The reference for locomotives and railcars
Tank Locomotives 0-12-0T, 2-12-0T and 2-12-4T[Inhalt]
UIC Classification F, 1'F and 1'F2
BDZ 46.03 in May 2015
BDZ 46.03 in May 2015
Ivo Radoev

Even if tank locomotives were built in many places with articulated chassis in order to achieve high tractive forces, there were a number of reasons against this. These were primarily the tendency of a chassis group to slip and the need for flexible steam lines. As a result, tank locomotives with six coupled axles in one frame were created in some places. However, since this places high demands on the construction of the running gear in order to be able to negotiate curves without problems, only very few locomotives of this type were built.

The following axis sequences have been implemented:

UICF t1'F t1'F2' tWhyte0-12-0T2-12-0T2-12-4TSwitzerlandE 6/6E 6/7E 6/9France060 T160 T162 TTurkey666769

The first twelve-coupled tank locomotives were built in 1912. One of them was the kkStB class 269 for the Erzbergbahn in Styria. This rack locomotive had no carrying axles. At the same time, Hanomag built the class F10 tank locomotives, with a leading and a trailing axle each, for the Staatsspoorwegen in the Dutch East Indies. The Bulgarian State Railways procured two different types of twelve-coupled tank locomotives for their heavy ore trains. These were the 1922 series 4000 without carrying axles and the 1931 series 4500. These had a leading axle and a bogie to carry the rear stores.

Bulgarian State Railway series 4500
later series 46
Bulgaria | 1931 | 20 produced

As early as 1922, the Bulgarian State Railways had procured tank locomotives of the series 4000 with an 0-12-0 wheel arrangement from Hanomag for transporting the heavy coal trains from Pernik to Sofia. At the end of the twenties, the train performance was to be improved. The challenge now was to transport trains weighing 420 tonnes up the gradient of 2.5 percent at 20 km/h and to negotiate curves with a radius of up to 275 metres. Since it was agreed to achieve a comparable standardization based on the standardization program of the Deutsche Reichsbahn, the boiler had to be interchangeable with the other heavy locomotives which were to be developed new. These were the 8000 series (later 01) 2-8-2 express locomotives and the 9000 series (later 10) 2-10-0 freight locomotive.

In order to be able to negotiate curves with a radius of 250 meters at the appropriate speed with the specified wheel arrangement of 2-12-4T, the running gear had to be designed in a correspondingly complex manner. The only axles which were fixed in the frame and had full flanges were the second and fourth coupled axles. The leading axle was radially adjustable by 80 mm and connected to the first coupled axle to form a Krauss-Helmholtz bogie. There were no wheel flanges on the third and fourth coupled axles. The sixth coupled axle could be moved laterally again and the rear bogie had a lateral play of 110 mm.

The first twelve examples were delivered by the Polish company Cegielski in Poznan in 1931 and actually had a boiler that, together with most of the fittings, could be exchanged with the sister series built by other manufacturers. With 18 cubic meters of water and ten tonnes of coal, the supplies were correspondingly large. The water supply was partly accommodated under the coal bunker at the back in order to be able to keep the side water tanks as short that the firebox was accessible from the sides for maintenance.

Schematic drawing
Schematic drawing
Die Lokomotive, September 1943

The firebox was over 2.70 meters long in order to have a sufficiently large grate for the low grade Pernik coal with a high proportion of ash and slag. Since this coal led to the formation of a large amount of smoke, this had to be taken into account when passing through the tunnels on the line. The solution consisted of a ventilation system in the cab, which sucked in the relatively clean air from the lower areas and blew it out again at the crew's head height.

The first twelve engines had only two cylinders with a diameter and stroke of 700 mm each. In 1943 another series of eight was ordered after the existing locomotives had already been renamed from the 4500 series to the 46 series. They had to have three cylinders, but despite the placement of the third cylinder under the smoke box, the boiler could not be much higher. The outer cylinders continued to drive the third coupled axle, while the inner cylinder drove the second. Since procurement from Poland was no longer possible due to the war, the order went to BMAG in Berlin.

Since the incline on the route between Pernik and Sofia only permitted 420 tonnes behind such powerful locomotives, the coal trains weighing up to 1,200 tonnes were pulled by up to three locomotives. There was a lead locomotive in front of the actual train locomotive and a pusher locomotive at the end. All having survived until the mid-sixties, they were retired by 1975. One each of the two- and three-cylinder locomotives are still existing today and the latter has been operational again since 2015.

