Page:The Kinematics of Machinery.djvu/455

 WATTS PLANET-TRAIN. 433

to the beam, and the wheel c fixed to the connecting-rod oscillates with it, but never turns. This mechanism of Watt is therefore a special form of the epicyclic train (CUCJ)*- Watt usually made

M

d, from which it follows that - 1

n

FIG. 284.

There is nothing here to prevent the use of an annular wheel as one of the pair c d. If this be done a becomes negative. If the outer wheel c be made the annular wheel, the value of a is always greater than unity, and the direction of rotation of d is negative i.e., it turns in the opposite direction to the frame e *.

Galloway's rotary steam-engine, now to be described, is simply a chamber-wheel mechanism formed upon a planet-train like that of Watt with an annular outer wheel.

The following three figures represent three forms given by Galloway to his engine, which he intended for screw propulsion.

of an annular wheel in the sun and [planet gear. Muirhead, p. 50. See also Bourne's Treatise on the Steam- Engine, p. 21. K. [There is now in the Patent Museum at South Kensington a model of Watt's in which the connecting-rod end is made an annular wheel. To keep this in gear with the wheel on the shaft there is a small roller placed upon a pin attached to its lower part, and this is made to roll iipon a suitably shaped cam touching it always on the side furthest from the point of contact of the wheels themselves.]
 * Watt himself in liis first specification mentioned specially the application

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