Bleeding Grapple cylinders? best way

[Schreib]

After installing new seals in my Grapple arm cylinders I believe there is air in them.

One of my problems is my preconceived concept of how the air is "stuck" in the cylinder body and can't get out to the reservoir. I figure that toggling the trigger to move the arms only happens for a few seconds not enough time for fluid to be flushed to the reservoir. Worse yet, it seems like if the fluid is moved one way to raise the arm and that only takes 10 seconds then the air can't get past the inside piston seal face so it is stuck there, so to speak. Tripping the direction back the other way similarly must trap air against the other side of the piston. So, using the normal method of running the hydraulics back and forth to force fluid to the reservoir seems like it CAN'T work in this "dead end" location?

Certainly, I am wrong. Please tell me what I am missing! thanks.:confused3:

 

[CADplans]

Lets assume that 3 cubic inches of air remains trapped, needing to get past the piston,, most will go out by cycling the rod in and out,,

Now, pressurize the oil with the hydraulic system, to 2500 psi,,

According to the Ideal Gas Law,, the air will compress,, approximately 160 to 1,,

You are left with less than 0.02 cubic inches of air that must get past the piston,,

Even if there were 30 cubic inches of air,, it would compress to 0.18 cubic inches of air that remains,,

Does that make you feel better?? :thumbsup:

 

[Schreib]

hmmm. not really. my only point is it is STILL there. After you release the pressure it pops back out to 3 cu inches. My concern is that the grapple jaws drop back down by gravity after you release pressure on the joystick button. They need to stay "up". I also don't buy into your point that "most will go out by cycling.. ." just the same, I will try it again and see if you are correct.

My fall back plan is to crack hydraulic lines on the downstream side, close them and then crack on the other side to "work it out". It just seems to me that running the hydraulics back and forth WITHOUT having some opening is just alternately compressing the air and decompressing it but not MOVING it away. I figured somebody here has had to do this before and has a better plan. Heck, Lenz makes hydraulic fittings for bleeding air. Why wouldn't a manufacturer of a quick-attach device incorporate that into an OEM design? still :confused3:

 

[ericm979]

Try opening and closing the lids a bunch of times. Then stop the lids partially open and see if you can move them and the cylinders (not just the play in the pins) by hand. That would indicate air in the system. I bet they'll be totally solid like mine are.

If there's some air in there, so what? You close the grapple until the thing in the jaws is held firmly. It doesn't matter if it's oil or air, the pressure is the same.

 

[CADplans]

The air, will go past the seal of the piston,, so, the air will get out of the cylinder, no bleeding is necessary,,
Start a thread about your land plane question,,
I do not have rippers on my land plane,, it is built for two angled cutting edges, But, I only use one,,

If the driveway is "dry" it simply skips over the top of the roadbed,,
so, I only work my driveway when the moisture suits the land plane,,
The 41HP tractor in the pic is not enough for my DIY land plane,, but, I have a 60HP tractor that pulls it perfectly.

 

[kennyd]

Trapped air can get past the seals to escape. Just cycle the cylinder(s) and it will go away. No need to overthink this with complicated math calculations or other stuff.

Do you think you're dealer did anything special what they installed the loader that has 3 or 4 cylinders? No, they just cycled it and then (hopefully) rechecked the fluid level.