Class F-10-S/F-21-S (Locobase 8801)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

Like the F-9 (Locobase 6194), when the F-10s cross-compounds were taken in hand for superheating, they had 12" piston valves and a near 1-for-1 trade in heating surface area when they removed 154 small tubes in favor of 28 superheater flues.

In later service, 2428's boiler was pressed to 200 psi while the 473's boiler was set at 185 psi. The rest were set at 170 psi.

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Class F-10/F-21 (Locobase 8800)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

These were slightly heavier than the F-9s of four years before (Locobase 5370), but were otherwise identical. It was very unusual for a cross-compound to be delivered to a North American railroad so late in the steam era.

In the normal course of events for a North American railroad, the class was later simpletd and superheated; see Locobase 8801.

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Class F-11 (Locobase 8802)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

Packing larger cylinders and a bigger boiler, this design was otherwise a typical Consolidation of the time. One subtle difference was the use of 5 1/4" flues for superheater elements in the first 4. The piston valves measured a relatively modest 12" in diameter.

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Class F-12 / F-22 (Locobase 8804)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

These were repeats of the F-11 / F-21 classes built for the Soo and the Wisconsin Central the year before (Locobase 8802). The big difference was the re-allocation of tubes and flues in favor of more flues when the class was superheated. The result was a higher superheat ratio.

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Class F-20 - original (Locobase 11405)

Data fromThe Railway Age (18 October 1907), p. 557 and from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.. Works numbers were 27946-27955 in October 1903, 37603-37609 in May 1905, and 45108-45115 in December 1907. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

The WC went to Brooks for this class of Consolidations over a four-year period. The design was relatively small and light locomotive fitted with a Belpaire firebox and 11" piston valves.

Later in its lifetime, a few were fitted with superheaters as shown in Locobase 8803.

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Class F-20 - superheated (Locobase 8803)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Locobase 11405 Later in its lifetime, at least were fitted with superheaters as shown in the diagrams. The makeover reflected the usual tradeoffs: 150 small tubes were sacrificed for 24 flues, which held enought superheater elements to afford an adequate amount of steam enrichment. The locomotive was otherwise essentially unchanged, retaining its Belpaire firebox . The 28 sq ft of arch tubes now reflected in the data may have been in the firebox when delivered.

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Class F-23 (Locobase 8805)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

Finishing off the 63"-drivered Consolidations supplied to the Soo over a 9-year period, this sextet had a slightly reordered boiler that had fewer tubes and more flues once the shops superheated the class.

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Class F-7-S (Locobase 6768)

Data from Soo 9 - 1943 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange .

Locobase 3950 described the original compound Consolidation locomotives. This entry tells us what happened when those compounds were simplified and superheated.

See 1919 Railway Mechanical Engineer (RME) -- Volume 93, #12, page 700 -- for a description of trials of that conversion (which used 468, an F-9 locomotive).

Note that the superheater area in the specs is estimated. It is a calculation based on taking the diagram value of 549 sq ft of "superheater equivalent" and deducting a third from it. See the logic presented in Locobase 1364.

Also, the diagram gives the boiler pressure as 200 psi, but the values for tractive effort and factor of adhesion show a working pressure of 175 psi. Reducing BP when superheating a boiler was a tradeoff several railroads chose and the Soo's decrease in BP on the superheated G-class decapod suggests that the railroad did the same with these Consolidations.

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Class F-8 (Locobase 8798)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

It must have been quickly apparent to the Soo that their latest cross-compounds (shown in simpled, superheated form on Locobase 8797) were too small. So the builder lengthened the tubes by 6" and created a more capacious heating vessel. At the same time, Schenectady enlarged the grate, but made the firebox shallower. Steam was admitted through 12" diameter piston valves. Later the locomotives were simpled and superheated; see Locobase 8799.

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Class F-8-S (Locobase 8799)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

Superheating the F-8s took the usual path of deleting dozens of small tubes in favor of some larger flues that held the superheater elements. Apparently the F-8's original boiler was large enough to accept this change without sacrificing too much combined heating surface. The locomotives retained the 12" (305 mm) piston valves. A few -- 439, 441, 444 -- ran at 200 psi (13.8 bar).

