Data from Bogdan Pokropinski, "Die Lokomotiv-Serie Tk dre Lettischen Staatland", Die Museums-Eisenbahn 3/1989, pp. 6-7; "OKa1" in Wikipedia at [], last accessed 31 October 2025; and Tomasz Galka , "OKa1 / TKa242" in Standard-Gauge Locomotives in Poland at []. last accessed 31 October 2025.
The first three Tks were built by Hohenzollern (works numbers 4635-4637) in 1928. Krupp supplied the next three in 1931 (works numbers 1196-1198) at the same time Henschel & Sohn produced three more. The others were Latvian-built. Daugavpils and Lepala in Latvia supplied 10 in 1933-1934.
The locomotive's layout included large-diameter leading wheels under the smokebox, the cylinders under the running board between the leading axle and the single powered axle under the firebox. The trailing axle used a Bissel truck and supported the cab and bunker. A pneumatic traction enhancer could be used to shift more of the engine's weight to the single driving axle.
As the dimensions and the 2-2-2 wheel arrangement suggest, the Tks provided the motive power for light suburban trains. After the Soviet Union occupied Latvia in 1940, twelve of the class served the Soviet railways into the 1950s. At that point, they worked as industrial locomotives. Poland operated two of the class as the only single-axle standard-gauge locomotives ever used in Poland.
Four others wound up in Germany, three in the West, one in the East, until the early 1950s.
| Principal Dimensions by Steve Llanso of Middle Run Media | |
|---|---|
| Class | Tk |
| Locobase ID | 1304 |
| Railroad | Latvian State Railway |
| Country | Latvia |
| Whyte | 2-2-2T |
| Number in Class | 20 |
| Road Numbers | Tk-231-250 |
| Gauge | 5' |
| Number Built | 20 |
| Builder | several |
| Year | 1929 |
| Valve Gear | |
| Locomotive Length and Weight | |
| Driver Wheelbase (ft / m) | |
| Engine Wheelbase (ft / m) | |
| Ratio of driving wheelbase to overall engine wheelbase | |
| Overall Wheelbase (engine & tender) (ft / m) | |
| Axle Loading (Maximum Weight per Axle) (lbs / kg) | |
| Weight on Drivers (lbs / kg) | 34,496 / 15,647 |
| Engine Weight (lbs / kg) | 83,328 / 37,797 |
| Tender Loaded Weight (lbs / kg) | |
| Total Engine and Tender Weight (lbs / kg) | |
| Tender Water Capacity (gals / ML) | |
| Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | |
| Minimum weight of rail (calculated) (lb/yd / kg/m) | 57 / 28.50 |
| Geometry Relating to Tractive Effort | |
| Driver Diameter (in / mm) | 59.10 / 1500 |
| Boiler Pressure (psi / kPa) | 205.70 / 1400 |
| High Pressure Cylinders (dia x stroke) (in / mm) | 12.6" x 20.47" / 320x520 |
| Tractive Effort (lbs / kg) | 9614 / 4360.84 |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 3.59 |
| Heating Ability | |
| Tubes (number - dia) (in / mm) | 55 - 1.772" / 45 |
| Flues (number - dia) (in / mm) | 26 - 4.252" / 108 |
| Flue/Tube length (ft / m) | 8.20 / 2.50 |
| Firebox Area (sq ft / m2) | |
| Grate Area (sq ft / m2) | 11.84 / 1.10 |
| Evaporative Heating Surface (sq ft / m2) | 556 / 51.70 |
| Superheating Surface (sq ft / m2) | 235 / 21.80 |
| Combined Heating Surface (sq ft / m2) | 791 / 73.50 |
| Evaporative Heating Surface/Cylinder Volume | 188.21 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 2435 |
| Same as above plus superheater percentage | 3166 |
| Same as above but substitute firebox area for grate area | |
| Power L1 | |
| Power MT | |