Saxon VII T (Hartmann type)
German Reichsbahn class 9870
The Saxon class VII T included various two-axle local railway tank locomotives, most of which still came from the private railways. Later, the state railway ordered another 42 locomotives that were similar to the existing ones. Like other local railway locomotives, they were of simple design, since cheap maintenance was more important than high speeds or high tractive effort. Because the production batches were a total of twelve years apart, there were some changes from batch to batch. For example, the first locomotives took the live steam from a regulator on top of the boiler, but the later ones had a large steam dome. They had not yet a continuous air brake for the train.
There was also a one-off that had a longer wheelbase, larger wheels, was lighter and was 5 km/h faster. However, it was not built in series and retired in 1927. The Reichsbahn took over 29 of the 42 production locomotives in 1925 as 98 7051 to 98 7079. After the Second World War, all remaining ones came to the Reichsbahn of the GDR and the last ones were used there until 1967. One of them still exists today in its original color scheme.
Technical data
General
| Property | light variant | heavy variant |
|---|---|---|
| Built | 1882-1894 | |
| Manufacturers | Hartmann | |
| Wheel arrangement | 0-4-0T (Four-coupled) | |
| Gauge | 1,435 mm (Standard gauge) | |
Dimensions and weights
| Property | light variant | heavy variant |
|---|---|---|
| Length | 7.88 m | |
| Empty mass | 19 t | 20.7 t |
| Service mass | 24.6 t | 26.7 t |
| Adhesion mass | 24.6 t | 26.7 t |
| Axle load | 12.3 t | 13.4 t |
| Water capacity | 2,900 l | |
| Fuel capacity | 0.9 t (coal) | |
Boiler
| Property | light variant | heavy variant |
|---|---|---|
| Grate area | 0.9 m² | |
| Firebox surface | 4.5 m² | |
| Tube heating surface | 39 m² | |
| Evaporative heating surface | 43.5 m² | |
| Total heating surface | 43.5 m² | |
Power plant
| Property | light variant | heavy variant |
|---|---|---|
| Driver diameter | 1,100 mm | |
| Boiler pressure | 12 bar | |
| Expansion type | simple expansion | |
| Cylinders | two, 355 x 530 mm | |
Power
| Property | light variant | heavy variant |
|---|---|---|
| Power source | steam | |
| Estimated power | 130 kW (177 PS) | |
| Top speed | 40 km/h | |
| Starting effort | 61.9 kN | |
Calculated values
| Property | light variant | heavy variant |
|---|---|---|
| Factor of adhesion | 1 : 3.90 | 1 : 4.23 |
| Optimal speed | 13 km/h | |
| Power-to-weight ratio | 5.3 kW/t | 4.9 kW/t |
| Heating Surface Equivalent | 66.0 m² | |
| Cylinder volume/HSE | 1 : 1,589.68 | |
| Adhesive weight/Total | 1 : 1.00 | |
| Tractive force/Heating surface | 1 : 29.74 | |
| Grate area/Heating surface | 1 : 48.33 | |
| Firebox/Tube surface | 1 : 8.67 | |