Hermes outlet

all exactly the same diameter, uniting them to one another with flush butt-joints. This plan is now carried out upon the Hermes bagsMidland Railway, as shown in Figs. 2153 to 2155, and exaggerated in thickness in Fig. 2156. The meeting ends 2153.
of each ring are turned in a lathe, and P^l
united by covering strips O 0, formed of J |
welded flush rings, shrunk on over the joints and double-riveted. Strengthening hoops P P are also shrunk on the centre of each of the plates, crossing the longitudinal welded joints, and are secured by a few rivets. These hoops and covering strips for the joints are carefully blocked before being shrunk on, aHermes Handbagsnd the whole of the rivet-holes are drilled after the hoops are in their places.
These boilers are consequently truly cylindrical at all parts, and no strain to which they are subjected has any tendency to change their circular form. ThHermes Birkin e effect of the longitudinal strain upon the transverse circular joints, as in Fig. 2157, is found to be altogether inappreciable in practice, because the covering rings 00 could not yield to it without contracting
in circumference in the form of a double 2155.
cone, Fig. 2157; and on this account, to- ^^m^^gK&m*m'^m^m^^B^^^mm^''^WUKB'm gether with their greater thickness, they ■ p"
offer a greatly increased resistance as compared with simple lap-joints. All possible effect of the longitudinal strain might indeed be entirely got rid of, if desired, by the further addition
nf inside covering strips at the bHermes outletutt-joints, as shown in Figs. 2158, 2159. At present the circular plates of these welded boilers are in two semicircular segments for theBirkin circumference of the boiler, and therefore require two welds; but Kirtley thinks the barrel of the boiler would be improved if each length were made of one plate only, whereby only one longitudinal weld would be necessary.
A remarkable corroboration of the correctness of this mode of construction is given by the samples, No. 658 engine, the boiler of which was conHermesstructed with butt-joints all flush throughout, the transverse joints being covered by external hoops and the longitudinal joints by internal strips. This boiler has been at work nearly nineteen years, having been started in 1847Hermes Kelly; but the engine being of smaller size than those now used with trains, has only been employed as a spare engine