3 point lift issues

[rScotty]

Back to the remedy of a Electric Winch. 5000 Lbs. At HF. 179$ Then only a couple cheap pullies would be needed HF. 8$ stainless steel. If the 3Pt. is rated 1600 Lbs. this is a easy and simple solution. Worst case front end weight added! or load the FEL bucket.

It will work, but weighting the front in order to lift more at the back sure can put a lot of bending stress on all the connecting castings of the tractor - the bellhousing and transmission cases especially.

If you are going to do that, it makes sense to check that it has a good full length loader subframe running from front to rear.
rScotty

 

[rScotty]

Scotty is correct. With the lower lift arms near horizontal, if you double the distance of the weight from the lower arm pivot points, you halve the lift capacity.
Triple the distance, your capacity is at 1/3.
Angles below and above horizontal, reduce this effect slightly.

Yes, I didn't mean to get into a debate and was surprised to see any different opinion. A horizontal boom pole is just simple leverage.

I am sure there are special cases - if the boom pole is exactly vertical that would be one of those - but that isn't what we were discussing.

To say it again: when the 3pt arms are extended by a boom pole so as to hold the weight farther out from the 3pt arm pivot, then less weight can be lifted at the end of that boom pole. The farther out you go, the less weight can be lifted.
The relief valve sets the limit. Leverage just works like that.

That is why most manufacturers specify 3pt lift at a particular distance - usually 24" behind the pivot.

Exactly the same thing happens at the front when you move the load farther forward on a set of FEL forks and try to tilt them up.

rScotty

 

[SPYDERLK]

Yes, I didn't mean to get into a debate and was surprised to see any different opinion. A horizontal boom pole is just simple leverage.

I am sure there are special cases - if the boom pole is exactly vertical that would be one of those - but that isn't what we were discussing.

To say it again: when the 3pt arms are extended by a boom pole so as to hold the weight farther out from the 3pt arm pivot, then less weight can be lifted at the end of that boom pole. The farther out you go, the less weight can be lifted.
The relief valve sets the limit. Leverage just works like that.

That is why most manufacturers specify 3pt lift at a particular distance - usually 24" behind the pivot.

Exactly the same thing happens at the front when you move the load farther forward on a set of FEL forks and try to tilt them up.

rScotty

Check out four bar linkage. Lift force does not diminish beyond the articulation point. This arrangement is widely used; lab scales, lift gates, suspensions etc. Even tractor 3ph ... although here, not dimensioned optimally for the full effect.

 

[Mike1955]

Is this the same principle as a prying pole?

 

[SPYDERLK]

Is this the same principle as a prying pole?

Im not familiar, but the term prying makes me think of leverage, which doesnt fit well. A parallelogram linkage acts to transmit and use an available force undiminished for a significant distance.

It does this by action reaction of forces on its active geometry. These forces stem from the cantilevered load "constructive" feedback at the articulation point. Constructive freeback increases with cantilever distance negating any loss of lifting force.

A 3 point hitch and attached implement form such a 4 bar //ogram system - not perfectly dimensioned, but still exhibiting lesser diminished force over distance than a simple leverage system.

 

[DarkBlack]

Check out four bar linkage. Lift force does not diminish beyond the articulation point. This arrangement is widely used; lab scales, lift gates, suspensions etc. Even tractor 3ph ... although here, not dimensioned optimally for the full effect.

The lower lift arm is the last mechanism before the load.
It’s a solid bar with a fixed pivot point of rotation, at the end closest to the tractor, as I circled in blue.
Everything before that… between the hydraulic cylinder and the lower lift arms are irrelevant if nothing else is changed. Doesn’t matter if there’s four bar linkages to top links, or a nuclear powered gear train, the resultant lifting force is inversely proportional to the mass distance from the lower bar’s axis of rotation.
Top links are only motion control links, and can effect the angle of the lifted object, so yes have effect , once the object is in motion, but to have motion, the lower lift arms must first have enough force to lift the load

 

[DarkBlack]

Distance of the weight outward from the lifting force is immaterial except its effect on backtip. Yours still had >850 lb at the boompole lift point.

Does what you said, make sense to you if you think about it? The load set far back can “effect backtip”, but has no effect on the force to lift it up?

 

[DarkBlack]

Spyderlk, and anyone else interested:

If you want to easily calculate how much your3 point hitch lift capacity is reduced by a given implement distance, without getting into confusing link motions and such, simply do the following:

1) With your implement attached and resting on the ground, measure the height of your lower lift arm pins where they attach to the implement.
Measure the ( boom lift point)

2) Raise the implement to the desired height with the tractor.
Measure the pin height again ( record the height change)

Measure the height of the raised implement., and record the change in height

3) Divide the lower lift arm pin height change , by the implement height.
That’s your lifting force reduction factor.

Example
Lower lift arm pins raised up 6” and the end of the boom pole raised 18”

6 divided by 18 = 0.33
1,200 lb lift specification * 0.33 = 400 lb capacity.

 

[SPYDERLK]

Spyderlk, and anyone else interested:

If you want to easily calculate how much your3 point hitch lift capacity is reduced by a given implement distance, without getting into confusing link motions and such, simply do the following:

1) With your implement attached and resting on the ground, measure the height of your lower lift arm pins where they attach to the implement.
Measure the ( boom lift point)

2) Raise the implement to the desired height with the tractor.
Measure the pin height again ( record the height change)

Measure the height of the raised implement., and record the change in height

3) Divide the lower lift arm pin height change , by the implement height.
That’s your lifting force reduction factor.

Example
Lower lift arm pins raised up 6” and the end of the boom pole raised 18”

6 divided by 18 = 0.33
[[1,200 lb lift specification]] * 0.33 = 400 lb capacity.

Thatll do it to get the fractional change at the end lift point. But to find the actual lift force you have to start with the actual lift force available at the pins. The lift spec is commonly given at 24" rearward from the pins and is conservative to boot.

 

[careyo63]

It will work, but weighting the front in order to lift more at the back sure can put a lot of bending stress on all the connecting castings of the tractor - the bellhousing and transmission cases especially.

If you are going to do that, it makes sense to check that it has a good full length loader subframe running from front to rear.
rScotty

This one should work and Really cheap!! Closer to 1600Lbs. Made for a ATV..
https://www.harborfreight.com/2500-...e-rope-and-wireless-remote-control-56258.html And it's to big Technically for my Yanmar.
I believe it's only 700Lbs. 3Pt. Max lifting weight.