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A forwarder is an off-road working machine that is used to transport logs from logging sites to a landing area that is accessible by trucks. Soil damage and operator comfort, especially whole-body vibrations when operating on hard and rough terrain, are crucial issues when developing novel forest machines. Most forwarders on the market are heavy machines with articulated steering and they are equipped with pairs of wheels mounted on bogies. For such bogie machines, only the flexibility and the dynamic dissipation in the tyres contribute to the ''chassis damping''. The roll and lateral motions are the most severe components of the whole-body vibrations. So, developing new traction units, chassis suspensions and/or cabin suspension are in focus. Model-based design relies on focused models that are as simple as possible, but not too simple. This paper presents a 12 degrees-of-freedom multi-body dynamics simulation model of a standard eight-wheeled bogie type of medium-sized forwarder. The presented model is targeted for assessing and comparing different design solutions. It is shown that a configuration of seven rigid subsystems and eight flexible tyres represented with the simple and computer efficient Fiala tyre model enables the forwarder dynamic simulation model to be used to predict the roll and lateral motions of a forwarder operating on hard and rough terrain.

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