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Caledonian class 721 “Dunalastair I to IV”
The increasing weight of the express trains in the 1880s and 1890s also presented the Caledonian Railway with the problem that inefficient double-headings had to be used more and more frequently. John F. McIntosh, who...
General
| Property | Caledonian class 721 “Dunalastair I to IV” Dunalastair IV |
|---|---|
| Built | 1904-1910 |
| Manufacturers | St. Rollox |
| Wheel arrangement | 4-4-0 (American) |
| Gauge | 1,435 mm (Standard gauge) |
Dimensions and weights
| Property | Caledonian class 721 “Dunalastair I to IV” Dunalastair IV |
|---|---|
| Wheelbase | 7.26 m |
| Rigid wheelbase | 2.97 m |
| Service weight | 55.2 t |
| Adhesive weight | 36.4 t |
| Axle load | 18.8 t |
| Total weight | 109.1 t |
| Water capacity | 16,228 l |
| Fuel capacity | 4.6 t (coal) |
Boiler
| Property | Caledonian class 721 “Dunalastair I to IV” Dunalastair IV |
|---|---|
| Grate area | 1.951 m² |
| Firebox surface | 13.471 m² |
| Tube heating surface | 136.568 m² |
| Evaporative heating surface | 150.039 m² |
| Total heating surface | 150.0 m² |
Power plant
| Property | Caledonian class 721 “Dunalastair I to IV” Dunalastair IV |
|---|---|
| Driver diameter | 1,981 mm |
| Boiler pressure | 12.4 bar |
| Expansion type | simple expansion |
| Cylinders | two, 483 x 660 mm |
Power
| Property | Caledonian class 721 “Dunalastair I to IV” Dunalastair IV |
|---|---|
| Power source | steam |
| Estimated power | 611 kW (831 PS) |
| Starting effort | 81.9 kN |
Calculated values
| Property | Caledonian class 721 “Dunalastair I to IV” Dunalastair IV |
|---|---|
| Factor of adhesion | 1 : 4.36 |
| Optimal speed | 45 km/h |
| Power-to-weight ratio | 11.1 kW/t |
| Heating Surface Equivalent | 217.4 m² |
| Cylinder volume/HSE | 1 : 1,111.36 |
| Adhesive weight/Total | 1 : 1.52 |
| Tractive force/Heating surface | 1 : 11.40 |
| Grate area/Heating surface | 1 : 76.90 |
| Firebox/Tube surface | 1 : 10.14 |
