South African Class NG G13 2-6-2+2-6-2

SAR NGG 13 Class and SAR NGG 16 Class
South African Railways Template:1ft11.5in gauge NGG16 class Garratt, preserved in operating condition on the Welsh Highland Railway
Built	1927 - 1968
Number of pieces	NGG 13 - 23 NGG 16 - 34, 2 converted to NGG 16A
Numbers of engines	NG 40 - NG 156
Wheel Arrangement	(2-6-2) + (2-6-2T) Garratt
Gauge	Template:1ft11.5in
Wheel arrangement	2-6-2 + 2-6-2T
Length over couplers	48ft5in
Total wheelbase of loco	43ft3in
Coupled wheelbase of each power unit	6ft3in
Power unit wheelbase inc. trailing axles	13ft10.5in
Driving wheel diameter	2ft9in
Trailing wheel diameter	1ft9in
Total heating surface	1,049.1 square feet
Heating surface of tubes	859 sq. ft.
Heating surface of firebox	82.1 sq. ft.
Heating surface of superheater	149 sq. ft.
Grate area	19.5 sq. ft.
Boiler pressure	180 pounds per sq. inch
Cylinders (x 4)	12" diameter, 16" stroke
Valvegear	Walschaert
Tractive effort @ 85% pressure	21,553 lbs
Water capacity	1,823 gallons
Weight in working order	62 tons (approx.)

The SAR NGG 13 Class and SAR NGG 16 Class are Garratt steam locomotives of South African Railways (SAR), built for Template:1ft11.5in narrow gauge railway tracks, the largest ever locomotives built for this gauge. The last locomotives of the NGG16 class were built in 1968, the last Garratts built.

History

The challenges of Africa created the regular need for double-heading of steam locomotives on heavy weight trains to keep speeds upwards. While West Africa resolved the solution at the turn of the century with larger Pacific and Mikado locomotives, the greater gradients and tighter curves in South Africa required a drove a different solution, solved in 1914 by the order of three NG/G 11 locomotives by South African Railways.

The locomotives were produced and delivered post World War One by Beyer Peacock in 1920, but the locomotives success resulted in a second order in 1925.

Freed in 1927 of the HW Garratt articulation patent, SAR approached Hanomag of Germany to develop a new class of Garratt locomotives, which lead to the first three NGG 13 locomotives of 1927. Performance trials of the NGG 13's proved them to be both powerful and free steaming, despite having a smaller grate area than the NG/G 11's. This lead to an immediate follow on order of two engines, and a further seven the following year.

In 1936 Hanomag's locomotive building business was sold to Henschel & Son's in Cassel, France; so SAR returned to Beyer Peacock. However, Peacock's workshops were full, so they designed the NGG 16 locomotives and outsourced the construction of the first batch to to John Cockerill of Seraing, Belgium. Further batches resulted in an additional thirty locomotives built until 1968, when the last ever Garratt's were built in Manchester.

Technology

With a track width of only Template:1ft11.5in, a powerful steam locomotive is problematic with turning radii of under 50m, which practically restricts powerful rigid-frame locomotives to four axles. A Garratt design connects two three axle locomotives (thereby providing six powered axles), in a double articulated format, and a more powerful locomotive.

However, the Garratt design has some inbuilt problems. The first problem is tractive effort, whereby locomotive traction reduces with reduced weights of water and coal. Standard gauge Garratt's often overcame this with use of water carrying wagons behind the locomotive, which were used to fill up the locomotives water capacity and hence keep tractive effort high. On long length journeys in central Africa the additional weight and resultant increased distance between refuelling brought speed advantages. The second problem was tilting. The NGG 13 and NGG 16 had inter changeable boilers of nearly 1.5 metre diameter on a frame width of 2.10 metres. This created the risk of the locomotive tilting over on tight radii curves.

All locomotives were controlled via efficient Walschaerts valve gear, with the only substantial difference being the addition of an improved flue system and roller bearings on the NGG 16. All locomotives were built to be coal fired, by some were modified locally to become oil fired.

The success of the design is proven by the forty years of procurement of the design, even into the oncoming diesel locomotive era.

Manufacture

23 locomotives of NGG 13 Class were built 1927 and 1928 by Hanomag (No. NG 49, 50, 58-69, 77-83). In 1937 the first batch of NGG 16 Class were built by Cockerill (No. NG 85-88), and eight from Beyer Peacock (No. NG 109-116). In 1951 a further seven machines followed from Beyer Peacock (No. NG 125-131).

