Hydraulic question for old Nuffield tractor

Dave M7040 · Aug 18, 2014

I had a Nuffield 465 for 40+ years which I did a lot of work on to keep in top operating condition although appearances were not a concern. Ill health finally forced me to sell it and buy an new Kubota but I still have warm feelings for the old girl. The new owner is a serious farmer and is getting great service out of the old girl. He has asked me a question which I cannot answer and am hoping forum members can guide me. I put a brand new loader on the tractor many years ago. It came with it own loader valve. All cylinders on the loader are double acting.
The Nuffield hydraulic system is quite basic. The hydraulic pump has two sections. The high flow section serves the 3 pt hitch or by using a selector valve, would send flow to an external device such as a dump cylinder on a trailer. The second part of the pump was much smaller and operated the automatic draft control.

When I installed the loader, I connected into the port which would serve external loads and would operate the selector valve which would stop the 3 pt hitch from working and would provide flow to the loader. The return hose from the loader valve just dumped oil back into the main gear box which served as the hydraulic reservoir. The gearbox used 10W-30 oil and this was the hydraulic fluid as well.

The new owner needs an additional double acting hydraulic cylinder to operate on a bailer. He needs to have the loader quickly available as well. He was asking me if he got a single control valve for a double acting cylinder could he connect it to the return line from the loader valve and then connect the original loader valve return line to the return of the new double acting valve. This would create a valve bank with three levers.
I know from reading this forum, particularly posts by JJ, that flow dividers could be a solution but since the main hydraulic pump is small, loader operation would suffer. The operator is doing one task at a time and benefits from having all pump flow directed to that task.

Thanks for any comments.

Dave M7040

J_J · Aug 18, 2014

What kind of loader valve did you use?

If it has PB port, it can be adapted to add another valve downstream.

You normally can not use the OUT port of a valve to feed another valve because of the port restrictions of about 500 psi. Some do it anyway and get away with it for a while.

If the hyd system is open center, all valves should be in series.

You could divide the 3pt flow and have two paths. Some of them are equal flow, and some have a set ratio.

Dave M7040 · Aug 21, 2014

Thanks JJ
I think the valves are in series. They came with the loader, an Allied 660, and were part of the package.The valves are part of a two valve assembly with a supply hose to the valve block and a return hose going back to the gearbox/reservoir. The hoses are in line with each other
When I use the valve closest to the inlet, in this case raising the loader arms, the other valve furthest has limited ability to operate the bucket cylinders.
I really dont understand the way a PB valve works or I could tell you what is installed. I suspect due to the age of the loader (1970's) that it was a simple valve.
Here is a picture. The hose in the middle on the right is the supply hose and the one in the middle on the left is the return.

Dave M7040

J_J · Aug 21, 2014

Since the valve shown in the picture sends the OUT fluid to tank, I would suspect the OUT port is low pressure and could not support any back pressure.

I think I would insert a new valve with PB in front of that valve and things would be OK since the PB would support the old valve. The PB would connect to the IN port of the ild valve.

Someone might take a look at all the fittings and ensure they are hyd fittings and not water pipe fittings.

I see one water pipe fitting on the OUT port.