When the Rock sold off some of their 4-8-2s, they sent seven of the earlier batch. These had received few changes during their time on the Rock Island. In particular, 4006-4007 and 4015 left for the Cotton Belt as coal burners. Locobase believes that 4033-4023, 4028, and 4031 were delivered in 1924 as oil burners. All still used 16" (406 mm) piston valves and included three thermic syphons in their fireboxes.
Almost as soon as they arrived on the St Louis-Southwestern, the seven engines were substantially rebuilt. As with the later M-50s described in Locobase 201, the 880s lost one of the three thermic syphons, which reduced to 82 sq ft (7.62 sq m) the component's contribution to firebox heating surface area. The three coal burners were converted to oil-burning and all trailed tenders with slight greater oil capacity than those of the Rock Island.
Although they retained the orginal count of tubes and superheater flues, the 880s raised boiler pressure to 220 psi to compensate for a 1 1/2" (38 mm) cylinder diameter reduction.that was now served by 14" (356 mm) piston valves. The alligator crossheads was replaced by multiple-bearing crossheads. The 1945 diagram shows that four of the engines--680-682, 686--were later fitted with "allservice" poppet valves.
Like the M-50a, the drivers were disc type and all engine axles turned in Timken roller bearings.
The seven also changed service, pulling only fast freights for the twelve years they ran on the Cotton Belt. All were sold for scrap in August 1953.
|Specifications by Steve Llanso of Sweat House Media|
|Railroad||Cotton Belt (StL-SW)|
|Number in Class||7|
|Locomotive Length and Weight|
|Ratio of driving wheelbase to overall engine wheebase||0.48|
|Overall Wheelbase (engine & tender)||79.08'|
|Axle Loading (Maximum Weight per Axle)||63800 lbs|
|Weight on Drivers||253400 lbs|
|Engine Weight||365000 lbs|
|Tender Light Weight||202850 lbs|
|Total Engine and Tender Weight||567850 lbs|
|Tender Water Capacity||11000 gals|
|Tender Fuel Capacity (oil/coal)||3700 gals|
|Minimum weight of rail (calculated)||106 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||220 psi|
|Cylinders (dia x stroke)||26.5" x 28"|
|Tractive Effort||49689 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||5.10|
|Firebox Area||360 sq. ft|
|Grate Area||63 sq. ft|
|Evaporative Heating Surface||4646 sq. ft|
|Superheating Surface||1196 sq. ft|
|Combined Heating Surface||5842 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||259.93|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||13860|
|Same as above plus superheater percentage||16632|
|Same as above but substitute firebox area for grate area||95040|