Scientific American Supplement, No. 384, May 12, 1883

Excerpt

LOCOMOTIVE FOR ST. GOTHARD RAILWAY.

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....