Hungarian State Railways MIa
Hungarian State Railways class 11, later 175, Romanian Railway class 11, and Yugoslav Railway class 160
The Mla was a small tank locomotive for passenger service on branch lines with a low axle load limit. It was developed from the MI, but was lighter with smaller cylinders and now had its single powered axle in the rear position. The boiler was still of the Brotan type and the cylinders still worked in compound. While the MI had been designed to haul 110 tonnes with 60 km/h on the level, the MIa only had to cope with 100 tonnes at the same speed.
The first 23 were produced by MÁVAG of Budapest in 1910. They were renamed to class 11 in 1911 and eight more were delivered two years later. After World War I, four came to Romania and one to the SHS state and later Yugoslavia. In Romania, the CFR retired its locomotives as early as in 1935. In Hungary, they were superheated and simpled starting in 1925. The first ones were scrapped in 1939 and after 1947, only four were remaining. In the new class scheme of 1957, they got the number 175. They were scrapped between 1959 and 1963.
Technical data
General
| Property | as built | rebuilt |
|---|---|---|
| Built | 1910, 1913 | |
| Manufacturers | MÁVAG | |
| Wheel arrangement | 2-2-0T | |
| Gauge | 1,435 mm (Standard gauge) | |
Dimensions and weights
| Property | as built | rebuilt |
|---|---|---|
| Length | 5.42 m | |
| Wheelbase | 3.10 m | |
| Service mass | 19.1 t | 19.4 t |
| Adhesion mass | 9.6 t | 9.7 t |
| Rigid wheelbase | 3.10 m | |
| Axle load | 9.6 t | 9.7 t |
| Water capacity | 2,000 l | |
| Fuel capacity | 0.7 t (coal) | |
Boiler
| Property | as built | rebuilt |
|---|---|---|
| Grate area | 0.78 m² | |
| Firebox surface | 5.03 m² | |
| Tube heating surface | 25.82 m² | 18.47 m² |
| Evaporative heating surface | 30.85 m² | 23.5 m² |
| Total heating surface | 30.9 m² | 30.5 m² |
| Superheater surface | 7 m² | |
Power plant
| Property | as built | rebuilt |
|---|---|---|
| Driver diameter | 1,040 mm | |
| Boiler pressure | 16 bar | 15 bar |
| Expansion type | compound | simple expansion |
| Cylinders | two, HP: 220 x 400 mm and LP: 330 x 400 mm | two, 220 x 400 mm |
Power
| Property | as built | rebuilt |
|---|---|---|
| Power source | steam | |
| Indicated power | 138 kW (188 PS) | |
| Top speed | 60 km/h | |
| Starting effort | 17.5 kN | 23.7 kN |
| Starting effort simple | 21.0 kN | |
Calculated values
| Property | as built | rebuilt |
|---|---|---|
| Factor of adhesion | 1 : 5.38 | 1 : 3.99 |
| Optimal speed | 48 km/h | |
| Power-to-weight ratio | 7.2 kW/t | |
| Heating Surface Equivalent | 56.0 m² | 62.7 m² |
| Cylinder volume/HSE | 1 : 576.99 | 1 : 485.40 |
| Adhesive weight/Total | 1 : 1.99 | 1 : 2.01 |
| Tractive force/Heating surface | 1 : 11.87 | 1 : 16.25 |
| Grate area/Heating surface | 1 : 39.55 | 1 : 39.10 |
| Firebox/Tube surface | 1 : 5.13 | 1 : 3.67 |
| Total/Superheater | 1 : 3.36 |
