Bavarian Pt 2/4 H
German Reichsbahn class 712
For the cost-effective use of passenger trains on lines with low passenger volumes, the Royal Bavarian State Railways developed a locomotive that reached sufficient speed in both directions and could be operated by one man. The solution was a tank locomotive with a 2-4-2T wheel arrangement, which had a tipping device for loading the firebox with coal.
Thanks to the superheater, it achieved adequate power and the driving wheel diameter of 1,546 mm ensured a good compromise between tractive power and speed. There was a gangway from the driver's cab to the train and the front platform could also be reached via running boards with railings. The water tanks were designed to be narrower than the locomotive so as not to block the way.
A special feature of the chassis was that the first driving axle was in a Krauss-Helmholtz bogie together with the leading axle, although there were only two driving axles. This resulted in a rigid wheelbase of zero with excellent curve guidance at the same time. The top speed was initially set at 75 km/h and later increased to 80 km/h. According to reports, however, they regularly ran in both directions at up to 90 km/h.
Twelve locomotives were built, some of which differed from one another in several aspects. The Reichsbahn took over all of these and classified them as class 712. Some survived the Second World War and were used until 1948.
Technical data
General
| Property | No. 5001 to 5010 | No. 5010 to 5011 |
|---|---|---|
| Built | 1906 | 1908 |
| Manufacturers | Krauss | |
| Wheel arrangement | 2-4-2T (Columbia) | |
| Gauge | 1,435 mm (Standard gauge) | |
Dimensions and weights
| Property | No. 5001 to 5010 | No. 5010 to 5011 |
|---|---|---|
| Length | 10.70 m | 10.74 m |
| Wheelbase | 7.30 m | |
| Service mass | 60 t | 58.5 t |
| Adhesion mass | 31.7 t | 31.4 t |
| Rigid wheelbase | 0.00 m | |
| Axle load | 16 t | 15.7 t |
| Water capacity | 8,000 l | |
| Fuel capacity | 1.8 t (coal) | |
| Empty mass | 46.1 t | |
Boiler
| Property | No. 5001 to 5010 | No. 5010 to 5011 |
|---|---|---|
| Grate area | 1.23 m² | |
| Firebox surface | 5.6 m² | |
| Tube heating surface | 62.4 m² | |
| Evaporative heating surface | 68 m² | |
| Superheater surface | 19.59 m² | |
| Total heating surface | 87.6 m² | |
Power plant
| Property | No. 5001 to 5010 | No. 5010 to 5011 |
|---|---|---|
| Driver diameter | 1,546 mm | |
| Boiler pressure | 12 bar | |
| Expansion type | simple expansion | |
| Cylinders | two, 490 x 540 mm | |
Power
| Property | No. 5001 to 5010 | No. 5010 to 5011 |
|---|---|---|
| Power source | steam | |
| Estimated power | 320 kW (435 PS) | |
| Top speed | 75 km/h | |
| Starting effort | 85.5 kN | |
Calculated values
| Property | No. 5001 to 5010 | No. 5010 to 5011 |
|---|---|---|
| Factor of adhesion | 1 : 3.64 | 1 : 3.60 |
| Optimal speed | 23 km/h | |
| Power-to-weight ratio | 5.3 kW/t | 5.5 kW/t |
| Heating Surface Equivalent | 135.2 m² | |
| Cylinder volume/HSE | 1 : 1,506.58 | |
| Adhesive weight/Total | 1 : 1.89 | 1 : 1.86 |
| Tractive force/Heating surface | 1 : 20.40 | |
| Grate area/Heating surface | 1 : 71.21 | |
| Firebox/Tube surface | 1 : 11.14 | |
| Total/Superheater | 1 : 3.47 | |