I may have discovered my curl issues on my tractor

[Tjdux]

This thread isn't even an "intense" one.

Some of these hydraulic threads pertaining to drift, especially the main lift cylinders, can get pretty heated. I agree, would be alot easier to tell (show) someone in person.

Those that think faulty seals can cause the main loader to drift (cylinders compressing,) and there are many here on TBN that believe this....I'd love to have a junk cylinder and 30 minutes and I would guarantee I could prove that it ain't possible.

But as it is, all I can do is the best I can trying to explain why and how hydraulics work. And give the best examples and analogies I can.

I Definitely dont have time/need/experience for intense dissucion and i appreciate that.

What do you mean by main loader? You mean the lift cylinders that move the bucket up on a FEL?

Also can you elaborate on how a cylinder that is "junk" can function fully?

 

[Luke'sScreenName]

Yeah a cylinder with poor seals will compress (especally with no regenerate pressure from the pump) no matter what. If the pressure can pass from one end to the other then with nothing to equalise (pump) it will fail (fall or drift)

Nope, that is definitely NOT what I was saying. Sorry. LD1 is right but it is difficult to explain in this format.

 

[LD1]

How about faulty rod seals?
Pretty sure if those leak you'll get leak-down (and a puddle)

Maybe it would be more accurate to argue that internal cylinder leakage can't cause leak-down in such applications?

Nothing like a little obtuse obfuscation to help the discussion along... :drink:

Yes, forgot the disclamer "assuming NO external leaks". OR should have clarified piston seals...

Yeah a cylinder with poor seals will compress (especally with no regenerate pressure from the pump) no matter what. If the pressure can pass from one end to the other then with nothing to equalise (pump) it will fail (fall or drift)

If this means what I think it means, its wrong

I Definitely dont have time/need/experience for intense dissucion and i appreciate that.

What do you mean by main loader? You mean the lift cylinders that move the bucket up on a FEL?

Also can you elaborate on how a cylinder that is "junk" can function fully?

By main loader lift cylinders I mean the ones that lift the loader arms up and down. These cylinders EXTEND to raise. Meaning if they drift down they are being compressed. And you could completely remove the piston seals....heck you could even remove the piston....and NO, the cylinder wont bleed down unless there is fluid leaking externally or the valve is bad. PERIOD.

When I say a junk cylinder, it is to prove that point. Never said it would fully function. A cylinder with the seals shot (or removed) will lack power (and probably speed to). But if it isnt leaking via a hose or fitting, and the valve is good and tight....NO the loader wont bleed down.

 

[aerojunkie]

All I can say is wow, and a very huge thanks to everyone that has posted it has helped me more than I can say. First let me apologize for jumping the gun and claiming the cylinders needed a rebuild right off the bat, that's just what my little hydraulic knowledge led me to believe and caused some confusion. I know the thread seemed to get off track but believe me its was all very much appreciated because it taught me a lot more than what I was asking. I did do some more testing today and have some better data to diagnose but after reading this thread I believe I know what is wrong now but I would like to see what you guys think first. I raised the loader bucket to about 5 feet up and leveled the bucket by eye and cut the tractor off. Then I measured from the end of the lift and curl cylinders to the pivot point on the other end of the piston and about every 15 to 30 mins I remeasured and wrote it down along with the time. The curl cylinders extended and the lift cylinders compressed 1/16" every 15 minutes. Even if I measured 30 mins apart it was the same consistent 1/16" every 15 minutes, I did this over a couple hours. I measured the cylinder extension to that I could isolate the change from affecting the other cylinder if I just measured to the ground. I just read about doing the test to remove the loader valve from the equation and will try that one tomorrow. I am going to my dealer this Friday to get this taken care of while its under warranty. I know the besko valve isn't much so I'm already looking at replacing it with this one. If anyone knows anything of this valve please don't hesitate to post. Thank you again for all the help!

2 SPOOL COMPACT 1 GPM JOYSTICK CONTROL VALVE | Directional Control Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com

 

[LD1]

It's alot of math, but doing it can tell if you are in spec for the valve.

We have established your leak rate at 1/4" per hour AT THE CYLINDER.

A 45mm bore cylinder is common for that size machine. So I'll assume that is what it is (but could be a 50mm).

