NP and SP&S road specific details
- Cast pilot with fold-down coupler
- Enclosed cab with side entry doors, fixed roof hatches and
- Smokebox-mounted air pumps
- Two sizes of wheels in the trailing truck
- NP-style expansion link, which supports much of the valve
- NP specific welded coal
- SP&S specific welded oil
Fully-assembled and ready-to-run
Boiler backhead with printed manual controls
Individually applied piping, valves, generators, etc.
Correctly operating eccentric cranks
Illuminated LED directional headlight and back-up light
in the tender
Illuminated number boards
Five pole, skewed armature can motor with flywheels
Pivoting front and rear engines for negotiating 11
Current pick-up on all driver and wheels
8-pin connector plug between loco and
McHenry operating knuckle couplers installled
Minimum radius: 11
Recommended radius: 15
The Northern Pacific ordered 21 Challengers from
Locomotive Company in 1936 and took delivery of them during
and 1937. These 4-6-6-4s were designated Z-6 and were assigned
numbers 5100 through 5120. They had four 23 x 32 cylinders,
a 250 psi boiler pressure, exerted 104,500 lbs of tractive effort
624,500 pounds. In 1941, another six Challengers
came from ALCO.
These were designated Z-7 and they carried road numbers 5121
5126. They had four 23 x 32 cylinders, 70 drivers, a 260
psi boiler pressure,
exerted 107,000 lbs of tractive effort and weighed 644,000 pounds.
steam locomotives bought by the Northern Pacific were the 20
it purchased from ALCO during 1943 and 1944. This group designated
Z-8 was assigned road numbers 5130 through 5149. The Z-8 locomotives
were virtually identical to those of Class Z-7. Two oil-burning
Z-8s were also
delivered to the SP&S.
This was essentially identical to the 1941 Z-7s. These locomotives
produced under a wartime mandate to replace certain high-strength
components with similar items produced with more common and
steel. Even so, the NPs diagrams show no difference in
the adhesion weight
and just a 1,000 lb difference on engine weight.
The firebox heating surface included 136 sq ft in eight circulators.
featured a bearing design that permitted smooth riding at higher