How do you make a hydraulic top link float?

[mars1952]

I plan on adding a Top & Tilt (with two tilt cylinders) to my JD4300. I already have the 3rd, 4th and 5th SCVs. I would like the top link to be able to float so that when I mow with the bush hog or rear finish mower they will have a greater range of motion and follow the contours of the land better. Most top link setups have a check valve to keep the top link in the set position. Is it possible to have a check valve and still have float?

It would also like to rig the two lift cylinders so that I could operate them one at a time or in parallel. My extra SCV levers are in a neat row on the right fender so I could just work two at a time to move both lift cylinders at a time but I would like to be able to do it with one lever.
Thanks in advance for your help,
Marshall

 

[Bird]

It seems to me that if you want a "float" option, you'd need to have a hydraulic valve with the float option; i.e., just as front end loader valves have the float position past a detent. I can't say for sure, but I don't think you can do that with the valves you have.

In order to be able to work the two tilt cylinders both independently and together with a single lever, the only way I'd know to do that would be with a joystick arrangement.

 

[SPYDERLK]

I think youll have to replace one of your remote valves with one having a detented float function. Surplus center lists one - Item#9-5490. It is a Cross. Dont know if you can retain the check valve function. Mad would know, but hes gone as I just learned today. Now weve all got to come to terms with that. Maybe it has been answered previously. Did you do a search?
larry

 

[jeffinsgf]

I very likely could be wrong, but I don't think you're going to get either of those jobs done.

You could rig a valve with a float position all right, but I don't think the response time is going to allow the amount of travel you're expecting in the time necessary for a smooth cut.

On the tilt cylinders, I think you can work them independently or together, but not both.

Do a search on "check chains" for rotary cutters. I think that might solve your issue easier and less expensively.

 

[SFish]

Mars:

For the top link put a T at each end of the cylinder and connect with hydraulic line and an appropriate valve. With the valve open fluid flows from one side to the other and the link will float. With the valve closed it acts as per usual.

Steve

 

[JerryG]

Like Jeff said, you can't do it. The valve on the tractor has to have a float and the cylinder can't have the check valve.

 

[bobodu]

Tie it to a log.........



Sorry...just couldn't pass that up.

 

[herringchoker]

Mars:

For the top link put a T at each end of the cylinder and connect with hydraulic line and an appropriate valve. With the valve open fluid flows from one side to the other and the link will float. With the valve closed it acts as per usual.

Steve

Steve's idea should work. The "appropriate valve" would be some sort of ON / OFF valve. When the valve is open the cylinder should float, but to extend or retract the cylinder you would have to close that valve. I suppose if you tried to operate the cylinder (either extend or retract) with that valve open, it would feebly extend due to the smaller surface area on the rod side of the piston.

 

[mars1952]

Mars:

For the top link put a T at each end of the cylinder and connect with hydraulic line and an appropriate valve. With the valve open fluid flows from one side to the other and the link will float. With the valve closed it acts as per usual.

Steve

Hi Steve: Your idea is what I vaguely had in mind and you have help me visualize it.
I made a crude drawing:
Float circuit
Gut wouldn't the differences in volume caused by one side having the piston displacing fluid make this not work?
Marshall

 

[mars1952]

Do a search on "check chains" for rotary cutters. I think that might solve your issue easier and less expensively.

I considered using a chain for the top link but I was worried about rear roll over. My pastures are very steep. I like the limiting effect on the mower height caused by check chains and I might make a set.
Thanks, Marshall

 

[SFish]

Marshall:

That is pretty much what I was thinking. If I were going to put it on my Bush Hog I would just extend the shunt hose a little way up toward the seat and have a pressure rated ball valve to flip instead of an electric valve when mowing. If you want to be sure if the reaction time is quick enough (as per Jeffinsgf above), connect the two hoses together and drive around with the mower before modifying. My top & tilt hoses have male and female ends for each cylinder so I can put them together when they are off the tractor. I can just barely move the cylinders by hand when they are hooked up like this, but I have only tried it when everything is cold, so I think this idea would work.

