Tank locomotives with two coupled axles (Type 0-4-0)

Based on O&K's experience, they have created a number of type 0-4-0 standard designs, which have proven to be particularly suitable for many companies. Locomotives of these standard designs were always under construction, and locomotives of the most common strengths were always in stock, so that they could be dispatched immediately on request. Two-axle locomotives were mainly used by construction companies and industrial establishments; accordingly, special emphasis was placed on simple and practical construction. In particular, the locomotives were characterised by high tractive power, while the smaller types were generally based on a lower speed in favour of tractive power.^[6]

The standard-gauge locomotives in this category were particularly suitable for shunting and for operating purposes on branch lines.^[6]

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. Therefore, larger locomotives with more axles were available, as shown below.

Tank locomotives with three coupled axles (Type 0-6-0)

As with the two-axle coupled locomotives, the full weight of the machines with three coupled axles was used as adhesion weight. However, since the wheel pressure was distributed over six wheels instead of four, locomotives of this category could run on much lighter rails than two-axle locomotives with the same weight and therefore the same tractive force. This type of locomotive could therefore be used wherever the existing track required the most powerful locomotive possible without exceeding the permissible wheel pressure, or where the superstructure was to be constructed relatively lightly. Particularly on longer lines, the latter was considered for the sake of substantial savings. However, the track curves must be larger when using this locomotive than with the four-wheelers.^[7]

Locomotives with two coupled axles and one svivelling axle (Types 2-4-0 or 0-4-2)

If the locomotive had to travel through small curves with a light superstructure, it was advisable to purchase a locomotive with two axles and a svivelling axle. 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. The design also had the advantage that the centre of gravity could be set lower than on other types. This, together with the large wheelbase, gave the machines a particularly smooth ride. It could also run at a relatively higher speed, so that, according to the above, it was mainly suitable for small railways and feeder lines. 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. Since the full weight of this type of machine could never be used as the adhesive weight, this construction was less suitable for carrying large loads. For such cases OK recommended the use of multi-axle coupled locomotives of the Gölsdorf type or, if small curves were available, to the locomotives of the Mallet or Klien-Lindner type, as shown below.^[8]

Coupled compound locomotives (Type 0-4-4-0, Mallet design)

In many cases, where 0-4-0 or 0-6-0 steam locomotives were no longer sufficient, O&K built 0-4-4-0 or 0-6-6-0 compound locomotives, Mallet design, which supplemented the more conventional looking 0-4-2 locomotives (in Germany categorized as 2×2/2 and 2x3/3 double compound locomotives in comparison to the more conventional looking 2/3 locomotives). Apart from the possibility of being used on light superstructures and small curves, the locomotive had the advantage of great tractive power due to the composite arrangement of the cylinders, as the full weight was used as adhesion weight. The design was such that the boiler, driver's cab and storage boxes were connected to the rear frame, which carried the high-pressure cylinders, while the front frame, on which the low-pressure cylinders were located, was connected to the rear frame by two vertical hinges. The boiler with the water boxes rested on a slide track of the front frame, so that the latter could move freely under the boiler. The steam passed from the regulator in fixed pipes to the high-pressure cylinders and, after expansion in these, through an absolutely steam-tight, flexible, well-insulated pipe to the low-pressure cylinders. The exhaust steam entered the exhauster through a vertical movable pipe. A special valve made it possible to feed boiler steam directly to the low-pressure cylinders, so that all four cylinders came into operation immediately when the locomotive was started-up.^[9]

Locomotives with coupled hollow axles with radial and lateral movement (Klien-Lindner design)

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. Where small curvatures precluded the use of long, fixed wheelbases, locomotives with steerable bogies or, for the sake of simplicity, locomotives with curvilinear coupled axles were often used. The acquisition of such locomotives was also advisable for such new designs where the track systems and bridges were easier and cheaper to build. Since 1901, locomotives with coupled hollow axles have been built in particular according to the Klien-Lindner design, which has proved extremely successful in operation. The advantages of this design were:

