Boston & Maine classes P-1 and P-2
The Boston & Maine's first Pacifics were 82 members of the classes P-1 and P-2. They were characterized by 73 inch (1,854 mm) drivers and cylinders which were sized 22 by 28 inches. The P-1 consisted of twelve saturated locomotives built in 1910 by ALCO. Between 1911 and 1916, ALCO delivered 70 P-2 which were superheated and had a much larger firebox.
In 1915, also all P-1 were superheated at the cost of much of the tube heating surface. Later additions added to many P-1 and P-2 included an Elesco or Worthington feed water heater. All in all, they were referred to as unexceptional locomotives which did their work without many problems, but also without noteworthy records. With a factor of adhesion of 4.5 for the P-1 and 5.0 for the P-2, it doesn't look like slipping was an issue.
Technical data
General
| Property | P-1 | P-1 superheated | P-2 |
|---|---|---|---|
| Built | 1910 | 1915 | 1911-1916 |
| Manufacturers | ALCO | ||
| Wheel arrangement | 4-6-2 (Pacific) | ||
| Gauge | 1,435 mm (Standard gauge) | ||
Dimensions and weights
| Property | P-1 | P-1 superheated | P-2 |
|---|---|---|---|
| Wheelbase | 10.21 m | ||
| Total wheelbase | 19.53 m | 19.36 m | |
| Service mass | 99.3 t | 100.2 t | 113.1 t |
| Adhesion mass | 64.4 t | 65.3 t | 71.6 t |
| Total mass | 162.8 t | 163.7 t | 185.3 t |
| Rigid wheelbase | 3.96 m | ||
| Axle load | 22.5 t | 22.9 t | 25.1 t |
| Water capacity | 25,741 l | 32,933 l | |
| Fuel capacity | 10.9 t (coal) | 21.8 t (coal) | |
Boiler
| Property | P-1 | P-1 superheated | P-2 |
|---|---|---|---|
| Grate area | 4.664 m² | 4.97 m² | |
| Firebox surface | 17.373 m² | 16.537 m² | 25.363 m² |
| Tube heating surface | 322.653 m² | 236.16 m² | 259.478 m² |
| Evaporative heating surface | 340.025 m² | 252.697 m² | 284.841 m² |
| Total heating surface | 340.0 m² | 313.3 m² | 361.3 m² |
| Superheater surface | 60.573 m² | 76.459 m² | |
Power plant
| Property | P-1 | P-1 superheated | P-2 |
|---|---|---|---|
| Driver diameter | 1,854 mm | ||
| Boiler pressure | 13.8 bar | ||
| Expansion type | simple expansion | ||
| Cylinders | two, 559 x 711 mm | ||
Power
| Property | P-1 | P-1 superheated | P-2 |
|---|---|---|---|
| Power source | steam | ||
| Estimated power | 1,305 kW (1,774 PS) | 1,715 kW (2,332 PS) | |
| Starting effort | 140.4 kN | ||
Calculated values
| Property | P-1 | P-1 superheated | P-2 |
|---|---|---|---|
| Factor of adhesion | 1 : 4.50 | 1 : 4.56 | 1 : 5.00 |
| Optimal speed | 56 km/h | 74 km/h | |
| Power-to-weight ratio | 13.1 kW/t | 13.0 kW/t | 15.2 kW/t |
| Heating Surface Equivalent | 426.9 m² | 456.5 m² | 564.6 m² |
| Cylinder volume/HSE | 1 : 817.16 | 1 : 764.11 | 1 : 617.88 |
| Adhesive weight/Total | 1 : 1.54 | 1 : 1.53 | 1 : 1.58 |
| Tractive force/Heating surface | 1 : 8.62 | 1 : 9.36 | 1 : 8.11 |
| Grate area/Heating surface | 1 : 72.90 | 1 : 67.17 | 1 : 72.70 |
| Firebox/Tube surface | 1 : 18.57 | 1 : 14.28 | 1 : 10.23 |
| Total/Superheater | 1 : 4.17 | 1 : 3.73 | |