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Class F-9 (Locobase 5370)

Data from a table in the June 1907 issue of AERJ and Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007. See also "Lesson 1: Changing Landscapes-Topic 6: Railroads

Section 4: Soo Line" on the North Dakota Studies website at [], last accessed 4 April 2021. Works numbers were 30458 in March 1905, 30459-30467 in June 1905, 39418-39427 in June 1906, 40514-40521 in September.

By the time the Soo bought this batch of cross-compounds, the railroad--named for two cities in Minnesota and had expanded so extensively into North Dakota that it had been nicknamed "North Dakota's Railroad."

Although the shallow firebox remained essentially the same as that of the F-8 of two years earlier (Locobase 8798), the motion and the boiler both were enlarged by Alco in this cross-compound class. Piston valves measuring a relatively generous 14" (356 mm) fed the high pressure cylinders while Allen-Richardson balanced slide valves supplied the low-pressure one. Cylinder volume increased because of an unusually long stroke for a compound. And the engine now turned much taller drivers. Alco delivered a single engine in March 1905, 9 more in June, 10 more in June of 1906, and 8 in September 1906.

The Minneapolis, St. Paul and Sault Ste Marie seems to have thought the cross-compound was worth exploring. This batch, the largest single class of compound Consolidations on the Soo, introduced superheating with an odd flue size (3 1/2") designed by Cole, Alco's energetic engineer (see Locobase 9709). In any case, the apparatus seems to have been removed shortly after delivery.

Drury (1993) notes that all 51 Schenectady cross-compounds were later simpled and superheated.

See Locobase 6194 for the 1919 Railway Mechanical Engineer (RME) description of that conversion.

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Class F-9 - superheater prototype (Locobase 9709)

Data from 1906 Railway Congress, Miscellaneous Information, pp.539-540; "Cross-Compound Consolidation for the "Soo" [sic] Line", . See also "The Compound Locomotive and the Superheater", Railway Age, Volume XXXIX [39], No. 15 (14 April 1905), pp. 586-587; and "Two-Cylinder Compound for the "Soo" Line, with Superheater", same issue, pp. 602-604; and "Compound Consolidation Locomotive with Superheater; Minneapolis, St. Paul & Sault Ste Marie Ry", Engineering News, Volume LIV, No. 21 (23 November 1905), pp. 537-538. Works number was 30458 in March 1905.

Before the Soo settled on the superheater conversions they would later apply to the F-9 class (and most others), they had to try out several versions. The unsigned analysis of the marriage of superheater and compounding viewed the combination as a logical step for a railroad whose traditions had been "entirely favorable to the 2-cylinder compound". Their experience was positive, "besides the saving in fuel in fuel and the increased hauling power on grades these engines have been uniformly light on repairs."

As Engineering News described it in 1906, the superheater tubes measured 3 1/2" (89 mm) in outside diameter. "In each of these large tubes (and close to the upper side of the tube) is placed a 2-inch [50.8 mm] tube closed at the firebox-end and extending beyond the smoke-box tube plate to the rear compartment of a header or chamber in the smoke-box and 13 1/4" [337 mm] from the tube plate." Gases from the fire-box passed along the outside of the 2" tube.

Inside of each of the 2" tubes was a 1.3" (33 mm) tube that was open at the fire-box end.. Saturated steam was let into the superheater header, passed through the smallest diameter tube to the rear, then back to the front in the 2" tube and then through the header to the HP cylinder.

Such an arrangement of nested tubes must have constricted steam flow pretty badly; moreover, the superheated percentage of the engine's combined heating surface area was quite small. The concurrent experiment with Soo Moguls, which used larger 5" (127 mm) tubes (Locobase 16376), pointed the way to the layout that was widely adopted.

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Class F-9-S (Locobase 6294)

Data from Railway Mechanical Engineer of December 1919; "Converting Cross Compound Locomotives to Simple," Railway Age, Volume 67, No 22 (28 November 1919, "issued 12 December 1919"), p. 1062;, and Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

When the F-9 cross-compounds (Locobase 5370) were taken in hand for superheating, they had already sacrificed their one LP cylinder for another slightly smaller HP cylinder. In the process, the shops reduced the piston valve diameter by two inches to 12" (305 mm). When the shops superheated the class, they achieved a near 1-for-1 trade in heating surface area when they removed 154 small tubes in favor of 28 superheater flues. As the shops made these changes, they took full advantage of the opportunity to drop the boiler pressure by 40 psi. The locomotives weighed a good deal less as well.

