A NEW STEAMSHIP PROPELLER.
& number of scientific gontlemen connected with the Royal Navy and Mercantile Marino attended at Qravesand oa August 16 for the purpose of taVin? a trial trip on board the steam yacht - Jolair, with tho object of testing the advantages of a newly-invented propeller, called "De Bay's Patent Direct Acting Propeller." with which it has been fitted. The. JoMr, which, w&b built by Scott aad Co., of Greenwich, in 1870, is in length 81ft Gin, breadth 12ft, and depth Bft 2in; she has two engines of 20-horso power nominal, and registers 40 tons. .Her original screw had a diameter of Gf 1 2in, with a 6f b 4in piton, whilst her now "Da Day " propeller has but a diameter of 4ft Sin, and a pitch of 7ft 6in. Its construction is of a very peculiar character, and consists of two screws of the same pitch, one, the largor, with four, and the other with fire blades; portions of tho blades of each are ont out. The screws are fixed on two shafts, one tabular, the other solid and rotating within it, eaoh screw being made to ravolva in opposite directions, the solid portions of ench blade of one screw parsing 1 through the trap3 cut ont in the other, and viee'versd. The effeot of this « to drive the eroateat weight of wntor astorn in a line with tho keel of the snip, thus obviating the wngto of power whioh is the coxscqnoncc of the effects of the ordinary screw. The influence of ono screw tending to deflect the water moviui? aatern to the right, is counteracted by tho other scrow, which tends to send it to tha left. Tho resnlt is that the water can only bo drivon direct astern by the eaiew?, and mores verr steadily in a right lino parallel with tho keel, tuna concentrating all tho force of the water on tho stem of the vessel. Tho .number of revolutions in&dopur niiim'o with tho new propeller wa* 133, the stoam pressura being 77, and tho 'vacuum 18$ In timo the mila was run with tide by tho old propel lor in Cinins 53sccs, while the time occupied by tho new propeller was smlns SOsecs; against tide, old propeller, Omins «s7fecs ; bqw propeller, (tains 82mcs, In important
feature WolKieoted with the test was to fhow that eTon fa ttke smallest riven and canals there was no aid* Wish to destroy banks.
A NEW STEAMSHIP PROPELLER.
Star (Christchurch), Issue 3596, 20 October 1879, Page 2
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