Mounted on the supports 10ª, 10^{b}, are four uprights, 12ª, 12^{b}, 13ª, 13^{b}. The uprights 12ª 12^{b} are connected at their upper ends by a longitudinal framing member 14ª, and the uprights 13ª 13^{b} are connected by longitudinal framing member 14^{b}, said framing members 14ª 14^{b} being also in turn connected at their ends by transverse bars (not shown), said members constituting an open frame for the working parts of the apparatus. Mounted respectively upon the longitudinal framing members 10ª 10^{b}, approximately midway thereof, are two standards, 16ª 16^{b}, which are rigidly secured together by a cross-bar 17, said standards and cross-bar constituting a rigid support for the gearing now to be described. Rotatably mounted upon the standards 16ª, 16^{b} is a driving shaft 18, one end of which is journaled in the standard 16ª, and the other end in a bearing-bolt 19 passing through the standard 16^{b}, which, being threaded, is capable of fine adjustment. Mounted upon and keyed to the shaft 18 is a wheel 19, the spokes 20 of which support a rim 21, within which are set a series of pockets 22, the inner surfaces of which are so shaped as to permit their receiving successively, at the bottom of the wheel, a series of balls 23 and holding the same during a travel of 180 degrees, or one-half revolution of the wheel, when they are discharged as hereinafter described. This wheel I will term an energy-storing wheel, since it acts through the force taken from the expansion coils to raise the balls, the lowering of which is to drive the wheel now to be described. Loosely mounted on the shaft 18 is a wheel 24, smaller in diameter than the wheel 19, the spokes 25 of which, secured to the hub 26, support a rim 27, within which are set a series of pockets 28, which are adapted to receive successively, at the top of the wheel, the balls 23, and discharge the same when they have been lowered through 180 degrees or, in other words, at the bottom of the wheel. The inner wall of the pockets 28 is formed, for the most part, with a pronounced rounded groove (indicated at 28ª), as shown above the ball in Fig. 18, which groove lies under the ball when the pocket is in its uppermost position, as shown in Fig. 17, said groove becoming less pronounced at one edge towards the opposite portion of the pocket, at which point it has an approximately level surface at one side, as shown in Fig. 18, and indicated at 28^{b}; the subject of this arrangement being that the ball may be readily discharged in this position, and securely held within the pocket when the ball and pocket are in other positions. The wheel 24--which I will designate as the power-transmission wheel--is supported upon ball bearings indicated at 28^{c}, 28^{d}, which are held in position by collars 28^{e}, 28^{f}, both keyed to shaft 18.