42 BULLETIN 198, UNITED STATES NATIONAL MUSEUM 



These gears are fully enclosed, and they operated without noise. The 

 outer end of the countershaft carries the driving sprocket, which trans- 

 mitted power to the rear axle by a chain. An adjustable distance rod 

 holds the countershaft at a constant distance from the rear axle. 

 Lubrication of the motor bearings and countershaft bearings was by 

 oil-soaked waste carried in a small pocket on each bearing, the pockets 

 being supplied with spring-closed covers. 



The differential is of the bevel-gear type, enclosed, and running 

 in oil. The hubs of the rear wheels carry drums upon which external 

 contracting brake bands act when operated by a pedal. The brake 

 pedal includes a ratchet for locking purposes. 



The controller handle moves in two slots having an offset between 

 them. The forward slot gives the three forward speeds and the rear 

 slot the two backing speeds. First speed is obtained by grouping the 

 two sets of batteries in parallel and connecting them in series with 

 the motor and a resistance, the latter carried in a frame beneath the 

 body. In the second speed the two sets of batteries act in parallel 

 on the motor without the resistance, and in third speed the two sets 

 are in series. The two backing speeds correspond to the first two of 

 the forward speeds, with the field commutated. The controller is of 

 the drum type, located under the driver's seat, and its contacts are 

 of hard drawn copper. Seven cables enter the controller. 



The body is of wood, the fenders are of leather stretched and sewn 

 over a metal frame, and the folding top is of leatherette. Step plates 

 are attached to each side of the vehicle. Kerosene lights and a Stewart 

 speedometer complete the equipment, the latter being of much later 

 date than the vehicle. 



ROLLS-ROYCE GASOLINE AUTOMOBILE, 1907 



U. S. N. M. No. 311998 ; one-quarter-size model ; gift of Rolls-Royce, Ltd., in 1947 ; 

 photograph No. 37754-A; plate 15. 



This nonoperative model represents the 40-50-horsepower, 6-cylinder 

 Rolls-Royce car which, in 1907, ran out a 15,000-mile reliability road 

 trial, officially observed by the Royal Automobile Club. At the con- 

 clusion of the trial, in which it ran 14,371 miles without an involuntary 

 stop for other than tire troubles, the car was dismantled and examined. 

 All parts in which the slightest measurable wear could be detected 

 were replaced, at a cost of just over $10. 



The full-sized car has a 6-cylinder engine of 4i^-inch bore and 4i/^- 

 inch stroke, developing about 48 horsepower. The cylinders are cast 

 in two groups of three, with the valves all on one side and operated 

 from a single camshaft located in the crankcase. The crankshaft is 

 hollow and has a main bearing between each two adjacent cranks. 

 Forced lubrication was provided. The crankcase is of aluminum, 



