The exact date of construction of this sports machine is not yet known. Historical records define them with the borders of 1935 - 1937. However, it should be assumed that the Sokół 500 RS prototype was created in early 1935, as a kind of "supplement" for the tourist Sokół 600 RT, which was put into production at that time.
Motorcycles of both types, according to the concept of their constructor, Eng. Tadeusz Rudawski, head of the motorcycle department of the State Studies Office of the Plant
Inżynierii in Warsaw, had many common elements, and the difference came down to the engine and small elements of equipment.
Drive units for prototype vehicles were made in the Experimental Department of PZInż. They were constructions with a traditional layout - single-cylinder, overhead valves with pushrod timing, long-stroke (stroke - 105 mm, cylinder diameter - 78 mm), with a displacement of 496cc and a variable compression ratio of 7.5 or 9.5:1. A certain innovative accent, constituting a patent of PZInż. was the method of solving the timing system - hanging valves with triple springs were controlled - by pushers - with two cams with symmetrical characteristics, mounted on a common shaft.
Depending on the type of piston (or cylinder head) and the fuel used (petrol-alcohol mixture for a higher compression ratio), the engine developed 18 HP at 4500 rpm or 22 HP at 5000 rpm.
In a weaker version, solo, he achieved maximum speed up to 124 km/h, and in the more powerful version, loaded with a rider and passenger - 125 km/h. Fuel consumption was 3.7 - 4.5 l / 100 km.
Operational data were comparable to foreign designs of this class. The only negative feature was too noisy timing work.
The drive unit was locked with a gearbox with three ratios (pedal controlled and unlike the Sokół 600 already with the so-called automatic) in a way characteristic of the design of engineer Rudawski. The gearbox formed a separate, easily replaceable unit and was mounted in a special hole in the engine block. The engine had battery ignition. The power source was a Bosch 6V - 36W generator.
The construction and dimensions of the chassis, adapted from the Sokół 600 RT, did not show any differences, while the weight of the motorcycle decreased and the sports version was 160 kg.
During possible production, the chassis of the Falcon 500 was to be slightly modernized. It was planned, while leaving the existing frame and rigid rear suspension, to introduce a modern telescopic fork in the front suspension. Construction sketches were prepared by engineers: Tadeusz Rudawski and Tadeusz Heryng.
The Sokół 500 RS showed undoubted design advantages, and the unification of the chassis and accessories with the mass-produced Sokół 600 RT. It created a great opportunity to develop production. However, the lack of interest from the military circles meant that it was limited to 3 or 5 prototypes.
Source: Polish History Archive
