MARINE ENGINES.

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power the eccentric is fitted with a brass hoop, bolted together, fortaking the eccentric rod, and large engines have the hoop forged

Fig. 251.—Eccentric and Hoop.a, Eccentric. b, Hoop for do. c, Catch, d, Balance.

on the eccentric rod, and lined with brass pieces at intervals. Thesiphon cup for lubricating the sheave is either cast on the brasshoop, or is separate, as when the hoopand rod are forged all in one piece.

Catch on shaft .—To determine thePosition of the catch on the shaft to suitthe forward and backward movements;the position of the eccentric centre forthe forward movement being directlyopposite to that for the backward move-ment Draw A B, the line of crank, anddescribe the circle in dotted lines equalto the throw of the eccentric; then findthe versed sine of the chord of arc ofsupply, and the point E can be fixed,

... Fig. 252.—Catch for Eccentric on Shaft.

that being the centre of the eccentric

for the forward movement; from the point E draw a line perpendi-cular to A B, and produce it until it cut the eccentric path on theopposite side, that is the point or centre of the eccentric for the

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