Fig. 13 is a front elevation showing my invention applied to another form of force storage mechanism; Fig. 14 is a plan view of same, on lines 14--14 of Fig. 13; Fig. 15 is a rear elevation on lines 15--15 of Fig. 14; Fig. 16 is a vertical section on lines 16--16 of Fig. 14; Fig. 17 is an enlarged detail of part of the apparatus shown in the upper portion of Fig. 16; Fig. 18 is an enlarged detail of the ball-discharging means shown in the lower portion of Fig. 16; Fig. 19 is an enlarged detail of the loading device shown in the opposite part of the lower portion of Fig. 16; and Fig. 20 is a plan view on lines 20--20 of Fig. 13. Referring to the construction illustrated in Fig. 1 to 11, inclusive, B represents the outer frame of the apparatus. Mounted within the outer frame B is an inner frame comprising the uprights C, C¹, which are rigidly secured by cross-bars D¹, D². The outer frame B, as well as the inner frame uprights C, C¹ are preferably formed of wood or other material capable of a low degree of expansion. Within the upper and lower ends of the inner frame are anti-friction knife-bars E, E^¹{1}, the upper one of which, E, has each end within a vertically disposed slot E² in the uprights C, C¹, within which said knife-bar may be moved vertically, as hereinafter described. Each end of the lower knife-bar E¹ lies immovable within a recess in a plate E³ mounted on each of the uprights C, C¹. These knife-bars, which are preferably formed of hardened steel, have oppositely disposed relatively sharp edges E^{5}, which act as bearings for a series of horizontally disposed anti-friction levers, F, F¹, which I will term balance-levers, since they are intended to balance evenly and freely on the thin edges of the knife-bars with little friction somewhat in the nature of a scale-balance. These levers are pivotally connected to a series of metallic expansion strips G, G¹, G², G³, etc., the construction and arrangement and manner of connecting up the same being more clearly shown in Fig. 3. It will be observed that the arrangement of the levers F and expansion strips G, G¹, etc., is such as to form, in effect, a spiral, the short strip G being connected to one end of one of the balance-levers F, and the strip G being connected at its lower end to the opposite end of said lever, the upper end of said strip G¹ being connected to one end of the first one of the levers F¹. To the opposite end of said lever F¹ the upper end of strip G² is connected, the lower end of said strip being connected to the left-hand end of the second one of the levers F, and so on to the final short strip G^{x}. The levers F, F¹ must be formed of a metal capable of withstanding great strain without bending, and for this purpose I prefer to use the metal known as macadamite.