Material Handling Equipment - Industrial and Systems Engineering

MATERIAL HANDLING EQUIPMENTwhereG = empty truck weight (lbs)B = front-axle to truck-load-center distance (in.)F = front-axle to fork-face distance (in.)L = actual load center, distance from fork face to load center of gravity (in.)= ULD if constant-density rectangular-shaped load2ULD = unit load depthL 0 = 24 in. = rated load centerM = load moment (in·lbs)W 0 = rated load capacity (lbs).Although it might seem preferable, in light of (0.1), to specify a truck’s load moment (M), its W 0is specified instead because it is easier to relate to the truck’s maximum allowable load weight.Two different adjustments can be made with respect to the load capacity of the truck:• Derating — (W < W 0 ) determining the maximum permissible load weight given that theload’s center of gravity, L, exceeds the rated load center, L 0 = 24 in.• Rerating — (new W 0 and L = L 0 ) modifying the truck’s rated load capacity due to changesto the truck; e.g., adding extra counterbalance weight, a fork attachment, or an extendedmast.Derating Example: Assuming a constant density rectangular-shaped load, ULD = 60, F = 12, andW 0 = 3,000 lbs, the derated load capacity is reduced to( + ) ( + )W0 F L0 3,000 12 24 108,000W = = = = 2,571 lbs.F + L6012 +422Rerating Example 1: Assuming F = 12 and W 0 = 3,000 lbs, if a 500 lb. counterbalance weight isattached to the back of the truck at a distance of 72 in. from the front axle, then the new ratedload capacity of the truck is( + )M +∆ M W0 F L0+∆M108,000 + 500⋅72 144,000W0′ = = = = = 4,000 lbs.F + L F + L12 + 24 360 0Rerating Example 2: The rated load capacity of a lift truck is 2,500 lbs and the distance from thefront axle to the fork face is 12 in. The forks of the truck are to be replaced with carton clamps.The clamps and forks weigh 225 and 100 lbs, respectively, with a center of gravity relative to thefront axle of 30 and 42 in., respectively. The truck’s actual rated load capacity assuming thedistance from the front axle to the clamp face is 15 in. is50