is the piezo electric sonic motor of the type developed at the sonic power laboratory of ohio state university a sonic motor of this type having an output of about 15 hp is particularly effective briefly such a motor consists of a solid 20 inch machined steel catenoidal shaped horn which tapers to a narrow working tip extending concentrically from the wide end of the horn is a cylindrical shaft about 61 2 inches long and 11 2 inches in diameter threaded at the far end in machining the horn a substantial flange is left partway along its length at the point which will be the 34 null point 34 or point of no vibration for the finished sonic motor this flange is eventually used for mounting the motor so that no vibration will be transferred to the support as long as the motor is free to vibrate at its designed frequency four piezo electric crystals of lead zirconate titanate in the form of rings about 31 2 inches in diameter 1 2 inch thick and protected by rubber are separated by metal rings as electrodes and the assembly slipped on the shaft and clamped by means of a large nut screwed on the threaded end of the shaft such piezo electric crystals are commercially available proper electrical connections and insulation are provided so that the crystals may be activated by a high frequency current having an emf of about 2 600 volts power is preferably supplied by a 10 000 cycle electric generator of the induction heating type which is stepped up to the required voltage by means of a suitable step up transformer such motors weigh about 22 pounds and have an efficiency.