45mm is 1.77". So with a little math, over one hour, two cylinders are bleeding off 1.23 cu in of oil (lift cylinders not curl)

I couldn't find specs on the valve you listed. But calling them, (it's a brand valve) or Calling the mfg of your current valve, you should be able to get a spec for maximum spool leakage.

Here is a generic 10gpm valve. VALVES | Trausch Dynamics
Notice they list 0.732 cubic inches a minute @ 1450psi and 120 degrees.

Assuming you have 45 mm cylinders, if you carried a load that required 1450 psi to hold (about 50% of your loaders capacity) over that same hour you would have leaked 44 cubic inches of oil out and still be considered acceptable. (Your cylinder would have compressed 9" instead of 1/4" in an hour.)

So like I say, without knowing specs, it's all opinion.

What does that 1/4" per hour equate to at the bucket? Usually on the lift it's about 5:1 ratio. So if your loader is drifting down a tad over an inch in an hour, I think your dealer is going to say it's within spec and tough luck.

And changing valves may not help. It might even make it worse

 

[oldpilgrim]

Sounds about normal to me.

 

[Snobdds]

If it was the valve, then the problem would be in both the lift and curl cylinders. If the problem is confined to just one of the functions, then the problem is in the cylinders of that function.

Now, one can not forget about gravity having an impact on cylinders. Over time, any cylinder will leak down due to gravity and is considered normal. If I keep the bucket up or my backhoe in the lift position, after a few weeks it will have rested a bit. But it always comes to rest at certain point and just stays there. The system becomes in equilibrium, where the air and fluid have equal forces in the system. Just like air over hydraulic break systems on trailers...

 

[Catskin]

This is the best explanation I've seen. Well worth the 6 mins.

Bypass testing a hydraulic cylinder - YouTube

 

[LD1]

If it was the valve, then the problem would be in both the lift and curl cylinders. If the problem is confined to just one of the functions, then the problem is in the cylinders of that function.

Now, one can not forget about gravity having an impact on cylinders. Over time, any cylinder will leak down due to gravity and is considered normal. If I keep the bucket up or my backhoe in the lift position, after a few weeks it will have rested a bit. But it always comes to rest at certain point and just stays there. The system becomes in equilibrium, where the air and fluid have equal forces in the system. Just like air over hydraulic break systems on trailers...

Alot of incorrect info here.

First, if a valve fails, it don't have to be all or nothing. There is two separate spools. A valve Val fail and cause curl issues and lift remains uneffected or vice versa. Just because the an issue don't effect both, does NOT rule out the valve as the culprit.

Second, if there is a problem with just one circuit...if that happens to be the curl....then it could either be cylinders OR the valve. Bit if it's just the lift drifting.....no way no how is it gonna be a cylinder issue unless there is oil leaking OUTSIDE the cylinder somewhere. If there are no external leak ITS THE VALVE.

Third, there should be no air in the system. This talk about equilibrium and air and fluid having equal forces is nonsense. A properly running and maintained hydraulic system should have no air. If you do have air in the lift circuit, then yes it will settle a little as the air is compressed. Then will come to rest and the only amount of drift thereafter is oil leaking past the spool in the valve.

It really isn't complicated at all guys. If a cylinder is drifting (assuming no leaks).........in a retract direction......ITS THE VALVE. If in an extend direction (,backhoe booms or loader curl usually) it can be either the valve or the cylinder. And it's simple to troubleshoot which is which.

 

[LD1]

This is the best explanation I've seen. Well worth the 6 mins.

Bypass testing a hydraulic cylinder - YouTube

Was an okay video and a good way to bench test.

He was real clear when he said seals can cause drift. Cylinder seals can only cause drift whereby drift is causing the cylinder to extend. Seals CANNOT cause drift if by drifting the cylinder is trying to compress (retract).

And I say that is a good bench test because that isn't always an accurate test in the field. Meaning with the loader still hooked up. Because he is basically operating a Regen cycle. Meaning if your loader has a pair of 45 mm bore cylinders and 25 mm rods, instead of having two cylinder pushing with the full force acting on the 45 mm piston, you are in a sense pushing as if you only had 25 mm bores. Or about 1/3 of the power they are supposed to have.

This 1/3 power is fine on the bench. But when hooked to your loader, 1/3 power may not even be enough to lift the dead weight of the loader. So you preform this test on the machine, and the cylinder don't extend so you think your seals are fine. However your seals could be shot and you just don't have the power.