COMPOUND CHAMBER-WHEEL TEAINS. 425
train, in which the pump-wheels are equal bevel-wheels with a very obtuse angle between their axes. The interior of the chamber forms a zone of a sphere, and is separated into suction and delivery spaces by two dividing plates in the plane of the axes. The constructive difficulties are here far greater than in the case of the spur-wheels, and, it may be added, this fact has already made itself felt. Spur-wheels, screw-wheels and bevel- wheels have thus already been used in chamber-trains. One variety only is wanting hyperbolic- wheels in which the difficulty of making a tight joint certainly reaches its maximum. It is none the less quite possible that any day we may be startled by the appearance of a " hyperbolic rotary steam-engine."
Compound Chamber-wheel Gear.
We examined in 61 a specimen of compound spur-gearing in the mechanism (C^ ")" which is represented in Fig. 279. This mechanism has been used as a chamber-train, by Justice, among others, who employed it as a steam-engine.* Justice, who also constructed a two-wheeled chamber-train, made the four wheels equal, so that I and c were represented by one wheel only gearing with both the others. The frame e was used as a chamber enclos- ing all the wheels. The design was correct and the construction good, but it is not clear what special advantage could be gained by it.f A compound chamber-train, consisting of four bevel-wheels, was constructed by Davies as early as 1838.J It was intended to serve either as a rotary steam-engine or a pump. One of the end wheels, say a, had a large tooth extending across to the opposite wheel d, and the double wheel I c had a slot of which the sides moved in very incomplete closure with this tooth. I have already ( 91) mentioned this machine, which intelligibly enough has long ago been forgotten.
- Practical Mech. Journal, vol. xix., 1866-7, p. 360 ; Propagation Industrielle,
vol. iv., 1869, p. 34.
+ For an old chamber-train of three wheels see Bataille et Jullien, Machines d Vapeur, vol. i., 1847-9, p. 442.
J Newton, London Journal of Arts, &c. Conjoined Series, vol. xix., 1842, p. 153.
