Abstract
<jats:p>Increasing labour productivity in mechanised logging is constrained by environmental damage from heavy machinery: specific ground pressure reaches 0.08–0.12 MPa, rut depth – 20–30 cm, root system damage to remaining trees – up to 60–70%. Reducing the negative impact is possible by using general-purpose tractors with mounted attachments. Based on the analysis of existing devices (LTN 50 skidding winches, ZT 140 M grapple grabs, UTU 2 “PAUK M”, HRZ and Uniforest grapples), it was found that the most effective is a mounted skidding trolley with a grapple operating in semi-suspended mode. The authors propose two patented design variants [24]. Key parameters: load capacity up to 5 t (bunch volume up to 6 solid m³), trolley weight 380 kg, clamping force of jaws at least 35 kN, hydraulic system working pressure 16–20 MPa, grab/release cycle time 5–8 s. Attachment to a tractor (e.g., MTZ-320) is via a category 2 three-point hitch (GOST 3480–76). During the working stroke, the trolley rolls on 6.50–10 pneumatic tyres, relieving the tractor’s rear axle by 35–40%, reducing traction resistance by 25–30% and specific ground pressure to 0.02–0.03 MPa (3–4 times lower than with choker skidding), and rut depth to 5–8 cm. During idle travel, the trolley is raised to a clearance of at least 400 mm, increasing tractor manoeuvrability (turning radius reduced by 20–25%) and reducing chassis wear. Traction calculation for the MTZ-320 tractor (power 26.48 kW, η=0.85) showed a tangential traction force of 16.55 kN, permissible bunch weight of 30.8 kN, bunch volume of 2.8–3.9 m³ depending on log length (4.5 m). Shift productivity at a skidding distance of 100 m and a log volume of 0.38 m³ is 97.7–104.8 m³/shift depending on the speed mode (idle speed 1.81–2.49 m/s, loaded speed 1.02–1.36 m/s). The developed 3D models and kinematic schemes confirm the trolley’s adaptation to terrain irregularities (angular movements up to ±15°) and high maintainability in field conditions.</jats:p>