Pennsylvania class AAn
Pennsylvania classes D7 and D7a
United States 1882 119 produced
In order to be able to burn anthracite coal efficiently, class AAn was developed from class K (later D6). The K already had a wide firebox above the drivers, which was optimized here for the use of anthracite. There were 58 locomotives with a driver diameter of 68 inches, which became class D7 from 1895, and 61 with a driver diameter of 62 inches, which became class D7a.
Technical data
General
| Property | D7 | D7a |
|---|---|---|
| Built | 1882-1891 | |
| Manufacturers | Altoona | |
| Wheel arrangement | 4-4-0 (American) | |
| Gauge | 1,435 mm (Standard gauge) | |
Dimensions and weights
| Property | D7 | D7a |
|---|---|---|
| Length | 17.69 m | |
| Wheelbase | 6.91 m | |
| Total wheelbase | 14.78 m | |
| Service mass | 42.3 t | 43.7 t |
| Adhesion mass | 29 t | 29.6 t |
| Total mass | 69.6 t | 70.9 t |
| Rigid wheelbase | 2.36 m | |
| Axle load | 15 t | 14.8 t |
| Water capacity | 9,085 l | |
| Fuel capacity | 5.4 t (coal) | |
Boiler
| Property | D7 | D7a |
|---|---|---|
| Grate area | 3.233 m² | |
| Firebox surface | 14.4 m² | |
| Tube heating surface | 105.352 m² | |
| Evaporative heating surface | 119.752 m² | |
| Total heating surface | 119.8 m² | |
Power plant
| Property | D7 | D7a |
|---|---|---|
| Driver diameter | 1,727 mm | 1,575 mm |
| Boiler pressure | 9.7 bar | |
| Expansion type | simple expansion | |
| Cylinders | two, 432 x 610 mm | |
Power
| Property | D7 | D7a |
|---|---|---|
| Power source | steam | |
| Estimated power | 522 kW (710 PS) | |
| Starting effort | 54.0 kN | 59.2 kN |
Calculated values
| Property | D7 | D7a |
|---|---|---|
| Factor of adhesion | 1 : 5.27 | 1 : 4.90 |
| Optimal speed | 60 km/h | 55 km/h |
| Power-to-weight ratio | 12.3 kW/t | 11.9 kW/t |
| Heating Surface Equivalent | 191.8 m² | |
| Cylinder volume/HSE | 1 : 931.09 | |
| Adhesive weight/Total | 1 : 1.46 | 1 : 1.48 |
| Tractive force/Heating surface | 1 : 9.42 | 1 : 10.33 |
| Grate area/Heating surface | 1 : 37.04 | |
| Firebox/Tube surface | 1 : 7.32 | |
