At the turn of the 50s and 60s, interesting and persevering experiments were carried out in difficult snowy terrain in Eastern Finland to assess and measure the potential performance of the full-trailer Jyry Sisu K-44, the so-called “forest-Sisu”. The aim was to develop a vehicle combination     which could go anywhere and pick up loads from the remotest of work sites. That was a time when logging in Finland began to switch from timber rafts and horsepower to motorized vehicles. The combination of heavy loads and poor roads called for increased pulling power, a more powerful power transmission to cope with difficult situations without outside help and speed up deliveries.

It was in the wee small hours that the ingenuity and creativity of Finnish engineer Ilmari Louhio (1919-2015) evolved the idea of building hydraulic motors into the trailer’s wheels so that a hydraulic pump connected to the vehicle’s engine would transmit part of the engine’s output to the trailer’s wheels through pipes, valves and hoses. In other words, transfer drive and rotating power to where the load is, the wheels of the trailer.

“If that worked, it would have already been invented.”
Words of doubt expressed to Black Bruin innovator Ilmari Louhio