Data from table entitled "Table of Dimensions of the Locomotives" in New England Association of Railway Superintendents, Report of the Trials of Locomotive Engines Made Upon 1st and 2nd October, 1851 (Boston: B J Yerrinton, Printers, 1852), p. 16.
The organizers of the 1851 trials expressed regret that some of the contestants supplied incomplete data for the table. The Union's entry reflects this lack. Enough was offered to show that this was an average-sized freight Eight-wheeler for the time.
The boiler pressure is the "effective pressure" as measured during the trials.
| Principal Dimensions by Steve Llanso of Middle Run Media | |
|---|---|
| Class | Union |
| Locobase ID | 13548 |
| Railroad | Fitchburg |
| Country | USA |
| Whyte | 4-4-0 |
| Number in Class | 1 |
| Road Numbers | |
| Gauge | Std |
| Number Built | 1 |
| Builder | Boston Locomotive Works |
| Year | 1851 |
| Valve Gear | V-hook |
| Locomotive Length and Weight | |
| Driver Wheelbase (ft / m) | |
| Engine Wheelbase (ft / m) | |
| Ratio of driving wheelbase to overall engine wheelbase | |
| Overall Wheelbase (engine & tender) (ft / m) | |
| Axle Loading (Maximum Weight per Axle) (lbs / kg) | |
| Weight on Drivers (lbs / kg) | |
| Engine Weight (lbs / kg) | 46,980 / 21,310 |
| Tender Loaded Weight (lbs / kg) | |
| Total Engine and Tender Weight (lbs / kg) | |
| Tender Water Capacity (gals / ML) | |
| Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | |
| Minimum weight of rail (calculated) (lb/yd / kg/m) | |
| Geometry Relating to Tractive Effort | |
| Driver Diameter (in / mm) | 66 / 1676 |
| Boiler Pressure (psi / kPa) | 97 / 520 |
| High Pressure Cylinders (dia x stroke) (in / mm) | 16" x 20" / 406x508 |
| Tractive Effort (lbs / kg) | 6396 / 2901.18 |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | |
| Heating Ability | |
| Tubes (number - dia) (in / mm) | 125 - 2" / 51 |
| Flues (number - dia) (in / mm) | |
| Flue/Tube length (ft / m) | 10.50 / 3.20 |
| Firebox Area (sq ft / m2) | |
| Grate Area (sq ft / m2) | 9.50 / 0.88 |
| Evaporative Heating Surface (sq ft / m2) | |
| Superheating Surface (sq ft / m2) | |
| Combined Heating Surface (sq ft / m2) | |
| Evaporative Heating Surface/Cylinder Volume | |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 922 |
| Same as above plus superheater percentage | 922 |
| Same as above but substitute firebox area for grate area | |
| Power L1 | |
| Power MT | |