The Americana; a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc., of the world . qualifications give a formthat allows the waves of replacement to flowin solidity to the propeller, and is the most ap-propriate for high speeds. Figs. I to 8 show a few of the 150 forms ofscrew propellers, designed at different periods,and illustrate in a general way its developmentfrom the primitive form designed by Ressel in1812. All of those used at the present tniie,however, are modifications of the Griffiths,Thornycroft, and Jarrow type
The Americana; a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc., of the world . qualifications give a formthat allows the waves of replacement to flowin solidity to the propeller, and is the most ap-propriate for high speeds. Figs. I to 8 show a few of the 150 forms ofscrew propellers, designed at different periods,and illustrate in a general way its developmentfrom the primitive form designed by Ressel in1812. All of those used at the present tniie,however, are modifications of the Griffiths,Thornycroft, and Jarrow types. They aremade of iron, steel, or bronze, and the bladesare cast solid with the boss, or made separateand bolted or attached to it in various screw propeller when in position is secured tothe end of the shaft of iron or steel called the pro-peller or tail shaft, which is connected to theline shafting attached to the crank shaft of thedriving engine. The push or thrust of the screw,which is equivalent to the resistance of thehull, and amounts to about 20,000 pounds per1,000 horse-power, is received on a thrust bear- — Thornycroft — 1885 power in this connection, the result ordinarilyreferred to is the apparent slip. The efficiency of dififerent forms of prnpol-iers (lifTers but slightly so long as their pitch,and their blade areas are designed correctly tosuit the conditions for which they are em-ployed. In general, the four-bladed propellersire the most efficient, and are freer from vi- Twin Propellers, V. S. S. New York. ing jirovided with a scries of collars and grooveswhich fit similar ones on the shaft. Small ves-sels, and those designed for slow speed, are usu-ally eipiipped with single screws; but for largehigh speed vessels, twin screws placed horizon-tally at right angles to the keel, one on eachside of the stern post, are the most vessels have been fitted with three screws. SCREW-WORM FLY —SCRIBNER but the amount of add
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Keywords: ., bo, bookcentury1900, bookdecade1900, bookidamericanaunivers14newy
