Good to hear you gott'er fixed. I had a feeling it was cylinder related.
Planning on replacing engine on log splitter
- Thread starter Leever2000
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Good to hear you gott'er fixed. I had a feeling it was cylinder related.
I never addressed the problems the OP was having. I will agree that bad cyl seals can reduce force. If the oil is bypassing the cyl seals, it has a open path to tank and therefore a pressure drop and loss of force. A new cyl fixed his problem so bad cyl seals where the likely problem. You can check for bad cyl seals by simply running the cyl all the way out or in, one way or the other, but not both at the same time, and unhooking a hose. Then try going past full out or extend and see if oil squirts out of the open port., If it does, the seals are bad or cyl is scored. Dont need a jack.
As for the cyl being able to be jacked to retract, Until you can explain how the cyl can hold more volume as the cyl rod is forced inside the bore, I will stand by my statements. The cyl bore will only hold a certain amount of volume, the oil as, well as the piston and the rod, takes up the entire volume of the cyl bore. Retracting the cyl, without a path for oil to leave the bore is trying to put more volume ( the actual rod),in a bore where there isnt anymore room. Take your spade cyl off and remove the piston seals, reassemble with the rod extended, fill competely with oil and cap both ends of the cyl ports. Dollar to a donut, you cant jack the cyl rod to a full retract position. If the rod can be retracted even a little bit, it will be because you didnt get all the air out of the cyl. Air will compress, oil wont. If both cyl ports are connected to a control valve and you can force the cyl closed, and there are no other leaks, the oil volume, (volume equal to rod volume), has to be returning to tank thru the control valve and 99% of the time, the CV is what is bad.
As for a cyl extending, I will agree you can force the cyl to extend by applying weights or with a jack. Oil is considered a non compressible fluid, but it will readily expand. Forcing a closed cyl to open will create a vacuum and actually shear the oil causeing the molecules to separate. This will cause foaming in the oil.
I tried to link a site to fully explain what I am trying to explain, but forum software wouldnt let me. If you have doubts, do a little research about cyl drift
I will say that I used a hand screw jack with nearly no effort to move the cylinder towards retracted position and I could hear a sucking sound as I did. Cylinder did not leak oil. Hoses and oil all were in good shape and valve was already replaced with no change in symptoms. I had checked pump by capping out line and pulling engine.
You answered your own question. If the seals are bad the oil can bleed in ether direction. The jack is just replacing gravity or the weight that may hang from it.
On a splitter, because of its design, it would simply be easier to push it in then push it out.
You're struggling with how displaced volume works in relation to drift caused by gravity ... drift happens because holding valves , check valves or directional control valves are bypassing.
I'm simply going by personal experience. I have seen it happen. Not once but many times.
The volume of oil doesn't change, it simply blows by a leaking seal from one chamber to another.
If the valve is in center position and is not bypassing oil internally, you will never jack a cyl into the retract position. I dont care if you take the piston off the rod and throw it in the trash can. The simple act of the rod going into the barrel of the cyl is displacing volume and that volume has to go some where other than stay in the cyl. You are giving bad information, Period. This is not related to the problem the OP was experiencing and my post had nothing to to do with diagnosing his problems. My post was in reply to you posting wrong information. In the morning, fill your coffee cup to the point of over flowing and then stick your finger in the cup and see if it overflows. This is what is happening when trying to force a ram into a closed cylinder. The fluid has to be displaced to make room for the rod to enter the cyl. If the oil cant be displaced, then the rod cant enter the cyl. If the hoses are connected to the cyl from the control valve and you can force the cyl into retract position, the oil is flowing back to tank thru the valve and has nothing to do with the conditions of the cyl seals. You are 100% correct, the volume of the oil doesnt change, but the volume of the rod does as it enters the cyl. Rod volume has to displace fluid volume in order to retract into the cyl. if the oil doesnt leave the cyl then the rod cant retract. The oil cant simply blow by the leaking seal from one chamber to the other because the rod is taking of the volume of the opposite chamber and the more rod that enters that chamber, the less room you have for oil. It wont matter if you have bad seals, no seals, or remove the piston entirely, if oil cant leave the cyl, you cant force the rod back inside the cyl. If you can you better be looking around because you have oil leaking somewhere.
