Single acting cylinder help

[CraigM]

Last month, we put a hoist on one of our rack wagons. We usually move wagons around with the B2150, so that was the tractor we tested the hoist with. Hooked the hose (one hose, it's a single acting cylinder) to the loader valve on the boom lift outlet and pulled the joystick back. Worked great until we tried to lower it. Pushed on the stick and nothing happened. We later found out that the bed was coming down at maybe an inch every 2 minutes. Putting the joystick in float was about the same. So there we were, with the wagon in full dump position holding the tractor hostage. We did the only thing we could think of...shut the tractor off and headed in for lunch. When the engine stopped, the bed started to come down. Seemed a very strange thing, but we weren't going to argue with success.

Can anyone explain what's going on?

 

[repete]

Just curious, how have you vented the cylinder?

 

[Couple of Achers]

You would probably get your answer quicker if you post this in the Hydraulic section. Those guys live and breath hydraulics. Very knowledgeable. But my guess is there is no return path for the oil to get back to the tractor. It is being blocked at the valve. They can explain it to you and come up with possible fixes for you. Good luck.

 

[tommu56]

1st thing you were deadheading the hydraulic system when lowering it
think of the loader fluid go's to the other end of the cylinder and pushes it down.

With the single acting the return was hooked to cylinder,and pressure was dead headed in valve and couldn't go anywhere.

Through in regeneration that most loaders have and that will create more problems.

Float is hooking both sides of a double acting cylinder to gether and any excess is going to tank

Pictures of your set up maybe we can work some thing out.

tom

 

[nostep]

If you only have a single acting cylinder, then you won't have any fluid going to the other side of the piston. In this case, if you only used one hose, then you need the fluid to go back to tank through the valve.

If you tipped something over and most of the load is no longer pushing back on the cylinder, then it won't go back in by itself. A proper example of how that is used is a snow plow. The cylinder pushes the plow up and holds the full weight of the plow (hundreds of pounds). When you go to float, it's the weight of the plow that pushes the cylinder back in and thus the fluid back into the tank. If your use was horizontal, or something tipped, but balanced, then that is why it won't go back in. It has to be pushed back in.

Like someone said above, photos may help. Plus, be darn careful with cylinders, especially with only one hose. One cut hose and whatever you were holding will come down like a ton of bricks (or straw, dirt, etc).

 

[CraigM]

The cylinder has a vent gizmo on the other end. We transplanted the hoist from another guy's wagon and tested it with his tractor before we did the transplant. It worked fine.

Putting the loader in float should be a no brainer as both sides of the boom valve are connected to the tank, but it won't lower the wagon unless the tractor is off. The hoist is similar to that on a dump truck and there is always weight pushing it down.

We also tried it on the bucket cylinder outlets but that didn't work either, and as I write this I'm remembering that the dump has regen, so that is probably messing with me there.

I didn't think that the boom was regenerative. I know that the bucket has fast and slow dump. I think that slow is non-regen and fast is regenerative, but putting the wagon cylinder on the bucket port doesn't work either. Didn't try that one with the tractor off.

Refresh my memory on regen. As I understand it, regen only works in one direction, when you are extending the cylinder. In regen, the fluid on the rod side of the cylinder is ported back to the piston side requiring less fluid from the pump. The pressures on both sides of the piston are equal and that reduces the force available to extend the cylinder (effective piston is the rod diameter) but makes it go faster than the it otherwise would.

If this is the case, then lowering the boom couldn't be regenerative because lowering powers the rod side and retracts the cylinder. This would mean that the piston side of the boom cyl has to be valved back to the tank when the stick is pushed forward. The wagon was connected to the boom up (piston side) valve port.

As for pictures, I didn't take any. If there is a particular area you are interested in, I might be able to get pix of it, but my options are limited as the wagon is in a shed and now full of ear corn. We have 2.5" in the rain gage and it's still raining...the ground won't be firm enough to get the wagon out for a while. I can get pix if necessary.

One thing that would show in a pix would be that the hoses were pretty long. That explains why the wagon only lowered slowly, but doesn't explain why only with engine off, or why only in float.

 

[Cooldmax]

I'm curious if you raised the wagon on the boom coupler and then switched to the other boom coupler and operated the lever in the same direction if it would lower the wagon faster. Not sure if there is too much pressure to re-connect the coupler with it lifted or not.

 

[kennyd]

Only the dump/curl circuit has Regen, not the lift/lower so that is not the problem...

In theory, it should-and does work on many machines, although the tractor will be in "relief" while it's lowering-the port is still open to the tank. And it is also open while in float

I can only think of dumb questions to ask right now like:

What size cylinder?
What size hose?
What size QD?

 

[PILOON]

Easy fix.

Place a 'T' in the line near the valve.
On the 3rd T port install a simple (rated) valve, ball or even a gate type and plumb that back to the reservoir, eg any appropriate access to the tractor tank.

Open control, pressure causes lift (and stays there) until you bleed the cylinder back to reservoir.

Installed a plow that way once using a simple hand pump.
Recall that 5 strokes gave full lift and cracking valve dumped the plow.

