Hybrid self-propelled carriage: fuel consumption and efficiency study via field data and simulation

Hybridization and electrification are rapidly advancing in off-road industrial equipment, including cable logging machinery. Electrified slack-pulling carriages have already become mainstream, while electrified dropline carriages, self-propelled carriages, and tower yarders are more recent developments. This work evaluates the fuel consumption and operational efficiency of a hybrid self–propelled carriage, and compares its performance with conventional diesel-hydraulic self-propelled carriages and tower yarders. The underlying hypothesis is that a hybrid system can achieve superior performance—particularly in terms of energy efficiency—compared with conventional solutions, due to its ability to recover braking energy and optimize power delivery. To test this, both extensive field measurements and complementary simulations were conducted using the HULK hybrid self-propelled carriage (HULK), developed by Leitalpin Ltd. As a result, consumption maps were generated for different line spans (300 m and 800 m), line slopes (0–100%, for downhill and uphill extraction), payloads (from 500 kg to 3000 kg), and fully and partially suspended loads. As compared to theconventional diesel-hydraulic self-propelled carriages and tower yarders, the hybrid system resulted in a minimum fuel savings of 39.9%, as well as the potential in downhill transportation for energy autarkic operation (100% fuel savings) when the fully suspended payload reaches at least 1400 kg and the skyline slope is 20% or steeper. Furthermore, the analysis reveals that a substantial share of the hybrid drivetrain energy losses originate from the mechanical transmission components (reduction gearing), particularly during regeneration. This work confirms and validates the initial hypothesis, demonstrating that hybrid technology offers substantial advantages in terms of energy performance.