Tractor Sizing How Much Can A Sub Compact Tractor lift?

[LD1]

The force of a hydraulic cylinder on an angle is the sin of the angle times the force of the cylinder.

Lets say at ground level, the cylinder to boom angle is 30 degrees and you have a pair of 2" bore cylinders operating at 2500psi.

Each cylinder can push straight with 7850# of force, or 15,700# combined between them. But account for the 30degree angle.

Sine30 = 0.5

15,700 * 0.5 = 7850# of force to lift.

AS you near the top, the angle becomes much less than the 30 degrees you started with. Dont know specifics and all loaders are different, but lets call it 10 degrees at the top.

Sin 10 = 0.17

15,700 * 0.17 = 2669# of force to lift with

ALOT less force. ITs all about the angles and geometry.

 

[Egon]

At height doesn't the effective length of the force arm ( vertical force ) get shorter??

 

[LD1]

Not enough so to overcome the angle change.

Don't even know whuweafe hashing it out. It's not like we are making this stuff up. It's a fact that the higher you lift, the less you can lift.

I have a pressure gauge on my lift hoses. A static load of whatever weight register on that gauge. Same load only lifted higher, reads a higher pressure.

 

[k0ua]

Not enough so to overcome the angle change.

Don't even know whuweafe hashing it out. It's not like we are making this stuff up. It's a fact that the higher you lift, the less you can lift.

I have a pressure gauge on my lift hoses. A static load of whatever weight register on that gauge. Same load only lifted higher, reads a higher pressure.

I know, this is not even a bone of contention to most. Most folks know you can lift a heavier weight off of the ground that you cannot lift to full height. Many times I have gotten a really heavy rock to maybe 3 or 4 foot off of the ground but no higher before going into relief.

 

[AxleHub]

I have a pressure gauge on my lift hoses. A static load of whatever weight register on that gauge. Same load only lifted higher, reads a higher pressure.

Your pumps are limited to what they can produce . . So if you get more pressure as the height goes overhead . . doesn't that support my idea that something else is creating that added pressure above and beyond your pumps (static support that the arms are contributing ???).

 

[k0ua]

Your pumps are limited to what they can produce . . So if you get more pressure as the height goes overhead . . doesn't that support my idea that something else is creating that added pressure above and beyond your pumps (static support that the arms are contributing ???).

Pumps don't put out pressure, they make fluid flow. The pressure rises when the load is lifted higher is because the mechanical advantage due to angle is changing as the the loader nears the limits of its travel, and the piston in the cylinder is giving more resistance to the flow of the hydraulic fluid in the cap end of the cylinder. The controlling factor in most cases (we all hope) to limiting the pressure rise is the Pressure Relief Valve. Otherwise if it does not open, something will burst (line) or grenade,(pump)

 

[LD1]

Yep. Pump can only make a certain amount of pressure. The higher a load is lifted requires more of it. If that is beyond what the pump is capable of, lift stops.

That's why you might only be able to lift something heave a few feet before you run out of power.

 

[AxleHub]

Yep. Pump can only make a certain amount of pressure. The higher a load is lifted requires more of it. If that is beyond what the pump is capable of, lift stops.

That's why you might only be able to lift something heave a few feet before you run out of power.

If someone has a gauge on their lines as you do and:

1. Pumps produce the pressure your gauge shows but

2. Your pressure goes higher at height

3. Then either
a. Something else is creating that pressure (static support from fel arms in more vertical position ???) or
b. Something allows the pumps to create more pressure because of weight relief on the pumps as the load goes to more vertical fel arm support.

What else can explain greater pressure being created. Gravity at 6 foot is the same as gravity at 3 foot . . but static support of gravity is much improved at 6 foot compared to 3 foot because of fel arm positions . . Isn't that true?

Either you or I can hold more weight up 30 inches over our head than we can at a 3 or 4 foot height 30 inches away from our body. Its the same weight but much differently supported. Right?

 

[GManBart]

1. Pumps produce the pressure your gauge shows but

No. Pumps produce fluid flow (volume). Restrictions within the system...line sizes, valves, pistons, cylinders, the weight of the load, etc create pressure by resisting the flow the pump creates.

As the FEL raises, the resistance increases because of the geometry of the loader arms and cylinders, so the pressure rises. At some point, the pressure relief valve opens and you can't lift anything additional.

 

[TomSeller]

I have a Kubota loader rated at around 2500 lbs at the pins. (not a scut, sorry, but the principle is the same). I have lifted with it a calculate-able load at around 3000 lbs centered about 2' forward of the pins. Kubota is conservative. It is about geometry, cylnder diameter, rear weight and available hydraulic pressure. The remainder is smoke screen snake oil marketing.