BrianGrenier
Senior Member
Op: pictures to comeI'd like to see a picture of the whole thumb before I comment any further
Op: pictures to comeI'd like to see a picture of the whole thumb before I comment any further
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 oneDid the one you received the advice from install the thumb?
Thumb cylinder and bucket cylinder are the same size but thumb was fully extended bucket was fully retracted
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
No retainer no service contract free advice just helping me with hoses and why the thumb was weak.
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.
The thing is there a many "Experts" around some truly know there stuff some we just assume must know the answer to every question because they work at the hydraulic repair shop Sometimes we ask different experts until we find the answer that we like. One thing is for sure the manufacture of the machine was not contacted and told you to remove or bypass a circuit protection devise that they designed
One has to sort all the advice given and use your own judgement even on the internet full of experts as you are the one putting the wrench to it as some would say if you have to ask you shouldn't be messing with it
Even given the poor advise followed the operator bent the cylinder pushing back on it with the bucket
Pressure relief prevents the pump from supplying too much oil (or oil pressure) to the cylinder. It is not designed to receive a large volume of oil back to the reservoir. A thumb needs a bypass valve. It moves pressure from one side of the piston to the other. Mine is a small block of steel with four ports for hoses, and an adjuster.
It is incumbent on you to sort advice. Does this make sense. Did he fully understand my question. I will counter that turning up the relief valve likely didn't cause your problem. The lack of a bypass valve did.
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
What is your make and model of machine?
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gray market 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.
damnThe valve:lock is your safety shutoff, it stops pilot pressure from going to all the controllers so all functions are dead. The hose 8 is the beginning of a daisy chain to all the pilot controls.