Hydraulic Top Link Drawbacks

[MtnViewRanch]

I hate to see you go, but know this is not a new issue, you will be missed.

I second that.

 

[dfkrug]

Is the check valve internal or an add on to the cylinder? I know they use these on cranes and
man hoist, but did not think of it for my T&T.

I can not speak to cranes, but the manlifts I have worked on do not use POCVs. Specifically, my Genie AWP24
uses a fixed-orifice flow restrictor on its hydraulic cylinder. That, in addition to a solenoid valve and an emergency
manual valve control down movement. That way, the lift can go down in a controlled manner even if the power fails.
A pilot-operated valve requires hydraulic power to open the pilot to open the main valve.

To the OP's question, a hydraulic toplink has 2 downsides: cost, and non-permanent adjustment. No one argues
that a conventional screw-type toplink or sidelink do not drift down. Even POCVs are not perfect (on cylinder
extension), tho they are near-perfect on cylinder contraction. Since hyd toplinks are primarily subject to leak-down
(cyl extension), the load draws a vacuum on the cylinder and gradual leakdown through the valve. With POCVs, the
much slower leakdown happens as air is drawn past the gland seals and oil is able to get by imperfect piston seals.
That is why you need TWO POCVs and good piston seals to keep leakdown at a minimum during extension.

 

[boggen]

I can not speak to cranes, but the manlifts I have worked on do not use POCVs. Specifically, my Genie AWP24
uses a fixed-orifice flow restrictor on its hydraulic cylinder. That, in addition to a solenoid valve and an emergency
manual valve control down movement. That way, the lift can go down in a controlled manner even if the power fails.
A pilot-operated valve requires hydraulic power to open the pilot to open the main valve.

To the OP's question, a hydraulic toplink has 2 downsides: cost, and non-permanent adjustment. No one argues
that a conventional screw-type toplink or sidelink do not drift down. Even POCVs are not perfect (on cylinder
extension), tho they are near-perfect on cylinder contraction. Since hyd toplinks are primarily subject to leak-down
(cyl extension), the load draws a vacuum on the cylinder and gradual leakdown through the valve. With POCVs, the
much slower leakdown happens as air is drawn past the gland seals and oil is able to get by imperfect piston seals.
That is why you need TWO POCVs and good piston seals to keep leakdown at a minimum during extension.

my bad on the previous examples i gave.

 

[Threepoint]

I can see where laving check valves can help in some cases such as mowing. I would also add that the jobs that require floating the top link are few and far between.

Buy whatever makes you happy. If I offended anyone I am sorry but I call it as I see it. I am signing off TBN for good. Over the years I just see too many armchair debates and recognize that I have personally spent too much of my time here without enough return on the time spent. I fully acknowledge how little difference it makes whether I am here or not. You guys have fun with it, life goes on.

Jenkinsph, for my part, I took no offense at your reply to my two posts. Hope you reconsider your decision.

 

[Threepoint]

Further to the OP's question about drawbacks, I recall something a tractor dealer said to me that I'm curious about. He wasn't a fan of hydraulic top links for use with very heavy implements, such as a large rotary cutter. He described a case where an owner with a Cat. 2 hydraulic top link was carrying his big rotary cutter in the fully raised position. He went over some hummocks too fast, causing the cutter to bounce up and down so violently that the cylinder was seriously damaged. Don't know more details, but it struck me as a pretty extreme case, and didn't deter me from going hydraulic. But I mention it here because the dealer felt that a conventional top link is less vulnerable with a big rotary cutter. Anyone else who's heard that?

 

[mikehaugen]

I can see where laving check valves can help in some cases such as mowing. I would also add that the jobs that require floating the top link are few and far between.

Buy whatever makes you happy. If I offended anyone I am sorry but I call it as I see it. I am signing off TBN for good. Over the years I just see too many armchair debates and recognize that I have personally spent too much of my time here without enough return on the time spent. I fully acknowledge how little difference it makes whether I am here or not. You guys have fun with it, life goes on.

Leaving because someone doesn't agree with you? I have seen a lot of arguing and heated debates here, some bad enough that I wouldn't blame someone for leaving (see all of the welding stuff that's been going on)... but I just don't see it here. I, and I'm sure many others here enjoy your posts and value your input. I believe you are misunderstanding something here, and if not I feel that was a pretty childish post to be honest.

I'm really not sure what you meant by "not enough return" but if you haven't taken any valuable information from here then you are more arrogant than I thought. I hope I'm wrong... "just calling it like I see it."

Since I am never going to be convinced that anyone actually "signs of for good" without coming back and seeing what people's response was, I truly hate to see you go and hope you reconsider. If not, good luck with your endeavors. Life goes on.

