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The reference for locomotives and railcars

Polish State Railways OKl27

Poland 1927 122 produced
OKl 27-41 in Chabówka railway museum Michal Derela CC BY-SA 4.0

The designation OKl27 stands for a passenger (O) tank locomotive (K) with the wheel arrangement 2-6-2 (l), which was designed in 1927. They were the first locomotives designed and built entirely in Poland and a total of 122 were built between 1928 and 1933. In terms of appearance, they were reminiscent of typical German steam locomotives, just when you look at the driver's cab with the bent side walls. They were delivered by H. Ceglielski from Posen.

Thanks to its symmetrical axle arrangement, it was equally suitable for fast driving in both directions, which made it suitable for the use on suburban railways. When it was introduced, it was the heaviest 2-6-2 tank locomotive in Europe and the maximum axle load was around 18 tonnes.

With good coal, the locomotives were able to pull a passenger train weighing 350 tonnes at 80 km/h on level ground, on a gradient of 1.4 percent this was still 60 km/h with 130 tonnes. Although the running characteristics became a bit unsteady from 50 km/h, this hardly disturbed the operation on suburban trains with many stops. After the invasion from the Germans, 120 of the locomotives were operated by the Reichsbahn as class 7512. After the end of the war still 95 engines remained in Poland, which were used by the PKP in the areas around Warsaw and Katowice. After retirement from passenger train service, some were sold to private railways. Today four pieces are preserved, half of which are set up as monuments and half in museums.

Technical data

General

Built
1927-1933
Manufacturers
Cegielski
Wheel arrangement
2-6-2T (Prairie)
Gauge
1,435 mm (Standard gauge)

Dimensions and weights

Wheelbase
8.80 m
Empty mass
67.7 t
Service mass
85.1 t
Adhesion mass
54.2 t
Rigid wheelbase
3.60 m
Axle load
18.1 t
Water capacity
10,000 l
Fuel capacity
4 t (coal)

Boiler

Grate area
2.6 m²
Evaporative heating surface
127.7 m²
Superheater surface
45.2 m²
Total heating surface
172.9 m²

Power plant

Driver diameter
1,500 mm
Boiler pressure
14 bar
Expansion type
simple expansion
Cylinders
two, 540 x 630 mm

Power

Power source
steam
Indicated power
684 kW (930 PS)
Top speed
80 km/h
Starting effort
145.7 kN

Calculated values

Factor of adhesion
1 : 3.65
Optimal speed
29 km/h
Power-to-weight ratio
8.0 kW/t
Adhesive weight/Total
1 : 1.57
Tractive force/Heating surface
1 : 17.60
Grate area/Heating surface
1 : 66.50
Total/Superheater
1 : 2.83
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