formula fou figuring lift capacity

[Mace Canute]

I have just startd working in at tractor manufacturing industry and lil confuse about the hydraulic calculation for three point linkage , how much pressure is required in addc to lift 500kg.

Another Zombie thread!

There is no one answer to that question because there are so many variables involved...different categories of three point hitches, different manufactures of tractors, different configurations for how the 3ph is constructed are just a few of the differences that make a one-answer-fits-all impossible . Each case has to be taken individually and the physics/geometry worked out for that particular 3PH.

 

[LD1]

Zombie thread full of bad info to. Nothing I saw skimming the old.posts is even remotely correct for a 3ph

 

[jmc]

Zombie thread full of bad info to. Nothing I saw skimming the old.posts is even remotely correct for a 3ph

Tell us what is incorrect about post #7.

 

[bcp]

I have just startd working in at tractor manufacturing industry and lil confuse about the hydraulic calculation for three point linkage , how much pressure is required in addc to lift 500kg.

Much more is involved than pressure.

Diameter of cylinder
Length of arm from cylinder ram to pivot of lift arm
Length of lift arm
Length of draft arm before and after lift link attachment
Angles through which all these links operate
Friction

And probably some I forgot.

Bruce

 

[LD1]

Tell us what is incorrect about post #7.

Everything.

3PH is not a simple lever. Its a parallelogram linkage.

Depending on how the toplink is set if (both length and if you have multiple mounting locations), and how the implement is configured (pin spacing between the lower links and toplink) changes the toplink angle in relation to the lower link angles, Will all yield different lift capacity results.

The lower you mount the toplink on the tractor side, the less you can lift as you are lifting the tail end of the implement higher (lifting and rotating) than if you choose the highest point on the tractor that font lift as high.

Lifting something a lesser distance takes less force. Or in otherwords, you can lift more.

 

[Egon]

Old thread. First post for member reviving it!

 

[LD1]

Old thread. First post for member reviving it!

Certainly a zombie thread. And the member that revived it has not even logged on to the site since.

Normally I would have just left it alone, but its full of bad info, and brought right back to the top of the board.

 

[jmc]

Everything.

3PH is not a simple lever. Its a parallelogram linkage.

Depending on how the toplink is set if (both length and if you have multiple mounting locations), and how the implement is configured (pin spacing between the lower links and toplink) changes the toplink angle in relation to the lower link angles, Will all yield different lift capacity results.

The lower you mount the toplink on the tractor side, the less you can lift as you are lifting the tail end of the implement higher (lifting and rotating) than if you choose the highest point on the tractor that font lift as high.

Lifting something a lesser distance takes less force. Or in otherwords, you can lift more.

We have to assume the tractor company knows where the sweet spot linkage position is when they give us maximum lifting force at two different points along that position.

From those two provided points, we can calculate the maximum lifting TORQUE applied to the linkage.

From the lifting TORQUE, we can calculate the lifting FORCE at any point along the linkage, in addition to the two points the company provided.

Before you start insulting everyone, you should do more than "skim"(your term) the thread.

 

[LD1]

Its not an insult to say a statement is wrong when it is.

Your figuring of the 3PH would be as if the implement were just an extension of the lower arms. IE: simple lever. Which the 3PH is NOT.

The 3PH is a parallelogram type linkage. And to further complicate things, it is an ADJUSTABLE one. Most modern tractors have at least 3 places where you can hook the toplink to the tractor. The highest hole is gonna have significantly MORE lift capacity than the lowest hole. Cause the lowest hole causes the implement to lift AND rotate much more.

Picture a bushhog attached to your tractor. When I hook mine up and use the top hole, it lifts nearly level. IE: at max height, the tailwheel is only lifted about 12". Doing nothing but putting the TL in the bottom hole, makes the tailwheel lift about 4' in the air with the same range of motion from the 3PH linkages. Lifting something HIGHER takes more input force. Since input force is fixed, it will lift less weight in this position. (or more weight with the TL in the highest hole on the tractor)

The fact is the 3PH is NOT a simple lever and there is NO simple way of calculating how much it can lift at a given distance. Too many variables that can change.

There are a bunch of threads on this very topic already.

Here is a good start if you are not too stubborn and open to learning something:

http://www.tractorbynet.com/forums/...ion-factor-3ph-load-capacity.html#post1682683
http://www.tractorbynet.com/forums/attachments/333848-lift-capacity-3-pt-hitch.html#post4089382

I dont know why, but for whatever reason people seem obsessed trying to simplify calculations for lift capacity for FEL and 3PH. there IS NO WAY to simplify things. They are what they are and thats not gonna change. There is no way to make simple lever calculations and come up with any kind of accurate result. But everyone keeps trying.

 

[Jerry/MT]

The relief valve pressure setting is always the limiting factor.

You can increase the valve setting, until either the pump shears something off (or stalls the engine if the pump is way overbuilt), or the lift cylinder blows something out. I suspect on a static lift-until-it-breaks, the pump would fail first, because the cylinder is built a little heavier to withstand shock loads from traveling over bumpy ground.

--->Paul

the relief valve may not be the limiting factor. My TO-30 will lift till the front wheels come off the ground and the relief valve doesn't blow.