Orenstein & Koppel (normally abbreviated to "O&K") was a major German engineering company specialising in railway vehicles, escalators, and heavy equipment.

[2][3] The Orenstein & Koppel Company was a mechanical-engineering firm that first entered the railway-construction field, building locomotives and other railroad cars.

First founded in 1892 in Schlachtensee, in the Zehlendorf district of Berlin, and known as the Märkische Lokomotivfabrik, the O&K factories expanded to supply the Imperial German Army under Kaiser Wilhelm II with field-service locomotives, or Feldbahn.

Because of strained capacity at the Schlachtensee shops, work transferred in 1899 to a site in Nowawes, later Babelsberg, near Potsdam.

Around 1908, O&K acquired the firm of Gerlach and König in Nordhausen, building petrol and diesel locomotives there under the trade mark "Montania".

The company also began manufacturing escalators, transmissions, rapid-transit railway lines, buses, tractors, and cargo ships.

With the collapse of Imperial Germany in November 1918, the victorious Allies put further restrictions on German manufacturing and military capacity, seizing all army Feldbahn engines as per the terms of the Versailles Treaty that ended the First World War.

The treaty also removed access to export markets; at the end of 1925, work stopped for three months as a result of the lost business.

[citation needed] After the war, O&K's American subsidiary, the Orenstein-Arthur Koppel Company, was seized by the Alien Property Custodian and sold at an auction where only United States citizens were allowed to place bids.

Under the German Democratic Republic, O&K changed its name to the VEB Company, and resumed heavy mechanical manufacturing at Nordhausen, producing cable-operated excavator shovels, among other things.

In West Germany, the enterprise resumed operation after World War II in 1949, under the name Orenstein & Koppel AG, with headquarters in Berlin.

In 1972, O&K had five working plants: West Berlin, Dortmund, Hagen, Hattingen/Ruhr, and Lübeck; it maintained a central spare-parts service in Bochum.

O&K also manufactured the world's largest hydraulic excavator,[citation needed] at 900 tons' service weight with a shovel capacity of over 52 cubic metres (68 cu yd) and an engine output of 2,984 kilowatts (4,055 HP).

The escalator-manufacturing division was sold to the company's majority shareholder at the time, Friedrich Krupp AG Hoesch-Krupp, in 1996.

[8] For light railways, especially for narrow-gauge railways, with steep gradients, tight curves and generally a light superstructure and substructure, locomotives with only two axles did often not meet the requirements in terms of tractive force and caused wear of the track and the wheel tyres due to their wheel load.

This type was especially suitable for longer distances because, it allowed a light superstructure and was also able, to carry larger supplies than 0-4-0 locomotives with the same wheel pressure.

Depending on the particular conditions, O&K installed the svivelling axle at the rear or at the front, but always in such a way that the greatest possible adhesive weight was maintained.

[11] For railways with steep gradients and relatively light track construction, locomotives with two or three coupled axles often did not meet the requirements of increased traffic.

Due to the high costs involved, the existing tracks could often not be converted, and heavier locomotives with a larger number of axles were used.

In order to counteract the unsteady running of the steering axles on the track and any lurching of the locomotive, these locomotives are fitted with an adjustable safety device which holds the drawbar frames in the central position on the track by means of spring tension; no pressure is exerted against the bearing points with this resetting device.

In addition the connecting and coupling rods, through which linear forces from the steam pistons were translated into the rotation of the wheels via the crank pins, also had to be able to move sideways.

The weight of this locomotive was relatively high and therefore it could develop a great performance immediately when starting up, even on short gradients.

[15] The fairing of all moving parts was intended to protect other road users such as pedestrians from serious injuries in case of accidents.

It also prevented horses from shying and protected the transmission from dirt and dust on the unpaved roads that were common at the time.

For use during tunnel construction or in underground mines, steam locomotives with oil firing equipment were particularly suitable, whereby smoke development and spark emission did not take place.

Furthermore, fireless locomotives were also very suitable for operation in tunnels and mines, as they completely avoid the nuisance of smoke, gases and sparks.

[16] Fireless locomotives were particularly suitable for use inside factories, yards etc., where it was essential to secure absolute freedom from any risk of fire.

The locomotive is able to work for several hours with one filling and can be operated with minimum expense as the driver needed less skills than that of a conventional steam engine.

Mixed railways were used in changing terrains with only single steep gradient, which could not be negotiated by ordinary adhesion locomotives.

The mode of operation was as follows: The two steam cylinders outside the frame drove the driving gearwheel for the rack by means of a double gearing with the appropriate transmission.