 

[mikehaugen]

Further to the OP's question about drawbacks, I recall something a tractor dealer said to me that I'm curious about. He wasn't a fan of hydraulic top links for use with very heavy implements, such as a large rotary cutter. He described a case where an owner with a Cat. 2 hydraulic top link was carrying his big rotary cutter in the fully raised position. He went over some hummocks too fast, causing the cutter to bounce up and down so violently that the cylinder was seriously damaged. Don't know more details, but it struck me as a pretty extreme case, and didn't deter me from going hydraulic. But I mention it here because the dealer felt that a conventional top link is less vulnerable with a big rotary cutter. Anyone else who's heard that?

There was a member here a while back that was transporting something heavy (a chipper maybe) and something caused the top link to break. Brian stepped up and sent him a new one. I do believe that the hydraulic top links are stronger than the aftermarket threaded ones. I can't speak for the factory ones as I have not looked closely at them.

 

[bumperm]

There was a member here a while back that was transporting something heavy (a chipper maybe) and something caused the top link to break. Brian stepped up and sent him a new one. I do believe that the hydraulic top links are stronger than the aftermarket threaded ones. I can't speak for the factory ones as I have not looked closely at them.

I've heard of one failure apparently caused by a piston retaining nut improperly installed. It came off, allowing the ram to depart the cylinder and drop the load. Absent that sort of thing, both hydraulic cylinders and screw type top links are mostly **** for stout and should not be prone to failure in normal use.

Edit . . . I just learned you can't say h e double l without getting asterisked! Okay, this is a test: heaven (just wondering :x)

It's obvious a hydraulic top link is more complex than a screw type, and this would provide more opportunity for failure, burst hose, that sort of thing. The counter argument would be that just because something is complex does not necessarily mean it's prone to catastrophic failure (airliners might not be a good example of complex yet reliable - even though they are. As any failure, however small, always makes the news).

In the bouncing rear rotary cutter example given, just a WAG, but it may be there were lateral or bending stresses placed on components designed for straight compression and tension. It would take much less force to bend a cylinder rod with side loading.

bumper

 

[MHarryE]

I was the one roading with something heavy. My original cylinder had the ports out the side but in the fully raised position that put the 90 out of the cylinder very close to the top link nuts on my Kubota L5740, in the dynamics of roading on a gravel road it swung over enough to hit, snag, twist and break dropping the bale and a lot of hydraulic oil because I pulled the lever when the bale dropped and sprayed oil everywhere until I realized what had happened. I contacted Brian to see if he could build me a cylinder to my specs and he asked me to return my damaged one and he welded a heavier Cat 2 end on the cylinder base (Kubota uses a Cat 1 at the tractor and Cat 2 on the implement end so Brian had duplicated that). He welded the end in the position that located the ports where I wanted them - lots if clearance - and it's worked like a charm ever since - except for 1 thing. I only have 2 remotes. When I pull my 13 foot wheel disk I need to disconnect the hoses, usually from the side link, and use that valve got the disk wheels. Also had to do that when I had my 5 bottom semi-mounted plow attached, but that was just for a parade to show off that little L5740 with a 5 x 18 Kverneland plow that dwarfed the tractor.

 

[MikePA]

The only 'problem' with a hydraulic top link is when you're not using it. The 'hook' that holds the stock toplink up and out of the way is too small to hold the larger hydraulic toplink.

 

[Ford850]

First thing to do so that you don't have to guess if the cylinders or the valves are the problem is to have the implement on the ground, set the hydraulics how you want them. Then un plug the QDs, mark or measure the cylinder rods so that you will know if and how much the rods extend under a load. Raise the hitch so that the implement is in the air. Watch for 10 or 15 minutes. If the rod extends more than 1/16"- 3/32" in that time frame then the cylinder needs to be looked at. This is not to say that your valves don't have a problem also, but it lets you know if the cylinders are bad and it gives you a place to start at when trouble shooting. With no to little movement, then the cylinders are fine and the problem is with the control valves.

In my experience with the product that I sell, almost always the cylinders are fine and the leakage is from the control valves. How you choose to deal with that is for you to decide.

Thanks Brian. I plan to do that test the next time I have the rotary mower attached. I have put it off till now so I could get a feel for how much it was dropping, etc. Or maybe I was in denial.
The valve for the bucket leaking is understandable to me, since I've used it for 7 years. But the remote valves are practically unused until now. I'll start another thread with questions on that when I get some testing done.

 

[Ford850]

The only 'problem' with a hydraulic top link is when you're not using it. The 'hook' that holds the stock toplink up and out of the way is too small to hold the larger hydraulic toplink.

