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

[4570Man]

You're falsely assuming the the seals are 100% leak proof. The fluid isn't compressed. It's transferred to the other side of the cylinder .

 

[npalen]

The rod side of the piston, being a smaller area than the other side, will intensify the pressure greatly when fluid leaks past the piston seals. Since oil is compressible by only a very small amount, the high pressure oil has to go somewhere if the lift cylinder continues to leak down. The path of least resistance is usually the valve spool which has to be microscopically smaller diameter than the bore of the valve that it fits in. (Has to have some clearance to allow for temperature expansion differential and manufacturing tolerances)
That's my interpretation, subject to debate, about the sequence of events.

 

[the old grind]

Well said. :thumbsup:

If a cyl is plumbed into the system any 'displaced' oil has lots of places to seep to. I'd be switching hoses around (FEL QDs) to point to which component is truly at fault. When a light quits working do we start by checking the switch or by changing-out a bulb?

In 'the old days' we had our crude hands-on trouble-shooting methods. Now that keyboard time is encroaching on seat time it seems we're often just 'trouble-guessing' vs getting our hands dirty 'old school' in the trenches. Some of us old-timers have been using 'scientific method' by our own logic vs by book-learning. (btw, can you say 'solutionism'?)

Depending on vendor or customer spec spool clearances/tolerances can vary within say +/- <.0005", which doesn't seem like much, but there seems to be a trend that what JD uses (source) and what NH uses for loader controls are quite different. (In my past work I've had to hold 50 mic tolerance when grinding similar. 'Tenths' are easy in the toolroom, can be more 'lenient' per customer spec.)

My ~'70 JD had way more hrs on it than my '98 NH but the bucket stayed up 3-4x as long as the NH's when parked. My '99 JD has >3k hrs more on it than my bought-new '14 NH. I must have mentioned which one 'drops' in wks and which in hrs.

Find the problem component first, no?

 

[npalen]

+/- <.0005"

Now that's machinist talk there, I don't care who you are.

 

[RNeumann]

Not sure if a cylinder that holds for 3 weeks is better than one that holds for 3 hours. I know tolerances and the type of fit has a million variables- and the design of cylinders would be a perfect example of this.

 

[CalG]

Sorry, that's just not true.

Where does the volume of fluid go? The "other side" is already full. At least most of us try to get all the air out if there is any in.
Consider the situation carefully.

Similarly
http://www.tractorbynet.com/forums/hydraulics/336588-fel-wont-hold-cylinders-fixed.html

 

[comancheflight]

OP here - a cylinder at rest and NO force exerted on it will be in equilibrium. Fluid pressure is equal and no fluid flows. IF a force (weight of bucket) increases the pressure on one side of the cylinder as opposed to the other side. In a perfect world the seals would hold a cylinder forever, but with even a pinhole, under pressure fluid will migrate to the other side due to pressure and fluid seeking equilibrium which, in turn, allows the bucket to lower.
My question was when is it considered to be enough to have warranty repair...obviously if your bucket hits the ground in 30 minutes but where is the magical point at which your dealer would say something is wrong. Where is the spec?

 

[CADplans]

You're falsely assuming the the seals are 100% leak proof. The fluid isn't compressed. It's transferred to the other side of the cylinder .

In my statement,, I did not assume the seal would hold,, heck, I said you could remove the piston seals,,,
AND the piston!!

The rod can not be pushed into the cylinder.

 

[4570Man]

The volume inside the cylinder remains the same regardless what position the ram is in. If the ram moves in an inch than the volume on the other side increased. Think about how a shock absorber works. What makes the cylinder any more likely to extend assuming the end seal doesn't leak ( other than the fact the pressure is higher to hold the same load )?

 

[CADplans]

The volume inside the cylinder remains the same regardless what position the ram is in. If the ram moves in an inch than the volume on the other side increased. Think about how a shock absorber works. What makes the cylinder any more likely to extend assuming the end seal doesn't leak ( other than the fact the pressure is higher to hold the same load. )

A shock absorber has gas in it,, not fluid,,
if you put fluid in a shock absorber, it would be ridgid,,,