Steve

 

[SPYDERLK]

"Gut wouldn't the differences in volume caused by one side having the piston displacing fluid make this not work?
Marshall"

Yeah. Good catch. There wouldnt be anywhere for the excess fluid to go when cyl was compressed - and extension would cause a vacuum - and alternate cycles may cavitate.
larry

 

[SFish]

I just went out and climbed onto the tilt link with the cylinder rigged with the up hose quick connected to the down hose and it readily lowered about 6 inches with my (somewhat hefty) weight. If this worked on a top link hooked to a mower I wouldn't be worried about cavitation because the bubbles would be mostly vacuum and would disappear when the cylinder moved back. Even air bubbles would immediatly flush out when the controls were used. I would just give this a try when the top and tilt is in hand to see if the movement is adequate for mowing before spending any money.

steve

 

[bobodu]

Don't know if this would help,but it's what I did on my WC.Haven't gotten around to cross drilling pin holes to stop any travel.

 

[PILOON]

Unless your tractoe is very different from mine---

Does not the factory 3-point not have a 'float' setting? and the hydraulic upper is added for remote adjusting from the seat vs adjusting the screw?
if so it seems that your float setting would be from the setting of the intregal valve all while leaving the 3-pt setting alone.

On my tractor dragging my back blade allows it to float and I screw the upper link to control debth.
So with the hydraulic you'd shorten to limit debth and longer would float unless you lock the intregal control .

 

[mopacman]

Mars:

For the top link put a T at each end of the cylinder and connect with hydraulic line and an appropriate valve. With the valve open fluid flows from one side to the other and the link will float. With the valve closed it acts as per usual.

Steve

I dont think steve's idea will work because their is a different volume on each side of the cylinder due to the shaft. When the cylinder goes in their will be more oil comming out than will fit in the shaft side.
Larry H

 

[herringchoker]

Larry - That's a good point. If the first action after the bypass valve is opened was to extend the cylinder, would it extend and create a vacuum on the side opposite the rod? I don't know. But if it did, would the fluid then have some space to move back and forth and thus allow some float? Again, I don't know. Now this is bugging me!

Marshall - If you try this, let us know if it works.

 

[mars1952]

Hi Piloon: My JD4300 3PH has a float mode but that is for the complete 3PH. I want my lower lift arms to remain in a fixed position and the top link to extend and contract on it's own. If the top link can extend and contract then the rear of the mower can move up and down more to follow the curve of the land. The front of the mower will go up and down with the lower lift arms
Good Luck, Marshall

Unless your tractoe is very different from mine---

Does not the factory 3-point not have a 'float' setting? and the hydraulic upper is added for remote adjusting from the seat vs adjusting the screw?
if so it seems that your float setting would be from the setting of the intregal valve all while leaving the 3-pt setting alone.

On my tractor dragging my back blade allows it to float and I screw the upper link to control debth.
So with the hydraulic you'd shorten to limit debth and longer would float unless you lock the intregal control .

 

[Renze]

Why spend $$$$ on modifying a hydraulic top link ? on my neighbor's pasture topper, we simply use a chain instead of a top link. the chain gives enough play to follow the land, and when you lift it, it leans over about 4 inches until th chains are tight and that's the trick...

Later design pasture topper have the 3pt lift frame attached to 2 pivot points, which are braced by 2 chains to the rear of the mower, so you can use your normal top link, which means no need for a chain with wide enough links on both ends to put a top link bolt through.

 

[Bird]

My JD4300 3PH has a float mode

Well . . ., sort of. There's one major difference. Your front end loader has power in both directions, up and down, in addition to the float position, while the 3-point on most tractors only has power to raise the 3-point, it's lowered only by gravity, so yes, if you have it lowered the all the way you have some float.