Toplink HYDRAULIC TOP LINK

[DavesTractor]

Brian, your warnings are good about not using a double acting cylinder, like a toplink cylinder, as a downforce cylinder. Downforce kits use single acting cylinders with a nifty pressure relief so that when you lift the post hole digger back out of the ground with the three-point it allows the downforce cylinder to collapse and the fluid returns to tank. Another common mistake is to use the correct downforce cylinder but to hook the return line to a remote controlled by a spool valve...same problem, the fluid cannot freely return when the PHD is raised. It bends or breaks something....don't ask me how I know this! So the one side of the cylinder is feed pressure, controlled by a spool valve and the other hose dumps back into the reservoir, unhindered.

 

[greg_g]

Brian, your warnings are good about not using a double acting cylinder, like a toplink cylinder, as a downforce cylinder. Downforce kits use single acting cylinders with a nifty pressure relief so that when you lift the post hole digger back out of the ground with the three-point it allows the downforce cylinder to collapse and the fluid returns to tank. Another common mistake is to use the correct downforce cylinder but to hook the return line to a remote controlled by a spool valve...same problem, the fluid cannot freely return when the PHD is raised. It bends or breaks something....don't ask me how I know this! So the one side of the cylinder is feed pressure, controlled by a spool valve and the other hose dumps back into the reservoir, unhindered.

I don't understand. Assuming the plumbing is correct in the first place, each pair of hydraulic remotes consists of a supply line, a control valve, and a return line. This configuration should render that particular set of remotes independent other remotes, and the hydraulic system in general. I have two sets of remotes, each will respond to supply/return taskings independently of what I may be doing with the other, or with the TPH. One example is my log splitter. I the splitter is raised/lowered by the TPH, one set of remotes goes to the HTL that levels it, the second set of remotes runs the splitter. Never had a problem using any/all hydraulics simultaneously

Same with a FEL, depending upon what you're doing with the joystick (or individual controllers), there's counterflowing fluid all the time. But it counterflows without conflict because of being routed through speparate lines. I'm apparently missing the reason one couldn't use a HTL with a TPH-type PHD.

//greg//

 

[DavesTractor]

Greg,
I didn't understand either until I broke a couple of things, and I am still learning. There is a difference in how to plumb single acting vs double acting cylinders.

I think the issue is that when you lift the three-point, the cylinder must collapse on it's own. Your remote spool valve will be closed, unless you are opening it at the same time as you lift the three-point. The oil can't leave the cylinder and go back through the spool if it is closed. I'm not so good at explaining these things, so maybe a hydraulic expert can chime in.

 

[3RRL]

Brian, your warnings are good about not using a double acting cylinder, like a toplink cylinder, as a downforce cylinder. Downforce kits use single acting cylinders with a nifty pressure relief so that when you lift the post hole digger back out of the ground with the three-point it allows the downforce cylinder to collapse and the fluid returns to tank. Another common mistake is to use the correct downforce cylinder but to hook the return line to a remote controlled by a spool valve...same problem, the fluid cannot freely return when the PHD is raised. It bends or breaks something....don't ask me how I know this! So the one side of the cylinder is feed pressure, controlled by a spool valve and the other hose dumps back into the reservoir, unhindered.

Good explanation, thanks.
I was wondering if you did use a top link (double acting) and returned the cylinder to it's original position, then lifted with the 3pt, could you do that?

Greg,
I think our Kamas have a ½ remote that could/might be used for something like that? But you can't have DPOCV on the cylinder though. Probably need the single acting for it's use? I've never used mine so I'm not sure. I read that it disables the 3pt when using it or something like that....that you can't use both at the same time?

 

[brsword]

I am new to this, being retired and all and just playing with my tractor, but a most basic question. Of all the brands I see mentioned on hydraulic top links, which one is the most recommended. The one from CCMachinery with the check valve for $185 or is the one I see on eBay from Redlandhill on sale for $152 good enough. Also what brand and type valves are recommended. Finally, has anyone successfully used a PTO pump hooked up to the tractor transmission as the reservoir. I will use this for a BB, LR, and BH on a 1984 Kubota L275, runs great. It has a FEL and I have T into the lines for hookup to the BH but then I have to disconnect the lines to the loader or the BH will not work. I have put a diversion valve in the pressure line to make this simpler when I operate the BH so I don't have to disconnect hoses. Just turn the valve when I get off the tractor to get on the BH and turn it back when I get back on the Tractor.
I have read much on this site and learned a lot, but still not sure about spool valves, power beyond,etc. As I said I am new at this and barely can make out the abbreviations most of the time. So if someone can say buy this model or brand and hook it up like such I would be most appreciative.
heck I am not even sure I am posting this right just thought I would get started under HTL topic.
I did buy a Harbor Freight QH based on what I read here and it seems to works just fine for a $69 item.
Thanks

Bryan Sword