In tests with the 468, the engine consumed 13.9% less coal per 1,000-ton miles despite an actual evaporation per pound of coal 10.9% less than the cross-compounds. RA speculated that the evaporation difference was "due no doubt to the reduction in tube heating surface resulting from the application of the superheater."

The Railway Mechanical Engineer of December 1919 described the results of tests on the line. In sum, "these runs showed that engine 468 [the simpled 2-8-0] would handle 100 cars better than engine 448 [a cross-compounder] would handle 90 cars."

On another trial run over a 200-mile subdivision, the cross-compound was rated at 2,200 tons, but the actual trailing load would need to drop to 1800-2000 tons to make the trip in less than 16 hours. RME notes that 468 hauled 2,157 of train over that distance in 10 hours 7 minutes or an average of 20 mph. (Locobase notes what passed for good drag freight speed in 1919.) Per thousand ton miles, the 468 consumed 13.9 percent less coal than the saturated compound.

In later service, some had boilers pressed to 200 psi (446, 449-453, 445-458, 460-463, 465-467, 470) and 185 psi (447-448, 454, 459, 464, 471).

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Class L/F-2 (Locobase 8785)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

As the Soo took delivery of its F-1 cross-compound Consolidations (Locobase 8784), it was sampling different cylinder volumes and compounding ratios. This single locomotive's compounding ratio ran to the high side, which likely meant that the LP cylinder wasn't delivering its fair share of power. The engine was later converted to simple expansion.

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Class N/F-3 (Locobase 8786)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

These were the same design as the cross-compound Consolidations supplied earlier in the year (Locobase 8784), except that the cylinders had a 2" longer stroke. So while the LP/HP ratio didn't change, the cylinder volume increased.

Like the others, these were later simpled.

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Class N/F-4 (Locobase 8787)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

Apparently the Soo & Schenectady were interested in tweaking the cross-compound idea. The F-1 (Locobase 8740) showed a 20" HP cylinder with the same stroke and F-3 kept that diameter and lengthened the stroke by 2". Here the builder increased the HP cylinder's diameter by 2 inches and retained the stroke.

And all of these were soon simpled anyway.

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Class O/F-7 (Locobase 3950)

Data from the 30 November 1900 Railroad Gazette and "Schenectady Locomotive on the 'Soo' Line", Railway and Locomotive Engineering, Volume 14, No 1 (January 1901), p. 38.

Mr. EA Williams, Mechanical Superintendent of the Minneapolis, St. Paul and Sault Ste Marie, must be described as adventurous at the least. In addition to a lone Vauclain compound Decapod, he procured these cross-compound Consolidations in the same year and would add to them over the next several years. Over the 165-mile (266 km) Minneapolis-Pennington Division these locomotives were rated at 1,692 short tons working compound.

R&LE commented that the design "is one of the best proportioned compound locomotives that we have examined for some time."Indeed, the compounding ratio was 2.42, in the theoretical sweet spot for achieving equal power from both cylinders. But Drury notes that all 51 Schenectady cross-compounds were later simpled and superheated.

See Locobase 6768 for a description of the F-7 makeover.

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Class P/F-1 (Locobase 8784)

Data from Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007.

In 1893, the Soo ordered more than two dozen cross-compound Consolidations of which these were the first. As such engines went, these had small cylinder volumes, grates, and boilers.

As was almost universally the case, the Soo later simpled these engines with two 19" x 24" cylinders. A calculated tractive effort of 25,999 lb was the result; the locomotives were otherwise unchanged.

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Class T/F-6 (Locobase 8788)

Data from "Locomotives at the Columbian Expostion - Second Article", Railroad Gazette, Volume 25 (27 October 1893), pp. 778, 780-781. See also Soo 9 - 1943 Steam Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange collection; and James Dredge, A Record of the Transportation Exhibits at the World's Columbian Exposition of 1893 (New York: John Wiley & Sons, 1894), pp. 261+. Roster data from Ron Kohlin's Soo Line pages at [], accessed 23 September 2007. Works numbers were 2842 in December 1892, 2843 in January 1893, 2878 in April, and 2969-2974 in July.

Locobases 8784-8787 showed the F-1 through F-4s as the Soo & Schenectady tweaked the cross-compound idea. In the same year, Rhode Island delivered two cross-compounds in February and six more in October. These were a bit bigger in the boiler and had larger fireboxes, but smaller grates.