Steam locomotive P42, Royal Prussian Railway Administration (K.P.E.V.), wheel arrangement 4-4. Body plastic, frame die-cast metal, motor with flywheel, drive on 2 tender axles and via shaft on both engine drive axles, four wheel with traction tires, suitable for radius R2 and larger. With load-regulated decoder. Total length 203 mm.
The class P4 locomotives are representatives of changing eras. In the years immediately preceding 1900, a number of technical breakthroughs had been, or were on the verge of being achieved. The two-axle lead bogies had for instance been introduced in many German locomotives and had contributed to improved running qualities.
Boiler pressure had been raised to 12 kp/cm2 and pneumatic brakes were introduced.
Compound locomotives were also already seen on German rails.
The K.P.E.V. ordered the first P4s, together with the S 3, as of 1892. The orders were preceded by the so-called "Erfurt test locomotives" with compound and twin cylinder technology. Whereas the S 3 was a compound engine from inception, the P4 was originally equipped with twin cylinders because, as a passenger locomotive, it had to be started up more often.
Although various technical improvements could be made with regard to the appropriate filling of the high and low pressure cylinders, it was the Dultz valve that finally made the compound P4 possible. The two versions were distinguished using the classification P41 for the twin, and P42 for the compound. At a total of 1260 engines, the P4 was a very important locomotive, and a P42 was presented at the Paris World Trade Fair in 1900.
The P4 also gained importance as the experimental engine for various tests, including the Schmidt super-heated flue, oil and coal-dust combustion, as well as preheaters; a truly pioneering class.
