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).
|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|
|Ratio of driving wheelbase to overall engine wheebase||0.22||0.22|
|Overall Wheelbase (engine & tender)||73.17'|
|Axle Loading (Maximum Weight per Axle)||57000 lbs|
|Weight on Drivers||316000 lbs||250000 lbs|
|Engine Weight||355000 lbs||305150 lbs|
|Tender Light Weight||152700 lbs||154700 lbs|
|Total Engine and Tender Weight||507700 lbs||459850 lbs|
|Tender Water Capacity||8000 gals||8000 gals|
|Tender Fuel Capacity (oil/coal)||3449 gals||13 tons|
|Minimum weight of rail (calculated)||88 lb/yard||69 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||200 psi||210 psi|
|High Pressure Cylinders (dia x stroke)||21.5" x 32"||20" x 30"|
|Low Pressure Cylinders (dia x stroke)||33" x 32" (2)||31" x 30" (2)|
|Tractive Effort||64193 lbs||54999 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.92||4.55|
|Firebox Area||225 sq. ft||214 sq. ft|
|Grate Area||78 sq. ft||53.42 sq. ft|
|Evaporative Heating Surface||5608 sq. ft||4007 sq. ft|
|Combined Heating Surface||5608 sq. ft||4007 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||417.07||367.33|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||15600||11218|
|Same as above plus superheater percentage||15600||11218|
|Same as above but substitute firebox area for grate area||45000||44940|