac valves at a much higher pressure if you want - I have a small stack of 33's in 200psi, and when I contacted them about a custom valve (working on it!) it they said it was really easy and common. It really is just a spring and seal change. No big. The Clippard... not so much.

    Throw some info out. And if you want some 200psi Mac33s feel free also.

    josh@j4pb.com
    Josh Coray
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    Insider new ion?'s Avatar
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    Bit of an update.

    I ordered some valves, some 1.8W MAC 34's to be exact. Using some 1-1/16" pistons, I'm pretty sure they are too small. I haven't done any bench tests yet... But I'm pretty sure they're too small. Also, I can't fit two of the fittings on the same side, which means I'm going to have to find another path forward for my clutch control.

    So yea, I goofed it.

    Now, before I run some bench tests to confirm my suspicions, I'm wanting to have a plan to fix it. Clippard part MMA-31PAS is an air piloted valve that's much larger.

    My initial thought is to use the valves that I have currently to pilot these valves. In theory, I will need 3 of these - one for the Shift Up, one for Shift Down, and one for the Clutch Fill. The clutch position (I think) can be a restricted orfice to slow down the release anyways.

    However, the electronic version of that valve isn't much more expensive. It would mean more or less completely writing off the cost of the valves that I purchased, but would eliminate latency in the pneumatic switching of the main valves.

    Does anyone have any opinions on the matter?

    Thanks all

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