Lift Arm
The short arm that carries cylinder movement to the lower links; its lever ratio largely sets the lift capacity and the retrofit kit never touches it.
The lift arms are the two short arms that carry the movement of the hydraulic lift cylinder to the lower links and that sit on top of the tractor body. The cylinder turns this arm on a shaft; the rotation is converted, by way of the lift rod, into vertical movement of the lower links. Lift capacity depends to a large extent on the length ratio of this arm.
Why the lever ratio determines the capacity
The lift arm acts as a lever: the short-stroke but high-force movement produced by the cylinder is turned, in proportion to the arm lengths, into a longer but lower-force movement at the linkage. That is why the same hydraulic pressure gives a different lift capacity on different tractors. If the lift rod that comes down from the end of the arm has alternative connection holes, the choice of hole changes the balance between force and stroke; a hole further out gives more stroke and less force. Where the catalogue value was measured matters as well: lift capacity comes out differently at the pin ends and at the centre of gravity of the implement. The factors that determine the capacity are not made up of pressure alone.
How wear is noticed
| Symptom | Probable cause | First check |
|---|---|---|
| The linkage responds late to the command | The key or the clamped joint of the arm on the shaft has come loose | The play between arm and shaft |
| The arms drop slowly under load | Shaft bush wear or internal hydraulic leakage | The bushes and the state of lubrication |
| The two sides sit at different heights | Different lift rod setting or hole choice | Rod lengths and connection holes |
| The linkage rises slowly | Pump flow or oil level | Oil level and pump output |
When lubrication is inadequate the shaft bushes wear; as the play grows both the delay and the lateral swing increase. The practical way of measuring the play is this: leave the linkage lightly loaded, rock the arm with your hand and watch the free movement before the cylinder moves. If there is visible play, attending to the joint and the bush comes before looking for a fault on the hydraulic side.
The retrofit kit does not touch the lift arm
On electronic retrofit kits the lift arm is not touched at all. The LFT20 and the LFT54 pull the control cable; the movement of the arm still comes from the tractor's own hydraulics. In practice this means the following: if the linkage rises slowly or cannot lift the load, the problem is not looked for in the kit. Pump flow, oil level and mechanical play are checked first. The pull force of the kit (10 kg on the LFT20, 15 kg on the LFT54) is only enough to move the control lever, not to lift the load. For a user who wants to increase the lift capacity, electronic conversion is not the right tool; that is a hydraulic and mechanical matter.
What to do in practice
When you notice a deterioration in the behaviour of the linkage, do not break the order: first the oil level and leakage, then the mechanical play in the three-point linkage, and the electronics last of all. Rock the arm on the shaft with your hand and see whether there is play; if there is play you can feel, the key or the clamped joint comes first. Lubricate the shaft bushes at the maintenance interval — lubrication neglected here comes back later as loss of capacity and as dropping under load.
The context in which this term is used: What is Lift-O-Matik and how does it work?