Mechanical Drawing Self-Taught Part 18

[Ill.u.s.tration: Fig. 328--100 H.P. HORIZONTAL STEAM-ENGINE--CROSS HEAD.

(Page 301.)]

[Ill.u.s.tration: Fig. 329.

Fig. 329 _a_. Working Drawings of 100 H.P. Steam Engine--Eccentric and Eccentric Strap--Scale: 3" = 1 Foot. (Page 301.)]

[Ill.u.s.tration: Fig. 330--100 H.P. HORIZONTAL STEAM-ENGINE--CONNECTING ROD. (Page 303.)]

A view of the steam-chest side of the cylinder is given in Figure 323, and a horizontal cross section of the cylinder, the steam-chest and the valves, is shown in Figure 324. The main valves are connected by a right and left hand screw, to enable their adjustment, as are also the cut-off valves.

Figures 325 and 326 show the cam wrist plate and the cut-off mechanism.

The cam wrist plate, which is of course vibrated by the eccentric rod, has an inclined groove, whose walls are protected from wear by steel shoes. In this groove is a steel roller upon a pin attached to the bell crank operating the main valve stem. The operation of the groove is to accelerate the motion imparted from the eccentric to the valve at one part of the latter's travel, and r.e.t.a.r.d it at another, the accelerated portion being during the opening of the port for steam admission, and during its closure for cutting off, which enables the employment of a smaller steam-port than would otherwise be the case.

The shaft for the cam plate is carried in a bearing at one end, and fits in a socket at the other, the socket and bearing being upon a base plate that is bolted to the bed-plate of the engine; a side view of the construction being shown in Figure 327.

Figure 328 represents the cross-head, whose wrist pin is let into the cross-head cheeks, so that it may be removed to be turned up true. The clip is to prevent the piston rod nut from loosening back of itself.

Figure 329 represents a side view; and Figure 329 _a_ a section through the centre of the eccentric and strap.

[Ill.u.s.tration: Fig. 327--WORKING DRAWING OF 100 H.P.

STEAM-ENGINE.--WRIST PLATE.--3" = 1 FOOT.]

The eccentric is let into the strap and is provided with an eye to receive a circular nut by means of which the length of the eccentric rod may be adjusted, a hexagon nut being upon the other or outer end of the eye.

Figure 330 shows the construction of the connecting rod, the bra.s.ses of which are adjustable to take up the wear and to maintain them to correct length, notwithstanding the wear, by means of a key on each side of each pair of bra.s.ses, the keys being set up by nuts and secured by check nuts.