Abstract
Vehicle mobility tests were conducted on a crawler skidder and a feller-buncher on courses of gravel soil, sandy loam soil, and sandy loam soil with muddy conditions. We measured the relationship between the tractive effort and slippage, and obtained the experimental equations. As the result, the vehicles performed at the maximum tractive coefficient of 0.6-0.9 at 0.2 slippage. However, in muddy conditions, it lowered to 0.2-0.4. We believe the tests in muddy conditions are important in order estimate the performance of forest vehicles. The function of tilting the cabin worked effectively to improve the tractive performance. Slope ascending ability was estimated by the experimental equations. We also applied the WES method to evaluate the vehicle mobility, which indicated a possibility as a simplified testing method for forest vehicles by estimating the vehicles' mobility by calculating the surplus vehicle cone index.