Beyer Peacock supplied a further seven locomotives in 1958 for the mines of the Tsumeb corporation in Southwest Africa (today Namibia), but they were transferred to SAR in light of Tsumeb's change to Cape gauge (No. NG 137-143). These locomotives were a modified design, in that they only had coal supplies on the rear chassis, as opposed to the earlier designs which had side water tanks with a central coal bunker. The front chassis had a lesser curvature to increase water capacity, but these locomotives were often attached to a water wagon like the standard gauge Garratt locomotives. These locomotives were painted red on delivery, and started the classes sub division of Red Devils.

SAR ordered a further eight locomotives in 1965, but as Bayer Peacock were already winding down their locomotive building activity the construction was outsourced to Hunslet Taylor. The locomotives (No. NG 149-156) were delivered in 1967 and 1968 supplied as last steam engines for the SAR, and the last Garratt locomotives at all. The increased front water tank of the Tsumeb supply was maintained, but the design of the rear chassis was returned to those supplied in 1951.

In 1989 and 1990, two locomotives of the Arnold County Railway (No. 141 and 155) were converted in order to improve their economy. Owing to the fuel savings of 20 to 25%, the works paid back financially within 12 months. The converted locomotives are called class NGG 16A.

Deployment and usage

The locomotives were first used on the route from Port Elizabeth to Avontuur, a 283 kilometre long track which was the longest Template:1ft11.5in gauge railway in the world. The abilities of the narrow gauge track enabled the trains to pick up fruit directly from the narrow gauge tracks of the fruit farms, and ship them directly without reloading to the ripening warehouses, distributors and ships at Port Elizabeth. This route became known under the Apple Express, after the main crop it transported. The locomotives also ran heavy limestone trains from Port Elizabeth to supply the cement factories which were located on the route.

From the mid-1970s, steam was replaced by diesel locomotives of the SAR 91 Class, which were both more powerful and being shorter in chassis length more able to access the growers farms.

SAR transferred the NGG13's and NGG 16's to Natal to the 122 kilometre route from Port Shepstone to Paddock via Izotsha. The route had some curves of 45 metres, but with gradients of up to 3 in 100/3%, the Garratt's were ideally suited to hauling both the diverse freight traffic of wood, sugar beet and banana crop to Port Shepstone, as well attracting additional tourist passengers to the trains which became known as the Banana Express. The route was shut by SAR in 1986, but in a new partnership sold on a long term lease to listed company the Post Shepstone and Arnold County Railway' in March 1988. The venture lost money heavily initially, but after making profits from year three failed when it lost a key contract supplying wood to a pulping plant that took 48hrs to deliver to the factory due to the requirement to transfer the goods from Template:1ft11.5in gauge to either the standard gauge railway or the vastly expanding truck industry. SAR forced the venture into bankruptcy, and although the popular Banana Express was continued the following summer by Patons County Railway, it is presently not running.

The locomotives of the PS&ACR were sold as a result of the failure to either state owned concerns, or to international railways. The early stages of the Welsh Highland Railway benefited from the purchase of three NGG 16's and excess track and sleepers, while the Sandstone Railway either took locomotives directly or via the Transnet Foundation.

Outside South Africa

At least 11 of the 21 NGG 13's, as well as most NGG 16's still survive. Since many of the surplus locomotives after the retirement were still in relatively good condition, and some some were purchased by museums and railways overseas:

• England: three were purchased for a project by the Exmoor Steam Railway which never came to fruition. No. 87 was purchased by the Welsh Highland Railway in January 2007
• Germany: NGG 13 No. 83 resides in the German Museum of Technology, Berlin
• Switzerland: NGG 13 No.60 is at Schinznacher, and an NGG 16 is at the National Railway Museum
• United States: NGG 13 No. 50 was brought in 1985 to the Hempstead and Northern Railroad in Hempstead, Texas; and is ever the first and presently only Garratt locomotive in North America
• Wales: In 1997 the Welsh Highland Railway bought three NGG 16's (No. 138, 140 and 143) from the Tsumeb supply. No.s 138 and 143 were overhauled on the Arthur County Railway before they left South Africa, and work the initial WHR route at present. No. 140 is presently at the Ffestiniog Railway's Boston Lodge engineering works at Porthmadog being overhauled in preparation for the scheduled full opening of the WHR in 2009

References

• A.E. Durrant: Garratt locomotives of the world. Birkhouse publishing ISBN 3-7643-1481-8

External links

• Wikipedia German language article and English language version
• Sandstone Railway, South Africa
• Article on NG/G13 and NG/G 16 Garratt's development and deployment