Page:The Kinematics of Machinery.djvu/430

 408 KINEMATICS OF MACHINERY.

The chamber- wheel gear can also be used in another way, viz., as a measuring instrument. It can, that is to say, if carefully con- structed, serve as awater meter; for if a stream of water be allowed to pass through it, driving the wheels, the number of revolutions made by the latter gives the quantity of water passed in terms of the tooth-ring volume. We shall find further on other similar applications of chamber- wheel gear.

Still another application of the machine may be obtained by arranging it with a delivery-pipe of which the sectional area can be varied. By reducing this to a suitable extent the chamber- wheel train, working either with water or oil, forms a brake, which by the use of one or of two valves can be made either single or double acting. If the passages be suitably arranged the same quantity of fluid can be used over and over again ; a brake of this kind, too, has no wearing parts, like those of an ordinary block-brake. Such a chamber-wheel brake, acting in the direction of rotation, and not preventing any other motion, may serve as a cataract, and be useful in those cases where it is wished to apply that apparatus in connection with rotary motions.

It will be seen that the chamber-wheel gear has a large range of applications. In its simplest form, without valves, it may be used as a pump (and is suitable for a fire-engine pump), as a steam- engine, or as a fluid meter ; a trifling addition makes it available also as a brake or a cataract. It is well suited for working with (driving or being driven by) water or other liquids, and also viscous or merely plastic materials (so that it probably might be used as a clay or pug-mill), as well as for driving gaseous materials, as air

used. The steam is admitted at the side of the wheels into the space between two teeth, and the resulting motion takes place in the one or other direction according to whether the admission opening be placed a little above or below the line of centres. This makes both expansion and reversing possible. The only security against leakage, however, is the higher pairing between the surfaces of the teeth. At the sides of the wheels there is lower pairing, but no means are provided (or at least shown in the engraving) for taking up the wear which must occur there. Altogether I see no reason for supposing that this inventor will be more successful than his predecessors in inducing two bodies to rub upon each other under considerable pressure and at a great velocity without wear taking place, and all the consequences due to that inconvenient action. See Engineering, Nuv. 14, 1873. From some correspondence in subsequent numbers of the same journal it seems probable that the first to propose this use of steam from the centre outwards in a chamber-wheel- train was John Hackworth (circa 1840-45).