I noticed that after installing mine, with nothing to rest it on.
I made a replacement hook from some 3/16" (?) rod. Made the same size as the original except with a larger hook. It works great.

 

[MtnViewRanch]

Further to the OP's question about drawbacks, I recall something a tractor dealer said to me that I'm curious about. He wasn't a fan of hydraulic top links for use with very heavy implements, such as a large rotary cutter. He described a case where an owner with a Cat. 2 hydraulic top link was carrying his big rotary cutter in the fully raised position. He went over some hummocks too fast, causing the cutter to bounce up and down so violently that the cylinder was seriously damaged. Don't know more details, but it struck me as a pretty extreme case, and didn't deter me from going hydraulic. But I mention it here because the dealer felt that a conventional top link is less vulnerable with a big rotary cutter. Anyone else who's heard that?

To the best of my knowledge, NONE of the many different hydraulic links manufactured are weaker than the OEM manual units that they replace. Maybe only as strong, but none that are weaker.

 

[bumperm]

When doing the disconnect quick connect creep down test, be sure to check the quick connect for leakage too.

I tied a short loop of nylon rope around my hydraulic top link. Slipping the loop over the original hook holds the top link up.

bumper

 

[dfkrug]

He described a case where an owner with a Cat. 2 hydraulic top link was carrying
his big rotary cutter in the fully raised position. He went over some hummocks too fast, causing the cutter to
bounce up and down so violently that the cylinder was seriously damaged.

I believe you can damage a HTL that way. My tractors all have a shock-RVs in the 3-pt cylinder ckt to avoid
such damage to a fairly robust 3PT cylinder. It is set to almost 3000psi on my Kioti. Driving any tractor
fast (over 10MPH) on less-than-smooth roads can put huge tension stresses on the HTL cyl, too. I would
not be as concerned about sideways stresses to the HTL since they have Heim joints at both ends. To
avoid these stresses to the HTL, drive slower, put a workport RV in the system, or buy a larger diameter
HTL cylinder.

Threaded OEM toplinks have all been pretty wimpy, in my experience. The many rental tractors I have
owned always had somewhat buckled threaded toplinks from aggressive box blade use. The $25
threaded aftermarket toplinks I have bought have all been stouter than the OEM units.

I love hydraulic toplinks, and the downsides are few. I did prefer my 2nd one, which I made to a
custom length, versus the off-the-shelf unit (my first one). Customizing the open and closed
length to your tractor and implements is nice.

 

[Rocky Hoffler]

P. O. check valves also called holding valves are some times external if they don't bolt directly to machined part of cyl they need to be plumed with steel lines from valve to cyl on larger diameter cyl the checks are ported in cyl and thread in with a oring seal and are sometimes adjustable working in the utility field all aerial units use check valves. have to be careful when servicing a cyl with a check valve as they hold pressure and just operating control will not relieve pressure and you have pso or pressure squirting out.

 

[/pine]

Hydraulic Top Link Drawbacks

Seeing the thread where it is...I digress backwards...

It may be a "drawback" to some...but...the tractor must be running to move/adjust a Hyd.T.L. when installing/removing attachments...but IMO just being able to reach up and move the top (or side) side link when having to fudge a heavy implement into position...is worth it...

 

[Ford850]

First thing to do so that you don't have to guess if the cylinders or the valves are the problem is to have the implement on the ground, set the hydraulics how you want them. Then un plug the QDs, mark or measure the cylinder rods so that you will know if and how much the rods extend under a load. Raise the hitch so that the implement is in the air. Watch for 10 or 15 minutes. If the rod extends more than 1/16"- 3/32" in that time frame then the cylinder needs to be looked at. This is not to say that your valves don't have a problem also, but it lets you know if the cylinders are bad and it gives you a place to start at when trouble shooting. With no to little movement, then the cylinders are fine and the problem is with the control valves.

In my experience with the product that I sell, almost always the cylinders are fine and the leakage is from the control valves. How you choose to deal with that is for you to decide.

I did this test, and found the cylinders dropped less than 1/16" over 24 hours. That proves the Fit Rite Hydraulics are rock solid. The weak link is the tractor's control valves. I'll start a thread in the Hydraulics section asking questions about that.

 

[MtnViewRanch]

I did this test, and found the cylinders dropped less than 1/16" over 24 hours. That proves the Fit Rite Hydraulics are rock solid. The weak link is the tractor's control valves. I'll start a thread in the Hydraulics section asking questions about that.

I just finished a test with my own cylinders on my 3215, 3 months with the same results that you had, less than 1/16" movement.

 

[dfkrug]

...working in the utility field all aerial units use check valves.

So, when power fails, how do you lower the aerial unit?

This is what Genie uses.