Hydraulic top link issues

[MtnViewRanch]

Brian, how would having the return line above fluid allow it to suck air? The return on wood splitters is above the fluid.

Post #19, that was not me saying that. :no:

To the best of my knowledge, the only time that the return line being above std fluid level comes into play is with a float function valve. And not that that affects the float function, but after you go to use the cylinder in normal use there could be air inside the cylinder and would not work properly at first, but would take a few cycles to get the air out.

 

[MtnViewRanch]

Update.

I went to the farm, cranked up the kubota, installed the BB. Ran the Top Link cylinder full in/full out several times. Extended the cylinder and then lowered the BB. The rear blade of the BB hits the ground first under this circumstance. Without activating a lever my top link cylinder would retract until the BB was able to sit level on the ground. Approximately 4" of cylinder movement. I recycled the cylinder several more times and then did it again. Same result, cylinder would retract.

I uncoupled the rod end hose. Held it up in the air above everything else and removed the quick coupler. The hose was completely full of oil. I installed one of the restrictors I had bought from Brian. Not sure what diameter hole it has, maybe he can chime in with the specs.

Restrictors for 3" cylinders are .060

Recoupled the hose, lifted the BB and fully retracted and extended the cylinder several times. Extended all the way and sat the BB down on the ground again. No compression at all.

I then removed the top link cylinder from the tractor and put on the top link cylinder from the Ford. Same diameter cylinder, just an 1" shorter. Cycled several times and sat the BB down on the ground. Cylinder retracted.

Uncoupled the rod end hose from the tractor, held it high in the air and removed the quick coupler. Same result, hose was full of oil. Added the second restrictor I got from Brian. Repeated the test. No compression at all.

One more thing. The Ford had never displayed this problem, only the Kubota. According to the tractordata.com the Ford is an open center system with 7.7gpm flow rate at 2500psi. The Kubota is an open center system with 17gpm flow rate, pressure not posted.


I believe this has solved my problem. It was too cold and snowy to spend any time trying it out in real world scenarios. I'll save that test for better days.

My curiosity is peaked as to where the air was coming from? Probably never know definitively. Obviously the Kubota's increased flow rate is causing this problem? I've got 3 rear remotes on the Kubota and had previously tried the top link cylinder on each of them with the same results. To me that eliminated a specific problem in one valve?

Just my opinion based on what I have seen first hand in other situations, there never was any air, just a vacuum created by the implement pulling the ram out faster than the oil could get into the cylinder at the base end.

Hope some part of this is helpful to the OP.

Just for visual effects, here's a pic of the Kubota's setup and the Ford. 3.5" diameter cylinders.

Just an FYI for everyone, the diameter of a hydraulic cylinder is based on what the inside diameter is, not the outside dimension.

Richard, I sure hope that this takes care of your problem in real world use. :cool2:

 

[LD1]

Sorry just woke up....(graveyard shift).

For clarity.....A pair of restrictors caused issues. No restrictors caused issues. A single restrictor on the rod side solved the issue on both machines and both toplinks?

 

[ovrszd]

Just my opinion based on what I have seen first hand in other situations, there never was any air, just a vacuum created by the implement pulling the ram out faster than the oil could get into the cylinder at the base end.


Richard, I sure hope that this takes care of your problem in real world use. :cool2:

I believe this to be true.

 

[ovrszd]

Sorry just woke up....(graveyard shift).

For clarity.....A pair of restrictors caused issues. No restrictors caused issues. A single restrictor on the rod side solved the issue on both machines and both toplinks?

It appears so.

And I tend to think as Brian stated, I may not have had an "air" intrusion into the system as much as I had a vacuum situation.

As I mentioned earlier, the Ford never has this problem with either top link cylinder that I know of.

In my pea size brain that equates to GPM flow on the larger tractor??

Now to get back to the OP. Is the same scenario playing out for him?

 

[LD1]

It appears so.

And I tend to think as Brian stated, I may not have had an "air" intrusion into the system as much as I had a vacuum situation.

As I mentioned earlier, the Ford never has this problem with either top link cylinder that I know of.

In my pea size brain that equates to GPM flow on the larger tractor??

Now to get back to the OP. Is the same scenario playing out for him?

It was air, caused by the vacuum.

Just as the fluid cannot compress, it cannot expand either. The volume of space it occupies is constant. So when "firm" the cylinder holds .5 gal of oil.....and the rod extends pulling a vacuum and creating your situation.....you may now have .7 gal of space in there but the same .5 gal of oil.

I guess more technically, the vacuum would be the absense of air in that extra .2 gallons of space.....but also the absence of oil.

 

[ovrszd]

It was air, caused by the vacuum.

Just as the fluid cannot compress, it cannot expand either. The volume of space it occupies is constant. So when "firm" the cylinder holds .5 gal of oil.....and the rod extends pulling a vacuum and creating your situation.....you may now have .7 gal of space in there but the same .5 gal of oil.

I guess more technically, the vacuum would be the absense of air in that extra .2 gallons of space.....but also the absence of oil.

Way beyond my paygrade. Just want it to work. Thanks for the suggestion concerning the restrictors. I never thought to try one on either hose.

 

[ovrszd]

Top link - YouTube
Not sure if the link posted correctly in tapatalk..

Sorry we sidetracked your thread. But maybe it will work out.

My local farm supply store carries a line of hydraulics. They stock restrictors. They're pretty cheap. You might try getting a restrictor and putting in your hose that connects to the rod end of the cylinder. Would be a cheap test. Hope it fixes your problem.

 

[MtnViewRanch]

Sorry just woke up....(graveyard shift).

For clarity.....A pair of restrictors caused issues. No restrictors caused issues. A single restrictor on the rod side solved the issue on both machines and both toplinks?

Not to say that 2 restrictors can't cause issues, apparently they did for Richard, but over all they do not. Very very seldom have I had anyone complain about the 2. Use to be a common problem with just one, ultimately because a single one got installed on the wrong end. I know for a fact that there are no issues with my unit on my tractor and it has 2. :thumbsup:

 

[ovrszd]

Not to say that 2 restrictors can't cause issues, apparently they did for Richard, but over all they do not. Very very seldom have I had anyone complain about the 2. Use to be a common problem with just one, ultimately because a single one got installed on the wrong end. I know for a fact that there are no issues with my unit on my tractor and it has 2. :thumbsup:

Again, in my pea size brain, is my 17gpm flow rate contributing to this problem?