Closed Center Systems

[MNBobcat]

I have a john deere with a closed center hydraulic system. I bought a big *** (16 foot) hydraulic post pounder with side shift. :dance1:

I have to bungee the hydraulic control lever open on the tractor to send hydraulic fluid to the remote port on the back of the tractor. From there, it goes to the pounder and then comes back via a return line stuffed into the fill hole on the tractor's reservoir tank (remove cap, stick hose in). It does not use the second remote port at all.

I hooked it up tonight and the hydraulics work fine. But I notice that when I have the lever held open on the tractor that nothing flows through the return line into the tank on the tractor. My arms aren't long enough to see if that holds true when operating the hydraulic levers on the pounder, but I assume fluid flows into the return when using the pounder.

I would have thought there would have been constant fluid flowing into the return line and then it gets diverted when using the pounder but eventually flows back into the return. It feels odd to have the tractor hydraulic lever open and no fluid flowing. I would think that would build heat and would be hard on the tractor.

I'm guessing that I'm thinking about this all wrong? I'm guessing that no fluid flowing is no different than having the control lever on the tractor closed. So thinking this through, am I correct in concluding that it doesn't hurt a hydraulic pump to be trying to pump fluid that can't go anywhere? Do they have some kind of internal bypass or something?

 

[Redneck in training]

Closed center hydraulic has variable delivery pump controlled by pressure. Once the pressure is achieved (assuming the valve(s) are in center position) the pumps deliver no flow or only enough flow to cover leakage in valve setup. So if you dead end the pump it will not deliver flow but maintain set pressure. When you move the valve on a pounder pressure will drop slightly and the pump will deliver flow to maintain the pressure.

 

[BHD]

on a JD spend the money for a power beyond block, it (at least on mine) fits between the present valve and the body of the tractor, put two quick connects one it (I suggest a male and a female connector so one can not reverse the hook up) and then when you hook up your remote valve, (it has to be set up for closed center as well) it will work the same as the factor valve but in a different place., and if for some reason one needs some extra vales on the tractor like a loader, tie in that port or tee in and leave the quick connectors,

have the loader (valves in the cab) and can hook up the back hoe or the post pounder via the power beyond,

 

[MNBobcat]

RIT,

Ah...interesting. Thanks for the education!

Closed center hydraulic has variable delivery pump controlled by pressure. Once the pressure is achieved (assuming the valve(s) are in center position) the pumps deliver no flow or only enough flow to cover leakage in valve setup. So if you dead end the pump it will not deliver flow but maintain set pressure. When you move the valve on a pounder pressure will drop slightly and the pump will deliver flow to maintain the pressure.

 

[MNBobcat]

BHD,

I have a 2-spool valve bank on my right fender for the loader controls. I know I can add more spools to it but so far I haven't had a need for more. It would be nice to be able to use that valve bank for the pounder. The control on the dashboard is touchy.

My tractor really needs some love. I just never have time to work on it and improve a few things.

on a JD spend the money for a power beyond block, it (at least on mine) fits between the present valve and the body of the tractor, put two quick connects one it (I suggest a male and a female connector so one can not reverse the hook up) and then when you hook up your remote valve, (it has to be set up for closed center as well) it will work the same as the factor valve but in a different place., and if for some reason one needs some extra vales on the tractor like a loader, tie in that port or tee in and leave the quick connectors,

have the loader (valves in the cab) and can hook up the back hoe or the post pounder via the power beyond,

 

[Tx Jim]

Is post driver hyd valve closed or open center? My guess is it's open center which is not good for use on a closed center system. What model JD tractor? Some models didn't have the option of PBY.

 

[MNBobcat]

Closed center.

Is post driver hyd valve closed or open center? My guess is it's open center which is not good for use on a closed center system. What model JD tractor? Some models didn't have the option of PBY.

 

[J_J]

Is the valve on the post pounder a closed center or an open center valve?

I believe most post pounders would have a convertible valvle on it.

If so, then install the closed center adapter to the post pounder and parallel the post pounder valve to the tractor flow.

 

[MNBobcat]

Its closed center. It was set up by the manufacturer for a John Deere with closed center hydraulics.

 

[Tx Jim]

MNBobcat
From reading your other post in JD forum I determined your 3020 is a '64-'68 model which didn't have the option of PBY but could be plumbed by teeing into hyd supply line by brake valve and returning oil to ether rockshaft return line or ported hyd filter cover as shown in attached photos. Bypassing rear remotes(SCV) as shown in photos should give you better hyd operation without the need to tie remote lever to activate scv.

