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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[May, 



CAPTAIN CARPENTER'S PATENT QUARTER PROPELLERS. 



In the Journal for February last, page 5G, we gave an abstract of 

 the above patent, we are now enabled through the kindness of the 

 Editor of the Mechanics' Magazine, to give the annexed engravings, 

 which better explain the action of the Propellers, together with an 

 account of some experiments communicated by Captain Carpenter. 



to 

 'A 





" The first experiments (on any thing like a large scale) were on 

 board the jlirnlite, a vessel (J9 feet long, and 9 feet beam. They were 

 intended only to ascertain how far the apparatus was adapted to sail- 

 ing vessels, for the purpose of moving them about in calms, or as an 

 auxiliary to the wind and sails. The powerful effect produced by the 

 rotation of these 'quarter propellers,' even by manual power, was 

 enough to establish the fact, that any vessel, however large, may be 

 moved in an opposite direction to that line in which the force is ap- 

 plied, quicker or slower, according to the extent of the motive power. 

 "The next experiments were made with a model of a steam-boat, 

 which is now exhibited at the Polytechnic Institution. This model is 

 sup|)lied with the means of applying a great variation of power to the 

 propellers, and it admits also of great variation in the shape of 

 them, by which means I have had an opportunity of judging upon 

 the merits of screws, sections of screws, and planes ; and of testing 

 the angle of incidence, the shape of the vane or blade, and the relative 

 proportions they should bear one to the other, according to the power 

 applied. Although a screw is decidedly a powerful instrument in the 

 water, I must nevertheless give the preference to the plane and to the 

 figure shown in the accompanying drawing, because it produces the 

 greatest speed with the least sacrifice of power, more especially when 

 the vanes are set at the angle of 30^ or 35° to the axis of the shaft. 

 And here I would remark, and hope without presumption, that if any 

 merit may be attached to this part of my invention, it consists in the 

 discovery by careful experiment, that a plane having the proportions 

 of my propeller, as represented in the drawing, will, when set at the 

 above angles, and revolving in the water, impel a vessel by means of 

 a locomotive power, and the resistance ofl'erod by the fluid, with a 

 greater effect than any other instrument yet adopted in navigation, 

 which may be proved by mathematical demonstration. 



" The next experiment was made in a boat 21 feet long, and 4 feet 

 8 inches wide. It is necessary here to remark, that only one pro- 

 peller was used, and that was placed in the stern. The object of 

 which was, to test the shape of the triangular propeller against the 

 screw, and other propellers with the same power, the same position, 

 and the same machinery ; but it is so difficult to make everything bear 

 in an equal proportion, that I doubt whether the experiments can be 

 considered conclusive. I do not apprehend there would be so great a 

 diiferei:ce as 3 to 6 between Mr. Rennie's propeller, Mr. Smith's screw, 

 and my triangular propeller, as stated in your journal, if the experi- 

 ments could be made equal in every respect, but that is impossible. 

 Mr. Rennie's experiments, I believe, were made in a heavier boat than 

 the one I used ; and although there may not be much difference in the 

 area of the midship section, still as there might have been a difference 

 in the strength of the men and other circumstances, I do not think a 

 comparison could be established ; I therefore only presume to give 

 you for data this fact, that with the very same propeller as I now send 

 you, the boat was propelled with two men turning the winch, SS mea- 

 sured yards in 33 seconds, and sometimes in timing it, it appeared to 

 be 30 seconds — the propeller making 119-5 revolutions in that time." 

 "A screw propeller placed in the dead-wood of the ./^rcAimerfts 

 Yacht, has, it would appear from the public papers, fully established 

 equality of speed with the common paddle-wheel. This propeller 

 differs \nform and position from the 'quarter' propellers to which this 

 paper immediately appertains, but the principle is the same; and on 

 the ocean it establishes that main that principal fact, which the small 

 model in the Polytechnic Institution under all its disadvantages also 

 fully bears out — 'equality of speed,' even in these early and imperfect 

 essays. In the 'quarter' propellers applied to this model will be found, 

 a more direct and faithful adherence to nature's prototype, and in their 

 rapid rotatory action in the water, under the most favourable angle of 

 incidence the blades display, the combined powers of wedge and screw. 

 No back-water ruffles their silent course. A gentle undulatory ripple 

 marks the tract described by each propeller, similar almost to that 

 which follows the action of the tail of a fish when swimming rapidly 

 near the water's surface. The same obedience to the helm with equal 

 facility of backing astern may also be observed, and in ease of accident 

 to the rudder, the power of steering is practicable by their alternate 

 and combined actions." 



EttstcrJi CoutilU's Railivay. — On Wednesday the "ih ullimo, the first stone 

 of the New Bridge over llie river C'helmer, in tlie parish of Sjiringfield, about 

 to be erected to connect the embankment of the tiastern Counties line, which 

 has been some time in the course of lormation, and wliich is now traversed 

 by means of a wooden viiducl. was laid by Mrs. Braithwaite, the lady of 

 John Braithwaite, Ksq , the engineer-in-cliief to the comiany. The design 

 for the bridge is distinguished by that neatness which characterizes those 

 already erected upon the line, and w ill consist of three arches, each of 45 feel 

 span. It will be 43 feet in height from the surface of the water to the coping. 

 — Kc7it and Essex Mi'rcury. 



