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PRR M1 Mountain Pack

This pack adds multiple variants of the Pennsylvania Railroad's M1, M1a, and M1b 4-8-2 Mountains. All feature lods for performance, dynamic weathering, random numbers, authentic sounds, functional marker lights, and where appropriate selectable class lights.

The M1 prototype was built in 1923, intended as a "dual-service" locomoive equally capable in both passenger and fast freight roles. It was based off of the large boiler of the very successful I1s Decapod, but with the front of the firebox extended by five feet to form a larger combustion chamber to ensure fuel was fully burned. Under this boiler was a four-wheel lead truck for stability at speed, four pairs of 72in. drivers for a balance of speed and tractive effort, and a 2-wheel trailing truck to support the extended firebox. After extensive testing both on the road and the static test plant at Altoona, the design entered series production with orders totalling 200 units.

In 1930 the PRR ordered 100 more of the Mountain type, but with several upgrades. These constituted a single-piece cast cylinder saddle first tested on the experimental K5 Pacific, a second air compressor, a Worthington SA feedwater heater, and a much larger tender. These improved locomotives formed a new subclass, M1a.

In the 1940's the class was further improved with 40 of the M1as being upgraded to the M1b standard during major rebuilds. This upgrade increased boiler pressure from 250psi to 270psi, and installed circulator tubes in the firebox for increased heating area. These changes gave the M1b greater tractive effort, and even greater power at speed.

While around 30 of the M1s hauled passenger trains over the hills of the Middle Division, the majority of the 301 strong class spent their careers hauling fast freight. In later years after electrification caused a surplus of K4s for passenger service, the M1s were nearly exclusively used for freight, however they retained the iconic Keystone shaped number plates normally reserved for passenger locomotives.

The M1a specifically was in many ways the high point of traditional PRR steam. After its introduction in 1930 steam power development was largely paused as the focus shifted to electrification. It would be nearly a decade before the PRR returned to designing new steam locomotives, but in a radical new direction with the S1 Duplex.

These locomotives can be found under the "multiple units", "steam" category in the buy menu. They also each have one passenger slot, which is not a bug. Both are a result of these locomotives supporting random numbering which allows for unique road numbers without cluttering up the buy menu or making you download additional textures.

• Top Speed: 75 mph
  
• Power: 4,034 hp (M1, M1a), 4,357 hp (M1b)
  
• Tractive Effort: 64,550 lbf (M1, M1a), 69,700 lbf (M1b)
  
• Weight: 303 tons, 383 tons, or 385 tons
  
• Available: 1923-1957

There are 15+ different variations in the pack (25 if you count class light options). In summary:

• Pennsylvania Railroad - M1 with small 110F75 tender. Passenger and freight versions, including variants with a doghouse on the tender or wearing the early striped passenger paint scheme.
  
• Pennsylvania Railroad - M1a with large 210F75 riveted tender. Freight and passenger versions. Passenger version has "Futura" style lettering, as used in the 1930's.
  
• Pennsylvania Railroad - M1 with large 210F75B welded tender. Freight and Passenger versions.
  
• Pennsylvania Railroad - M1, M1a, and M1b semi-modernized with drop coupler pilot and "Tombstone" style marker lights.
  
• Pennsylvania Railroad - M1, M1a, and M1b fully modernized with swapped headlight and generator, "Bullseye" style markers, and Trainphone.
  
• Generic colorable version