Post Hole Digger (PHD) Hydraulic Down Pressure (HDP) Kit Installation

[Roehm Farms]

In the picture you posted it appears to have a solid plug in the other non used port on the cylinder, in every application I have seen with a two way cylinder used in a one way application it would have a mesh screen in that fitting. That could be locking the cylinder also.

 

[J_J]

The SA cyl is powered down by the tractor hyd, and the relief is there for the 3pt as it tries to raise the auger and make the SA cyl retract.

https://www.youtube.com/watch?v=xPRqoGyyA_Q

 

[Roehm Farms]

This is what should be in the other port of the cylinder or it will air lock.

1/2" NPT BRONZE BREATHER

Take the solid plug out and see if it works correctly, if it does get one of these breathers that fit you cylinder.

 

[JD 4520]

This is what should be in the other port of the cylinder or it will air lock. 1/2" NPT BRONZE BREATHER Take the solid plug out and see if it works correctly, if it does get one of these breathers that fit you cylinder.

This makes sense. I will check it out. I would think that if I took out the plug as you mention, that hydraulic fluid would spew out.

 

[JD 4520]

So a further question to the same subject matter, how does this single cylinder really work? When the 3rd SCV is invoked and the cylinder extends, how does the cylinder know the difference between the pressured applied from the ground vs the pressure applied by the 3 point retraction? What causes the cylinder to retract as desired vs not?

The DA cylinder makes all the sense in the world but the SA does not make sense.

 

[J_J]

There is no fluid on the rod side of a SA cyl, unless the piston seals is leaking.

You can use a DA cyl for a SA cyl.

 

[jmc]

....Is the relief valve adjustable? If so, it is set too high.

This gets my vote. Or maybe the relief valve is not even working. Ted's video on another brand cautions against messing with that valve but maybe if you count knob turns you could restore it to the factory setting if need be.

If they used a solid plug instead of a vent the cylinder would move a little as retracting it would draw a partial vacuum. Like pulling the plunger out on a syringe with your thumb over the tip.

A test that might be diagnostic would be to lift the 3PH while the remote valve is in the retract position. I know that would merely pressurize an unused port but it should also vent the trapped fluid back thru the extend port and then to the tank.

I'm no hydraulics expert but getting a remote valve with the float option may be necessary only if you don't have your relief valved design. Otherwise, redundant.