BrianGrenier
Senior Member
Op: pictures to come
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Cylinder rod moral question
- Thread starter BrianGrenier
- Start date
BrianGrenier
Senior Member
the guy who installed the thumb is dead killed by the doctors who tried to cure him of cancer. The guy who was operating the previous machine thumb was installed in died in an accident with the machine the thumb was salvaged. The thumb came from a bigger machine than this one
Thumb cylinder and bucket cylinder are the same size but thumb was fully extended bucket was fully retracted pressure too Great from the bucket to the thumb no pressure relief valve
Is this a geometry problem, instead of a hydraulic problem? Did the thumb get side pressure on it from the thumb or mount?
CM1995
Administrator
- Joined
- Jan 21, 2007
- Messages
- 13,431
- Location
- Alabama
- Occupation
- Running what I brung and taking what I win
The guy that gave you the advice free of charge has no moral or legal obligation to repair or pay for repairs. If the one that installed it told you to do it then yes I would say he should help pay for repairs but he's dead.
Willie B
Senior Member
I ruined two thumb cylinders. The first, a hydraulic expert told me was because when the bucket cylinder crushes it, it can't eject fluid fast enough to the tank. He sold me a valve to move it from a high pressure side of the cylinder to the side with lower pressure. The other was when a pivot pin tube I had relocated failed. I was concerned about too much heat on the cylinder. I had under welded it reasoning it was pushing, not pulling. The weld failed, and before I noticed, it bent the rod.
I couldn't find a cylinder with the bore, stroke, pin center distance I needed. The choice was a compromise. I settled for an anemic cylinder with small rod.
They will take a pounding. Stop blaming someone else. Either buy with warrantee, paying the price, or accept some fault yourself. I get it, everything is somebody's fault. My perception is the expert wasn't. Your taking his advice wasn't good judgement.
Willie
I couldn't find a cylinder with the bore, stroke, pin center distance I needed. The choice was a compromise. I settled for an anemic cylinder with small rod.
They will take a pounding. Stop blaming someone else. Either buy with warrantee, paying the price, or accept some fault yourself. I get it, everything is somebody's fault. My perception is the expert wasn't. Your taking his advice wasn't good judgement.
Willie
Valves plumbed to move oil from the butt end to the rod end of a cylinder will create pressure intensification. I worked at a place with a Deere 690B had a thumb plumbed that way. Before I got there they had blown hose after hose, finally replacing them with CAT XT5 hoses.... I warned them but they said it was fine now with the new hoses. Couple months later the cylinder fractured from butt to gland, they said it sounded like an explosion. If it hadn't been a cold day with the front window down the operator may well have been badly burned, it covered most of the machine in hot hydraulic oil.
Thumb reliefs need to go to tank. If it won't handle the flow, use a bigger valve and lines. Motors can use crossport reliefs, not cylinders. YMWNV.
Thumb reliefs need to go to tank. If it won't handle the flow, use a bigger valve and lines. Motors can use crossport reliefs, not cylinders. YMWNV.
Willie B
Senior Member
Thanks for the advice. A mechanic for the local hydraulic rebuilder has just opened his own business. I'll take it up with him.
Willie
mitch504
Senior Member
The reason you get pressure intensification is because of the size difference in the two ends of the cylinder.
The old Ford backhoe service manuals had a good explanation of this, and even took advantage of it to test the circuit reliefs that had higher settings than the main relief, by switching some hoses around.
The old Ford backhoe service manuals had a good explanation of this, and even took advantage of it to test the circuit reliefs that had higher settings than the main relief, by switching some hoses around.
BrianGrenier
Senior Member
OP: Yep, I agree!
OP: My 'removed' pressure relief was located before the thumb piping and was piped to the tank return. Is that a bypass valve? See, I don't even really know, lol. I think what I have is actually a bypass valve. I will need to get it back from the shop where it is being tested and post pictures.
Definitely, I need to sort advice...I just thought it would be OK to bleed the system and then I could see that it was all working. So I guess the thumb is strong and does work. I wil straighten the rod, inspect and test the relief and reinstall a known good valve.
He doesn't owe me. He was trying to help me troubleshoot; He tested the thumb cylinder for 'internal leakage'.The thumb cylinder was taken to him for inspection. There was no internal leak. I had told him the thumb was weak and the valve was capped off. He sold me a cap saying that the valve wasn't doing anything, so it could be removed (removed! instead of hey you need a safety)
He's a good guy that will likely not give advice like what he gave me.
Usually, it feels like the thumb cyl has a crossover relief valve where the hoses leave the boom, the bucket can always shove the thumb back on every machine I've rented. Altering a relief valve without a pressure gauge verification to back it up can be a recipe for disaster. Often a slow thumb or any other cyl I've run across has already been bent, internal drag in the bore makes it move really slow. Its possible it had some bend already. Agree though, pull it off, pin it back and that rod might be a candidate for straightening.
