Hydraulic cylinder orientation

OneWithWood · February 09, 2016, 01:15:08 PM

Does it make a difference which way the hydraulic cylinder is mounted on a grapple arm?
I had the cylinder that controls the up down motion of the Farmi 50D arm on my JMS log trailer rebuilt. When I put it back on I reversed the direction because it was much easier to install. When I first bought the trailer the fixed end of the cylinder was attached to the arm and the piston end attached to the mast. Seemed odd to me and it was a lot easier to install the bushings and pins mounting it with the fixed end attached to the mast. Only difference I am sure of is the up down control operates exactly opposite than before.
It seems that the lift capacity is not what it used to be but that is so subjective I thought I would solicit some opinions from folks who know a lot more about these things than I do.
TIA

jmouton · February 09, 2016, 03:30:34 PM

hyd are hyd i am pretty sure it doesnt matter which way the cylinder goes, fluid doesnt know the difference , if you get longer hoses to switch them around then your function would be the same as before ,,

jim

Corley5 · February 09, 2016, 03:50:02 PM

A hydraulic cylinder has more capacity from the piston end than from the rod end. There's more surface for the fluid to press against on the piston. The end with the rod has less surface area because of the rod attachment. That's what I learned in Wood Splitter 101 ;) ;D

pineywoods · February 09, 2016, 04:05:10 PM

It does make a difference. Depending on the diameter of the rod, you are loosing as much as 50% of your lift...

WRONG, BUM INFO. see my following post, I must have been half asleep. No, I had not been into the adult beverage :

Dave Shepard · February 09, 2016, 04:22:06 PM

If it's only swapped end for end, it wouldn't change the lift capacity.

John Mc · February 09, 2016, 04:28:58 PM

It shouldn't change the lift if swapped end for end: "Out" is still "out" and "in" is still "in".

pineywoods · February 09, 2016, 04:36:00 PM

Quote from: John Mc on February 09, 2016, 04:28:58 PM
It shouldn't change the lift if swapped end for end: "Out" is still "out" and "in" is still "in".

Yeah, but the indications are he put the hoses back different. Up control is now down, it will make a difference if the hose that used to go to the rod end now goes to the other end..

WRONG BUM INFO. I must have been half asleep when I made this post and the previous one. Won't make a bit of difference except the the valve operation will be reversed. From a practical point of view, I would put it back as original due to likelyhood of hose damage...

Autocar · February 09, 2016, 05:41:49 PM

The only thing to think about if you put the cylinder where it moves up and down and the rod end is stationary the hoses will need to travel with the cylinder and will be hard to keep them protected from getting ripped off from brush ect.

beenthere · February 09, 2016, 08:02:15 PM

As I understand it, the push/pull forces are not the same (as Corley5 suggests) for a double acting cylinder. Push is push, regardless of position of cylinder.

Calculating the two may be of interest, from a Surplus Center tutorial
https://www.surpluscenter.com/Tech-Help/Hydraulics/Calculators/Cylinder-Force-Speed/

Ed_K · February 09, 2016, 08:46:01 PM

I changed mine the same way, the only thing is to watch the hoses & fittings as it turns left & right. I sheared off the upper hose as it swung to the left.

Adrian lucas · February 09, 2016, 08:55:26 PM

Hi mate it was originally fitted that way for a reason the piston end has Moore surface area and there fore requires less pressure to move it hence more power
Cheers

Ljohnsaw · February 09, 2016, 09:09:58 PM

When a piston is pushing (expanding, getting longer), you have the entire surface area of the piston (bore diameter) that the fluid is hitting. When the cylinder is pulling (compressing, getting shorter), you have the difference in surface area of the piston minus the rod diameter. There is no fluid pushing where the rod is.

For example: You have a 4" bore with a 2" rod. (numbers used to make it simple) On the push, the bore diameter is 4", the radius is 2". The surface area is Pi x R squared. In this case 3.14 x 2 squared or 3.14 x 4. On the pull, the surface area is the bore (3.14 x 4) minus the rod (3.14 x 1 squared, or 3.14 x 1). So the pull surface area is 3.14 x 3.

In this example, the pull is 75% of the push force. Flipping a ram end-for-end has no affect on how much it can push. It does make a difference on the hoses - how much they need to move and/or flex.

OntarioAl · February 09, 2016, 11:02:23 PM

The hoses have to be switched if you turn the cylinder end for end. Just change them over at the valve bank.
Al

Maine logger88 · February 10, 2016, 12:20:28 AM

If it's switched end for end the function stays the same so the hoses stay the same

OntarioAl · February 10, 2016, 08:01:41 AM

I am replying to the OP 's comment that the control function on his valve bank is now reversed. The reversing of the cylinder has no bearing on the lifting capacity it stays the same.
" Only difference I am sure of is the up down control operates exactly opposite"
Al

Hilltop366 · February 10, 2016, 08:27:31 AM

Quote from: Corley5 on February 09, 2016, 03:50:02 PM
A hydraulic cylinder has more capacity from the piston end than from the rod end. There's more surface for the fluid to press against on the piston. The end with the rod has less surface area because of the rod attachment. That's what I learned in Wood Splitter 101 ;) ;D

All true but if you reverse the position of your wood splitter cylinder it will still be extending when splitting having the same power, the only difference will be that the cylinder (and hoses) will be moving instead of the rod end.

With out seeing the loader I would be inclined to put the cylinder back on the way it was to prevent future hose trouble.

Corley5 · February 10, 2016, 08:37:57 AM

Quote from: Hilltop366 on February 10, 2016, 08:27:31 AM
Quote from: Corley5 on February 09, 2016, 03:50:02 PM
A hydraulic cylinder has more capacity from the piston end than from the rod end. There's more surface for the fluid to press against on the piston. The end with the rod has less surface area because of the rod attachment. That's what I learned in Wood Splitter 101 ;) ;D

All true but if you reverse the position of your wood splitter cylinder it will still be extending when splitting having the same power, the only difference will be that the cylinder (and hoses) will be moving instead of the rod end.

With out seeing the loader I would be inclined to put the cylinder back on the way it was to prevent future hose trouble.

Very true. My reference to "Wood Splitter 101" was an intro to hydraulics and pneumatics course I took at our local community college once upon a time. The nick name came about because many people took it to learn how to build their own splitters ;) ;D

cuznguido · February 10, 2016, 07:07:48 PM

A question like this always elicits differing opinions, with each one having a certain amount of fact. For the sake of discussion, even IF the power in both directions were to be the same, the durability is most assuredly different. All things being equal, which it never is, the rod end is a bit weaker since the pressure is pulling against the rod end which merely by its thickness can never be as strong as the pther direction which is pushing against the pin and more supported and therefore less likely to pull the end out of the rod end. Probably not explaining it like I am thinking it. Just trust me and nearly 30 years of working on heavy stuff. Put the cylinder back like it was before you bust the end out of it. Bossy bossy bossy ;D.

Dave Shepard · February 10, 2016, 08:05:14 PM

The forces on the cylinder are the same regardless of which way it's attached. If it's pushing out with 1,000 pounds of force, it doesn't care if it's upside down. Yes, a cylinder does have more force when extending than retracting, but OWW didn't change that, it's still extending to raise the boom.