On the other hand, if you are using the valve to activate the cyl, then you are providing a open path to tank for the oil to flow. If the valve is worn and bypassing internally, you have a path for oil to return to tank and at that point, you would be able to jack or force the cyl closed.
On the other hand, if you are using the valve to activate the cyl, then you are providing a open path to tank for the oil to flow. If the valve is worn and bypassing internally, you have a path for oil to return to tank and at that point, you would be able to jack or force the cyl closed.
I think your the one that is not understanding what I'm saying.
Take a cylinder full of fluid and cap off both the input and output sides so no oil can go into or out of the cylinder.
Now try and move the rod in or out. If the seals are bad the ram will move because the oil in one side of the cylinder can blow by the seals and transfer to the other side. The ram can move without changing the volume of the oil in the cylinder. It's not bad advice, your just not following along.
I understand fully. If you cap both ends of the cyl and it is full of oil with no air, you will be able to apply enough force to extend the cyl. You will never push the rod into the cyl unless you blow out the gland seals or split the side of the cyl. The oil can not move from one side of the seals to the other simply because the other side is already full of oil andyou are trying to overfill that side by adding more rod to the inside of the cyl. It cant get any more plain than that and it is you who doesnt understand. I know you didnt read the link I provided so I will just paste what it says here.
"A popular misconception about hydraulic cylinders is that if the piston seal is leaking, the cylinder will drift down. Fact is, if the piston seal is completely removed from a double-acting hydraulic cylinder, the cylinder is completely filled with oil and its ports are plugged, the cylinder will hold its load indefinitely - unless the rod-seal leaks."
"A popular misconception about hydraulic cylinders is that if the piston seal is leaking, the cylinder will drift down. Fact is, if the piston seal is completely removed from a double-acting hydraulic cylinder, the cylinder is completely filled with oil and its ports are plugged, the cylinder will hold its load indefinitely - unless the rod-seal leaks."
Sorry partner, When the internal seals go bad, I have seen cylinders bleed in both directions. Your telling me something is impossible when I have seen it for myself.
I have seen them bleed down in both directions. Explain that!
NSMaple1
Addicted to ArboristSite
You're not grasping the situation.
Forget about the internal seals. And the piston.
With the cylinder fully extended, all that rod is outside in the air and outside the cylinder. That rod has volume. If you try to push the rod back in the cylinder that is full of oil and capped, that rod volume that is coming back into the cylinder will have to displace oil volume that is already in the cylinder before it can enter the cylinder. Pistons & their seals have nothing to do with that. The only way that rod will push back into the cylinder, is if oil leaks out the cap seal around the rod, or if it leaks out through one of the two oil ports which would mean it is also going past or through a valve somewhere. Or out a simple leak somewhere else. It has nothing to do with the internal piston & seals.
You are imagining the rod being inside the cylinder all the time, for its full length - and that the end of the rod moving in and out is only moving the piston back & forth on the rod. Which is obviously not the case.
Its simple, oil is either leaking back thru the control valve, or thru a relief or other componet, or you have a leaking hose or fitting or shaft seal.In other words, the oil has to be going somewhere, you just have'nt found the where yet.
There is also the possibility that the cyl was forced outward under load, which would shear the oil and cause foaming. The vacuum created by forceing the cyl to extend by external means, (your jack), has sheared the air molecules out of the oil. You cyl now can recompress that air as it ties to retract under load and this would allow the cyl to "drift", how much would depend on how much shear was created. At no point would the cyl retract any more than the point that the shear was created, and it would be very difficult to even reach that point.
I did not read what Problem the Op had. When the thread was started it was about swapping current engine to a pressure washer engine. He wasnt having a hyd problem. When I checked back in, he had already fixed his problems so I had no reason to comment. I did feel it necessary to respond to one of your comments, which I knew to be wrong. I think if you will consider what I, and NSMaple, have said, read the link I provided, and if not convinced, then do a little more research, you will realize what we are saying is true.
Not worth arguing or disagreeing over something that doesn't help the thread. The thread is dead, he fixed his problem witch was the cylinder. Case closed.
Your choice to believe or not to believe.
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