Rule for Finding Pressure or Strain on Bolts.
The absolute stress or strain on a flat surface of a steam boiler, which is carried by the stays, can be easily determined by a simple rule:
Choose 3 stays as A B C in [Fig. 46], measure from A to B in inches, and from A to C. Multiply these two numbers together and the result is the number of square inches of surface depending upon one bolt for supporting strength.
Example.
Suppose the stays measure from center to center 5 inches each way with steam at 80 lbs., then
5 × 5 = 25 × 80 = 2,000 lbs. borne by 1 stay.