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Three-point Hitch

In Stressman engineering we like to look at components from a global perspective. Simple components just interacting with a couple of other components can at first look easy to analyze locally. Traditionally systems are broken down into smaller sub-systems and analyzed separately. This is still in use today, and still will be for a long time, but the correctness of the loads and assumptions are given by the engineer’s skills and experience.

When running the components relations in a complete system we will often discover effects that we were not able to predict. An example of a relatively easy system is the 3-point hitch of a traditional agricultural tractor. This was introduced in the 1940s.

This system is quite simple but still can generate some load situations that may seem strange for an untrained eye.

For example, lifting equipment with center of mass past the one of the 3-point hitch

This will actually try to lift the arm on the opposite side of the mass, and the arm the closest experience more load than the equipment weight because of moment.

This means that the lifting components on the tractor need to be over dimensioned because of load condition that can apply more torque to the system than the tractor hydraulic forces can do by itself.