OF
A CRANE,
Which combines VARIABLE POWERS with speed and safety.
Doctor Gregory (in his Mechanics 2d. volume page 157,) thus introduces the description of this Crane, and the observations with which he tags that description.
“The several Cranes described in this article, as preferable to the common walking Crane, while they are free from the dangers attending that Machine, lose at the same time one of it’s advantages, that is, they do not avail themselves of that addition to the moving power which the weight of the men employed may furnish: yet this advantage has been long since insured by the mechanists on the continent: who cause the labourers to walk upon an inclined plane, turning upon an axis, after the manner shewn in the figure referred to under the article foot-mill,—where we have described a contrivance of that kind, well known in Germany nearly 150 years ago. The same principle has been lately brought into notice (probably without knowing it had been adopted before) by Mr. Whyte, (White) of Chevening in Kent: His Crane is exhibited,—fig. 2 and 4, Plate 10, as it was described in the Transactions of the Society for the Encouragement of Arts.”
“A, [Plate 9], [fig. 4], (of this Work) is a circular inclined plane, moving on a pivot under it, and carrying round with it the axis E. A person walking on this plane at A, and pressing against a lever, throws off a gripe or brake, and thus permits the plane to move freely, and raise the weight G by the coiling of the rope F, round the axis E. To shew more clearly the construction and action of the lever and gripe, a plan of the plane connected with them, is added in [fig. 5], where B represents the lever, and D the gripe: where it is seen that when the lever B is in the situation in which it now appears, the brake or gripe D, presses against the periphery of the plane; but when the lever B is driven out to the dotted line H, the gripe D is detached, and the whole Machine left at liberty to move: a rope or cord of a proper length, being fastened to B, and to one of the uprights in the frame, to prevent this lever from being pushed too far towards H, by the man working at the Crane.”
“The supposed properties of this Crane, (says Dr. Gregory) for which the premium of forty guineas was adjudged by the society to the Inventor, are as follows:”
“‘1. It is simple, consisting merely of a wheel and axle: