Hydraulic cylinder jerky

[yarg]

Hello Gentelmen,
I built a well drilling machine. It is hydraulic and all is great,,,,but? The cylinder for raising and lowering the mast does not operate right. Here are the issues :
1. Cylinder is double acting.
2. Valve is log splitter type.
3. Hoses are 1/2 inch.
4. Actuating valve causes engine stall and sever cylinder speed= very jerky mast action close to damage if not fixed.

Tried 1/16 orifice hole on one line but the same thing happened.
Your thoughts?
Thanks

 

[Stimw]

I would guess that the valve is the wrong one for your application. With double acting cyl. the non pressure side needs to be able to drain.
You might need to ask this in the Hydraulic forum.

 

[yarg]

The valve is for a wood splitter so it is for a double acting cylinder.
Stalling the engine is also a huge concern?

 

[bigdeano]

Maybe the cylinder is not large enough to lift the mast with the pressure available. It may be pushing at an angle which cuts down the lifting force on the mast. Have you worked out the math to be sure its strong enough.

 

[BHD]

air trapped in cylinder?

low on oil or filter plugged?

some thing bent and binding?

faulty valve?

the engine is either not big enough for the pump or pump to big, or the pressure relief is not working to stall out the engine,

hose coming apart in side?

rusted up cylinder inside?

a pictuer could be helpfull,

some thing slipping on the drive between engine and pump or in pump?

 

[yarg]

Air? Will bleed tomorrow. Could be but would this stall the engine?
Engine could be bigger but this is only 600 pounds of mast.
Maybe too much pressure and flow through the valve?
All else is working.

 

[stuckmotor]

I'd sure like to see some photos of that machine.

 

[yarg]

Will do photos tomorrow and post if I can figure out how?

 

[yarg]

Tried my iPad but no luck so will send pics from office computer in the am.

 

[stuckmotor]

Thank-you very much.

 

[yarg]

I will try these pics for you. You may understand my issues?

 

[bigdeano]

Very nice machine.
Is the problem only when the boom is all the way down. Will the boom lift if someone helps it by hand. I can't see the cylinder geometry when it's down from the photos. You could take the hose off the pressure end of the cylinder, put it in a clean container and see if the oil flows smoothly from the hose. If it does then the valve is ok.
I suspect you don't have enough lifting force, but can't tell from the photos. If you built that machine you know what you're doing.

 

[BHD]

how many valves are you using, and how are they plumbed in,

if using multiple valves are you using a power beyond port to feed it or a return line, off of another valve?

i can not see the hose configuration clear enough to make out what you have,

I see no issuers with the mast,

how does the mast lift with out the cylinder? with a chain hoist or other? is it smooth and not binding in some way?

my guess is it is an open system on the hydraulics, are all valves for the same type of system?

I do not think air in the system would cause the problem stall problem, are all other functions working the way they should, (guessing hydraulic motor, and a cylinder to lift and lower the head)

my guess is it is either in the valve faulty or wrong type of internal construction, (and the valve should have a relief valve in it so the engine should not stall, and the valve should be able to throttle the flow of hydraulic fluid some, with locking up), or a plumbing problem of how some thing is routed or plumbed If other parts are working OK and the only circuit is the mast lift, I would think that is where the problem would be found, if the rod on the cylinder is not bent or have some kind of internal flow circuits, my guess is it is not the cylinder,

may be draw out the system on paper and show how it is plumbed, show all hoses and valves and there conections,

If your stalling the engine to a stop, then the fluid is not flowing (and it should be flowing via return or the over flow circuit)

all it takes is a small hunk of dirt and or some Teflon tape to mess up a hydraulic circuit, if Teflon tape was on some of the fittings (used fittings) that is some thing to consider, even if Teflon tape was used new on new stuff.

could put a pressure gaged in the line to see what is happening on the pressure from the pump, and one on the pressure to the cylinder a (5000 psi unit should surive a stall out)

also does the jerky ness come in both directions or just in raising of it?

http://northernhydraulics.net/hydraulics101.php

 

[WilcoKubota]

You said you have installed a log splitter valve, maybe you crossed the hoses so the fast retract function on a log splitter is now on the lift side of the cylinder?
Just a thought.

 

[yarg]

Hello,
Here is what I have figured so far:
The pump supply goes to the first two spool valve set the has a 1500 psi setting.
This set runs one head motor that gives little back pressure unless under huge loads, not too likely.
The second spool runs the chain hoist motor that has so much torque that even with my 200 pound friend staining on the head, the motor did not even breath hard to lift and little pressure build up.
From this valve I placed a power beyond port to the second valve that is a log splitter type set for now at 1500 psi.
Here is where the issue begins. The ram takes very little oil and does not need 1500 psi but now gets that. The rest of the flow goes to the relief valve and has to make it through the 1500 psi setting.
This causes two issues,,,,1. Heavy uncontrolled jerking of the mast due to the psi and fill speed and 2. The huge bulk of the flow when this valve is triggered has to go through the relief valve facing 1500 psi in a sudden shock thus stalling the engine.

My current lowest cost fix is:
1. Place a needle valve in the large ram end line slowing the fill to a crawl.
2. Replace the relief cart rage with a 500-1500 psi setting it at the low end if this range in hopes of this not stalling the engine?

More input on these ideas is welcome.
Thanks,
Gray

 

[yarg]

The lifting force is more than sufficient. The ram needs power to raise or lower.
The ram is fine. The power source is a 21 hp Briggs direct coupled to a 1.8 ci pump.
The engine could be bugger but us mire than enough for the motor needs I think because the motors allow flow though and no sudden back pressures.

I explain below that I think it is a combination of pressure shock when the valve is in full flow setting and the lack of flow needed for the tiny ram ID!

 

[bigdeano]

Very slowly move the valve handle to apply pressure to the cylinder. The cylinder should smoothly raise the mast. Any excess flow will go to the tank without going through the pressure relief.

You should be able to control the speed of the cylinder to a crawl. This will prove or disprove your shock theory. If the engine lugs down before the mast raises then it's a problem with cylinder geometry or size.

It's hard to see what's happening without being there. Hope you get it fixed.

 

[yarg]

Bigdeano,

The geometry is very edgy but if I can get a good slow flow into the ram, I think this will do it.
I ran out of gas as I was trying that very experiment this evening?
It happens. No time for the five mile trip to get more. 4 empty cans
I should be able to check it all out this weekend.

 

[stuckmotor]

Thanks for putting up the photos. My advise on a fix would probably make things worse, so I'l just say, good luck!

 

[WilcoKubota]

Try to switch the hoses from the log splitter valve to the cylinder.