Data from "Sierra Leone Government Railways-Design 1111", Beyer-Garrrat Patent Articulated Locomotives (Manchester, England: Beyer-Peacock & Company Limited, 1931), archived on flickr's Historical Railway Images at [], et seq, p. 19.
Five batches of Prairie Garratts before and during World War II from Beyer:
50-52/6297-6299 (1926)
53-54/6497-6498 (1928) (later Kenya-Uganda EC4 class)
55-56/6578-6579 (1929)
57-60/7045-7048 (1942)
61-62/7049-7050 (1943)
(6966-6969 postponed until after 1945 then sub- contracted to Henschel)
All were classic Beyer, Peacock Garratts using a Belpaire firebox and short, thick boiler to produced steam to power four simple-expansion cylinders. The lead engine carried the road number 50. Its unusual configuration and the placement of road numbers on both the leading and trailing tank and bunker, most likely inspired its nickname of "Fifty-Fifty".
B-P cited this railway as "a typical example of a condition of working for which the 'Beyer-Garratt' locomotive is eminently suitable." Its permanent way was laid with 30 lb/yard (15 kg/metre) that limited axle loading to 5 metric tons, 2% ruling grades, and sharp curves as tight as 5 chains (330 ft). These locomotives quickly replaced the 4-8-0 and 2-6-2T double-heading power setup that had served the railway until then.
B-P also reported that the locomotives were "operated solely by African native enginemen."
As demand continued to grow, the SLGR converted five engine to 2-8-0+0-8-2s, increasing adhesion power by replacing the two Bissel trucks under the boilers with two more axles' worth of driver.
In either configuration, most of the engines operated until the SLGR discarded all steam locomotives.
Convinced by the conversions' operational effectiveness, the SLGR ordered the much bigger Mountain Garratts described in Locobase 1956.
Data from Gavin Hamilton's excellent compilation of Garratt data posted at [] (6 September 2005); and A[rthur] E[dward] Durrant, Garratt Locomotives of the World (revised edition) (Newton Abbott, UK: David & Charles, 1981), p . Works numbers were 7707-7726 in 1955-1956
These Double Mountain Garratts represented an increase of 35% in power over the 2-6-2+2-6-2s that had entered service 30 years earlier (Locobase 741). Durrant pointed out that these were the smallest eight-coupled Garratts ever produced. These fourteen-axle freighters traveled over 30 lb/yard (15 kg/metre) rail and up grades as steep as 3.3%. SLGR's main line covered 227 miles from Freetown inland that began with 22 miles (35 km) that Durrant described as the "most difficult" that included "a steeply graded section where Garratts and banked trains run through the streets! [exclamation point in the orginal]."
Both bogies had four wheels that turned in roller bearings. All of the orthogonal features (edges of Belpaire fireboxes, tank corners and edges) showed more rounded "streamlining" (although 33" drivers didn't provide much opportunity for speed work).
Like the earlier locomotives, these engines had a max axle load of 11,200 lb (5,080 kg), but the tonnage rating up the 2% grade increased from 200 to 270 metric tons.
Principal Dimensions by Steve Llanso of Middle Run Media | ||
---|---|---|
Class | 50 | 63 |
Locobase ID | 741 | 743 |
Railroad | Sierra Leone Government Rly | Sierra Leone Government Rly |
Country | Sierra Leone | Sierra Leone |
Whyte | 2-6-2+2-6-2 | 4-8-2+2-8-4 |
Number in Class | 13 | 14 |
Road Numbers | 50-52 | 63-76 |
Gauge | 2'6" | 2'6" |
Number Built | 13 | 14 |
Builder | Beyer, Peacock | Beyer, Peacock |
Year | 1926 | 1955 |
Valve Gear | Walschaert | Walschaert |
Locomotive Length and Weight | ||
Driver Wheelbase (ft / m) | 12 / 3.66 | 18.80 / 5.73 |
Engine Wheelbase (ft / m) | 27.50 / 8.38 | |
Ratio of driving wheelbase to overall engine wheelbase | 0.44 | |
Overall Wheelbase (engine & tender) (ft / m) | 43.33 / 13.21 | 64.63 / 19.70 |
Axle Loading (Maximum Weight per Axle) (lbs / kg) | 11,200 / 5080 | 11,200 / 5080 |
Weight on Drivers (lbs / kg) | 67,312 / 30,532 | 89,600 / 40,642 |
Engine Weight (lbs / kg) | 104,496 / 47,399 | 148,512 / 67,364 |
Tender Loaded Weight (lbs / kg) | ||
Total Engine and Tender Weight (lbs / kg) | ||
Tender Water Capacity (gals / ML) | 1440 / 5.45 | 1920 / 7.27 |
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 3.30 / 3 | 4.40 / 4 |
Minimum weight of rail (calculated) (lb/yd / kg/m) | 19 / 9.50 | 19 / 9.50 |
Geometry Relating to Tractive Effort | ||
Driver Diameter (in / mm) | 28 / 711 | 33 / 838 |
Boiler Pressure (psi / kPa) | 175 / 1210 | 175 / 1210 |
High Pressure Cylinders (dia x stroke) (in / mm) | 10" x 16" / 254x406 (4) | 12.63" x 16" / 321x406 (4) |
Tractive Effort (lbs / kg) | 17,000 / 7711.08 | 23,009 / 10436.72 |
Factor of Adhesion (Weight on Drivers/Tractive Effort) | 3.96 | 3.89 |
Heating Ability | ||
Tubes (number - dia) (in / mm) | 124 - 1.875" / 48 | |
Flues (number - dia) (in / mm) | 15 - 5.5" / 140 | |
Flue/Tube length (ft / m) | ||
Firebox Area (sq ft / m2) | 76.50 / 7.11 | 95 / 8.83 |
Grate Area (sq ft / m2) | 18.20 / 1.69 | 22.50 / 2.09 |
Evaporative Heating Surface (sq ft / m2) | 724 / 67.26 | 924 / 85.84 |
Superheating Surface (sq ft / m2) | 120 / 11.15 | 178 / 16.54 |
Combined Heating Surface (sq ft / m2) | 844 / 78.41 | 1102 / 102.38 |
Evaporative Heating Surface/Cylinder Volume | 248.89 | 199.13 |
Computations Relating to Power Output (More Information) | ||
Robert LeMassena's Power Computation | 3185 | 3938 |
Same as above plus superheater percentage | 3631 | 4568 |
Same as above but substitute firebox area for grate area | 15,262 | 19,285 |
Power L1 | 6139 | 6225 |
Power MT | 1206.40 | 1225.34 |