BrianGrenier
Senior Member
The valve had a hose coming out of it there was a cap on that. Without the cap it was supposed to go back to the piping tank return
John C.
Senior Member
Free advice is worth what you paid for it. You can't expect any recourse except in certain situations which require very expensive lawyers.
The thumb cylinder rod is bent because the base of the cylinder is welded too far forward on the stick letting the thumb go past parallel with the stick. Removing the circuit relief for the base end of the thumb and leaving the control valve for the spool controlling the thumb in the hold position meant the bucket had the mechanical advantage of putting down pressure in the middle of the extended cylinder. The weak link was the cylinder rod which bent. You are actually very lucky the cylinder was in the position it was in. I've seen cylinder barrels split from a dead head and it is much more expensive.
From the description we don't know if the circuit relief was actually removed and the passages capped off as it sounds like the Mr. Grenier doesn't know where it would be or even what it looks like. When I was installing thumbs I used a cross over relief setup that was an aluminum or stainless steel block drilled for two relief valve cartridges and a return to tank. In latter years the manufacturers came out with provision for low pressure circuit reliefs to be installed in the auxiliary valve blocks operating the thumbs and we didn't need the cross over relief blocks anymore.
At any rate you need to have a circuit relief for each side of the thumb cylinder. The common setting was 2,100 PSI on the piston side and up to 2,400 PSI on the open side. You also need to check the thumb for being past parallel when fully open. If it does so you should cut out the welding on the thumb cylinder base bracket and move it back to the point of the thumb only reaches parallel with the stick.
Expensive lesson in hydraulics but good you allowed all of us the reminder of the possibilities.
The thumb cylinder rod is bent because the base of the cylinder is welded too far forward on the stick letting the thumb go past parallel with the stick. Removing the circuit relief for the base end of the thumb and leaving the control valve for the spool controlling the thumb in the hold position meant the bucket had the mechanical advantage of putting down pressure in the middle of the extended cylinder. The weak link was the cylinder rod which bent. You are actually very lucky the cylinder was in the position it was in. I've seen cylinder barrels split from a dead head and it is much more expensive.
From the description we don't know if the circuit relief was actually removed and the passages capped off as it sounds like the Mr. Grenier doesn't know where it would be or even what it looks like. When I was installing thumbs I used a cross over relief setup that was an aluminum or stainless steel block drilled for two relief valve cartridges and a return to tank. In latter years the manufacturers came out with provision for low pressure circuit reliefs to be installed in the auxiliary valve blocks operating the thumbs and we didn't need the cross over relief blocks anymore.
At any rate you need to have a circuit relief for each side of the thumb cylinder. The common setting was 2,100 PSI on the piston side and up to 2,400 PSI on the open side. You also need to check the thumb for being past parallel when fully open. If it does so you should cut out the welding on the thumb cylinder base bracket and move it back to the point of the thumb only reaches parallel with the stick.
Expensive lesson in hydraulics but good you allowed all of us the reminder of the possibilities.
Well, that would have had the same effect, so what he said was true, the relief could not have done you any good. What he should have said was you needed to connect it to tank and adjust the valve properly. My opinion only.
BrianGrenier
Senior Member
OP: The Vickers Valve was located on circuit #23 #36 and controlled by the foot valve
John C.
Senior Member
What is your make and model of machine?
The parts break down shows a typical gray market machine pilot controlled auxiliary circuit. The photo is usually associated with an articulated boom machine. Item number 23 and 36 are hoses going to some kind of block which appears to be some kind of shuttle valve. Item number 31 may be a hose or a wire going to the block that has a component identified as a pressure switch but has no number. Those hoses are pilot control hoses and have nothing to do with the pressure in the lines going to the thumb. They are to shift the control valve spool that controls the implement function.
The parts break down shows a typical gray market machine pilot controlled auxiliary circuit. The photo is usually associated with an articulated boom machine. Item number 23 and 36 are hoses going to some kind of block which appears to be some kind of shuttle valve. Item number 31 may be a hose or a wire going to the block that has a component identified as a pressure switch but has no number. Those hoses are pilot control hoses and have nothing to do with the pressure in the lines going to the thumb. They are to shift the control valve spool that controls the implement function.
BrianGrenier
Senior Member
It is a Hitachi EX100-3 and purchased from Assetline, JP back when the Yen was 136/$
It had a breaker once, aftermarket, and the piping was used to hook up the thumb. The piping comes from the valve:control, has a Vickers Valve on the positive and there is a hose from that Vickers to the hydraulic return
Great advice... I am unsure if there is pressure adjustment, would it be both in the Vickers and the Valve:Control
Vickers is getting tested
BrianGrenier
Senior Member
You are right...additionally, the foot pedal is 10 in the right sheet and has hose 8 to a valve:lock. (Vickers valve) This is the one removed, if I am not mistaken.
BrianGrenier
Senior Member
damn