Variantmodel 1931model 1943
Axle config2-12-4T (Bulgaria) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length59 ft 8 3/4 in59 ft 6 3/4 in
Wheelbase47 ft 6 7/8 in47 ft 4 7/8 in
Fixed wheelbase15 ft 3 1/16 in
Empty weight244,713 lbs263,717 lbs
Service weight328,599 lbs343,480 lbs
Adhesive weight224,210 lbs238,099 lbs
Axle load37,479 lbs39,683 lbs
Water capacity4,755 us gal
Fuel capacity22,046 lbs (coal)
Power sourcesteam
Estimated power2,079 hp (1,550 kW)
Optimal speed17 mph24 mph
Starting effort78,273 lbf55,625 lbf
Power Plant
Driver diameter52.8 in
Boiler pressure232 psi
Expansion typesimple
Cylinderstwo, 27 9/16 x 27 9/16 inthree, 19 11/16 x 25 9/16 in
Grate area52.4 sq ft
Firebox area187.5 sq ft
Tube heating area2,224.4 sq ft
Evaporative heating area2,411.9 sq ft
Superheater area903.2 sq ft881.7 sq ft
Total heating area3,315.1 sq ft3,293.5 sq ft
Calculated Values
steam locomotive
tank locomotive
last changed: 07/2022
Staatsspoorwegen class F10
Indonesia | 1912 | 24 produced
Locomotive Magazine, November 1922

The state railway of the Dutch East Indies on Java had the challenge of moving heavy loads on cape-gauge mountain routes with a maximum axle load of 9.5 tonnes and curve radii of up to 140 meters. To solve these requirements, Hanomag proposed a tank locomotive with six coupled axles in one frame in order to be able to avoid building a Mallet with its disadvantages. Among these disadvantages were listed the tendency to slip, flexible and long steam lines, greater complexity of the running gear and unstable mounting of the boiler.

In the locomotive developed as a result, the four inner coupled axles were all firmly mounted in the frame. Only the first and sixth coupled axles could be moved laterally by 30 mm according to the Gölsdorf system, and the leading and trailing axles could be deflected laterally by 100 mm as Adams axles. The water tanks were drawn low between the frames in a new way. Now the boiler could be placed higher without raising the center of gravity to improve accessibility for maintenance.

Schematic drawing with dimensions
Schematic drawing with dimensions
Locomotive Magazine, August 1912

The last batch was built by Werkspoor in the Netherlands. The total of 24 examples built were the first of only two types with the axle configuration 2-12-2T in history, which is why this wheel arrangement is also known as “Javanic”. On the route for which the locomotives were developed, there was a high level of wear on the wheel flanges. They were then moved to another mountain route that had bigger curve radii. There they did very well.

ManufacturerHanomag, Werkspoor
Axle config2-12-2T (Javanic) 
Gauge3 ft 6 in (Cape gauge)
Dimensions and Weights
Wheelbase42 ft 10 15/16 in
Fixed wheelbase12 ft 3 5/8 in
Service weight164,465 lbs
Adhesive weight125,663 lbs
Axle load20,944 lbs
Water capacity2,245 us gal
Fuel capacity6,614 lbs (wood)
Power sourcesteam
Estimated power905 hp (675 kW)
Optimal speed19 mph
Starting effort30,938 lbf
Power Plant
Driver diameter43.4 in
Boiler pressure174 psi
Expansion typesimple
Cylinderstwo, 21 1/4 x 20 1/16 in
Grate area28 sq ft
Firebox area104 sq ft
Tube heating area1,311.5 sq ft
Evaporative heating area1,415.5 sq ft
Superheater area387.5 sq ft
Total heating area1,803 sq ft
Calculated Values
steam locomotive
tank locomotive
last changed: 06/2022
Philadelphia & Reading “Pennsylvania”
United States | 1863 | only one produced

The “Pennsylvania” of the Philadelphia & Reading wasn't only the biggest of the camelbacks designed by James Milholland, but also the biggest locomotive in the world when it was completed in 1863. It was a 0-12-0 that was used as pusher on the steep Falls Grade near Philadelphia, Pennsylvania.

A special feature of this locomotive was that it didn't have a tender, but wasn't a real tank locomotive either. This meant that it had no coal bunker and no water tank, but was stoked before each of the short climbs. Since it was found out that the freight cars of the time couldn't handle the forces of this massive locomotive, it was rebuilt in 1870. It now had only five axles, a tender and a new cab.

Axle config0-12-0T (Twelve-coupled) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase19 ft 7 in
Fixed wheelbase19 ft 7 in
Service weight110,250 lbs
Adhesive weight110,250 lbs
Axle load18,375 lbs
Fuel capacitycoal
Power sourcesteam
Estimated power500 hp (373 kW)
Optimal speed16 mph
Starting effort20,558 lbf
Power Plant
Driver diameter43 in
Boiler pressure100 psi
Expansion typesimple
Cylinderstwo, 20 x 26 in
Grate area31.5 sq ft
Firebox area198 sq ft
Tube heating area1,230 sq ft
Evaporative heating area1,428 sq ft
Total heating area1,428 sq ft
Calculated Values
steam locomotive
tank locomotive
James Milholland
last changed: 04/2024

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