Hydraulic Cylinder Leak Down on Box Blade???

[LD1]

Is there a reason you won't share that information??

I have many times.

Leaky piston seals would equal the same result as one of those piston valves leaking. That your are correct about.

You are unsure what the results will be....

The piston won't drift (in the retract direction), as a result of either of those scenarios. For the exact same reason that a crossover relief won't work on a DA cylinder

 

[Piston]

You guys are hilarious

Why don't one of you do an experiment? You know, actually prove something? I would, but I really don't care the reasons.

I'm just happy it's all still working perfectly. Didn't drift at all playing in the snow today.

 

[muddstopper]

You already proved it. You rebuilt the cyl and got rid of the air and it started working.

 

[ovrszd]

Since a small shaving was stuck in the piston valve it is feasible that the shaving was holding the valve "cracked open" so the fluid exited through this valve slowly. Air space on the back side of the system allowed this fluid to escape. That is my opinion or gut feeling as to why the cylinder retracted slowly along with simple friction.

Very possible.

 

[ovrszd]

You already proved it. You rebuilt the cyl and got rid of the air and it started working.

Yep...

 

[ovrszd]

I'm just happy it's all still working perfectly. Didn't drift at all playing in the snow today.

Me too.

 

[LD1]

You guys are hilarious

Why don't one of you do an experiment? You know, actually prove something? I would, but I really don't care the reasons.

I'm just happy it's all still working perfectly. Didn't drift at all playing in the snow today.

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Shouldn't have to do an expired the to prove what is already a known and proven fact.

Someone who wants to disprove what is a known and proven fact....The burden of proof is on them.

But even if I attempted an expirement to prove a point, I am sure there will be those that still wouldn't believe. There was a perfect example a few posts ago, where someone linked a computerized model province the same thing I have been saying. What more can be done???

Some don't believe me and many others that a cylinder won't drift....That's fine. But stop spreading the false information as gospel when you clearly don't know.

Take it upon yourselves, to learn something. Take a cylinder and remove the piston seals. (Or even easier, just connect the two ports together after filling with oil.) Then see if you can. Compress the cylinder.

Or...Many are familiar with snow plows. Well,the single acting cylinders are nothing more than a rod with a pair of c-clips to keep the rod from extending out the end of the tube. No piston, no piston seals. Ever try to angle the plow manually with the lines uncoupled? Since there is no piston or seals, shouldn't the oil just freely bypass the keeper rings? And be free to collapse?

 

[LD1]

Yep...

At this point, I still haven't a clue where you stand on this subject.

Sometimes you say some things that I agree with and makes me think you understand, other times not.

 

[ovrszd]

At this point, I still haven't a clue where you stand on this subject.

Sometimes you say some things that I agree with and makes me think you understand, other times not.

I fully understand. I also carefully read posts and base comments on the details offered. Whether those details are fact or not isn't for me to judge. In this case Piston only did one change. He plugged the bypass holes. His drift problem went away. I accept that as fact. Why would he lie about it.

 

[npalen]

This is another article in regard to this thread:
The Root Cause of Hydraulic Cylinder Drift

I replaced the seals in one of the lift cylinders on my FEL several years ago because of an external leak at the gland. I noticed, at the time, that the piston o.d. seals consisted only of a pair of flat rings one on top of the other. There were no o-rings or backup rings like I expected to see. I didn't understand how this would keep the lift cylinders from leaking down fairly fast as it was definitely not a positive seal. The lack of a positive seal on the pistons makes more sense to me now after reading this current thread. Kubota was (is) apparently relying on the valve to prevent/minimize down drift and if the valve has some leakage it won't matter anyway if the piston isn't a positive seal. Make sense?

http://www.tractorbynet.com/forums/hydraulics/266499-cylinder-drift-fel.html

I started a thread regarding this (URL above) which turned out to be very interesting. Post #6 was of particular interest.

 

[LD1]

I fully understand. I also carefully read posts and base comments on the details offered. Whether those details are fact or not isn't for me to judge. In this case Piston only did one change. He plugged the bypass holes. His drift problem went away. I accept that as fact. Why would he lie about it.

Exactally what I am talking about. You claim you fully understand, then say that plugging the piston holes solved his issue and you accept that as fact. So that tells me you don't understand. Plugging the piston holes didn't fix his problem, getting all the air out the second time is what solved his problem.

 

[muddstopper]

Exactally what I am talking about. You claim you fully understand, then say that plugging the piston holes solved his issue and you accept that as fact. So that tells me you don't understand. Plugging the piston holes didn't fix his problem, getting all the air out the second time is what solved his problem.

Exactly! But answer this question, if the piston had holes in it, which would allow oil to pass from base end to rod end, how was the cyl able to build force or pressure. It would seem to me the oil passing thru the piston would just flow out the out port back to valve. The cyl might exhibit some regen tendencies as the pressure is equalized on both side of the piston, but it shouldnt be able to build any pressure or force.

Another thing I wonder is how long the JB weld is going to hold up before high pressure just blows it out of now plugged holes.

 

[LD1]

Another thing I wonder is how long the JB weld is going to hold up before high pressure just blows it out of now plugged holes.

Might have already happened. Wouldnt know, because those ports even if open wouldnt exhibit a leak-down problem. It would just be a lack of force (like regen as you mention)

Getting old having to watch what you type word for word, because someone wants to pick apart everything you type and lose the meaning of what I am saying.

IE: In the context of the thread I say a cylinder cannot and will not retract with faulty piston seals.

Then am asked why the OP's cylinder retracted and replacing the seals/plugging the holes solved the problem.

I say its because the cylinder still had air in it.

They say......I never said it didnt have air in it....

