A history of the growth of the steam-engine . Fio. 140.—Tug-boat Screw. Fig. 141.—Hiraeh Screw. diameter. The diameter of the screw is made as great as possible, since the slip decreases with the increase of the area of screw-disk. Its length is usually about one-sixth of the diameter. A greater length produces loss by increase of surface causing too great friction, while a shorter screw does not fully utUize the resisting power of the cylinder of water within which it works, and increased slip causes waste of power. An empirical value for the probable slip in vessels of good shape, which is c
A history of the growth of the steam-engine . Fio. 140.—Tug-boat Screw. Fig. 141.—Hiraeh Screw. diameter. The diameter of the screw is made as great as possible, since the slip decreases with the increase of the area of screw-disk. Its length is usually about one-sixth of the diameter. A greater length produces loss by increase of surface causing too great friction, while a shorter screw does not fully utUize the resisting power of the cylinder of water within which it works, and increased slip causes waste of power. An empirical value for the probable slip in vessels of good shape, which is closely approximate usu- Mally, is yS = 4-j-, in which S is the slip per cent., and Jlfand A are the areas of the midship section and of the screw-disk in square feet. 402 THE STEAM-ENGINE OF TO-DAY. The most effective screws have slightly greater pitch atthe periphery than at the hub, and an increasing pitch fromthe forward to the rear part of the screw. The lattermethod of increasing pitch is more generally adopted thrust of t
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Keywords: ., bookcentury1800, bookdecade1870, bookidc, booksubjectsteamengines