 

[CraigM]

We did try switching the lines with the bed up. It didn't make any difference. I don't think I'd try it now with the load of corn on it. I'd be afraid that the weight would create too much pressure and I wouldn't be able to attach the coupler.

The cylinder is at least 3" dia, maybe 4" and has a stroke of about 18". It has about 8' of 1/2 or 3/4 hose with a 'standard pioneer' coupler on it, typical of many farm implement setups. That hose plugs into a hose-end female pioneer coupler reduced down to 3/8 hose. There is about 12' of 3/8 hose with the 3/8 QD on it for my loader. It's far from an optimal setup with 20' total feet of hose, some of it small, but it's what I have. I'm sure that less hose would allow it to come down faster, but I can live with it the way it is.

What I want to find out is why it only works in float with the engine off. Sounds like we have established that there is no obvious reason for it not to work by simply pushing the stick forward, or by putting it in float. So why does it only work in float, and only with the engine off? Maybe another way to ask that is...why should having pressure in the center gallery of the valve mess with exhausting the boom cylinder to the tank?

 

[tommu56]

you said it had some sort of vent fitting right?

How hard would it be to add the second hose?

plumb in the second line to were the vent fitting is and see what it does.

with out pictures and or schematics suggesting whats wrong is an educated guess on out part
I'm sure it as some thing to do with the regenerative or the flow in the valve. Was it connected to the rear remotes on the other tractor what brand ect?

tom

 

[CraigM]

Tom:

I'd bet the tractor that a second line in place of the vent would fix the problem, but it's just not worth the trouble. The other tractor was an old Farmall H.

I'm sure you are right about the cause being some wierdness in the valve, I just wish I knew what.

Pictures are just not in the cards right now. It will take at least a week for the ground to dry out enough to get the tractor out. It's so wet in front of the shed where we have it parked that I wouldn't be able to get back up the little slope in front even in 4WD. I can lower the wagon when I need to, even if it's inconvenient so it's not a real big deal. We would probably be hauling any load with the JD 3020 anyhow, and I know that works with single acting cylinders.

Thanks to all for the ideas

 

[Leejohn]

Where is the loader valve out port going to? It should be going to tank and no where else.

 

[CraigM]

I assume it goes to the tank. I haven't modified it in any way.

 

[Leejohn]

I'm just shooting in the dark, but check it out. The loader valve might not be plumbed right. If it is and everything else seems to be right, then maybe, then I would look at the valve. How many hoses are hooked to the Valve?

 

[ol'George]

Maybe I missed something here, but the load check valves most loader valves have, seem to be comming into play, they make sure you have pressure to lower/raise the load in a controlled motion so it don't drop/raise the load unsafely. with no pressure from the pump,( engine stopped) they uncheck and the "float" position drops the wagon (& loader)
you need to hook the wagon cyl. to the remote cyl. outlet and select "single action cyl"

 

[J_J]

In an open center valve, in neutral, and when the engine is off, the work ports are blocked, but they can leak down over time. Load checks inside the valve only work to prevent the FEL arms/bucket from moving when you are shifting the valve. There are external load checks that can be pilot operated. The float position opens the work cyl so the cylinder can move freely. If a single action cyl does not have sufficient force on the shaft in the vertical plane, it must be helped in some way. Maybe modify the geometry, add springs, etc.

 

[ol'George]

You speak what I have experanced to be true, no question
I understood him to say it would only go down in float with the engine off (not withstanding normal leakage)
I feel that would be caused by the load check on it's seat by the absence of pressure in the valve from the other side of the cylinder,to uncheck the ball.

We both understand the dead heading of the pressure relief because no circuit to the other side of the cyl with the pump running ( valve in down position). if it were not for the load checks it would of dropped
( understanding with sufficient load on the cyl to compress it)
now, please point out what I'm am missing?

 

[J_J]

If those QD's are not seated fully, there will be blockage, and maybe enough to slow the flow of hyd fluid to build up some pressure, and if the cylinder has pressure in the float mode, it will not or maybe not come down. You can do a quick test, turn engine off, take the out/return hose going back to tank, and place in a bucket. Cylinder should stay extended, because the spools are blocking the work ports from the main flow galleries. When you go to float, you open the spools to let fluid flow freely. If the out or return hose is in a bucket, then the fluid from the cyl should bleed out into the bucket when float is activated. It should lock the cyl if valve is in neutral.

 

[CraigM]

J_J and George. Sorry, I was away for a few days. Sounds like you guys have explained my problem. It seemed like there must be something going on in the valve that I didn't know about. I had never heard of load checks. I guess I could run those tests and confirm things, but load checks explain my symptoms and that's good enough for me.

I don't have any remotes, that's why I used the loader valve. Sounds like remote valves come with load checks that can be turned on and off by selecting single acting cyl?

It's not worth the trouble, so this question is academic...what if I used the power beyond port on the loader valve to run the wagon cylinder? Would a valve that I'd connect to PB come with load checks? Are they a default standard in open center systems...would it be a good assumption that any OC valve I found would have them?