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The latter is, in this form of turbine, made in the shape of a paddle-wheel of very small circumference but considerable length, the paddles being set at such an inclination as to obtain the greatest possible rotative impulse from the outward-rushing steam.
Soon after which, John Steed, who was engineer at Wasborough's mill, took a patent for a rotative motion with a crank, and applied it to their engine. Suspicions arising of Cartwright's treachery, he was strictly questioned, and confessed his part in the transaction when too late to be of service to us.
The introduction of the centrifugal pump would obviously extinguish the single acting engine, as rotative engines working at a high speed would be the most appropriate form of engine where the centrifugal pump was employed. Q. This would not be a heavy deprivation? A. The single acting engine is a remnant of engineering barbarism which must now be superseded by more compendious contrivances.
Rotative engines are engines provided with a crank, by means of which a rotative motion is produced; and in this important class stand marine and mill engines, and all engines, indeed, in which the rectilinear motion of the piston is changed into a circular motion.
From this fact Professor Bjerknes and his son, reasoning that, to produce a similar field of energy around a vibrating body, the vibrations of that body must partake of a circular or rotary character, constructed apparatus for producing the hydrodynamic analogue of electric currents, in which a conductor transmitting a current of electricity is represented by a cylinder to which oscillations in circles around its axis are given by suitable mechanical means, so as to cause the enveloping medium to follow its motion and make similar rotative vibrations.
As all rotative Blowing Fans draw in the air at their centres, and expel it at their circumference, it occurred to me that if we were to make a communication between the upcast shaft of the mine and the centre or suctional part of the Fan closing the top of the upcast shaft, a Fan so arranged would draw out the foul air from the mine, and allow the fresh air to descend by the downcast shaft, and so traverse the workings.
The piston in a long-stroke compressor travels through considerable space before the pressure reaches a point where the discharge valve opens, and after reaching that point it has to go on still further against a prolonged uniform resistance. This makes rotative speed difficult.
The action of a paddle wheel in the water resembles in this respect that of the wheel of a carriage running along the ground: that point in the radius of the paddle of which the rotative speed is just equal to the velocity of the vessel will describe a cycloid; points nearer the centre, prolate cycloids, and points further from the centre, curtate cycloids.
Thomas Young, in his article on Bramah in the Encyclopaedia Britannica, describes the "rotative principle" as consisting in making the part which acts immediately on the water in the form of a slider, "sweeping round a cylindrical cavity, and kept in its place by means of an eccentric groove; a contrivance which was probably Bramah's own invention, but which had been before described, in a form nearly similar, by Ramelli, Canalleri, Amontons, Prince Rupert, and Dr.
Q. What is the usual proportional length of stroke of the valve? A. The common stroke of the valve in rotative engines is twice the breadth or depth of the port, and the length of the valve face will then be just the breadth of the port when there is lap on neither the steam nor eduction side. Whatever lap is given, therefore, makes the valve face just so much longer.
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