Single Action Cylinder Problems

txnolan · Jun 13, 2016

I reworked an older bat-wing shredder, so that my Dad wouldn't have to crank the wings up every time that he went thru a gate. I added two cylinders that raise the wings by retracting the extended cylinders. The cylinders are connected via a t connection to one line connected to the hydraulics on the tractor. The lift (retract) works great. My problem is getting the single action (double action cylinders with breathers) to extend so that gravity releases the wings. The cylinders don't extend reliably, sometimes I can work the mechanism several times and eventually get the cylinders to extend, sometimes I turn off the tractor. I have occasionally had to disconnect the hose to the cylinder. Any ideas? Please I don't know much about hydraulics, and plan to try separate lines for the cylinders if no better answers are forthcoming.

Tx Jim · Jun 13, 2016

Welcome to TBN
Hello neighbor because Johnson Co Tx isn't that large. I've seen compression springs installed in hinge area to get wings jump started to fold down. Does towing tractor have a float position on hyd control valve?

txnolan · Jun 13, 2016

Thanks, neighbor. I have tried standing, pulling on the wings, not sure how the spring would work. Yes, the tractor does have float. The fluid won't go to the cylinders reliably to make them extend, is it a plumbing issue?

Tx Jim · Jun 13, 2016

Have you lubed hinge pins? Have you considered hooking both wing cylinders together as double acting cylinders? I presume wings won't go down when placing hyd control in float.

LD1 · Jun 13, 2016

txnolan said:
Thanks, neighbor. I have tried standing, pulling on the wings, not sure how the spring would work. Yes, the tractor does have float. The fluid won't go to the cylinders reliably to make them extend, is it a plumbing issue?

Any pics of how its plumbed?

Are they truly SA cylinders or just DA cylinders with a breather in one port.

To raise the wings by retracting the cylinders is telling me your hydraulic lines goes to the Rod side ports. And you have a breather installed in the Base end port???? Is this correct?

Its highly confusing when in the first post, you say this.

I added two cylinders that raise the wings by retracting the extended cylinders.

Then say this

The fluid won't go to the cylinders reliably to make them extend, is it a plumbing issue?

If it is a SA cylinder, NO fluid should be going "to" the cylinder to lower them. Rather oil should be exiting the cylinder and returning to the tractor to let them bleed down.

txnolan · Jun 13, 2016

No pics of how it is plumbed. Raining, muddy and the mower is at my Dad's. Each cylinder has one line, each cylinder also has one breather. The lines are connected via a t connection to a single line attached to the tractor. The breathers are on the correct side of each cylinder. I asked the hydraulic guy who made the lines for me, and I double checked his knowledge by looking at other single action cylinders that I have on a field cultivator and a wheel rake. I know little about cylinders and probably misspoke about fluid going to the cylinder to make it extend. I just thought it had to, as I assumed fluid left the cylinder to make it retract. I can buy more lines and make the cylinders double action. I might also try to cap one side and see if the remaining side works properly without the other. I just don't understand, if the cylinders retract properly then the fluid is leaving the cylinder, so for the cylinder to extend, where does the fluid go?

Thank you all for your help. I appreciate your knowledge and regret that I don't understand, it just seems so easy. As I stated my wheel rake and field cultivator always work great on one single action cylinder lowering both sides of those implements. Why wouldn't two cylinders work together to lower each side of a different implement?

txnolan · Jun 13, 2016

Lube is OK . May have to convert back to double action as you suggest, but would like to avoid the cost of the hose. Thanks.

Tx Jim · Jun 13, 2016

txnolan said:
I just don't understand, if the cylinders retract properly then the fluid is leaving the cylinder, so for the cylinder to extend, where does the fluid go?

When cylinder retracts to raise wings oil is pumped into rod end of cylinder. When hyd control valve is pushed to lower wings oil should leave rod end of cylinder and air enter butt end via breather

LD1 · Jun 13, 2016

Weather fluid leaves or enters the cylinder, and weather that makes the cylinder extend or retract, is all dependent on How its plumbed.

Assuming you actually have double acting cylinders....let's if the hose is connected to the base of the cylinder.....fluid entering will extend it. Fluid leaving will retract it.

If the hose is on the rod end, fluid entering will retract it. Fluid leaving will extend it. Just the opposite as if it were plumbed to the base end.

If I am envisioning the design correctly, to lift the wing you need to retract the cylinder. Thus you need power this direction. And the hose should go to the rod end. Under pressure retracts the cylinder and lifts the wing. With the valve in neutral, gravity "should" lower the wing. And as it does it expelled out the fluid back through the valve and to the tractor.

