We give engravings of one of a type of eight-coupled locomotives
constructed for service on the St. Gothard Railway by Herr T.A. Maffei,
of Munich. As will be seen from our illustrations, the engine has
outside cylinders, these being 20.48 in. in diameter, with 24 in.
stroke, and as the diameter of the coupled wheels is 3 ft. 10 in.,
the tractive force which the engine is capable of exerting amounts to
(20.48² x 24) / 46 = 218.4 lb. for each pound of effective pressure per
square inch on the pistons. This is an enormous tractive force, as it
would require but a mean effective pressure of 102½ lb. per square inch
on the pistons to exert a pull of 10 tons. Inasmuch, however, as the
engine weighs 44 tons empty and 51 tons in working order, and as all
this weight is available for adhesion, this great cylinder power can be
utilized. The cylinders are 6 ft. 10 in. apart from center to center,
and they are well secured to the frames, as shown in Fig. 4. The frames
are deep and heavy, being 1 3/8 in. thick, and they are stayed by a
substantial box framing at the smokebox end, by a cast-iron footplate at
the rear end, and by the intermediate plate stays shown. The axle box
guides are all fitted with adjusting wedges. The axle bearings are all
alike, all being 7.87 in. in diameter by 9.45 in. long. The axles are
spaced at equal distances of 4 ft. 3.1 in. apart, the total wheel base
being thus 12 ft. 9.3 in. In the case of the 1st, 2d, and 3d axles, the
springs are arranged above the axle boxes in the ordinary way, those of
the 2d and 3d axles being coupled by compensating beams. In the case of
the trailing axle, however, a special arrangement is adopted. Thus, as
will be seen on reference to the longitudinal section and plan (Figs. 1
and 2, first page), each trailing axle box receives its load through the
horizontal arm of a strong bell-crank lever, the vertical arm of which
extends downward and has its lower end coupled to the adjoining end of a
strong transverse spring which is pivoted to a pair of transverse stays
extending from frame to frame below the ash pan. This arrangement
enables the spring for the trailing axle to be kept clear of the
firebox, thus allowing the latter to extend the full width between the
frames. The trailing wheels are fitted with a brake as shown.
[Illustration: LOCOMOTIVES FOR ST. GOTHARD RAILWAY.]
The valve motion is of the Gooch or stationary link type, the radius
rods being cranked to clear the leading axle, while the eccentric rods
are bent to clear the second axle. The piston rods are extended through
the front cylinder covers and are enlarged where they enter the
crossheads, the glands at the rear ends of cylinders being made in
halves. The arrangement of the motion generally will be clearly
understood on reference to Figs. 1 and 2 without further explanation.
The boiler, which is constructed for a working pressure of 147 lb. per
square inch, is unusually large, the barrel being 60.4 in. in diameter
inside the outside rings; it is composed of plates 0.65 in. thick. The
firebox spreads considerably in width toward the top, as shown in the
section, Fig. 5, and to enable it to be got in the back plate of the
firebox casing is flanged outward, instead of inward as usual, so as to
enable it to be riveted up after the firebox is in place. The inside
firebox is of copper and its crown is stayed directly to the crown
of the casing by vertical stays, as shown, strong transverse stays
extending across the boiler just above the firebox crown to resist the
spreading action caused by the arrangement of the crown stays. The
firegrate is 6 ft. 11.6 in. long by 3 ft. 4 in. wide.
[Illustration: ST. GOTHARD LOCOMOTIVES.]
The barrel contains 225 tubes 1.97 in. in diameter outside and 13 ft. 9½
in. long between tube plates. On the top of the barrel is a large dome
containing the regulator, as shown in Fig. 1, from which view the
arrangement of the gusset stays for the back plate of firebox casing and
for the smokebox tube plate will be seen. A grid is placed across the
smokebox just above the tubes, and provision is made, as shown in Figs.
1 and 4, for closing the top of the exhaust nozzle, and opening a
communication between the exhaust pipes and the external air when the
engine is run reversed. The chimney is 15¾ in. in diameter at its lower
end and 18.9 in. at the top. The chief proportions of the boiler are as
follows: