The main objective of this study is to reduce the aerodynamic drag of tractor-trailer combinations used in the forest industry. In most cases, logging trucks on their return trips are usually travelling in unloaded conditions with upright stakes, which add drag. CFD and wind tunnel testing suggested a drag reduction of up to 35% with no upright stakes, which corresponds to 17% in fuel savings in unloaded conditions. One of the proposed fuel reduction concepts was therefore to have foldable stakes so that the stakes could fold down into a horizontal position while travelling in unloaded conditions.
Fuel savings of 15% for a vehicle with stakes in the horizontal position were confirmed with track testing when compared to the fuel consumption of a vehicle with stakes in the vertical position. The coastdown test indicated 28% reduction in drag. The difference in drag reduction between the coastdown test and initial simulation was due to stake size and profile. The simulation was therefore conducted again with the stakes' profile similar to the one used in the track test and the same drag reduction of 28% was obtained.
The foldable stakes concept can cut annual fuel consumption by 3000 to 4000 liters, with GHG emissions reduction of up to 8 tonnes per vehicle. Trailer manufacturers should look into the possibility of incorporating foldable stakes into hayrack semi-trailer configurations in order to maximize potential fuel savings, with safety taken into account in the design process, for vehicles operating under certain conditions.
