Single acting cylinder help

CraigM · Nov 17, 2009

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 · Nov 17, 2009

Just curious, how have you vented the cylinder?

Couple of Achers · Nov 17, 2009

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 · Nov 17, 2009

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 · Nov 17, 2009

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 · Nov 17, 2009

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 · Nov 17, 2009

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 · Nov 17, 2009

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 · Nov 18, 2009

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 · Nov 18, 2009

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?