 

[MNBobcat]

MNBobcat
From reading your other post in JD forum I determined your 3020 is a '64-'68 model which didn't have the option of PBY but could be plumbed by teeing into hyd supply line by brake valve and returning oil to ether rockshaft return line or ported hyd filter cover as shown in attached photos.

I think that has already been done when the control valve on the fender was added for the front end loader. I have the line coming off the hydraulic filter cover that you show in the first photo.



Redneck answered my question which was trying to get my head around how you could dead-end the hydraulic flow and not have problems. I was thinking about it akin to having your well pump running with nowhere for the water to go. Usually that is bad for a pump and builds heat and pressure.

I do need to figure out some way to increase the lift capacity on the front end loader. Don't know if that means more hydraulic pressure and/or different cylinders. I tried to lift 2550 pounds yesterday off a flat bed with no luck. Once the weight was on the ground I could lift it a bit but higher up it wouldn't lift it.

 

[Tx Jim]

1st & simpllest thing to do is check stand-by pressure by plugging a 5000# gauge in a QD. I suggest 2350 psi.

 

[J_J]

I think that has already been done when the control valve on the fender was added for the front end loader. I have the line coming off the hydraulic filter cover that you show in the first photo.

View attachment 439613

Redneck answered my question which was trying to get my head around how you could dead-end the hydraulic flow and not have problems. I was thinking about it akin to having your well pump running with nowhere for the water to go. Usually that is bad for a pump and builds heat and pressure.

I do need to figure out some way to increase the lift capacity on the front end loader. Don't know if that means more hydraulic pressure and/or different cylinders. I tried to lift 2550 pounds yesterday off a flat bed with no luck. Once the weight was on the ground I could lift it a bit but higher up it wouldn't lift it.

Increase pressure will provide an increase in lifting power, but at some risk.

Larger cyl would definitely increase the lifting weight, but you might need more weight on the back.

Tilting the load back over the bucket pins will transfer the center of gravity.

 

[Tx Jim]

Increase pressure will provide an increase in lifting power, but at some risk.

Increasing stand-by pressure on a JD 3020 to 2350 psi involves very little extra risk.

 

[MNBobcat]

Increase pressure will provide an increase in lifting power, but at some risk.

Larger cyl would definitely increase the lifting weight, but you might need more weight on the back.

Tilting the load back over the bucket pins will transfer the center of gravity.

Is there a way to increase the stand-by pressure? I didn't know if there was an adjustment or if it meant swapping something out, etc. Would appreciate hearing how I would increase the pressure if you happen to know.

My rear tires are filled with Chloride so weight shouldn't be an issue.

 

[Tx Jim]

Stroke control adjustment screw can be accessed under frt of tractor. Loosen lock nut then screw in the screw(parts key 37) while observing a 5000# gauge plugged into rear remote with remote control lever activated. As I previously stated I'd set stand-by psi @ 2350 if it was my tractor.

 

[J_J]

The tractor pressure setting is there for a reason, be it the limit of the cyl, hoses, mechanical parts, strength of the metal parts, etc.

If Jim says it s no big deal, go ahead and take your chances, and if it blows up, or burst, etc,, call Jim.

A 2 in cyl 1 in shaft and 2500 psi will lift about 7854 lbs.

A 2 in cyl 1 in shaft and 3000 psi will lift about 9425 lbs.

The potential is there if you can get away with it.

 

[Tx Jim]

J_J
100 extra psi will not hurt a JD 3020 hyd components or attachment but will increase FEL lifting a little bit. BTDT several times as a former JD dealer service manager. 2350 is the very maximum I'll recommend,any more psi and one takes a chance of blowing seals. Besides MNBobcat by installing gauge may determine that his tractor's stand-by pressure is nowhere near the factory setting of 2250 psi.
Jim

 

[MNBobcat]

I only have 2,000 psi. I've been crawling around under the tractor and can't find the stroke control. Do you have any more info on where I can find it? Is it in front of the engine somewhere?

The dealer said it should be 2350 psi.

My manual says there are selective control valves that control the rate of operation for each remote. 2 control valves located by removing the left side shield and reaching under the hood. But I'm not clear if that is different than the stroke control?

 

[MNBobcat]

Found it. I called a friend of my dad's who has been working on John Deere's forever. Old farmer. He clued me in that the pump runs off the front of the crankshaft and he thought it was right by the front axle. Sure enough! I ended up setting it at 2,300. It got dark on me and I called it good.

Thanks again!