Top-Link Draft Sensing
The method in which draft resistance is read through the top link. On implements such as ploughs, when resistance increases the top link comes under compression; this force is measured by a spring pack or a sensor and used as the input signal to draft control. It is a classic and structurally simple solution.
The logic of the method is geometric: when the implement is pushed backwards in the soil, the triangle of the three-point hitch compresses the top link. This compression force presses the spring-loaded sensing assembly inside the housing and moves the control valve.
- Since measurement is taken from a single point, the mechanism is simple.
- If the implement forces the top link into tension (some shallow implements) the signal weakens or forms in the opposite direction.
- Fatigue of the spring pack causes the draft response to come late or incorrectly over time.
In practice this distinction determines the following: wherever your tractor's draft control is fed from, that is also where you make adjustments and look for faults. Electronic retrofit kits are not part of this sensing chain; LFT20 and LFT54 operate the quick lift mechanism via the cable. So if the draft response is faulty, check the top link sensing assembly and the valve connection first.
Context in which this term is used: Converting a tractor hydraulic lever to electronic control