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