Live hydraulics, the continuing saga

So back to the drawing board I went, having read up on hydraulic systems. I think I finally figured it out. It doesn't screw the pump up, and is completely reversable.

The intake valve for the pump body has two ports in it directly across from one another, for feeding both banks of the pump cylinders. It is controlled with a tapered insert (I'll call it a valve) sliding back to allow fluid in, and sliding forward, to block it off. This motion is caused by the control rod.

Ok, what I propose is to use that intake valve, but in a very different matter, setting it up as an open center valve, with a live hydraulic pump feeding it at all times.

Instead of having both ports of the intake valve draw fluid, I will have fluid sent across them. With one side being pressurized, and the other receiving the pressurized fluid. It will be exactly like the open center spool valve used to control a front end loader lift cylinder. In the neutral position, fluid would be vented out the front of the intake valve assembly, in reverse of how fluid flows in the oem unit.

To do this, I would install the intake valve spool backwards. It would have a groove cut into it that would run fluid across the two ports when the valve spool is pushed back by the control arm, and bleed the fluid out through the front in the neutral position. I've spent a fair bit of time measuring this, and it should work. It may involve a little cutting back of the intake valve cylinder to help fluid flow in the neutral position.

To make this work, I need pressurized fluid coming in from one side, and going to the lift cylinder on the other. This is easily done by taking the heads off and installing them backwards. This blinds the pump cylinder intake and exhaust passages.

By drilling and tapping the head on one side, I can attach the pressurized line from the live pump to that intake port of the intake valve assembly. Then on the other side, I can drill and tap at both intake and exhaust, joining them with an external line. This allows the pressurized fluid that has passed through the modified intake valve to lift the hitch. You could also grind a grove in the head to create a passage instead of attaching an external line.

This modification would only affect the lift assembly prior to the four pump cylinders. So things like the exhaust valves and check valve and safety valve would all operate unchanged.

I believe this modification will work, and I'll be starting the modifications shortly on my old pump body. No machine shop will be needed, as all the modifications can be done at home with a drill being the only power tool required. I can cut the intake valve spool by chucking it into the drill, and holding a stone against it as it spins. Not high tech, but completely effective.

The pump I'm going to use is the gear or vane type pump already on my loader frame. The pump does not leak, so once it's been bled out it shouldn't lose prime. Since it's inline with my crankshaft, it doesn't have to draw fluid up high, which helps ensure I won't have cavitation problems.

I'll probably switch to the newer fluid when I do this job. I'm getting all mightly sick of cavitating the pump in cold weather with the thick oil. Leakage losses in the pump system due to the thinner fluid shouldn't matter since the gear pump is so much more pump then the oem scotch yoke unit.

I can see a possible need for a flow restrictor or diverter device to the hitch. Otherwise, I could end up with a unit that throws impliments into the air, instead of lifting them. Since I'm going to be using the loader pump, and mounting it with a loader frame (so I can use the loader at times), I'll also be mounting the loader type controls. Simple enough matter to install the flow diverter there, between the loader controls and the three point hitch controls.

Being a military type, who loves redundant systems, I will also probably tap in a line directly to the 3 point lift cylinder from the loader controls. For the sole purpose of being able to lift with the loader control if I wish. Snow plowing was far to exciting this winter, and I want more then one way to get the blade up, now, so I can shoot back across the road and out of the way. True, this secondary lift would have no quadrant controls, but that's ok by me.

Comments, critisizm, questions and advice are being sought by me on this. I think it'll work, but if you don't I'd like to know why.

If you have the back copies of the N-Newsletter look at the summer 1987 issue volume 2,number 3 page 3 on the 2nd column. it even has a drawing of the system. It uses the pump on the crankshaft and then plumbed back.

Good luck
Tom

The secondary lift control is in addition to the regular lift. This could be done to any N as they sit, and is something that tOTG does. All you do is tap into the pressure line between the lift cylinder and the pump with another pressurized line. It defeats the quadrant when this secondary lift is used, but doesn't damage it or render it defunct.

Imagine you've got a front end loader. Now take the pressure line from the lift arm cylinder(s) and run it over to the pressure gauge tap on the side of the hydraulic pump. If you then use the loader control and try to raise the loader, the pressure will go into the 3 point hitch lift cylinder instead. If the quadrant were in the down position, the pressurized fluid coming from the loader would bleed into the transmission. If the quadrant were in the up position, the exhaust valve would be closed, so the loader controls would totally control the 3 point hitch. You'd have no draft control, and no feedback height control, just the height and position control that you have with a loader. Which would probably be just fine for winter snow plowing.

On a tractor with a regular pto driven pump, using the hydraulic pump from the front end loader as a secondary emergency lift boost or such, it wouldn't really matter either what mode the pto was in. If the pto is engaged, and the hydraulic pump is working, this emergency lift probably wouldn't be needed. In my case, with cold days and thick oil, my pump likes to cavitate. So having the loader pump lift wouldn't hurt the pump, and would only mix fluids. The check valve would still work holding fluid from being pressed through the pump backwards, and the quadrant controls would shut the pump intake off once the hitch was raised.

In my case, for what I want to do with the gutted pump body, all fluids will be drawn from the main transmission/differential area and up to the crankshaft mounted loader pump. This will involve some priming, and I'm counting on the pump being able to hold that prime when it sits for days. We'll see about that priming.

If you were to rig up a combination of the pto hydraulic pump with the loaders pump available as a secondary lift to the three point hitch, you'd want them both to be running the same fluids, as cross contamination is going to happen.

By just crossing the complete loader unit to the tractors 3 point hitch, the loader would still draw its fluid from its own reserve. You would get some loss from leakage, and some more possibly from having the quadrant in the lowering position, but it's going to take a while and some mistakes to accidently empty the loaders oil supply. It's a simple matter if that does happen to drain some of it back out of the transmission area and refill the loader with it.

Come to think of it, you might even be able to make the tractors pump backfeed into the loader frame, refilling it. With the tractor running, and the loader just sitting static, the loader pump is circulating fluid, but at a low pressure because the circuit is completely open. Attach a heavy impliment to the 3 point hitch, and raise the quadrant lever to lift the load. The pto pump builds up high pressure to lift it. Now open the valve joining this high pressure area to the loaders low pressure flow, and the fluid should go from the tractor to the loader, with the impliment being dropped in the process.

Backfilling the loaders hydraulics. That's interesting, and something I hadn't considered before. Now I've got to see if I can come up with a way to exploit that! :-)

Ken

I don't think an on/off valve would do what you want. I think you'd want to be able to divert the flow, not simply cut it off. Though two on/off valves would achieve that end.

It would also matter greatly just how the impliment needed the hydraulic flow. If it was just a one way cylinder, this would work fine. If it is a two way cylinder, you'd need to install two diverter valves. And if it's a hydraulic motor, you'd need a return line.

Another possibility would be to have a third control valve installed, for the rear hydraulics. I'm not sure how you would do this, as I do not have committed to memory the setting up of multiple open center control valves. But I do know it can be done. Not sure about it being cost effective.

As for the plumbing, I am certain that copper isn't adequate. It may hold with minimal loads, but shock it, and it will most likely blow. The iron or steel lines are probably adequate to even correct. I blew a rubber line on my loader when I hit a wall with it. The old pitted metal lines held, while the old rotted rubber one blew out.

I would think that installing rubber line(s) to the rear would be the simplest way to physically get them there. I would then have them mate with a quick connector, attached to a bracket at the rear of the tractor, probably under the seat.