WTH. Why are we dancing around the facts and trying to play on every word literally. A freakin cylinder full of oil (purged of all air) cannot and will not retract. Put all the force in the world on that rod if you want. The only way it is gonna compress is if you blow hydraulic oil OUT of the cylinder somewhere. Blow the gland seal out....leak back through the valve.....blow a hose......split the cylinder barrel in two. But it WONT simply bybass the piston seals and resume happy life on the other side of the piston. Until the laws of physics are change and hydraulic fluid becomes compressible....it just aint gonna happen.

 

[ovrszd]

Might have already happened. Wouldnt know, because those ports even if open wouldnt exhibit a leak-down problem. It would just be a lack of force (like regen as you mention)

Getting old having to watch what you type word for word, because someone wants to pick apart everything you type and lose the meaning of what I am saying.

IE: In the context of the thread I say a cylinder cannot and will not retract with faulty piston seals.

Then am asked why the OP's cylinder retracted and replacing the seals/plugging the holes solved the problem.

I say its because the cylinder still had air in it.

They say......I never said it didnt have air in it....

WTH. Why are we dancing around the facts and trying to play on every word literally. A freakin cylinder full of oil (purged of all air) cannot and will not retract. Put all the force in the world on that rod if you want. The only way it is gonna compress is if you blow hydraulic oil OUT of the cylinder somewhere. Blow the gland seal out....leak back through the valve.....blow a hose......split the cylinder barrel in two. But it WONT simply bybass the piston seals and resume happy life on the other side of the piston. Until the laws of physics are change and hydraulic fluid becomes compressible....it just aint gonna happen.

You Sir pick my words apart, I am not picking yours. I am actually on your side thru most of this conversation. But if I question anything you say you get worked up and start making derogatory comments toward me. Obviously that's not going to change and I accept it.

I am only repeating what's stated in this thread. Originally the scarifier was drifting downward during use. Piston video'd it drifting with tractor running. He video'd it drifting with the hoses unhooked. He disassembled the cylinder and altered it. Now the scarifier no longer drifts downward.

I'm only saying we, you and I, still don't know why it was drifting do we? He made no valve repairs or replacement of hoses, connectors, etc. So what was the original problem? And if you say it had air in it, how did that happen before he tore it apart the first time? And since no other alterations were made, how is he to prevent air from entering the cylinder again?

I think discussions like this have great value. As long as we keep it civil and open minded.

I'm glad he got it working, regardless of the cause of original failure.

 

[ovrszd]

Maybe the "word of the day" applies here: coddiwomple, to travel purposefully toward an as-yet-unknown destination.

 

[muddstopper]

And if you say it had air in it, how did that happen before he tore it apart the first time? And since no other alterations were made, how is he to prevent air from entering the cylinder again?

One can only speculate how the air got in the cyl. He could have had a fitting leaking and the cyl was able to suck air thru that leak. He could have had the pump cavitating from a low oil level, this would put air in the system. His quick attach hose assembly could be bad and dripped dry when not connected and when he hooked up the attachement, air was pumped into the cyl. I am not trying to pick apart anyones post, I too am glad he got it figured out, but plugging the piston holes isnt what fixed the cyl. In fact, if those holes went completely thru the piston, I think he might have created future problems with his jbweld fix. We will know that when hes back asking about sticky valves.

 

[ovrszd]

One can only speculate how the air got in the cyl. He could have had a fitting leaking and the cyl was able to suck air thru that leak. He could have had the pump cavitating from a low oil level, this would put air in the system. His quick attach hose assembly could be bad and dripped dry when not connected and when he hooked up the attachement, air was pumped into the cyl. I am not trying to pick apart anyones post, I too am glad he got it figured out, but plugging the piston holes isnt what fixed the cyl. In fact, if those holes went completely thru the piston, I think he might have created future problems with his jbweld fix. We will know that when hes back asking about sticky valves.

I agree.

 

[jenkinsph]

Exactly! But answer this question, if the piston had holes in it, which would allow oil to pass from base end to rod end, how was the cyl able to build force or pressure. It would seem to me the oil passing thru the piston would just flow out the out port back to valve. The cyl might exhibit some regen tendencies as the pressure is equalized on both side of the piston, but it shouldnt be able to build any pressure or force.

Another thing I wonder is how long the JB weld is going to hold up before high pressure just blows it out of now plugged holes.

If the flow through the hydraulic system is higher than the flow thru the piston holes you can develop back pressure and have a limited amount of force. Gravity does most of the work lowering the rippers, you only need a small amount of force to latch the rippers in place. The rippers need to be clear of the ground to latch properly, the cylinder does not develop enough force to push them through the ground or raise the box blade. This is to prevent damage to the linkage imo.

I have to say after participating in the thread that I went out and played with my box blade (same identical model) which is in good working order. It is obvious to me that the purpose of the valves or holes in the cylinder piston is to limit the force the cylinder has on the linkage. With the rippers down in the latched position the cylinder is fully retracted. If you miss the latch and drive forward the rippers will swing up instantly at the same time the cylinder is extending with the oil moving from the rod side to the back side. This will happen with the spool valve in neutral position. With the piston ports blocked if you miss the latch and drive forward as above the linkage rods are being compressed and will bend up.

All of that said the piston valves or holes (probably one way check valves) are there to protect the linkage from damage.

I have no comments about the JB weld as I have no experience with it.

 

[npalen]

FAQs


| J-B Weld

 

[muddstopper]

If the holes in the piston contained check valves it could limit force. Much in the same manner that regen would let a cyl extend but at much lesser force. With a check the cyl would build a set amount of pressure before the cyl went into regen mode to extend. As you say, it shouldnt take much force to lower the rippers and the check valve would allow the cyl to make force to lift with out making a lot of pressure to push. It could be a way to protect from bending and breaking parts.