1. Large tractive force at a given permissible wheel pressure
2. Large wheelbase with the best curve mobility and equal spring loading on both sides of each end axle and thus safe running of the locomotive
3. Shock-free running into curves, as well as safe return to the centre position when running on straight track
4. Equally good running when driving forwards and backwards
5. Low wear of the rails and wheel tyres

The arrangement and mode of operation was as follows: The laterally and radially movable coupled axle was installed as the end axle, and in the case of eight- or ten-wheelers, these steering axles arranged at both ends ensured that the locomotive could enter the curves without difficulty. All axles were coupled in the usual way by fixed rods and mounted in axle bushes "bb" outside the wheels, following the spring play. The axle bushes sit in a continuous, fixed frame on which the steam cylinders are arranged in the usual way. The steering axle consists of a core axle "a" fixed in "bb" and driven in the usual way, and a hollow axle "c" which is firmly connected to the wheels and can be moved laterally and radially and which encloses the core axle, which is provided with a ball attachment in the middle, by means of a two-part ball cup "d".^[10]

The load on the axle was distributed by the ball pivot of the core axle "a" as it were by a transverse balancer on both wheels of the axle and thus equal wheel pressures and safety against derailment are obtained. The hollow axle is driven by a driving pin "f" pressed into the ball pivot of the core axle with sliding pieces at both ends, which have the necessary lateral play in the housing of the hollow axle for the deflection of the axle. In order to return the hollow axle to its central position after deflection, either return springs are arranged in the central housing, or, as can be seen in the following illustration, counter-guides "g" are arranged which, by means of brackets, enclose the hollow axles in the auxiliary bearing positions "ee" and effect unconstrained, shock-free adjustment of the hollow axle, since both end axles must execute their radial or lateral movement simultaneously. 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. These axles do not require any maintenance except for periodic lubrication. The periodic lubrication mentioned is only necessary at intervals of 1 to 2 months and is carried out after loosening the two lubricating screws "s" located on the centre of the axle by introducing grease or viscous oil into the sliding boxes of the driving pin. Only during a general inspection of the locomotives is it necessary to also inspect the hollow axles to make sure that the internal parts are in good condition.^[11]

O&K have used the Klien-Lindner axles for the Royal Prussian State Railways and many other railway in large numbers. The administration of the military railway has also introduced 0-8-0 locomotives with steerable coupled axles in place of the 0-6-0 field railway locomotives previously built.

Locomotives with laterally movable coupled axles (Gölsdorf design)

Locomotives of the Gölsdorf design were only suitable for lines, on which there were relatively few and large curvatures. In this case it was sufficient to shift one or more coupling axles sideways in such a way that the movable axles were not guided in their axle bearings but by their own flanges. The bearings of the coupling rods have the same lateral play on their journals as the axles in the axle bearings. This type of construction has proven itself well on eight- and multi-wheel locomotives, but it was not suitable for very small curvatures. In terms of performance and even load distribution, etc., it was equivalent to the more common Klien-Lindner locomotives. They were used for main, branch and small railways.^[12]

Two of the five axles of a ten-wheel locomotive could move sideways relative to the frame because their axle boxes fixed them rigidly to the frame. The other axles, however, were fitted into their bearings and attached to their drives in such a way that they can be moved sideways during curve running, depending on the sideways forces acting on them. 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.

Tramway locomotives (Type 0-4-0)

O&K built tramway locomotives, which were used for operation on tramways serving public traffic, either with a driver's cab at the front and rear or with only one driver's cab in the middle of the locomotive; furthermore with a power unit cover in two different designs. Whereas one version only served to conceal the engine from road traffic, the other version served to protect the engine parts against dust. The desired type of covering is to be specified. The weight of this locomotive was relatively high and therefore it could develop a great performance immediately when starting up, even on short gradients. This was effectively supported by a high steam overpressure, which O&K usually provided for these locomotives with 14 bars (200 psi).^[13]

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. Often there was no stoker on tram locomotives, which meant they were operated by the driver in one-man operation. The short axle stands also ensured that narrow curves could be negotiated in city centres. Often, standing boilers were used for reasons of space.

