FEL how long 'should' bucked remain up when parked?

[k0ua]

Let me see if I can pontificate on piston extension and its causes which I did not consider or comment on during my previous "thought experiment".

Lets say we have a top link cylinder with a heavy implement pulling on the top link cylinder rod. What would cause the piston to move within the cylinder bore?

Well one thing that could cause this would be if we had a leak in the control valve on the rod side connection. This would allow the fluid in the rod side to flow thru the valve and a partial vacuum to form on the cap side space or if the tractor was running and the pump/control valve circuit leaked also it would allow fluid from the pump to flow into the cap side space.

If we had a leak in the piston seals that would allow fluid to flow from the rod side to the cap side past these leaky piston seals as the volume of oil on the rod side would be less than the cap side as the steel rod is in there taking up volume. As the rod come out of the cylinder then the oil is free to flow towards the cap side past those leaky seals.

Third way is if the end seals of the cylinder leak and lets oil flow out onto the ground so the rod and piston will move towards the implement. or of course if a hose or fitting leaks.

I think some of the problems people have in understanding why the rod cannot be "stuffed" back into the cylinder even if you have leaky seals is because many folks don't understand that BOTH sides of the piston has oil in their spaces. Perhaps some people think the rod side of the piston has air or even a vacuum in it therefore they think oil from the cap side could leak past the piston seals and go into the rod side space.

 

[comancheflight]

OP - I understand I was incorrect according to physics and those on here. I think I need lab time with experiments to understand why. Lots of explanations and a few websites and still have my college physics books but it ain't takin. It just 'seems' like over time the cylinder could move via pressure and equilibrium.
Regardless, this phenomenon has nothing to do with my original post. I was just curious as to where is the point at which the speed of your bucket drop is considered a warranty repair? At least I think ....now I have forgot..lol

 

[ch1ch2]

I am amazed at the answers.

Put a penny in a jar, fill it with water, put a lid on it. Turn it over and the penny falls to the bottom every time you turn it over.
The water goes around the penny to the other side.

The are shocks that are filled with oil. They have pistons in them with holes. The pistons move though the oil only at the speed of which the oil can flow though the holes.

Some how the above principles do not work in some situations?

I am open to everyones thoughts. Both sides believe they are correct.

I believe the hydraulic fluid can and does go from one side of the piston to the other side if the piston internal seal leaks just as a penny will move inside a jar of water.

 

[the old grind]

.... The leakage is in your control valve unless fluid is dripping out on the ground.

... With hydraulics, there is a clear right and wrong. That rod that is disappearing down into the cylinder, is displacing oil. That oil has to go somewhere. If it aint leaking out of the hoses and fittings all over the ground.....it is leaking through the VALVE. The VALVE is what is faulty.

^^^ yyyyyyyyup!

So easy to over-think the OP's issue and the answer is so simple. If one really wants their bucket to stay up all night they can plumb-in some shut-offs ('full-open'-type) and not extend/waste warmup time getting the bucket back up in the air every morning.

OP, IMO it's up to you to decide if the tendency is 'too much', or to visit a dealer say two days in a row and test/see which on the lot drop from 18" o/night. I'd be concerned if a bucket drifted noticeably while operating but of six I've owned and four still on site I've never seen that happen. 'New' or 'old' doesn't seem to matter much, either.

Have you measured time/distance with full vs empty? We and the dealer could use a bit more detail to chew on.

 

[k0ua]

I believe the hydraulic fluid can and does go from one side of the piston to the other side if the piston internal seal leaks just as a penny will move inside a jar of water.

Well, you can believe what ever you want to believe as it is still a free country. but you penny in a jar analogy does not apply as the penny is already totally immersed in the jar. You are not trying to displace the water in the jar by adding pennies now are you?

Here try this. Solder a 1/4 inch rod to your penny, and put a nice rubber O ring seal in the jar lid that will just pass the 1/4 inch rod and not leak. Now fill your jar fully with water and close the lid with the penny halfway or anywhere in the jar except the bottom. So far so good?

Now try to shove the rod into the jar. You will not be able to do so. According to your analogy, the fluid below the penny is free to flow to the top side of the penny as there is no seal at all is there? You are missing the larger point that you cannot shove the rod into the jar, as the water is more or less incompressible. Or incompressible to such a small extent you cant shove that little 1/4 inch rod into that jar no matter what you do.

