# Closed loop



## Hacker (Sep 4, 2013)

I'm wanting to use a double acting cylinder where it will either be floating or locked.
I see that they exhaust through the control valve and my question is can they then be utilized in a closed loop system by using a 2 way solenoid valve between the inlets, that would lock the cylinder in any position when closed and allow floating when opened.
System would be charged through a schrader valve teed into the loop.
If the cylinder itself does not vent off the pressures, barring leaks, would it hold pressure and function as intended?
Thanks for any input on this.


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## bfjou812 (Aug 15, 2008)

Are you trying to make a cylinder move partially a few times then go to full extension? I think it could be done but the thing is the piston side of the cylinder will have more area than the rod side. Which means more force on one side than the other. I had thought of doing this using 2 seperate solenoids and a lot of crazy plumbing. Sort of a poor mans feedback system.Hope this helps.


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## Death Master (Jul 1, 2007)

You need a 3 Position 5 Way Double acting solenoid to do what you want. or a Servo-pneumatic valve.


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## bfjou812 (Aug 15, 2008)

Death Master said:


> You need a 3 Position 5 Way Double acting solenoid to do what you want. or a Servo-pneumatic valve.


That's what I was thinking of ,for some reason I had a brain fart. I've worked as a Maintenance Mechanic for 20 + years and couldn't think of it. Thanks for jogging my old memory!!


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## Hippofeet (Nov 26, 2012)

If I understand what you are saying, you could just use a shut-off in place of the 2 way solenoid to test it. I will make a vid, and see if I can make what you are talking about.


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## Hippofeet (Nov 26, 2012)

For some reason when I try to upload a vid to youtube, IE keeps crashing. I made two vids, man, they were great. You should see them. :/

Anyway, I couldn't get it to work with a 4 way, 5 port solenoid and a shutoff. In order for it to float back and forth, you would need both the exhausts open at the same time. Which must be what the 3 position, 5 way double acting solenoid does. I didn't even know they made those, but now I will have to get one.


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## Hacker (Sep 4, 2013)

The application is going to be a stabilizer on a sidecar rig, allowing locking it into a rigid rig for parking, in town, adverse conditions, etc., yet normally allow the sidecar to float and the motorcycle to handle like a motorcycle.
Sorry you couldn't get your vids loaded after your efforts. 
I spoke with a tech rep at automation yesterday after posting and he felt it would work fine excepting losses and possibly having to add a compressor.
With the same pressure on both sides of the piston, i thought it should float when the loop / solenoid valve is open.


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## Hippofeet (Nov 26, 2012)

What about just a ball valve? When open the cylinder would float, when closed the cylinder would lock.


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## Hacker (Sep 4, 2013)

I thought it that simple...just substitute a 2 way solenoid valve for your ball valve so that it can be activated at the handlebar. 
I had not considered that the volume displaced when the stroke is reversed is not equal due to the rod being in one chamber and not the other.
If i'm understanding correctly the solenoid valve above (I haven't located a description of it yet) must control a position for float with both chambers exhaust being opened simultaneously and another with both activated for locking it. I do not understand how it could lock in any predisposed position that it may be in.
Also if exhausting air, closed loop is out of the question.


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