For convenience of designation, I will refer to each of these groups of balance-levers F, F¹, and expansion strips G, G¹, etc., as expansion coils, and while I have herein shown but two sets of such expansion coils, it is to be understood that there may be any number of such sets desired, and any desired number of strips and levers composing such coils, depending upon the character of the work to be performed. Furthermore, I desire it to be understood that when I use the terms “strips"--as characterizing the members connecting the balance-levers--either in the specification or claims, I do not limit myself to the form of connecting member or “strips” shown, but mean to include in the use of the term “strips” any other form such as wires, rods or bars of either square, round, hexagonal or other cross sectional shape. The ends of the short strips G, G^{x} are connected by wires H, H¹ with the opposite ends of what I will term a coil lever I, which, as more clearly shown in Fig. 5, is keyed to a shaft J, which latter has its end journaled upon the cross-bars J¹, J² secured to the uprights C, C¹ of the inner frame of the apparatus, and this shaft I will name a coil shaft. Keyed to the coil shaft J is a lever K, which it may be proper to designate as a stress lever, since from it is suspended a weight K¹, the function of which is to place a certain amount of stress upon the series of expansion strips and balance-levers composing the expansion coil, keeping the metal of the strips slightly stretched and preventing any loss of motion at the different points of connection, and thereby furthering a very important object, which is to make of each series of expansion strips [Illustration: _Fig. 2._ BANGERTER’S PERPETUAL TIME CLOCK] and balance-levers a single spiral unit, throughout which the expansion and contraction of the strips are transmitted. Also keyed to the shaft J is a power transmisson lever L, and any rotary motion imparted to said shaft is necessarily imparted to the lever L in the form of reciprocating motion. Referring now to the power storage device, one or a number of which may be used in connection with my expansion coils.