The issue may be when the wing is up, there is not enough gravity pulling down on the wing to overcome the resistance of the fluid and cylinder. Just the geometry of it. And why I requested some pics.

And DO NOT plug the port thats vented. The air has to go somewhere. Best case scenario....the cylinder will just fail to work properly. Worst case, blow out seals or the blue you install. Just don't do it

bigdeano · Jun 13, 2016

I'm thinking if you replace the vents in the base of the cylinders with plugs when the cylinders are extended, the air will compress when they're retracted, and will help to extend the cylinders and lower the wings. The plugs will have to be air tight. Don't see how it could hurt anything. The pressure could be no higher than the hydraulic pressure.

LD1 · Jun 13, 2016

Correct that the air will go no higher than hydraulic pressure....in this case. Actually a bit lower due to differing piston size.

But once air pressure equals hydraulic pressure, the wing will stop raising. And air will eventually bleed off into the hydraulics.

And we haven't even discussed the heat generated when you compress air from 0psi to 2500 psi in a single stage and no cooler or cooling time.

Just not a good idea.

Leejohn · Jun 13, 2016

Were does your tank/out port go to? Does it feed any other valve without a PB fitting?
Make sure your out/tank port does not have a plug in it.

DLTTrekkers · Jun 13, 2016

Returnoil is never under pressure !
If your ancker point let the wing go oversenter it can not go down by itself !
Rearrange your anckerpoint or make your sil dubbleacting !

DT86 · Jun 13, 2016

I had one side of my mower lock in the up position. After much head scratching, and a few dirty words, the breather ended up being the problem.

txnolan · Jun 14, 2016

Thanks all. I can try a few of these ideas in the next few days. If all else fails, I can make the cylinders double action.

LD1 · Jun 14, 2016

I am thinking DA setup would be best since it seems the wings are raising too far, going over center, and dont have enough help from gravity to lower on their own.

Only other option I can think of, is to but limiters on the cylinders, so you dont raise them so far they dont go back down.

Still would like to see some pics. I am curious, if you use a cylinder to raise and lower, do the wings still articulate over uneven terrain?

bigdeano · Jun 14, 2016

LD1 said:
Correct that the air will go no higher than hydraulic pressure....in this case. Actually a bit lower due to differing piston size.

But once air pressure equals hydraulic pressure, the wing will stop raising. And air will eventually bleed off into the hydraulics.

And we haven't even discussed the heat generated when you compress air from 0psi to 2500 psi in a single stage and no cooler or cooling time.

Just not a good idea.

There is probably enough dead volume in the end cap to limit the air pressure to a few hundred PSI. There has to be a recess for the rod nut, and the volume of the connecting holes. If the piston seal is good it will be a long time before much oil gets past it. I would try it personally. Some people just worry too much.

Jabonee · Jun 14, 2016

txnolan said:
I reworked an older bat-wing shredder, so that my Dad wouldn't have to crank the wings up every time that he went thru a gate. I added two cylinders that raise the wings by retracting the extended cylinders. The cylinders are connected via a t connection to one line connected to the hydraulics on the tractor. The lift (retract) works great. My problem is getting the single action (double action cylinders with breathers) to extend so that gravity releases the wings. The cylinders don't extend reliably, sometimes I can work the mechanism several times and eventually get the cylinders to extend, sometimes I turn off the tractor. I have occasionally had to disconnect the hose to the cylinder. Any ideas? Please I don't know much about hydraulics, and plan to try separate lines for the cylinders if no better answers are forthcoming.

If it lowers every time if you shut the tractor off its a pressure issue. Had the same problem with JD 5200s with dump trailers. Would go up OK but not down. Remember there is always a little pressure on the return side. In your case it sounds like the cylinders do not exert enough pressure to overcome whats in the tractor return side. :thumbsup:

CCWKen · Jun 14, 2016

Wow! Your hydraulic pump/bypass must be screaming when you activate the remote to lower. I assume you're doing that to allow the pressurized side to empty through the valve. Otherwise, it will never come down unless you relieve the pressure on the up side and provide a way for the fluid to return. And if the wings are vertical or over the gravity centerline, there's not enough weight to push the fluid out of the cylinder. You'll need some type of spring.

To keep it simple, I'd just go with DA plumbing and Tee the down side the same way you did the up side. That way your valve will work as intended and your pressure relief/pump will thank you for it. Hose is cheap compared to replacing tractor parts.