Pere Marquette 4-6-2 "Pacific" Locomotives in the USA


Class Details by Steve Llanso of Sweat House Media

Class P2 (Locobase 9286)

Data from PM 3 1929 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster information developed by Art Million and Tom Dixon and presented on the Pere Marquette Historical Society website (http://www.pmhistsoc.org/stmrostr.shtml, accessed 1 March 2008). Works numbers were 48001-48005 in June 1910.

This quintet of high-drivered Pacifics went into service with saturated boilers. They were pretty small in comparison to other US 4-6-2s when delivered and among the express-passenger sub-group they were perhaps the smallest to go into service. Near-cousins were the Harriman Pacifics delivered to several lines, but these had bigger grates.

A year later, the PM took delivery of five more near-sisters (Locobase 7604) that were equipped from the start with superheaters. Two years later, RLE reported on the PM's comparison between the earlier 4-6-2s and the superrheated engines, noting that fuel savings in the later set averaged to 22% in normal use and up to 27% under "severe operating conditions".

Conversion of this class to the same specifications followed soon. and the class served the railroad for more than three decades before being scrappedin 1944 (701, 704 in September, 703 in October), 705 in February 1945, and 702 in January 1946.


Class SP (Locobase 7604)

Data from reproduction of 1913 Alco Bulletin 1016 on Richard Leonard's http://www.railarchive.net/alcopacifics/index.html (accessed 16 June 2006). See also "Pacific and Consolidation Locomotives for the Pere Marquette", Railway and Locomotive Engineering, Volume 26, No 1 (January 1913), p. 24-25. Works numbers werew 50044-50048 in June 1911.

These were the second quintet of Pacifics to come on the PM; see Locobase 9206. Compared to other 4-6-2s of the time, the design was relatively small and light. On the other hand, the class introduced the Schmidt-type fire tube superheater to the Pere Marquette. RLE reported on the PM's comparison between the earlier 4-6-2s and this quintet, noting that fuel savings amounted to 22% in normal use and up to 27% under "severe operating conditions".

But useful, apparently, and so in service until 1948.


Class SP2 (Locobase 9288)

Data from PM 3 1929 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 50, pp. 175+. Roster information developed by Art Million and Tom Dixon and presented on the Pere Marquette Historical Society website (http://www.pmhistsoc.org/stmrostr.shtml, accessed 1 March 2008).

Works numbers ran 41310-41314 in April 1914.

This set of Pacifics was so like those of the Chicago Great Western (Locobase 4175) that they might as well have been built as a single batch. They were the biggest Pacifics on the PM and were comparatively large for the time, as were their 15" (381 mm) inside adminssion piston valves. When delivered, their tenders had the same capacity but weighed 144,000 lb (65,317 kg). The locomotives had Gaines combustion chambers, which divided a large firebox into two sections using a half wall. (For a full description of the Gaines combustion chamber's intended effect on combustion, see Locobase 4228.)

Presumably they were intended for similar service as mainline passenger engines, a service doubtless responsible for the injunction: "Particular attention to be given to make tender ride easily and smoothly.".

Like the PM's other 4-6-2s, these locomotives operated into the late 1940s. In the last two years of their careers, they wore the colors of the Chesapeake & Ohio and fell in the F-12 class as 405-409. 406 was scrapped in April 1948; the others went in April 1949 (405, 407) and May (408-409).


Class SP3 (Locobase 9287)

Data from PM 3 1929 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster information developed by Art Million and Tom Dixon and presented on the Pere Marquette Historical Society website (http://www.pmhistsoc.org/stmrostr.shtml, accessed 1 March 2008).

Works numbers ran 62582-62593. Sized to meet the PM's express-passenger needs, these were relatively small and light Pacifics. Firebox heating surface, which included 25 sq ft of arch tubes, was surprisingly low, yet the whole heating system seems appropriately sized for the cylinder volume.

They remained in service until 1950.

Principal Dimensions by Steve Llanso of Sweat House Media
ClassP2SPSP2SP3
Locobase ID9286 7604 9288 9287
RailroadPere Marquette (PM)Pere Marquette (PM)Pere Marquette (PM)Pere Marquette (PM)
CountryUSAUSAUSAUSA
Whyte4-6-24-6-24-6-24-6-2
Number in Class55512
Road Numbers701-705706-710725-729711-722
GaugeStdStdStdStd
Number Built55512
BuilderAlco-SchenectadyAlco-SchenectadyBaldwinAlco-Brooks
Year1910191119141921
Valve GearWalschaertWalschaertWalschaertBaker
Locomotive Length and Weight
Driver Wheelbase (ft / m)13.33 / 4.0613.33 / 4.0613 / 3.9613.33 / 4.06
Engine Wheelbase (ft / m)33.83 / 10.3133.83 / 10.3135.33 / 10.7734.50 / 10.52
Ratio of driving wheelbase to overall engine wheebase 0.39 0.39 0.37 0.39
Overall Wheelbase (engine & tender) (ft / m)65.27 / 19.8963.27 / 19.2866.03 / 20.1369.06 / 21.05
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)139,000 / 63,049142,500 / 64,637156,000 / 70,760149,000 / 67,585
Engine Weight (lbs / kg)216,000 / 97,976220,000 / 99,790257,000 / 116,573243,000 / 110,223
Tender Loaded Weight (lbs / kg)144,000 / 65,317141,700 / 64,274153,000 / 69,400172,900 / 78,426
Total Engine and Tender Weight (lbs / kg)360,000 / 163,293361,700 / 164,064410,000 / 185,973415,900 / 188,649
Tender Water Capacity (gals / ML)7000 / 26.527000 / 26.528000 / 30.308000 / 30.30
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)14 / 12.7014 / 12.7011 / 1014 / 12.70
Minimum weight of rail (calculated) (lb/yd / kg/m)77 / 38.5079 / 39.5087 / 43.5083 / 41.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)77 / 195677 / 195673 / 185477 / 1956
Boiler Pressure (psi / kPa)200 / 13.80200 / 13.80190 / 13.10190 / 13.10
High Pressure Cylinders (dia x stroke) (in / mm)22" x 26" / 559x66022" x 28" / 559x71125" x 28" / 635x71123" x 28" / 584x711
Tractive Effort (lbs / kg)27,783 / 12602.1729,920 / 13571.5038,716 / 17561.3031,067 / 14091.77
Factor of Adhesion (Weight on Drivers/Tractive Effort) 5.00 4.76 4.03 4.80
Heating Ability
Firebox Area (sq ft / m2)185 / 17.19152 / 14.13258.20 / 22.40185 / 17.19
Grate Area (sq ft / m2)43.90 / 4.0843 / 456 / 5.2050.20 / 4.67
Evaporative Heating Surface (sq ft / m2)2762 / 256.692733 / 2543746 / 344.892803 / 260.50
Superheating Surface (sq ft / m2)557 / 51.77557 / 51.77794 / 71.10648 / 60.22
Combined Heating Surface (sq ft / m2)3319 / 308.463290 / 305.774540 / 415.993451 / 320.72
Evaporative Heating Surface/Cylinder Volume241.45221.85235.48208.18
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation8780860010,6409538
Same as above plus superheater percentage10,27310,06212,44911,350
Same as above but substitute firebox area for grate area43,29035,56857,39841,829
Power L119,52117,72217,70417,313
Power MT928.84822.53750.59768.50

Reference