Which side has more power?

blackd · Sep 20, 2005

Re: Which side has more power?

A real world reason: when building my FEL the bucket mounts for the cylinder end was narrower than the rod mounting. The cylinders would mount with the ram reversed; therefore, I mounted them in that direction as opposed to reworking the FEL. Works great, only need to watch the hydraulic lines so that they don't get damaged as they are more exposed.

DaveNay · Sep 20, 2005

Re: Which side has more power?

( A real world reason: when building my FEL the bucket mounts for the cylinder end was narrower than the rod mounting. The cylinders would mount with the ram reversed; therefore, I mounted them in that direction as opposed to reworking the FEL. Works great, only need to watch the hydraulic lines so that they don't get damaged as they are more exposed. )

Another valid reason might be to put the rod end down, and therefore lessen the chance of moisture collecting on the seal, and rotting it away.

Dave

MikeD74T · Sep 22, 2005

Re: Which side has more power?

The most logical reason for mounting the cylinder in a stationary location is to keep the hoses shorter. For example on a woodsplitter the hoses don't move at all ( they move a little on a FEL, usually rotationally). If the rod were anchored , both hoses would have to be lengthened to move with the cylinder.
In vertical applications sometimes the rod is mounted down to allow less dirt accumulation on the packing. In such cases the hoses usually go around a rotation point but do not change length.
As for power, it's strickly a function of surface area. A 4" cylinder with a 2" rod (as found on many splitters) will push twice as much as it will pull.

AntrimMan · Sep 22, 2005

Re: Which side has more power?

Geee,
I just spoke with Cliff Clavin about this and he said that a 4" cylinder with a 2" rod will push about 1.3 times what it will pull.
Who is correct?

All the best,
Martin

TonyV · Sep 22, 2005

Re: Which side has more power?

Ok...hydraulics class is now dismissed (where we learned that force = pressure times area) and geometry class is now in session. /forums/images/graemlins/grin.gif

The area of a circle is equal to pi times r squared. A 4" diameter cylinder has a radius of 2" so its area is about 12.6 square inches. A 2" diameter rod has a radius of 1" so its area is about 3.14 square inches. Subtracting the area of the rod from the area of the cylinder gives us 9.46 square inches. This is the area that the hydraulic fluid engages on the rod end. The ratio of 12.6 to 9.46 is about 1.33. Therefore the force exerted on the open cylinder end will be 1.33 times greater than the force exerted on the rod end. Or, if you'd rather the force on the rod end is about 75% of that on the cylinder end. Geometry class dismissed.

Tomorrows topic will be "Hair Tonics...do they really work?"

/forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
Tony

Defective · Sep 22, 2005

Re: Which side has more power?

( Tomorrows topic will be "Hair Tonics...do they really work?")

Sorry Tony...

Looking at your avatar, the answer's already been determined.

/forums/images/graemlins/tongue.gif

TonyV · Sep 23, 2005

Re: Which side has more power?

 ( Tomorrows topic will be "Hair Tonics...do they really work?")
Sorry Tony...
Looking at your avatar, the answer's already been determined.
/forums/images/graemlins/tongue.gif )


This is a new low in my forum posting experience...dissed by a defective visitor. /forums/images/graemlins/crazy.gif /forums/images/graemlins/grin.gif
I'm glad to see that my brand of humor isn't lost on everyone here though. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

....Tony

willfick · Sep 24, 2005

Re: Which side has more power?

I think you're right about the determining factor being the hydraulic line layout rather than lifting force. On the FEL on my sister's JD 5310 the lift cylinders are set up what I would call upside down. The hyd. lines for all four cylinders on the loader use short hoses to jump from the tractor to the loader frame then have hard lines to close to their respective cylinders, then another short hose to connect from frame to cylinder. She doesn't have to deal with any of the two to four foot hoses that my old Ford has rubbing themselves to death on both sides.
Wm

bobodu · Sep 24, 2005

Re: Which side has more power?

"With equal pressure at
either end, a cylinder
can exert more force
when extending because
of the greater piston
area. In fact, if equal
pressure is applied to
both ports at the same
time, a cylinder will
extend because of a
higher resulting force
on a head end."

Taken from US ARMY Hydraulics Manual FM 5-499

For what it's worth... /forums/images/graemlins/grin.gif

MikeD74T · Sep 24, 2005

Re: Which side has more power?

Tony V, You got me on my own math. I should have subtracted the smaller diameter rather than compared their diameters. And obviously the correct ratio is 1.333 to 1. where the rod is 1/2 the cylinder diameter.
The real point being the closer the diameter of the rod is to the diameter of the cylinder, the greater the difference in force. i.e. telescoping truck body hoists have great pushing force with no pulling force or hydraulic cranes where large forces are needed to extend the boom & much smaller to retract. The difference in needed force is crucial in piston selection along with the need for rigidity of the extended rod. If equal force is needed in both directions it becomes difficult to have large diameter differences yet maintain rigidity. Thats why many backhoes have 2 single acting swing pistons mounted to oppose each other.