The winch capacity (number of cars tha can be moved) can be approximated by considering the following factors*:
A (Starting Resistance)
25 lbs./ton of cargo for operation in ambient temperatures above freezing and up to 35 lbs./ton for operation below freezing.
B (Curve Resistance)
0.8 lbs./ton of cargo per degree of curvature.
C (Grade Resistance)
20 lbs./ton of cargo per percent of grade.
D (Track Condition)
0 lbs./ton of cargo for track in excellent condition to 10 or more lbs./ton for track in poor condition.
E (Condition of Railcar)
0 lbs./ton of cargo for a well maintained car to 10 or more lbs./ton for cars in poor condition.
Pulling capacity required per ton of cargo
A + B + C + D + E
N (Number of cars that can be moved)
(A + B + C + D + E)(Cargo tonnage per car)
With the following conditions, how many 80-ton railcars can be moved?
A + B + C + D + E = 25 lbs./tons + 0.8 lbs./ton + 20 lbs./ton + 0 lbs./ton = 45.8 lbs./ton
N = 22,000/(45.8)(80) = 6 railcars
If B, C, D and E are all 0, eleven 80-ton railcars can be moved.
*Factors are based on the average requirements given in the A.R.E.A Manual for Railway Engineering and on railcar pull tests conducted by NABRICO. These factors are only guidelines.