Improved Stability and Handling of Truck Combinations with the Double Drawbar Dolly

The double drawbar dolly eliminates articulation of the conventional single drawbar converter dolly to improve the stability of multiple trailer truck combinations. It is usually provided with a self-steering axle to improve maneuverability.

This paper describes double drawbar dolly types, factors in their design, and findings from tests of a specific dolly and computer simulation results pertaining to a range of dolly concepts. Performance topics investigated include low and high speed offtracking, stability characteristics and loads at the dolly hitch.

The results showed vehicle performance is highly dependent upon friction and stiffness in the dolly self-steering system. Both test and simulation showed that compared with the single drawbar dolly, a double drawbar dolly having properties equivalent to that tested would significantly improve vehicle stability. If steer stiffness is diminished to the free castering condition, stability becomes poorer than with the conventional single drawbar dolly. The double drawbar dolly can impose high longitudinal and vertical loads on the pintle hooks. Therefore, the latch mechanism must be capable of resisting these large upward loads.