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.