1904.] on New Developments in Electric Railways. 469 



engineer of the Allgemeine Elektricitats Gesellschaft, described to 

 the Engineering Conference in Glasgow, in September 1901, the car 

 which had been built by his company. 



Before, however, the design of the car could be decided on, some 

 preliminary experiments had to be carried out, to determine the 

 power necessary for propelling the car at the unprecedented speed of 

 '200 km. per hour. 



It was very evident that the resistance of the air would be the 

 most important factor, but the usual formulae relating to the air 

 resistance of railway trains gave such high values that a confirmation 

 of these results by a special experiment a2)peared very desirable. 



Messrs. Siemens and Halske, therefore, fixed up a 200 horse- 

 power motor, with its axle in a vertical position, and an ordinary 

 tramcar w^heel was pressed on it on top. To this tramcar wheel a 

 wooden plank was bolted 85 mm. thick, 500 mm. broad and 6350 mm. 

 long. On the ends of this plank two jjlain boards were fixed in the 

 first instance, to represent the surface of a car, and the powder supplied 

 to the motor was measured while it was revolving at various speeds. 



Afterwards, instead of the j^laiu surface, a broken surface, roughly 

 parabolic in plan, was substituted, and the air resistance dropped very 

 considerably to about 90 kg. per square metre at a speed of 200 km. 

 per hour. 



Thus it was found that for air resistance and for mechanical 

 friction, the motors had to develop 950 horse-power to drive a car 

 weighing 96 tons at a speed of 200 km. per hour. 



For safety's sake the motors were, however, made capable of 

 developing about 50 per cent, more power as their normal output, 

 and the actual experience afterwards proved the wisdom of this 

 increase. 



In any case it was necessary to provide nearly 3000 horse-power 

 for the period of acceleration, and allowing an overload of 100 per 

 cent, for this period, the normal output of the four motors together 

 was fixed at about 1500 horse-power. 



There were a number of other investigations to be made in order 

 to determine the safest way of collecting the high tension current, 

 transforming it to the working pressure, and regulating the motors, 

 so that the actual experiments did not begin until the autumn of the 

 year 1901. 



The line from Marienfelde to Zossen is about 23 km. (14J statute 

 miles) long, and the smallest radius of a curve is 2000 m., while the 

 ruling gradient is 1 : 200. 



Along this line the three conductors are carried in the way settled 

 by experiment for the trial line at Gross-Lichterfelde. 



The three wires are supported by insulators at a vertical distance 

 of 1 m. from each other, and the insulators in turn are elastically 

 supported, as shown by the slide, so that the collectors, in passing 

 the supporting posts, do not receive violent blows. 



Each conductor is connected at the insulators to a loop, which 



