Norfolk & Western 4-8-0 "Mastodon" Locomotives in the USA


Class Details by Steve Llanso of Sweat House Media

Class M (Locobase 2500)

Data taken from "Locomotives for Heavy Service on the Norfolk & Western", Railroad Age Gazette, Volume 45, No 3 (19 June 1908), pp. 170-171. , supplemented and amended by N&W 3-1955 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also Thomas Dressler, "N&W's Remarkable 4-8-0s" at http://www.railfan.com/a081995.html (link no longer active). (Thanks to Chris Hohl for his 2 January 2021 email querying the valve gear description, commenting on the firebox differences, and supplying the original tender capacity.)

Richmond works numbers were 40271-40274 in June 1906, 40275-40294 in July; 40295-40299 in August; 40300-40314 in September; 40315-40320 in October; 40321-40343 in January 1907; 40344-40345 in February. Baldwin works numbers were 27958, 27982-27983, 27991, 28012, 28034, 28044 in April 1906; 28055-28057, 28079, 28095, 28104-28105, 28124-28125, 28220-28221, 28233, 28241, 28262-28263, 28278-28279 in May; 28306, 28315, 28343-28344, 28387, 28389-28390, 28422, 28453-28454, 28466-28467, 28479 in June; 28520, 28559-28560, 28581, 28617, 28663, 28669-28670 in July; 28762, 28792-28793, 28822, 28863 in August

The first of the N&W's "Mollies" (as the crews called these 4-8-0s), these engines were supplied by Alco-Richmond (75) and Baldwin (50). In a long, and very good essay on the N&W "Remarkable 4-8-0s", Thomas Dressler (on http://www.railfan.com/a081995.html) notes that these engines were the railroad's main-line freight haulers and very successful this first batch were. Described as a Consolidation with a four-ft longer boiler, these engines didn't break any new ground, but did provide better riding qualities and more power on essentially the same wheelbase.

Other features in these engines were the two arch tubes (which contributed 19 sq ft/1.77 sq m) to the firebox heating surface area) and high-grade refractory brick, 12" (305 mm) piston valves, main rod on the second driving axle, no deck behind the firebox (soon outlawed).

The last detail deserves a little more explanation: N&W's Consolidations and Mastodons all had long fireboxes that extended rearward to the back edge of the footplate. So the fireman stood on the tender's deck to shovel and wedged himself into a seat to the side of the firebox.

The RAG profiled these engines and noted in particular the very small leading bogie wheels (27"/686 mm in diameter) and the long piston stroke. At that time the boiler had 258 tubes with a total heating surface of 2,778 sq ft. As with most locomotives, the design gained weight. Originally the adhesion weight was 168,000 lb and the engine grossed an even 100 tons in operating order. The small tender carried 6,000 US gallons of water and 10 tons of coal; the locomotive and tender's total length at that time was 53 ft 7 in (16.33 m).

RAG reported that two of the class would be delivered with Walschaert gear. The problems caused by adopting that valve gear for production are described in Locobase 939.

10 were eventually superheated, and 30--including the preserved 433 and 475--were refitted with Baker valve gear. All were equipped with power reversing gear in the late 1930s.

An M was rated at an even 1,000 tons eastbound from Norfolk to Petersburg and 1,050 westbound.


Class M1 (Locobase 2501)

Data expanded and confirmed by a table in the June 1908 issue of American Engineer and Railroad Journal (p.231); DeGolyer, Volume 30, pp. 60-61;and Thomas Dressler, "N&W's Remarkable 4-8-0s", Railfan (August 1995) at http://www.railfan.com/a081995.html (link no longer active). Baldwin works numbers were 31598-31599, 31631-31633 in August 1907; 31683-31684, 31699, 31730, 31765, 31773-31775, 31811-31812, 31833 in September; 31866, 31881, 31910-31911, 31930-31933, 31956-31957, 31982, 31989, 32009-32010, 32024-32025, 32062-32065, 32089, 32097-32098 in October; 32122, 32146, 32165, 32196-32198, 32272-32273, 32296 in November; 32349-32350 in December.

Richmond works numbers 43168-43171 in October 1907, 43172-43203 in November, 43204-43217 in December.

A follow-on order of "Mollies" produced by Alco-Richmond (50), Baldwin (50). Thomas Dressler (on http://www.railfan.com/a081995.html) notes that these engines were essentially the same as the Ms delivered a year earlier (Locobase 2500) except that they used Walschaert valve gear and 12" (305 mm) piston valves instead of Stephenson link motion. And therein lay the rub, according to Dressler: "...the centerline of the piston valve was two inches inside the centerline of the cylinders, and a rocker arm was needed to actuate the valve rod. Due to a poor design, scuffing between the link block and face resulted in excessive wear. It was virtually impossible to keep the valve gear in alignment and the valves properly set."

Only one of the 100 received a superheater. Not surprisingly, when the N&W began phasing out older freight power, these M1s were the first to go.


Class M2 (Locobase 939)

Data from DeGolyer, Volume 35, p. 222. Baldwin works numbers for 1101-1149 were 35108-35113, 35146-35149 in August 1910; 35225-35238, 35299 in September; 35331-35345 in October; and 35676-35679, 35774-35775, 35806-35809 in December.

