Dolly with hinged drawbar

Sammanfattning: Volvo trucks are involved in a project with vehicle combinations longer than 25.25 meters and/or with a weight of more than 64 tons. Those combinations are called high capacity transport (HCT). Some of the vehicle combinations are now driven with exemptions for the coupling equipment. The exemption is needed because according to a standard the theoretical transmitted forces between the dolly and the truck exceed the value that the coupling components have been certified for. The theoretical transmitted forces are called performance indexes. This limits the development but the exception could be avoided by using a hinged drawbar on the dolly.  This thesis aims to investigate what needs to be done in order to introduce dolly with hinged drawbar in longer and heavier vehicle combinations. A literature study and interviews were conducted to find problems that could be expected when using hinged drawbar on dolly and to investigate how the performance indexes for a specific vehicle combination should be calculated. Thereafter a dolly was put together through a product development process. Then concepts to solve a problem that was noticed through the literature study were developed. The concepts were sketched, evaluated in a matrix and thereafter the winning concept was modelled in detail in computer aided design (CAD).   According to the traffic definition in Sweden a dolly with hinged drawbar is violating the law. It defines a dolly as a module with rigid drawbar. On the other hand, the European Union defining a dolly as a trailer with fifth- wheel made to convert a semi-trailer into a full trailer. They don’t mention anything that contradicts to the usage of hinged drawbar. So the Swedish definition of a dolly needs to be challenged.   Simulations have shown that the braking performance will be worse when using a dolly with hinged drawbar compared to using a dolly with rigid drawbar. Therefore concepts to improve the braking performance of the dolly have been developed. The concept was to look the fifthwheel from pivoting around a horizontal axle perpendicular to the driving direction. By doing so the dolly and semi-trailer will become more like a full trailer and that would better the braking performance.  Through interviews and literature study it was noticed that the high performance indexes were calculated in an incorrect way. The highest forces are generated through interaction forces which are only affected by the vehicles closest to the coupling components. Therefore a calculation model need to be modified for this. Three calculation models were tested on the vehicle-combination. Two of these generated performance indexes that were reasonable. The calculation models were ISO-combination 3 and a model developed by Sweatman (1980). These two calculation models are modified for vehicle combinations that includes three vehicles.