With the view to obviate the loss of power which has place in the ordinary wheel, owing to the oblique action of the radiating floats, Mr. Buchanan invented a wheel in which the whole of the paddles constantly preserve a vertical position during the entire revolution.
The annexed figure is an elevation of Mr. Buchanan's wheel.
a a is the paddle-wheel, b b the floats attached to spindles working in the rims of the wheel; c c a guide wheel revolving on an eccentric disc or ring d, fastened to the vessel's side; the main shaft e passes through the ring or disc: on to each of the spindles of the paddles is keyed a crank f f, the length of which is exactly equal to the distance between the centre of the paddle-wheel and the centre of the guide wheel, and in the guide wheel are a number of pins which work in the other end of the cranks. The diameter of the paddle-wheel from centre to centre of two opposite spindles being exactly equal to the diameter of the guide wheel at the centre of the pins, the guide wheel is drawn round by the cranks with the same velocity as the paddle-wheel, and the cranks retaining their parallelism throughout the revolution of the wheels, the paddles attached to spindles of the cranks of course do the same and are kept constantly vertical.
Oldham's Vibrating Float-wheel, (1827.) - This wheel in its general appearance and construction, greatly resembles Buchanan's invention already described, but by an extremely ingenious arrangement, the paddles, instead of being constantly vertical and parallel to each other (as in Buchanan's wheel), are constantly varying the angles which they form with each other, and are in every part of the revolution directed to the highest point of the wheel, or of the circle in which their axes are situated. By this peculiar position of the paddles the wheel is capable of working at any depth of immersion. The annexed figure is a side elevation of Mr. Oldham's wheel.
a a is the paddle-wheel, b b the floats or paddles, fastened to horizontal axles which are supported in bearings in the arms of the paddle-wheel, and which project beyond the arms on that side of the wheel which is nearest the vessel's side; c c a guide wheel revolving upon an eccentric disc d, placed upon the main shaft, between the paddle-wheel and the vessel's side. The guide wheel c c is connected to the paddle-wheel by means of short cranks, e, keyed on to the projecting ends of the axles of the floats, and having holes in their other extremity, in which work pins set in the face of the guide wheel. The length of these cranks must be exactly equal to the eccentricity of the disc d, and the distance of the pins in the face of the guide wheel, from the centre of the disc, must be equal to the distance of the float axles, and with these proportions the cranks will in all positions of the guide wheel remain parallel to each other. The eccentric disc is attached to a tube or long collar passing through the vessel's side, and the main shraftf of the paddle passes through the tube.
The collar or tube revolves in bearings fixed upon the vessel's side, and upon the inner end is fixed a wheel working into a wheel, upon an intermediate shaft, which shaft carries a second wheel, working into a wheel on the main shaft. These four wheels are so proportioned, that two revolutions of the main shaft shall cause the eccentric disc to revolve once upon the main shaft; thus, whilst the guide wheel by its connexion to the paddle-wheel revolves upon the disc, the disc itself is also revolving upon the shaft. All the paddles are fixed upon their spindles at different angles with the connecting cranks, so as to stand in the position shown in the figure; and as the disc during half a revolution of the wheel performs a quarter of a revolution on the shaft, the cranks, which in the figure are all vertical, would in half a revolution of the paddle-wheel stand horizontal, and therefore the whole of the paddles would in that time describe a quarter of a revolution on their axes, and the paddle which stood in a horizontal position at the top of the wheel, would, when at the lowest point of the wheel, stand vertically.