Anyone changed their hydraulic cylinders on their grappler for more grab.

[Smokeydog]

You are unfortunately missing the technical argument perhaps because it is not clear enough or explained well enough.

Remember, my initial post claimed the larger cylinder on the grapple would increase the back pressure said cylinder could exert into the tractor's hydraulic system.

I was wrong! When my point was challenged, I went back through my logic and realized it was flawed.

My point is not to argue with you or dismiss your points but rather to ask you to go back and re-read the simple example of a load applied to the push rod of a simple vertical cylinder and measuring the pressure the load generates inside the cylinder.

Dave M7040

That’s a good observation and point.

A larger cylinder would have higher clamping force from the tractor hydraulics.

A larger cylinder would cause a lower pressure increase from external forces trying to pump fluid back to tractor.

Like my 50 ton shop press manual pump works. The larger pump cylinder produces lower pressure at higher flow from my external force.

So how does this help the OP? Larger cylinders would increase the clamping strength. Should not hurt the tractor hydraulics except to slow down the action. But the design of the grapple bearings, steel frame, type of steel, and fabrication could suffer. Lot more to consider than just the cylinder size. Better money might be to sell it and buy a better designed grapple.

 

[CoyPatton]

You’re missing the point on what’s generating the pressure. The scenario was applying pressure to the grapple lids using the FEL. When you push against the sealed ram it’s going to generate pressure. The harder you push the more pressure it builds. If you’re pushing 10,000 pounds on a ram with 4 square inches of area the pressure inside will be 2500 psi. If you increased the ram size to 10 square inches area and applied the same 10,000 pounds the inside pressure will only be 1,000 psi. Now if you’re using the hydraulic system as intended and pushing fluid inside the cylinder the bigger cylinder will push more.

Ok if I accept your position on this topic, that means that since a larger rod and cylinder produce less pressure than a small rod and cylinder, then that would translate that the larger rod and cylinder are weaker in a hydraulic system than a smaller one!
Since you insist that pressure is not pressure. That a larger rod and cylinder reduces pressure.

 

[4570Man]

Ok if I accept your position on this topic, that means that since a larger rod and cylinder produce less pressure than a small rod and cylinder, then that would translate that the larger rod and cylinder are weaker in a hydraulic system than a smaller one!
Since you insist that pressure is not pressure. That a larger rod and cylinder reduces pressure.

You still don’t understand. You better keep working your day job and not offer hydraulic consulting. What’s generating this pressure you keep talking about?

 

[Dave M7040]

Ok if I accept your position on this topic, that means that since a larger rod and cylinder produce less pressure than a small rod and cylinder, then that would translate that the larger rod and cylinder are weaker in a hydraulic system than a smaller one!
Since you insist that pressure is not pressure. That a larger rod and cylinder reduces pressure.

Years ago a friend who was big in radio controlled model planes explained to me that the biggest challenge in piloting the model was when it turned from flying away from you to flying towards you.

Instantly everything became backwards, left was now right and right was now left.

My friend further said that some pilots could turn their plane around and never skip a beat while to others it was an impossible task.

In my opinion, no one has explained the issue well enough for you to grasp that, like the model plane, things are now the opposite to what has been your normal experience. Now bigger is less pressure back into the system.

Dave M7040

 

[4570Man]

If you were using a 30 ton bottle jack ( big diameter) and a 10 ton bottle jack ( smaller diameter) to lift the same 10 ton load you’d find that the 30 ton jack was a lot easier to pump. The reason is it takes a lot less pressure to lift the same load. If you were able to measure the pressure inside of both jacks while they’re both holding the same load the pressure inside of the big jack would be less. How do you think a bottle jack works anyway? They’ve got a little cylinder that’s maybe 1/4 diameter that when you pump it pushing the fluid into the bigger cylinder ( the jack body) and lifts it. Due the small area you can generate a lot of pressure inside the small cylinder.

 

[Redlands Okie]

Interesting video. Good info on the back pressure due to improper use of the grapple. Thanks for posting the link to it. Sort of knew it but was surprised to see him triple the pressure.

 

[WoodDuck]

Anyone changed their hydraulic cylinders on their grappler for more grabbing / Crushing power.

On my grappler more often than not when I got to pick up something bulky/heavy the grapple doesn't hold it's grip. It's like that crane game you played as a kid and try and gran that watch but the watch is just too heavy to be picked up by that claw and drops it.

Any thoughts on going bigger with the cylinders?

I'd stick a hydraulic gauge on it before trying anything else. If your grapple "doesn't hold its grip" like your saying and opens back up on its own without you doing anything, you could have air in the system, or you could be loosing fluid pressure through a valve setting or a leak. Plug the pressure gauge into your "closing" grapple hose, then "dead-head" against the gauge using your grapple function. It should spike to your machine's OEM relief valve setting, then hold close to there when you release the button. It should then drop when you function your switch back the other direction. If it spikes when you hit the button, but bleeds off quickly when you let go of the button, its bleeding your hydraulic pressure off somewhere it shouldn't be. Now if your pressure test goes well, and it still opens itself under a heavy load, you might be exceeding your relief valve pressure value, and bleeding pressure back to tank that way. Putting on a larger diameter cylinder would increase its closing force for sure, but might also damage the grapple in the process. I'd definitely verify my fluid system before changing anything on the grapple. Could also try your grapple on a friend's machine to verify where the problem lies as well, if that's an option for you. Hopefully this helps you a little. Good luck!

 

[CoyPatton]

You still don’t understand. You better keep working your day job and not offer hydraulic consulting. What’s generating this pressure you keep talking about?

Ut the one that insist pressure is not pressure and that a larger diameter cylinder reduces pressure. So by that you are saying a bigger cylinder produces less force.

And yet you insist I am an idiot! While exhibiting your foolishness! Why? Because you missed you have been feed the rope and hung yourself!
You fell hard!

 

[wdchyd]

.......threads like these really bring out the unedumacated amongst us. :laughing:

 

[4570Man]

Ut the one that insist pressure is not pressure and that a larger diameter cylinder reduces pressure. So by that you are saying a bigger cylinder produces less force.

And yet you insist I am an idiot! While exhibiting your foolishness! Why? Because you missed you have been feed the rope and hung yourself!
You fell hard!

I don’t think you understand the topic of the discussion. Everyone knows that if you’re supplying 3000 psi or any amount of pressure with a pump into 2 cylinder the bigger one will push harder. But that’s not what we’re discussing here. We’re talking about pushing on a grapple lid while its valve was closed using the tractor. The fluid can’t escape the cylinder because it’s sealed off and if you push on the cylinder harder than it could push itself pressure is going to increase beyond design spec. If you’re pushing the same LOAD against 2 different cylinders the BIGGER cylinder will build LESS pressure than the little one. You didn’t reply to the bottle jack analogy. If you’re using 2 different size bottle jacks to lift the same load which one will require less pressure to lift?