Loader Lift Capacity vs Curl Capacity

[Hilbilly]

The LA 1055 loader on my Kubota is rated to lift 1784 lbs (500 mm forward of the pins) and the rated breakout force is 3171 lbs (500 mm forward of the pins), yet the loader will easily lift a load that it will not curl. Today I was moving some large pallets of sand and could lift them easily with the tractor running at 1400 rpm but the loader would not curl the load even at full rpm. Seems to me something is not right.

Do other experience the same thing?

I recall the loader on my 2 previous Masseys would curl more than they would lift.

 

[Industrial Toys]

Everything seems to be built with very modest pressure relief settings. My JD 6200 and Kubota Wheel Loader are the same. I know a guy (that can fix things he breaks) that overrides all his relief valves. If he tells his loader to do something, it does it! BUT, he has older more overbuilt equipment.

 

[BoylermanCT]

My tractor is the same way. I can lift up to 1500lbs but lose the ability to curl at much lower weights.

 

[4570Man]

Mine will curl more than it will lift especially when you start to lift higher.

 

[MossRoad]

I can lift the rear wheels of my machine off the ground with lift or curl, so I don't know what the limits actually are.

 

[k0ua]

If you will think about how a hydraulic cylinder is built You will understand why a double acting cylinder will NOT have the same force after it develops the same pressure both ways. It is because of the rod in the way, taking up space on the rod side of the cylinder. Therefore there is less surface area for the fluid to push against. The cap side of the cylinder has X amount of surface area. The rod side of that same cylinder has X-R where R is the surface area taken up by the Rod. Sure the developed pressure pushes on the sides of the rod, but that does not do useful work.

So that is why ANY hydraulic double acting cylinder has much more force one direction than the other direction. Also the amount of fluid needed to fill up the cylinder for a given flow rate is less one direction (filling up of rod side) than the other direction (cap side) because there again you have that rod in the way. Also for a given flow rate, the cylinder will fill much more quickly on the rod side than the cap side.

Once you have this triad of surface area, fill volume and fill rate understood, you won't have any more questions.

Once you understand that open center (like 99 percent of our tractors have) system pumps DON"T make pressure either, but instead make flow, you won't have any more question about pumps or relief valves either. Understanding this will also help you understand why there is some heat generated in hydraulics system components like valves, and hoses, and why a gauge will show some pressure even when the fluid flow is not being directed to any cylinder or motor. Because there is resistance to the flow of the fluid going thru the plumbing and valves. And that resistance builds some heat. And it also develops some pressure. No where near full relief valve pressure, but a small amount.

 

[bcp]

Extension is stronger than retraction, and it doesn't matter which end goes where.

And that's how the fight started.



Bruce

 

[k0ua]

Extension is stronger than retraction, and it doesn't matter which end goes where.

And that's how the fight started.



Bruce

And that is because of that pesky rod, always in the way. Always reducing your surface area for the fluid flow to push against. And always taking up space so the cylinder fills up quicker too. Same problem..

 

[metalbender]

I notice that the curl cyls are larger dia but shorter than the lift ones. More curl than lift even at rhe bottom of travel.

 

[MossRoad]

If you will think about how a hydraulic cylinder is built You will understand why a double acting cylinder will NOT have the same force after it develops the same pressure both ways. It is because of the rod in the way, taking up space on the rod side of the cylinder. Therefore there is less surface area for the fluid to push against. The cap side of the cylinder has X amount of surface area. The rod side of that same cylinder has X-R where R is the surface area taken up by the Rod. Sure the developed pressure pushes on the sides of the rod, but that does not do useful work.

So that is why ANY hydraulic double acting cylinder has much more force one direction than the other direction. Also the amount of fluid needed to fill up the cylinder for a given flow rate is less one direction (filling up of rod side) than the other direction (cap side) because there again you have that rod in the way. Also for a given flow rate, the cylinder will fill much more quickly on the rod side than the cap side.

Once you have this triad of surface area, fill volume and fill rate understood, you won't have any more questions.

Once you understand that open center (like 99 percent of our tractors have) system pumps DON"T make pressure either, but instead make flow, you won't have any more question about pumps or relief valves either. Understanding this will also help you understand why there is some heat generated in hydraulics system components like valves, and hoses, and why a gauge will show some pressure even when the fluid flow is not being directed to any cylinder or motor. Because there is resistance to the flow of the fluid going thru the plumbing and valves. And that resistance builds some heat. And it also develops some pressure. No where near full relief valve pressure, but a small amount.

It's not the cylinder, it's the piston. The piston has more surface area on the extend side than it does on the retract side because the piston rod takes up surface area on the piston face on the rod side of the piston.