Mining and tunnel locomotives

For operation in tunnels or mine, O&K built locomotives in compliance with specific profiles. In the case of steam locomotives, it was possible to run them at high speed by fitting suitable devices and using particularly large boilers that could store a larger quantity of steam before passing through the tunnel. 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. The handling of these locomotives did not differ in any other respect from that of an ordinary locomotive. Furthermore, fireless locomotives were also very suitable for operation in tunnels and mines, as they completely avoid the nuisance of smoke, gases and sparks. Compressed air locomotives, which, however, required a special stationary system to generate the compressed air were also made and sold in smaller numbers.^[14]

Fireless locomotives

Fireless locomotives were particularly suitable for use inside factories, yards etc., where it was essential to secure absolute freedom from any risk of fire. They were largely used for shunting purposes for paper mills, oil mills, wool mills, timber yards, gunpowder factories and similar works. These locomotives were constructed without fire boxes, the necessary steam being taken from a stationary boiler. 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.^[15]

Rack locomotives

O&K delivered several types of cogwheel locomotives for mixed railways, on which ordinary operation alternated with cogwheel operation. Mixed railways were used in changing terrains with only single steep gradient, which could not be negotiated by ordinary adhesion locomotives. Accordingly, only these steep gradients were equipped with toothed bars. 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. This driving gear wheel sat on a special axle fixed in the frame and was connected to the friction axles by coupling rods, so that the gear wheel axle and friction axles were driven simultaneously. The locomotives could therefore run on normal rail tracks as well as on toothed tracks. On the toothed track, the driving gear and the friction wheels worked together. The effect of the latter was also utilised on the toothed track and the load on the rack was relieved accordingly. The locomotives worked either on a simple flat steel rack or on Riggenbach ladder rack.^[17] A cumulative number of only 6 to 9 rack steam locomotives were made by O&K in total. Their track gauge ranged from 400 mm (15+3⁄4 in) to 1,300 mm (4 ft 3+3⁄16 in).^[18]

Locomotives with a separate tender

Locomotives with a separate tender did not carry all their fuel and water on board the locomotive and were thus particularly useful for travelling long distances without being refuelled. The locomotives were equipped to be either heated by coal, wood or oil, because a larger heating and grate area were required. The main types had from four to twelve wheels for the locomotive and four, six or eight wheels on the tender.

The water tanks were firmly fastened to the frame of the tender, while maintaining a low centre of gravity. The coupling between locomotive and tender was similar to that of the waggons, to ensure that the locomotive could be driven without the tender for shunting or on short distances. The tender was easily accessible from the engineer's cab. If the locomotive was heated by wood, the tender had a special fence to increase the volume of its load.

Coupled compound locomotives (Type 0-6-6-0, Kitson-Meyer design)

After Orenstein & Koppel (O&K) had delivered the prototype of a Kitson-Meyer locomotive for the 600 mm gauge to the Chilean military railway in 1927, an order for three locomotives followed in 1937. In 1939, the locomotives with the factory numbers 13306 to 13308 were completed. The locomotives had riveted bridge and bogie frames. The boiler, cab, reservoir and ash box were also riveted. The engines located at the two bogie ends worked on the centre axle set. This wheelset could also be sanded. The control system was of the Heusinger type. While the prototype had a Westinghouse brake, the production locomotives had a Knorr brake. The air pump was attached to the rear water tank, while the main air tank was above it on the water tank. The locomotive had electrically operated headlights.

Due to the beginning of the Second World War, the vehicles could not be delivered to Chile. They were then tested by O&K on the Rehagen-Klausdorf army training area and probably also on lines of the Mecklenburg-Pomeranian narrow-gauge railway. In 1944, the Deutsche Reichsbahn acquired the locomotives to use them on lines in occupied Poland. Therefore, in the second half of the same year, they were handed over to Gedob Direktion Krakow, where they were stationed at BW Jedrzejow.^[19]