Calvo Angela, PhD.

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.