Baldwin-built M2s had Walschaert gear, but the Roanoke-built M2a (3), M2b (2), and the M2c (6) all had Baker gear. Many later received superheaters and mechanical stokers; see Locobase 6654. Arch tubes contributed 13 sq ft (1.21 sq m) to the firebox heating surface area.

Even when upgraded, says Thomas Dressler (http://www.railfan.com/a081995.html), they were "very unpopular" because of their rough riding qualities and poor steaming. The poor steaming -- probably due to a very small firebox heating surface area -- persisted despite substantial modifications to the front end. Most survived until the late 1950s because they were the only non-articulated freight engines the N&W ever had. Their tonnage rating eastbound from Norfolk to Petersburg was 1,750 tons slow freight, 1,850 tons westbound. From Williamson to Portsmouth (Ohio), , an M2 was expected to move 3,600 tons. On a route that included the 0.32% ten-mile Kingston hill between Portsmouth and Joyce, the rating was 3,100 tons.

Farrington (Railroading Coast-to-Coast, 1976) says this was the heaviest Mastodon (4-8-0) class ever built. Two were rebuilt after World War II for yard duties.


Class M2c - superheated (Locobase 6654)

Data from 1955 Norfolk & Western locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

See the full entry at Locobase 939 for this last of the Twelve-wheelers produced for the N&W. Sometime after their introduction, the Roanoke shops turned out eleven more to which they added superheat. In the generous confines of the M2's boiler, Roanoke managed to put in more small tubes (although of smaller diameter from than the earlier 2 1/4"/57 mm tubes) and three dozen flues for superheaters.

Principal Dimensions by Steve Llanso of Sweat House Media
ClassMM1M2M2c - superheated
Locobase ID2500 2501 939 6654
RailroadNorfolk & Western (N&W)Norfolk & Western (N&W)Norfolk & Western (N&W)Norfolk & Western (N&W)
CountryUSAUSAUSAUSA
Whyte4-8-04-8-04-8-04-8-0
Number in Class1251006111
Road Numbers375-4991000-10991100-11601150-1160
GaugeStdStdStdStd
Number Built1251006111
BuilderseveralseveralseveralRoanoke
Year190619071910
Valve GearStephenson or BakerWalschaertBaker or WalschaertBaker
Locomotive Length and Weight
Driver Wheelbase (ft / m)15.50 / 4.7215.50 / 4.7216 / 4.8816 / 4.88
Engine Wheelbase (ft / m)26.42 / 8.0526.42 / 8.0527.08 / 8.2527.08 / 8.25
Ratio of driving wheelbase to overall engine wheelbase 0.59 0.59 0.59 0.59
Overall Wheelbase (engine & tender) (ft / m)58.37 / 17.7953.58 / 16.3361.96 / 18.8962.21 / 18.96
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)169,800 / 77,020165,850 / 75,228221,780 / 100,598239,530 / 108,649
Engine Weight (lbs / kg)206,200 / 93,531204,500 / 92,760261,100 / 118,433279,530 / 126,793
Tender Loaded Weight (lbs / kg)167,500 / 75,977116,600 / 52,889167,500 / 75,977167,500 / 75,977
Total Engine and Tender Weight (lbs / kg)373,700 / 169,508321,100 / 145,649428,600 / 194,410447,030 / 202,770
Tender Water Capacity (gals / ML)9000 / 34.096000 / 22.739000 / 34.099000 / 34.09
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)14 / 1310 / 914 / 1314 / 13
Minimum weight of rail (calculated) (lb/yd / kg/m)71 / 35.5069 / 34.5092 / 46100 / 50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)56 / 142256 / 142256 / 142256 / 1422
Boiler Pressure (psi / kPa)200 / 13.80200 / 13.80200 / 13.80200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)21" x 30" / 533x76221" x 30" / 533x76224" x 30" / 610x76224" x 30" / 610x762
Tractive Effort (lbs / kg)40,163 / 18217.6540,163 / 18217.6552,457 / 23794.1252,457 / 23794.12
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.23 4.13 4.23 4.57
Heating Ability
Tubes (number - dia) (in / mm)242 - 2.25" / 57242 - 2.25" / 57386 - 2.25" / 57255 - 2" / 51
Flues (number - dia) (in / mm)36 - 5.375" / 137
Flue/Tube length (ft / m)18.41 / 5.6118.40 / 5.6118.83 / 5.7418.50 / 5.64
Firebox Area (sq ft / m2)173 / 16.07173 / 16.07192 / 17.84179 / 16.63
Grate Area (sq ft / m2)45 / 4.1845 / 4.1844.70 / 4.1545 / 4.18
Evaporative Heating Surface (sq ft / m2)2797 / 259.852797 / 259.854473 / 415.553586 / 333.15
Superheating Surface (sq ft / m2)765 / 71.07
Combined Heating Surface (sq ft / m2)2797 / 259.852797 / 259.854473 / 415.554351 / 404.22
Evaporative Heating Surface/Cylinder Volume232.50232.50284.72228.26
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation9000900089409000
Same as above plus superheater percentage90009000894010,620
Same as above but substitute firebox area for grate area34,60034,60038,40042,244
Power L156825682645613,505
Power MT295.09302.12256.71497.20

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