 

[4570Man]

I am amazed at the answers. Put a penny in a jar, fill it with water, put a lid on it. Turn it over and the penny falls to the bottom every time you turn it over. The water goes around the penny to the other side. The are shocks that are filled with oil. They have pistons in them with holes. The pistons move though the oil only at the speed of which the oil can flow though the holes. Some how the above principles do not work in some situations? I am open to everyones thoughts. Both sides believe they are correct. I believe the hydraulic fluid can and does go from one side of the piston to the other side if the piston internal seal leaks just as a penny will move inside a jar of water.

That's where I messed up earlier. Try your jar of water experiment using a golf ball and fill the jar before the ball goes in. Water will have to spill before the ball can enter the jar. The only explanation I can think if for the oil filled shock is the cylinder wasn't filled entirely with oil and has air space. If a hydraulic cylinder also wasn't filled entirely with oil it could leak until the air space is used up. If the end cap seals of the cylinder leak the rod could leak in either direction.

 

[rd_macgregor]

While it is true that there is incompressible fluid on both sides of the piston seal, the cylinder can still move if the seal is leaky; the total fluid, and average pressure, stays the same in the cylinder, but it moves from one side to the other past the seal based on force somewhere causing a pressure differential between the two sides of the cylinder. If the seal does not leak, this pressure diffrential can be maintained and the FEL (or whatever) doesn't move.
I think a leaky valve is likely a more common cause, though.
9 pages of discussion about how long FELs stay up and nobody mentioned Viagra yet???

 

[k0ua]

The are shocks that are filled with oil. They have pistons in them with holes. The pistons move though the oil only at the speed of which the oil can flow though the holes.

Some how the above principles do not work in some situations?

Yes shocks have oil and metering valves, and they also have gasses in them. Gasses are compressible, fluids are not, or not very much.

Hydraulic cylinders have fluid in them on BOTH sides of the piston and its seals. If you push down on the rod of a hydraulic cylinder and try to stuff it into the cylinder that has fluid in both sides of the piston, it doesn't matter if the seals leak or not, or EVEN if there is not a piston in there any more, you just cannot shove that rod into that cylinder space that is filled with oil. You just cannot do it no matter how much force you place on that rod trying to compress that fluid in there. Don't overthink this, it is as simple as that.

 

[LD1]

I am amazed at the answers.

Put a penny in a jar, fill it with water, put a lid on it. Turn it over and the penny falls to the bottom every time you turn it over.
The water goes around the penny to the other side.

The are shocks that are filled with oil. They have pistons in them with holes. The pistons move though the oil only at the speed of which the oil can flow though the holes.

Some how the above principles do not work in some situations?

I am open to everyones thoughts. Both sides believe they are correct.

I believe the hydraulic fluid can and does go from one side of the piston to the other side if the piston internal seal leaks just as a penny will move inside a jar of water.

Penny in a jar is not the same scenario. Because the volume of the penny, and the volume of the water inside the jar....do NOT change when you flip the jar around.

With a hydraulic cylinder, as you compress it and force the rod into the body of the cylinder.....volumes change. So instead of a penny in a jar, a better comparison would be to cut a hole in the lid of the jar, and get a ~1.5" wooden dowel rod. This dowel rod represents our piston rod.

Now put the rod in the jar and fill the jar clear full with water. Pull the rod out.....and you will notice the water level went down right? Now if this rod where tightly sealed to the jar....that air space would be vacuum. This is what happens when a bucket or toplink drift (extension)

Now take that same jar, and fill it clear full without the rod in there. Once clear full, shove the rod in there. What happens to the water? It overflows right? The EXACT same thing has to happen inside a cylinder. In order to compress a cylinder (shove the rod down inside there), the oil that gets displaced HAS to go somewhere. The only place it can go is either back through the control valve, or all over the ground via a leaky hose/fitting.

 

[k0ua]

While it is true that there is incompressible fluid on both sides of the piston seal, the cylinder can still move if the seal is leaky; the total fluid, and average pressure, stays the same in the cylinder, but it moves from one side to the other past the seal based on force somewhere causing a pressure differential between the two sides of the cylinder. If the seal does not leak, this pressure diffrential can be maintained and the FEL (or whatever) doesn't move.
I think a leaky valve is likely a more common cause, though.
9 pages of discussion about how long FELs stay up and nobody mentioned Viagra yet???

I am sorry, but it cannot happen. how can the fluid from the cap side possibly move into the rod side? How can you possibly push that piston into that cylinder full of fluid and steel? It CANNOT, WILL NOT ever ever go in there.

This makes me want to scream and go take an aspirin...