Open Center Hydraulic question

I need another valve to run hydraulics out of the front end loader on my NH3930. It has open center hydraulics.

Right now everything runs off the two rear remotes. If both valves are open, the fluid goes the easiest route, instead of where you want it.

If I put a 6 port divertor valve in the tree spade circuit to run the grapple, when I go to clamp hard on something, the fluid will circulate through the loader, not giving me full pressure.

I want to be able to move/contol the loader and clamp at the same time. Can this be done?

I attached a quick drawing of the hydraulics, the way I understand them.

Which valves does the 3930 have? Most I've seen had the Closed center valves mounted on the rear with the handles off to the right side and a priority pack under the seat. Some may still have had the basic open center with the valves mounted under the seat tho... Which one you have makes a world of difference to the answer.

Rod

Rod,

I have the two valves on the right side that are mounted behind the seat. The manual calls them "deluxe remote contol valves". Two control levers come forward next to the seat. The pressure line from under the seat and the return line to the axle both come off the top of the valves.

I assumed the remotes were open center too, when I run my tree spade off the one remote, I have to put the other remote into neutral or I have no pressure.

Thanks,
Rick

(quoted from post at 23:49:12 03/04/13) I assumed the remotes were open center too, when I run my tree spade off the one remote, I have to put the other remote into neutral or I have no pressure.Thanks,
Rick

Click to expand...

By putting "other lever in neutral" do you mean putting lever in "float"? If your tractor has the CCLS hyd's then it's a little different to add a remote valve.

By neutral I mean the off or "home" position on the valve.

Position
1 2 3 4
Cyl. down. Off/neutral cyl. up float.

On valve one, I always leave the loader in position #3. If I want to run the rear blade or spade on valve two, I have to put the valve one in position #2 or I only have minimal hydraulics to the blade. That is why I thought they were open center valves.

I dug out my hydraulics book from 25 years ago, and there is no mention of closed center or open center.

Rick

I don't know the hydraulics on a New Holland,but this is how I do it on my Oliver 1600 amd 1550 with open center without using the power beyond. I just block the lever to the remote back in to the "raise" position so there is oil flowing all the time.

Those valves are Closed Center with Load sensing... and flow control.
The reason you need to kick one valve into neutral to use the other one is simply because the tractor doesn't flow enough oil to operate both at the same time. If you turned the flow controls down to the very slowest setting and the tractor has two pumps... then it might operate both at once.

If you want to add valves in such a way that you don't tie these two rear ones up, the only option you have is to get a valve stack of CCLS valves. That could be tricky. Certainly, NH will get you a set like you have... and they're not cheap. Local hyd shops can probably get you what you need.... but let me tell you, it can be hard to convince them that what you need is a closed center valve with load sensing. Particularly after you tell them it's an open center system. I wish I had the Rexroth numbers for that monoblock... then you could just call a Rexroth dealer and give them a number.
Anyhow... what you need is CCLS valves. Then you tee the supply line to feed them. You also need a 'shuttle check tee' for the load sense line and tee that in place. If you don't have it, or you just use a standard tee, the load sense oil will bleed back through the other valve you're not using and nothing will work.... To complete, you tee the returns together and you're done.

Another option... if you didn't need one of the rear remotes... you could just buy a basic tandem center valve with power beyond and plumb it's inlet and return into one of your present remotes and use that to feed it....

Rod

What sort of valve is on your loader? If your tractor is indeed closed center, (I don't know NH) and your loader valve is open center it would operate as you describe. A closed center loader valve would solve your problems. The loader valve may be convertible.

moresmoke
NH's CCLS is a unique hyd system. I once owned a Ford 5610 that had CCLS. I understand open & closed hyd systems and how they operate. I studied Ford's service manual and never understood the advantage of CCLS. When CCLS fails one understands the dis-advantage. I now have a Ford 6700(open center) that's performing the same tasks that the 5610 did perform towing disc cutter & hay rake with no hyd problems.

I'm sure someone will explain the advantage of CCLS.

RodinNS and TxJim,

You guys hit the nail on the head with this hydraulic system. The rear valves are indeed CCLS. Anything that is hooked to them, ie loader, must have an open center valve so the fluid can circulate.

I am messing around wiht Rods idea of the backing the flow down to the loader to help run the other valve. The NH dealer agreed. And both think that it likely wont work, since I am trying to do too much with only so much hydraulics.

Loader circuit takes roughly 20gpm, I will turn the flow down, to try to run the second remote. The entire flow on the tractor to the remotes is only 12gpm. I have the dual pumps on mine. Single pump is less.

More to come later. Thanks for the help.

Rick

I thought they do a bit better than 12 gpm but I may have a bit larger engine pump on mine...
What I'd suggest is that you turn the detent screw on the remote valve in a turn or so... just enough to prevent the loader supply spool from kicking out on it's own... then you don't need to tie it off. All I've ever done is give the valve handle a whack down when I need to use something else, then haul it back up when I need the loader again.

Also... mabey I should have reread your original post... but are you trying to hook a third function on the loader arms? You should look at your present loader valve and see if it's got a plug on the side directly above the return port... if it does, it's likely a power beyond type of valve. IN that case you can simply buy a single spool Gresen tandem center valve and plumb it to the PB port... and then tee the returns together from the two valves. That's how ours has been setup for 20 years. On the other hand... I'd much rather have a 3-4 spool stack of CCLS valves on the loader frame and eliminate all of the OC valves...

Rod

The big advantage is that it allowed them to add a second pump on those 10 series tractors that would give 66% more flow at the remotes... without the need to change the internal porting of the lift covers.
They do also give some multifunction capability on the 18 gpm systems where the flow controls are turned down... and they marketed it as a closed center system which was all the rage at the time.

Rod

(quoted from post at 08:04:53 03/06/13)

Click to expand...

Rod,
That is exactly what the mechanic at the dealer suggested, if i could not get the flow I needed.

The way you both describe by adding the valve to the loader valve, the loader and the 3rd function (grapple) will be on the same circuit. Plus it makes sense that way because I wanted to mount the grapple valve right next to the loader joystick anyways. With the loader and grapple in series, I should get all the flow I need instead of most of the flow running through the valve at the back of the tractor. Plus I will shut off the 2nd valve in back to the tree spade when I am running the loader and grapple.

The quickattach plate wont be here for 3 more weeks, so I have a little more time to plan and start laying out the lines and valve.

Thanks again,
Rick

It works... it's just that it can be hard to keep all of the pipe fittings tight. This one has always had a drip of some sort no matter what you do... Put it this way... if I was starting from scratch with all new valves I would without a doubt get the CCLS valves and midmount them with hard plumbing. If you can get away with teeing one gresen valve into a PB port then it's certainly your cheapest option...

Rod