OSCILLATING ENGINES.

\

i

227

Et.

In.

'Width of Shell at Delivery Side

. 1

3

Diameter of Steam Cylinders .

. 0

8

Length of Stroke of Piston

. 0

8

Width of Supply Port

. 0

0,1

Width of Exhaust Port .

. 0

1*

Length of Ports . . . ' .

. 0

4

Length of Stroke of Slide Valve

. 0

2h

Diameter of Piston Eod .

. 0

li

Diameter of Slide Valve Eod .

. 0

Of

Length of Connecting Eod

. 1

4

Diameter of Block Pin

. 0

H

Thickness of metal of Shell of Pump

. 0

0|

Ditto ditto of Steam Cylinders

. 0

o.v

STEAM CYLINDER PISTON ROD MOTION, ANDCONNECTIONS.

The details in connection with the piston rod,although similar in principle to those for theair pump, are entirely different in their ap-plication, and therefore in proportion. Thecause for this is that with the air pump thepiston connecting rod is the prime mover,whereas with the cylinder the piston impartsthe motion.

On further entering into this question, it willhe remembered that the steam is the main agent,and has to overcome the load on the pump. Itwill he apparent therefore from these facts,that the steam has to be considered whendetermining the proportions of the detail underNotice, as far as the direct line of strain isconcerned, but of course the lateral resistancetoast not be overlooked. The strain on thepiston rod will be the greatest when the cylin-der is at its utmost angle, but if the latter iscorrectly balanced, the lateral strain will belessened and friction also reduced : and it ispartially to sustain the rod from deflectioncr bending, that the deep bushes are generallytoserted in the lower portions of the stuffingboxes. It will be remembered in the propor-

tions of the rods in relation to Figs. 39 and 40—pages 194 and 195—that the former is 9inches in diameter, and the latter 7| inches,the diameters of the cylinders being respectively64 inches and 61 inches. Very simple cal-culation only is requisite to prove the differ-ence in the relative proportions of the rods tothe areas of the cylinders, this being dulyrecognised by the difference in the depths ofthe bottom bushes.

Fig. 57.

CYLINDER PISTON ROD HEAD.

The design of the head of _ the rod that ismost universal, is as that shown aboveby Fig. 57, in half sectional and completeelevations. The cap is flat, and the brasses ofsimilar design, where in contact, for stability.The lower portion of the head is a T socket,into which the rod is secured by a key. In theend view it will be noticed the diameter of thesocket and width of the cap are unequal: this,however, is not a general proportion, it beingpreferred by some makers to retain equaldimensions, and introduce a circular flange tothebrasses to prevent lateral disturbance. Thislatter mode is the design of the head in com-mon with the cylinder illustrated by Fig. 39—page 194—and the following are thedimen-

2 k 2