4o THE POPULAR SCIENCE MONTHLY 



in connection with Figs. 33 to 36. This action continues until side 

 B is heavier than side B', when the reversed unbalanced condition of 

 the car body causes a reversed precessional movement of the gyrostat 

 wheels. This reversed precession continues steadily and unhastened 

 so long as the heavy side B is balanced by the contact of the idle wheel 

 i' with the table L', that is, until the projecting ends of the axles of 

 spin A and A' are brought forwards (in the figure) into the plane of 

 the paper. Then the continuation of the reversed precession brings the 

 axle A' upon the table H', the reversed precessional motion is then 

 hastened, and this hastened precession raises the side B and lowers the 

 side B' of the car-frame, thus bringing the car-frame into its initial 

 unbalanced condition (side B' heavier than side B). The above-de- 

 scribed action is then repeated, and so on. 



The stability of the Brennan car is due to the hastened precession 

 which is caused by rolling action of one or the other of the projecting 

 axles of spin upon the tables H and H ', while the axles of spin are 

 departing from a line at right angles to the length of the car, and to 

 the steady and unhastened precession, while the axles of spin are 

 moving towards a line at right angles to the length of the car. The 

 hastened precession on the one hand quickly alters the condition of 

 balance of the car so as to limit the departure of the axles of spin from 

 a line at right angles to the length of the car, and the steady and un- 

 hastened precession, on the other hand, insures the complete return of 

 the axles of spin to a line at right angles to the length of the car. 



The hastened precession is accomplished with great friction losses 

 by the rolling axles A and A' in Fig. 37, and it is reported that 

 Brennan is working upon an automatic motor-driven mechanism to 

 produce the hastened precession without exhausting the energy of the 

 gyrostat wheels. 



Two devices like Fig. 37 with their rocker- axles at right angles to 

 each other would hold a one-legged body in equilibrium; indeed, such 

 a double mechanism would make it possible to use a one-wheeled car, 

 but the wheel would have to have a deep double flange to make it roll 

 along a rope or rail. Such a one-wheeled car, a sort of hyper-wheel- 

 barrow car, would be of no value for practical use, and, indeed, most 

 of us believe that Brennan's two-wheeled car is nothing more than 

 a scientific toy. 



Calculation" of Torque-Keaction Due to Precession" 



Let n be the revolutions per second of a spinning wheel, P the 

 revolutions per second (or the fraction of a revolution per second) of 

 the axis of spin due to the precession, and E the moment of inertia 

 of the spinning wheel in pound X feet squared. Then the torque 

 reaction is equal to 4:ir 2 nPK poundal-feet or ^nPK pound-feet. 4 



4 See Franklin and MacNutt's "Elements of Mechanics," p. 150. 



