Strop Size Strop Size (breaking strength in tonnes) (breaking strength in tonnes) This table represents an approximate guide to the weight of vehicle (GVM in tonnes) that these strops will recover under various conditions. The figures have been calculated for wheeled vehicles 4 x 2 or 6 x 4 axle configurations. The estimates are based on a Factor of Safety of two- that is the load applied to the strop is half of its breaking strength. Level #2 incapacity (medium bogged) Level #3 incapacity (severely bogged) Gradient 1 in 10 Incline 6° Gradient 1 in 6 Incline 9.5° Gradient 1 in 5 Incline 11° Gradient 1 in 4 Incline 14° Gradient 1 in 3 Incline 18° 68 100 150 200 300 68 100 150 200 300 273 407 610 813 1220 173 258 386 515 772 144 215 322 429 644 118 178 264 351 527 92 138 206 275 412 140 200 300 400 600 Level #1 incapacity (slippery surface) 45 70 100 140 200 70 100 150 200 300 Recovering Bogged vehicles Level #1 - Slippery surface, vehicle unable to move under it own tractive capability because of wet, slippery surface conditions, but not sinking into the ground much. (Calcs from applied force = 25% GVM) Level #2 - medium Bogged - drive wheels have sunk into the ground about one third of the wheel diameter (Calcs from applied force = 50% of GVM) Level #3 - seriously bogged - drive wheels have lost all traction and the axle assembly is resting on the ground. (Calcs from applied force = 66% of GVM) Towing up inclined roadways or ramps SPECIALITY SLINGS- Recovery Strops SPECIALITY SLINGS- Recovery Strops This table displays the advised GVM for towing up ramps of different inclines with various strop sizes. The calculations are derived from a Safety Factor of two, where the load on the strop is half of its breaking strength. Additionally, a rolling resistance factor of 15% of the GVM is considered. 34
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