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

[ddbackhoe]

If you have a grapple you need to watch this video produced by Messicks which shows how easy it is to create very high pressures in the loader hydraulic system.

Increasing the grapple cylinder size will just further increase the pressures you can create possibly leading to damage

How grapples can be dangerous! Protect your hydraulic system. - YouTube

Dave M7040

Why not install a cushion valve to try and limit the damage along with better operator training?

 

[mikester]

Amazing video - sure woke me up.
Video told me my loads were too heavy, bulky, off-center.
Looks like I better stick to lifting brush, branches, twigs, rather than some of the things I was lifting.

Thanks for sharing

Strikes me as a bit of fear mongering...your hydraulic system has relief valves and everything has an engineered factor of safety. If it didnt guys would be blowing hoses constantly. Your 3000psi hoses generally wont fail at 3001psi. If you constantly run at max psi then you will get a lot of heat and excess wear and tear on your pump parts and seals and your system wont be making full pressure after a while.

Now if you are one of those guys who monkey with their relief valves because they think their 1500 lb SCUT should be lifting what a full sized TLB does then there will more problems. The weakest links will likely fail first.

After watching that video it makes me realize I dont want the “ brand new “ demo model tractor.

 

[CoyPatton]

The back pressure is limited by the force the loader could apply so the big cylinder would be less. I really don’t see that as a problem anyway. The value is holding the pressure. Blowing a hose is about the worst that could happen. But bending the probably dinky grapple is almost a certainty with the bigger cylinder.

Seems to be if you have (just a number pulled out of nowhere) 3500 psi of back pressure from the load, the size of the cylinder is only going to effect how long it takes to build up the back pressure. However once pressure is built up is equaled as the load creating the back pressure is the same.
As in any plumbing the size of the cylinder/hose/pipe influences the amount of fluid held and the time to build up pressure, but does not control the pressure applied in a back pressure especially. While a bigger cylinder (diameter or length) may change the pressure applied, back pressure is not a function of said cylinder only volume.

 

[Dave M7040]

Seems to be if you have (just a number pulled out of nowhere) 3500 psi of back pressure from the load, the size of the cylinder is only going to effect how long it takes to build up the back pressure. However once pressure is built up is equaled as the load creating the back pressure is the same.
As in any plumbing the size of the cylinder/hose/pipe influences the amount of fluid held and the time to build up pressure, but does not control the pressure applied in a back pressure especially. While a bigger cylinder (diameter or length) may change the pressure applied, back pressure is not a function of said cylinder only volume.

I had to change my initial position on this matter so have been thinking a lot more about the subject.

The relationship between the diameter of a cylinder and the back pressure that a cylinder can generate is the opposite of the force a larger diameter cylinder can exert.

A bigger cylinder will generate less back pressure into the system than a smaller cylinder.

Imagine a simple scenario. A cylinder partially filled with oil and a pressure gauge connected to its port.

Place a weight on the end of the pushrod. Observe the increase in pressure. A larger diameter cylinder will display less pressure to support the same weight than a smaller diameter cylinder.

This is the back pressure situation.

Dave M7040

 

[4570Man]

Seems to be if you have (just a number pulled out of nowhere) 3500 psi of back pressure from the load, the size of the cylinder is only going to effect how long it takes to build up the back pressure. However once pressure is built up is equaled as the load creating the back pressure is the same.
As in any plumbing the size of the cylinder/hose/pipe influences the amount of fluid held and the time to build up pressure, but does not control the pressure applied in a back pressure especially. While a bigger cylinder (diameter or length) may change the pressure applied, back pressure is not a function of said cylinder only volume.

You’re completely off the mark on pretty much all that. A sealed and non compressible system like a hydraulic system builds pressure pretty much instantly. How long it takes to reach peak pressure after additional load is applied would be measured in milliseconds. Not like it actually matters. And the back pressure for a given load will be lower the bigger the cylinder gets. Say you apply a 10,000 pound load to a 3” and 4” cylinder. The 4” cylinder has more area so the pressure inside the cylinder will be lower. If you apply the same input pressure the bigger cylinder will lift more. And you’re wrong about the length of the cylinder. It makes no difference. 1’ long cylinder will push an equal amount to a 5’ or any length cylinder of the same diameter at the same pressure.

 

[CoyPatton]

You’re completely off the mark on pretty much all that. A sealed and non compressible system like a hydraulic system builds pressure pretty much instantly. How long it takes to reach peak pressure after additional load is applied would be measured in milliseconds. Not like it actually matters. And the back pressure for a given load will be lower the bigger the cylinder gets. Say you apply a 10,000 pound load to a 3” and 4” cylinder. The 4” cylinder has more area so the pressure inside the cylinder will be lower. If you apply the same input pressure the bigger cylinder will lift more. And you’re wrong about the length of the cylinder. It makes no difference. 1’ long cylinder will push an equal amount to a 5’ or any length cylinder of the same diameter at the same pressure.

So you say! But pressure is pressure! How can 10,000 psi be less because it is a larger tube! Yes you claim so but your justification is so circular that it makes no sense!
Pressure applied is pressure. No hydraulic cylinder system is going to work partially full it will self bleed to the reservoir. If 10,000 psi is pushed against A 4” ram or a 3” ram is is still 10,000 psi and 10,000 psi will be transferred past the ram to the remaining system.
You guys thinking the size of a nonmoving object is kin to a subcompact car and a semi crashing is all wet! Never are moving so mass is min ad both are supported by the same pressurized hydraulic system so any reduction is min and back pressure will produce damage to the hydraulic system—same as a dead head!

 

[Dave M7040]

So you say! But pressure is pressure! How can 10,000 psi be less because it is a larger tube! Yes you claim so but your justification is so circular that it makes no sense!
Pressure applied is pressure. No hydraulic cylinder system is going to work partially full it will self bleed to the reservoir. If 10,000 psi is pushed against A 4” ram or a 3” ram is is still 10,000 psi and 10,000 psi will be transferred past the ram to the remaining system.
You guys thinking the size of a nonmoving object is kin to a subcompact car and a semi crashing is all wet! Never are moving so mass is min ad both are supported by the same pressurized hydraulic system so any reduction is min and back pressure will produce damage to the hydraulic system—same as a dead head!

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

 

[4570Man]

So you say! But pressure is pressure! How can 10,000 psi be less because it is a larger tube! Yes you claim so but your justification is so circular that it makes no sense!
Pressure applied is pressure. No hydraulic cylinder system is going to work partially full it will self bleed to the reservoir. If 10,000 psi is pushed against A 4” ram or a 3” ram is is still 10,000 psi and 10,000 psi will be transferred past the ram to the remaining system.
You guys thinking the size of a nonmoving object is kin to a subcompact car and a semi crashing is all wet! Never are moving so mass is min ad both are supported by the same pressurized hydraulic system so any reduction is min and back pressure will produce damage to the hydraulic system—same as a dead head!

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.

 

[Mat4644]

Issue would be how strong is the grapple and will it hold up. Many are purposely designed light to allow heavier loads and a bigger cylinder might start bending things.

 

[Industrial Toys]

I havenever had an issue with not enough clamping force. Only many times on my single lid grapple, the one side is firmly engaged and the other side not. Only thng I hate about my grapple design, and I would never buy another single lid grapple.