178. Using a diesel engine indicator P-V diagram, the cylinder mean effective pressure is calculated to be 21.3 kg/cm². What is the scale of the spring used on the indicator if the diagram area is 18.46 cm² with a length of 13 cm?

The spring scale is calculated using the formula p_m = (A/L) * S, where p_m is the mean effective pressure, A is the diagram area, L is the diagram length, and S is the spring scale. Substituting the given values (p_m = 21.3 kg/cm², A = 18.46 cm², L = 13 cm) yields a spring scale of 15.0 kg/cm.