South African class MJ1
The class MJ1 was created in World War I when the SAR had found out that not only German manufacturers were now out of reach, but also British companies didn't have huge capacities. This became especially apparent with the 2-6-6-0 class MJ Mallet of which only two could be delivered by Maffei and another eight came from North British. So Montreal Locomotive Works designed the MJ1 based on the same specifications set up by D.A. Hendrie.
It was the last new class of Mallets introduced by the SAR. The MJ1 had a somewhat larger boiler compared to the MJ and had a sand dome mounted on the boiler in American fashion. The drivers of the eight locomotives were only 42 1/2 inches, but were also increased to 42 3/4 inches with new tires in 1922. In 1939, W.A.J. Day equipped this class and the MJ with a new common standard boiler. The last ones were retired in 1960.
Technical data
General
| Property | as built | rebuilt |
|---|---|---|
| Built | 1918 | 1939 |
| Manufacturers | Montreal Locomotive Works | |
| Wheel arrangement | 2-6-6-0 | |
| Gauge | 1,067 mm (Cape gauge) | |
Dimensions and weights
| Property | as built | rebuilt |
|---|---|---|
| Length | 20.91 m | |
| Wheelbase | 9.96 m | |
| Total wheelbase | 18.50 m | |
| Service mass | 89.9 t | |
| Adhesion mass | 82.3 t | |
| Total mass | 141.5 t | |
| Rigid wheelbase | 2.54 m | |
| Axle load | 14.3 t | |
| Water capacity | 19,321 l | |
| Fuel capacity | 10.2 t (coal) | |
Boiler
| Property | as built | rebuilt |
|---|---|---|
| Grate area | 3.716 m² | |
| Firebox surface | 12.635 m² | 12.356 m² |
| Tube heating surface | 177.073 m² | 165.368 m² |
| Evaporative heating surface | 189.708 m² | 177.724 m² |
| Superheater surface | 38.369 m² | 32.516 m² |
| Total heating surface | 228.1 m² | 210.2 m² |
Power plant
| Property | as built | rebuilt |
|---|---|---|
| Driver diameter | 1,080 mm | 1,086 mm |
| Boiler pressure | 13.8 bar | |
| Expansion type | compound | |
| Cylinders | four, HP: 419 x 610 mm and LP: 660 x 610 mm | |
Power
| Property | as built | rebuilt |
|---|---|---|
| Power source | steam | |
| Estimated power | 969 kW (1,317 PS) | 932 kW (1,267 PS) |
| Starting effort | 165.8 kN | 164.8 kN |
| Starting effort simple | 198.9 kN | 197.7 kN |
Calculated values
| Property | as built | rebuilt |
|---|---|---|
| Factor of adhesion | 1 : 4.87 | 1 : 4.90 |
| Optimal speed | 35 km/h | |
| Power-to-weight ratio | 10.8 kW/t | 10.4 kW/t |
| Heating Surface Equivalent | 329.6 m² | 304.5 m² |
| Cylinder volume/HSE | 1 : 1,143.73 | 1 : 1,237.95 |
| Adhesive weight/Total | 1 : 1.09 | |
| Tractive force/Heating surface | 1 : 15.18 | 1 : 16.37 |
| Grate area/Heating surface | 1 : 61.38 | 1 : 56.58 |
| Firebox/Tube surface | 1 : 14.01 | 1 : 13.38 |
| Total/Superheater | 1 : 4.94 | 1 : 5.47 |
