Trailer Overturning during Wood Transportation: an Experimental Investigation of Effects of Trailer Joint Point and Frame Structure

Trailers may increase the risk of tractor overturn during wood transportation in dangerous conditions. In this work, tests were carried to simulate a trailer rollover using three two wheel tractors and a crawler tractor and three trailers (two single-axle and one two-axle), all of their combinations moving downhill along the path on a short dirt road. The trailers were always loaded with the same load of logs cut at a length of about 1.5 m and put transversely to the longitudinal axis of the trailer. During each test, the following parameters were measured: the lateral dragging of the rear wheels/crawler of the tractor, the ground detachment of the rear upstream wheel/crawler and both the longitudinal and transversal strains (released over the tractor hooking system) produced by the trailer overturn. The study highlighted that the biaxle trailer structure with a turntable steering had the best performances compared to the single-axle in terms of safety during trailer overturning. Independently of the trailer type considered in this work, a tied load is more dangerous than a load restrained only by steel struts, because during the overturn the load forms a single unit with the trailer mass, which increases the transversal and longitudinal strain.