Data from [], a website that focuses on the Saxon 750-mm gauge locomotives that were so much a part of German local operations for 100 years. (last accessed 25 Feb 2006). See also "Baureihe 99.73" on Albert Gieseler's Dampfmaschinen und Lokomotiven website at [
], last accessed 29 November 2021.
These were the model for the East German 99.7s. They had a narrow grate and a bar frame and were among the first narrow-gauge designs to emerge after the nationalization of 1923. According to the Sachsendampf webpage, the demands of the 535 miles of 750-mm lines that came under the Deutsche Reichsbahn beginning in 1923 included some pretty severe, 1 in 20 (5%) grades. The IV K mallets (see Locobase 5070) simply couldn't handle the traffic. Although the VI K 0-10-0Ts (Locobase 7463) did add needed power, a still more powerful locomotive was needed and this standard locomotive design, which contributions by the noted Richard Paul Wagner, went into production.
Like many other 750-mm locomotives, this design had an "oversquare" cylinder layout in which the diameter was greater than the stroke. A photo on the Sachsendampf site shows the Heusinger gear's visual dominance over the very small drivers, the third of which was driven by the pistons.
Sachsische Maschinenfabrik delivered the first thirteen (works numbers 4678-4687, 4691-4693) with first acceptance coming on 21 December 1928 and the last in November 1929. They were an immediate hit. Locomotive 99 735 traveled 3,579 km (2,222 sm) on a line that measured only 18.5 km (11.5 sm) long.
Schwartzkopff added seven in 1929 (works numbers 9533-9539) and twelve more in 1933 (works numbers 10142-10153).
(Although they usually recorded the external diameters (water side) of the tubes, German locomotive designers calculated the tube heating surface using the interior diameter (fire side). In this locomotive, fire side heating surface area was 73.6 sq m (792 sq ft). Adding 6.7 sq m of direct heating surface area brought total area to 80.7 sq m (864 sq ft). Locobase specs show the water side area calculated from the tubes' external diameters.)
Only 10 had been withdrawn from service by the end of World War II and the remainder operated under East German control on the same railways they'd served before. Fourteen of these were fitted with new boilers in 1963-1965
Principal Dimensions by Steve Llanso of Middle Run Media | |
---|---|
Class | K.57.9 / BR 99.73-99.75 |
Locobase ID | 4926 |
Railroad | DRG |
Country | Germany |
Whyte | 2-10-2T |
Number in Class | 32 |
Road Numbers | 99.731-99.750 |
Gauge | 75 cm |
Number Built | 32 |
Builder | several |
Year | 1928 |
Valve Gear | Heusinger |
Locomotive Length and Weight | |
Driver Wheelbase (ft / m) | 13.12 / 4 |
Engine Wheelbase (ft / m) | 24.93 / 7.60 |
Ratio of driving wheelbase to overall engine wheelbase | 0.53 |
Overall Wheelbase (engine & tender) (ft / m) | 24.93 / 7.60 |
Axle Loading (Maximum Weight per Axle) (lbs / kg) | 20,283 / 9200 |
Weight on Drivers (lbs / kg) | 101,633 / 46,100 |
Engine Weight (lbs / kg) | 125,002 / 56,700 |
Tender Loaded Weight (lbs / kg) | |
Total Engine and Tender Weight (lbs / kg) | |
Tender Water Capacity (gals / ML) | 1531 / 5.80 |
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 3.30 / 3 |
Minimum weight of rail (calculated) (lb/yd / kg/m) | 34 / 17 |
Geometry Relating to Tractive Effort | |
Driver Diameter (in / mm) | 31.50 / 800 |
Boiler Pressure (psi / kPa) | 203.10 / 1400 |
High Pressure Cylinders (dia x stroke) (in / mm) | 17.72" x 15.75" / 450x400 |
Tractive Effort (lbs / kg) | 27,104 / 12294.18 |
Factor of Adhesion (Weight on Drivers/Tractive Effort) | 3.75 |
Heating Ability | |
Tubes (number - dia) (in / mm) | 92 - 1.772" / 45 |
Flues (number - dia) (in / mm) | 28 - 4.646" / 118 |
Flue/Tube length (ft / m) | 11.48 / 3.50 |
Firebox Area (sq ft / m2) | 72.12 / 6.70 |
Grate Area (sq ft / m2) | 18.73 / 1.74 |
Evaporative Heating Surface (sq ft / m2) | 953 / 88.50 |
Superheating Surface (sq ft / m2) | 312 / 29 |
Combined Heating Surface (sq ft / m2) | 1265 / 117.50 |
Evaporative Heating Surface/Cylinder Volume | 211.99 |
Computations Relating to Power Output (More Information) | |
Robert LeMassena's Power Computation | 3804 |
Same as above plus superheater percentage | 4755 |
Same as above but substitute firebox area for grate area | 18,309 |
Power L1 | 9776 |
Power MT | 1060.30 |