# Saxon XV HTV

Saxon XV HTV
DRG Class 79
Number(s) 1351 and 1352
79 001 and 79 002
Quantity 2
Manufacturer Sächsische Maschinenfabrik, Chemnitz
Year(s) of manufacture 1916
Wheel arrangement 0-6-6-0
Axle arrangement C C h4v
Type Pt 66.15
Track gauge 1,435 mm (4 ft 8 12 in)
Length over buffers 14,660 mm (48 ft 1 in)
Wheelbase 7,500 mm (24 ft 7 in)
Overall wheelbase 11,100 mm (36 ft 5 in)
Minimum curve 170 m
Empty weight 74.6 t
Service weight 92.2 t
Top speed 70 km/h (43 mph)
Coupled wheel diameter 1,400 mm (4 ft 7 in)
Valve gear Walschaerts (Heusinger)
No. of cylinders 4
LP cylinder bore 680 mm (27 in)
HP cylinder bore 440 mm (17 in)
Piston stroke 630 mm (25 in)
Boiler Overpressure 15 bar
No. of heating tubes 124
Heating tube length 4,500 mm (14 ft 9 in)
Grate area 2.5 m2 (27 sq ft)
Radiative heating area 11.29 m2 (121.5 sq ft)
Tube heating area 78.90 m2 (849.3 sq ft)
Superheater area 40.9 m2 (440 sq ft)
Evaporative heating area 127.20 m2 (1,369.2 sq ft)
Water capacity 8.5 m3 (1,900 imp gal)
Fuel 2.2 t coal
Auxiliary brake Counterweight brake
Locomotive brakes Knorr compressed-air brake

The Saxon Class XV ${\displaystyle \textstyle {\mathfrak {H}}}$T${\displaystyle \textstyle {\mathfrak {V}}}$ was a class of goods train steam locomotive operated by the Royal Saxon State Railways, which had been conceived for hauling trains and acting as banking engines for routes in the Ore Mountains. In 1925 the Deutsche Reichsbahn grouped them into their DRG Class 79.0.

## History

The two locomotives were built in 1916 at the Sächsischen Maschinenfabrik, formerly Hartmann.

The undercarriage of the locomotives was unusual. Instead of an alternative proposal for a twelve-coupled locomotive with sideways-sliding Gölsdorf axles, as was realised a year later in the shape of the Württemberg K, the Saxon Railways decided on a proposal by their head of the engineering department, Lindner, for a design that was unique in Germany: the Saxon XV HTV was given two, fixed, six-coupled drives. This was mainly because they had doubts about the suitability of the Gölsdorf system for twelve-couplers. The outside axles were designed as Klien-Lindner axles and could be slid sideways by about 37 mm from their centre position. The design of these axles required them to be fixed into an outside frame. In the centre of the locomotive was a double cylinder on each side, each with a high-pressure cylinder for the rear and a low-pressure cylinder for the front drive.

This design with its low stress on the rails, low inherent resistance and simple weight compensation was promising especially as it also avoided the use of cranked driving axles. Similar thoughts in the USA during the 1930s led to the development of duplex locomotives. Because the cylinders of adjacent axles also had 28 mm of side play, the locomotive could negotiate radii of as little as 170 m. Through the special design of the cylinders, the use of crank axles (Kropfachse) was avoided. Whilst this design enabled the steam lines between the high- and low-pressure cylinders to be extremely short, long admission and exhaust tubes were necessary.

The XV HTV soon proved to be expensive to maintain, particularly with regard to the drives and the hollow axles; as a result no more were procured. Even the usual tendency of all compound engines to sway could not be eliminated by the Klien-Lindner configuration. Wear and tear on the wheel tyres changed the crank settings of the driving gear. That meant that the synchronisation of the drive had to be constantly adjusted, in order to ensure a balanced distribution of effort.

Nevertheless, the engines were successful in practice. They had impressive riding qualities right up to their top speed and wear and tear on the wheel flanges was low. The Deutsche Reichsbahn took both locomotives over as 79 001 and 79 002, but retired them by 1932.

The serial number 79 001 was allocated from 1938 to 1947 to BLE No. 44 of the former Brunswick State Railway Company and from 1951 it was given to the former French locomotive, 242 TA - 602, which ended up in German hands after World War II.

## Design features

The boiler barrel comprised 2 shells with a diameter of 1,450 mm. On the top were two steam domes which were connected by a pipe inside the boiler. Between steam dome and chimney was a sand box. The firebox was made of copper and position over the first axle of the rear drive. The smokebox superheater was of the Schmidt type.

The locomotive frame comprised an inside frame of 28 mm thick plate, and an outside frame for the hollow axles of 20 mm thick plate.

The four-cylinder compound cylinders were arranged horizontally on the outside and each drove its centre axle