Identical to the Great Northern's L-1s (Locobase 819) and fitted with a Belpaire firebox. Placed in helper service where they were rated at 850 tons up 2.2% grades. These were slow-speed engines, held by the railroad to 15 mph or less.
A 10 December 1907 report in the Baldwin specs file summarized interviews held with General Manager George P Slade, Superintendent of Motive Power William Moir, and Mechanical Manager W L Kinsell. "The above gentlemen, although interviewed separately, united in commenting favorably on the work done by the Mallet compound locomotives now operating west of Livingston."
The letter goes on to report on the "howevers" that such an opening often preceded. Most were relatively minor, as in the ash pans being too level and too close to the grate, which led to grate-bar burnthroughs. A criticism of the starting-valve pipes' small diameter, which the railroad had remedied by installing 1 1/4" pipes, was annotated "These were specified to be 1" dia."
But "the most serious trouble complained of is due to the loosening and leaking of the studs holding the bearing saddle to the waist of the boiler." Not only was repair time-consuming and immobilizing, but the steam and water leakage onto the bearing surfaces might lead to derailments, they feared.
Follow-ons to the Zs (record 1046), but significantly lighter and fitted with smaller cylinders. As with the Zs, these were a copy of a Great Northern design, in this case the L2 (Locobase 3554). They had straight boilers, 13" (330 mm) piston valves serving the HP cylinders and slide valves on the LPs, and small fireboxes with wide grates.
3103 was retired in August 1932, 3101 in June 1934, and 3104-3105 in October 1934. 3102 lasted until October 1940
3100 was sold to Polson Logging Company in December 1940. Operating out of Railroad Camp, Wash, the 3100 operated until 1945 with the Polson herald on its tender, then for successor company Rayonier, Inc until 1959.
|Specifications by Steve Llanso of Sweat House Media|
|Railroad||Northern Pacific (NP)||Northern Pacific (NP)|
|Number in Class||16||6|
|Builder||Burnham, Williams & Co||Baldwin|
|Locomotive Length and Weight|
|Driver Wheelbase (ft)||10||9.83|
|Engine Wheelbase (ft)||44.83||43.75|
|Ratio of driving wheelbase to overall engine wheebase||0.22||0.22|
|Overall Wheelbase (engine & tender) (ft)||73.17|
|Axle Loading (Maximum Weight per Axle) (lbs)||57,000||49,600|
|Weight on Drivers (lbs)||316,000||262,350|
|Engine Weight (lbs)||355,000||305,150|
|Tender Light Weight (lbs)||152,700||154,700|
|Total Engine and Tender Weight (lbs)||507,700||459,850|
|Tender Water Capacity (gals)||8000||8000|
|Tender Fuel Capacity (oil/coal) (gals/tons)||3449||13|
|Minimum weight of rail (calculated) (lb/yd)||88||73|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in)||55||55|
|Boiler Pressure (psi)||200||210|
|High Pressure Cylinders (dia x stroke) (in)||21.5" x 32"||20" x 30"|
|Low Pressure Cylinders (dia x stroke) (in)||33" x 32"||31" x 30"|
|Tractive Effort (lbs)||64,193||54,999|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.92||4.77|
|Firebox Area (sq ft)||225||186|
|Grate Area (sq ft)||78||53.42|
|Evaporative Heating Surface (sq ft)||5608||4007|
|Superheating Surface (sq ft)|
|Combined Heating Surface (sq ft)||5608||4007|
|Evaporative Heating Surface/Cylinder Volume||417.07||367.33|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||15,600||11,218|
|Same as above plus superheater percentage||15,600||11,218|
|Same as above but substitute firebox area for grate area||45,000||39,060|