DRG Class 99.73-76
| Class 99.73-76 | |
|---|---|
 |
|
| Number(s) | 99 731 - 762 DRG / DR 99 1731 - 99 1762 DR |
| Quantity | 32 |
| Manufacturer |
Sächsische Maschinenfabrik Berliner Maschinenbau |
| Year(s) of manufacture | 1928, 1933 |
| Retired | from 1945 |
| Wheel arrangement | 2-10-2 |
| Axle arrangement | 1'E1' h2 |
| Type | K 57.9 |
| Track gauge | 750 mm (2 ft 5 1⁄2 in) |
| Length over couplers | 10,540 mm (34 ft 7.0 in) |
| Height | 3,550 mm (11 ft 7.8 in) |
| Overall wheelbase | 7,600 mm (24 ft 11.2 in) |
| Service weight | 56.7 t (55.8 long tons; 62.5 short tons) |
| Adhesive weight | 46.1 t (45.4 long tons; 50.8 short tons) |
| Top speed | 30 km/h (19 mph) |
| Indicated Power | 600 PS (440 kW; 590 hp) |
| Starting tractive effort | 83.35 kN (18,740 lbf) |
| Driving wheel diameter | 800 mm (31.50 in) |
| Carrying wheel diameter | 550 mm (21.65 in) |
| Valve gear | Walschaerts (Heusinger) |
| No. of cylinders | 2 |
| Cylinder bore | 400 mm (15.75 in) |
| Piston stroke | 450 mm (17.72 in) |
| Boiler Overpressure | 14 bar (1,400 kPa; 200 psi) |
| Grate area | 1.74 m2 (18.7 sq ft) |
| Radiative heating area | 6.70 m2 (72.1 sq ft) |
| Superheater area | 29.00 m2 (96.9 sq ft) |
| Evaporative heating area | 80.30 m2 (864.3 sq ft) |
| Water capacity | 5.8 m3 (200 cu ft) |
| Fuel | 2.5 t (2.5 long tons; 2.8 short tons) coal |
| Locomotive brakes | Knorr compressed-air brake |
| Train brakes |
Körting vacuum brake Heberlein brake initially |
| Couplers | Scharfenberg couplers |
The German Class 99.73-76 engines were standard locomotives (Einheitslokomotiven) in service with the Deutsche Reichsbahn for Saxony's narrow gauge railways. Together with their follow-on class, the DR Class 99.77-79, they were the most powerful narrow gauge locomotives in Germany for the 750 mm (2 ft 5 1⁄2 in) track gauge.
Although there was already a very powerful locomotive for operations on the mountain lines in the Ore Mountains (Erzgebirge) of eastern Germany in the shape of the ten-coupled ex-Saxon Class 99.67-71, there was a further requirement for an even more powerful class. So it fell to the newly formed Reichsbahn railway division of Dresden to procured an Einheitslok with a 750 mm (2 ft 5 1⁄2 in) track gauge. The Standardisation Office of the German Locomotive Union in Berlin-Tegel prepared the design for this class.
The first series of 13 locomotives was built by the Sächsische Maschinenfabrik, previously Richard Hartmann, in Chemnitz. According to the supply agreement, the Sächsische Maschinenfabrik was supposed to deliver more locos, but as a result of its bankruptcy and liquidation in 1930, this order was transferred to the Berliner Maschinenbau AG (BMAG), previously Schwartzkopff. In 1928, seven locomotives were supplied by BMAG and another twelve followed in 1933.
The locomotives were very modern for their time, and were similar in design to the standard gauge Einheitslokomotiven. The engines fulfilled expectations; by double-heading it was now possible to haul even very long (up to 56 axles) narrow gauge trains uphill.
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Wikipedia