Lift at Pins

Lift capacity measured directly above the lower link pins; as the measuring point moves back the moment arm lengthens and the value read comes down.

Lift at the pin ends is the value of a tractor's lift capacity measured directly above the lower link pins. On the same tractor, when the measuring point is carried back from the pins the value read falls, because the load lengthens the moment arm. If two values are given together in the catalogue, the larger one is almost always the value at the pin ends.

Why there are two different values

Lift capacity is not a force but a force-and-distance relationship. When the load is directly above the pins the moment arm is at its shortest; as the load is taken further back the same hydraulic force has to work against a larger moment and the weight that can be lifted falls. Nothing changes in the hydraulics — the only thing that changes is where the load is hung.

There is a logic to the manufacturer giving the two values together: the pin end value defines the physical upper limit of the linkage mechanism, while the value at the rearward point defines the situation that will be met with a real implement. The trouble arises when a single value is passed on without the measuring point being stated; in second-hand accounts the higher one is generally written down and the measuring point is not.

When reading the catalogue

• If you see two values in the catalogue, always check which is the pin end and which the rearward point; the measuring point is usually written in small print in a footnote.
• When choosing an implement, look not at the pin end value but at the value that corresponds to the real centre of gravity of the implement.
• The same implement is lifted more easily if it can be hitched further forward.
• This value tells you what the linkage can lift; carrying the load across the field is a separate capacity matter.

What it is good for in the field

Its practical use is in asking the question "will my tractor lift this implement" properly. If you compare the weight of the implement with the pin end value the result is optimistic, because no implement has its centre of gravity directly above the pins. The right comparison is to look at how far behind the pins the centre of gravity lies and to use the rearward point value. Which components the capacity arises from is explained separately under the heading what determines lift capacity.

To make it concrete: a fertiliser spreader whose weight gathers behind the linkage is harder to lift than a cultivator of the same weight; the mass of the cultivator is close to the pins and spread over a wide area. That is why comparing the empty weights of two implements is not enough. On implements with a hopper, how full it is counts as well: when the hopper fills, both the weight increases and the centre of gravity generally shifts backwards.

The retrofit kit does not change this value

This distinction is meaningful for the user of a retrofit kit too: the kit lets you raise and lower the linkage electronically, it does not change the lifting limit. If the linkage is straining with a heavy implement, the problem is not in the control but in the load being far from the pins or in the tractor's own lift capacity. In a case such as "I fitted the kit and now it does not lift", the first place to look is again not the electronics but the hydraulic side.

What to do in practice is short: find out the weight of the implement, estimate roughly how far behind the pins its centre of gravity lies, and look up the value in the tractor catalogue for the measuring point nearest to that distance. If you fall between two values, take the lower one as the basis. The implement weights given in catalogues are mostly empty weights; when the tank, the hopper or the blade set fills, both the weight and the centre change, so make the calculation for the heaviest working condition.

The context in which this term is used: Converting a tractor hydraulic lever to electronic control

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