Hydraulic Questions

[centex]

I bought and installed a 3rd SCV kit on my John Deere 4700. The dealer told me it was what I needed to operate the single acting dump cylinder for a cement mixer. I can operate it but I have to plug and unplug the hose to the dump cylinder to move it between the two ports of the 3rd SCV. I think I need to buy and plum in a transfer valve to allow me to switch the hose without the plugging and unplugging.

I have a couple of questions that I hope someone can help with:

1. Is there a simpler way to connect up a single acting cylinder? I would be nice to have it operate like the loader where you push to extend and pull to retract the cylinder.

2. The 3rd SCV is a one way valve. It has two hydraulic ports. When you operate the control lever it applies pressure to one port and releases pressure on the other port. When you release the control it closes both ports. In other words it can only operate a hydraulic cylinder in one direction no matter if it is a single acting or double acting cylinder. You have to switch the hoses around to move the cylinder in the other direction. So my question is what kind of implement is this intended to operate???

 

[EdKing]

<font color=blue>The 3rd SCV is a one way valve. It has two hydraulic ports. When you operate the control lever it applies pressure to one port and releases pressure on the other port.</font color=blue>

Can't you move the control in the other direction ? My rear SCV's operate Push/pull, and if you move the control one direction it pushes out of one port and pulls from the other. If you move the control in the other direction it reverses the push/pull. I thought single action cylinders would retract if you pull the hydraulic oil back out. You should be able to get both the push and pull from the single outlet.

 

[RonL]

Don

Try reversing the hydraulic cylinder ( end for end ) if the hose is long enough. Usually, when you pull the lever one way it pressurizes the line and pulls ( pushes ) the mixer up. When you reverse the lever it opens the line to the unpressurized return line. The weight of the mixer should push the oil out, thus lowering itself.

RonL

 

[RonL]

Don

On rereadingyour post I realized that my suggestion would not help. It seems that your valve cannot reverse itself. Strange!

RonL

Sorry, I'm a little goofy this morning after staying up all night to finish my taxes.

 

[centex]

That's the way I thought it would work but the cylinder on the control valve only operates in one direction so the 3rd SCV seems useless to me. I guess I need to double check the adjustment but I am sure it is right or maybe something in the valve body is causing to stick and not move the other way.

 

[Darren]

I agree with the other posters. There's no reason why you can't connect the hose to any of the outlets and have it work. The valve should either send fluid to the cylinder or suck it from the cylinder depending on the position of the
lever.

I have no idea why you needed a third SCV. I run a one way cylinder on a sickle bar exactly the way I described. One hose and one connection does it. It doesn't matter where I plug it in.

 

[RobS]

It sounds like this SCV is designed to operate a one-way hydraulic motor, perhaps for a rotary broom or something. Valve open and the fluid flows, off and it doesn't /w3tcompact/icons/smile.gif

 

[Darren]

Do all your remotes work like that? Does the control lever only work in one direction for the factory remotes?

 

[jimgerken]

It doesn't really suck though, does it? My understanding is that if there is a load on the cylinder the oil will be allowed to flow back being pushed by the load pressure. If there's no load to push the oil back to the valve, you will have to either change to a dual-acting cylinder or add an artificial load such as a weight or a spring to the mixer. Adding a weight or spring will push the cylinder back together, pushing the oil back to the valve. If I understand the open-center system correctly, there's nothing pulling the oil back to the valve, but I could be wrong.
Put on an inexpensive double-acting cylinder and buy it sized for versatility on other implements like a top link or something.

 

[Spencer]

I bought a Agrex cement mixer a couple of weeks ago. I couldn't believe the cheap single acting cylinder that came with it. I still haven't gotten the pto shaft cut yet and I am not sure that this mixer will work with my NH TC33D yet. I have had it hooked up and I just had to manually push the mixer into the dump position while I was holding the remote valve in the correct position. It did take a time or two to get the cylinder working smoothly and I attribute that to getting it filled with hydraulic fluid instead of air.

So what brand did you buy? Have you cut the pto shaft yet? Do you have full range of movement on the lower lift arms and the cylinder with the pto shaft hooked up? Post some pics if you can.

Spence

 

[bgott]

Check your owners manual. On my TN 65 New Holland there is a screw on the side of the valve you turn in or out to switch between single and double acting cylinders. You might have something like that on your JD valve.

 

[centex]

Thanks for all the suggestions. After reading them I went back and found that I had the linkage from the control adjusted wrong. After readjusting it, it now works correctly. John Deere provided a nice thick set of instructions with lots of drawings and pictures but the actual instructions were poor if not down right wrong. They said to do a lot of disassembly that was not necessary and the instructions for adjusting the linkage were wrong.

 

[centex]

Spence, I bought my mixer from Tractor Supply. It is made in Italy. It too has a cheap single acting cylinder and I sometimes have to push on the mixer to make it dump but then the mixer barrel is not very heavy. I am sure that when it has any cement in it there will be no problem getting it to dump. There are five sets of holes on mine for the 3PT lift pins. I used the holes that are on the level of the drive shaft so that the change in length of the PTO shaft is minimized when the mixer rotates to dump. Otherwise there is too much change in length of the shaft. I set the lift arms to have the PTO shaft horizontal to thus the shortest to find the maximum lenght to cut it. I then raised and lowered the arms and raised and dumped the mixer to find the operating limits for the mixer. You will find that you have to limit the operating range of the lift arms. I found that I need to raise the lift arms for mixing and lower them to just below horizontal when dumping so that I do exceed the maximum angle of 35 degrees on the u-joints. If I lower the arms too much I will extend the PTO shaft too much. I think this is a very difficult application for a 3PT implement. A hydraulic drive motor on the mixer would be a much better solution but of course more expensive.