The Locomotive - Lighthouse Survival Blog

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PUBLISHED BY THE HARTFORD STEAM BOILER INSPECTION AND INSURANCE COMPANY.
Vol. XXII. HARTFORD, CONN., AUGUST, 1901. ZbutXo. 3.
On the Strength of Brace Pins.
An esteemed correspondent has sent us a sketch of the brace fastening shown in
Figs. 1 and 2, all the dimensions being marked upon it, except the diameter of the pin;
and he has requested us to calculate the size of the pin, in order that the pin may be
equally as strong as the body of the brace. It is stated that both pin and brace are to
be of open hearth steel, and it is requested that failure by both shearing and bending
Fig. 1. — Illustrating the Jaws, Lug, and Pin.
be considered. We have thought that this problem might be of sufficient interest to be
discussed in The Locomotive.
The way in which a brace pin gives out will depend upon the proportions of the
pin, and of the parts which it unites. If the ear (or lug) that is attached to the boiler
head is narrow, and the brace jaws are wide, so that there is considerable space between
the two (as is indicated in Figs. 3 and 4), the pin may fail by bending; but if the lug
and the jaws come close together, as in Fig. 1, failure can hardly take place by bend-
ing, but is usually due to the direct shear of the material of the pin. When the struc-
ture is so proportioned that the space between the lug and the jaws is intermediate
between the limits here roughly suggested, failure may occur by a sort of compound