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the wick at each revolution of the crank pin,and thus the use of the oil is regulatedaccordingly.
When the bearings become heated, whichUnfortunately they often do, oil and talloware useless as a lubricant, as the intensetemperature of the surfaces and surroundingUietal destroy the natural effect of the samevdien cool. It is obvious, then, that somerecourse must be introduced when requisite,and the best yet known is the sea water flow-ing as a stream or spray over the bearingsrequiring it. As the adoption of the water isan independent means, separate lubricatorsa re essential, with pipes leading from the“ Kingston valve ” or the ship side. Toregulate the admission of the water, plugcocks are often used; and in some instancesValves with handles, to open and close them,extended to the platform, are adopted. An
Fig. 174.
WATER LUBRICATORS AND VALVES.
example of the latter kind is shown by*§• 174, being an arrangement for the main
shaft bearing and crank pin. The tube com-municating with the shaft’s bearing is sup-ported on the main frame, and the spray cup,shown in two sections, is located directly overthe centre of the crank pin. The tubing con-nects the lubricators. The branch pipe andcock at the side of the vertical tube can bearranged for the main supply, or as an ex-tension to the guide block and channel, andother surfaces liable to heating.
Some firms prefer the oil cups to be castwith, or secured on, the metal above the bearings.The wick is passed through tubes above thelevel of the oil, and extends to the bearing,the continuous flow of the oil being insured bythe contact of the wick and the bearing inmotion.
MAIN FRAMES.
The side elevation of an engine owes muchof its appearance to the design of the mainframe, and doubtless from this cause makers ofside lever engines displayed such extravagantnotions in days past. In the present periodmuch of the architecture has dwindled intostraight lines, and no attempt is now made toimitate any of the orders once held supremeeven with marine engines.
The main frame supports the crank shaft,and resists the strain imposed by the motion ofthe piston rod; and the aim of the designershould be to produce the most simple butcorrect form to perform these requisitions.As cast iron can be shaped in almost anyconceivable form, it is natural that the detailsin question are mostly made of that material,and an example of the same is shown by
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