Page:Shop management.djvu/166

necessary delay, are recorded and the percentages of rest are calculated.

Formulæ are convenient for combining the elements. For simplicity, in the example of barrow excavation, each of the unit times may be designated by the same letters used on the note sheet (Fig. 2) although in practise each element can best be designated by the initial letters of the words describing it.

Let

a = time filling a barrow with any material.
b = time preparing to wheel.
c = time wheehng full barrow 100 feet.
d = time dumping and turning.
e = time returning 100 feet with empty barrow.
f = time dropping barrow and starting to shovel.
p = time loosening one cubic yard with the pick.
P = percentage of a day required to rest and necessary delays.
L = load of a barrow in cubic feet.

B = time per cubic yard picking, loading, and wheeling any given kind of earth to any given distance when the wheeler loads his own barrow.

Then

B=(p+[a+b+d+f+distance hauled100(c+e)] 27L)(1+P) ... (1)

This general formula for barrow work can be simplified by choosing average values for the constants, and substituting numerals for the letters