The Locomotive - Lighthouse Survival Blog

114 THE LOCOMOTIVE. [August,
shear and bend, such as is suggested by the form of Fig. 5, which is sketched from a
pin which failed in this way, and which is now in the museum at the Home Office of
the Hartford Steam Boiler Inspection and Insurance Company.
We will consider these different modes of failure separately, beginning with the
simple shear of the pin, as this is the simplest to describe, and is, moreover, the way in
which the pin may be expected to fail, if everything is properly proportioned and well
made.
The pin in Fig. 1 cannot fail by shearing unless it gives way simultaneously at the
Fig. 2.
—
Side View op the Lug Shown in Fig. 1.
A
± .
two sections that lie on either side of the lug, and between the lug and the jaws of the
brace. (These sections are indicated in Fig. 1 by the letters a and I.) Now if the pin
and the brace be made of practically the same material, we might safely take the shear-
ing strength of the material of the pin to be equal to 85 per cent, of the tensile
strength of the material of the body of the brace, if the pin were to shear at only one
of the sections a and b. In other words, if the pin could fail by shearing at only one of
the sections ab, we should have to give it a sectional area 1.18 times as great as the sec-
tional area of the body of the brace. But, as we have already said, it cannot fail in this