1930
The "Mountain" Class:The "Mountain" type of locomotive (4-8-2) first appeared on the Chesapeake & Ohio Railroad in 1911. These locomotives excelled at hauling heavy freight trains at high speeds. The Pennsylvania Railroad adopted the M1 design in 1923 with the intention of using it to replace its slower fleet of L1 and II locomotives. Although it was larger than anything the railroad had built previously, the M1 relied on technologies and designs proven in earlier, smaller models.
Originally the M1 was to be used for both freight and passenger service. The entire fleet of M1 locomotives were decorated with the signature "keystone" style number plate typically used for passenger locomotives, rather than the standard round number plate used for freight locomotives. The entire class of locomotive was eventually used exclusively for freight service, owing to the locomotive's ability to accelerate tonnage quickly. M's were a familiar sight all across the railroad on the point of priority freight and express trains from the late 1920's to the end of steam in 1957.
Builder: Pennsylvania RR, Altoona, PA
Build Date: 1930
Retirement Date: January 1957
Wheel Arrangement: 4-8-2 "Mountain"
Class: M1B (Originally M1A)
Number built: 301
Weight of Engine: 385,000 lbs.
Length: (including tender) 109 ft.
Driving Wheel Diameter: 72 in.
Tractive Effort: 69,700 lbs.
Fuel Capacity: Coal: 35.1 tons, Water: 22,090 gal.
Boiler Pressure: 270 psi.
PHMC Catalogue No. RR79.40.12
* Listed on the National Register of Historic Places *
No. 6755:PRR No. 6755 was built in 1930 and ran until 1957, when the Pennsylvania Railroad retired all of its remaining steam locomotives.
In 1953, No. 6755 was rebuilt from a class M1A to M1B. This conversion included an upgrade to a nickel-steel boiler, which increased the boiler pressure to 270 p.s.i., and the addition of firebox circulators. A welded-steel drop-coupler pilot was also added as part of the new "modernized" front end designed to ease maintenance on the front of the locomotive.
This particular M1 is equipped with an oversized "coast-to-coast" tender, which enabled it to cover longer distances between water stops. A brakeman was assigned to the "dog house," a shelter situated on the top of the tender deck, where he would monitor the train's status. The tender itself is also equipped with a water scoop, which allowed the locomotive to take on water without actually stopping at a station. The locomotive would reduce its speed to about 45 miles per hour or less, after which the scoop would be dropped into a water-filled trough called a "track pan."
(Banner at Bottom):No. 6755 is the largest surviving Pennsylvania Railroad steam locomotive.
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