SAR NG15 Class
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 NGG15 class locomotive Beddgelert awaiting restoration at the Welsh Highland Railway |
|
| Power type | steam |
|---|---|
| Builder | Henschel & Sohn, Societe Anglo-Franco-Belge |
| Build date | 1931 - 1957 |
| Configuration | 2-8-2 |
| Driver size | 34 in (0.864m) |
| Length | 54 ft 4 in (16.56 m) |
| Axle load | 6.7 tons |
| Locomotive weight | 36.6 tons (loco) plus 31.2 tons (tender) |
| Tender capacity | 5½ tons coal, 2860 gallons (13000 l) water |
| Boiler pressure | 171 psi (1.18 MPa |
| Heating surface: Total | 1028 ft² (95.5 m²) |
| Cylinders | 2 |
| Cylinder size | 15¾" x 17¾" (400mm x 450mm) |
| Tractive effort | 18,820 lbf (83.7 kN) - at 85% boiler pressure |
The NG15 class of locomotives (sometimes called Kalaharis) were a development of the HD class of 2-8-2 locomotives of the Otavi Mining and Railway Company in German South West Africa. Three HD class locomotives, built by Henschel & Sohn, were supplied on lease to the Otavi Railway Company by the German government in 1912. These locomotives had piston valves. At 59 tons, these locomotives were considerably larger than earlier main line Otavi Railway locomotives, which were typically less than 23 tons in full working order.
Six similar locomotives from Henschel & Sohn were placed in service during 1922, being classified NG5 by SAR who were responsible for operating railways in SWA (South West Africa) at this time. These locomotives had slide valves.
One of the NG5 locomotives was sent east to the Avontuur line for trials, but it jammed on the tighter curves. This was despite having one pair of flangeless driving wheels. The locomotive was returned to SWA.
The drawing board work for the NG15s has been attributed to the one time Chief Mechanical Engineer of the Otavi Railway, a German engineer called Mr. Peters, pronounced as Pay-tarz(?).
Mr Peters was employed as a draughtsman by SAR. The usual practice of the SAR at this time was to design locomotives in their own drawing offices and to then go out and find a builder.
All five batches of NG15 locomotives were built for service on the 600 mm. gauge Otavi Railway. The 30 2-8-2 locomotives operated in a common pool until the narrow gauge Otavi Railway was replaced beginning on 24 November 1960 by a new railway built to the Cape standard gauge of 42 inches (1067 mm). At this time all 21 NG15 locomotives were transferred to the Eastern Cape for further service on the two foot (610 mm) gauge Port Elizabeth to Avontuur line. The six 1922 built NG5 locomotives were sold to a scrap dealer in 1962.
Since the earlier trials with the NG5 locomotive the sharper curves of the Avontuur line had been eased. The leading pair of driving wheels of the NG15 also have a limited amount of sideplay and are linked to the leading pony truck. The axle of the leading driving wheels remains parallel to the other three driving axles at all times.
This linking of a pony truck and driving axle is known as a Krauss-Helmholtz bogie, an invention of Richard von Helmholtz who was chief designer at the Krauss works in Munich from 1884 to 1917. The inclusion of a Krauss-Helmholtz bogie has allowed the use of large 2-10-0 locomotives on sharply curved mountain sections of standard gauge railways in Europe. Some early electric locomotives also used Krauss-Helmholtz bogies.
When first introduced onto the Avontuur line, the NG15s were not allowed to work beyond Humansdorp to Avontuur because of a lack of turning facilities on this section. This was rectified by the construction of a triangle at Avontuur.
| Batch | SAR number | Manufacturer | Builder's numbers | Build dates |
|---|---|---|---|---|
| 1 | 17 - 19 | Henschel & Sohn. | 21905 - 21907 | 1931 |
| 2 | 117 - 119 | Henschel & Sohn. | 24475 - 24477 | 1938 |
| 3 | 120 - 124 | Societe Anglo-Franco-Belge | 2667 - 2671 | 1949 |
| 4 | 132 - 136 | Societe Anglo-Franco-Belge. | 2682 - 2686. | 1952 |
| 5 | 144 - 148 | Henschel & Sohn. | 29585 - 29589 | 1957 |
| Number | Current location |
|---|---|
| 17 | Sandstone Estates. |
| 18 | Hempstead & Northern RR, Texas, United States of America. Exported from South Africa to the U.S.A. in 1985. |
| 19 | Sandstone Estates. |
| 118 | Bennett Brook Railway, Perth, Western Australia. In service on the railway from 15 October 1994 through to 2003. Stored awaiting an overhaul. Exported from South Africa to Australia in 1985. |
| 120 | Welsh Highland Railway (Porthmadog). Reported as being available for sale. |
| 121 | Phyllis Rampton Trust, Surrey, United Kingdom. |
| 122 | At a museum in George, South Africa. |
| 123 | Bennett Brook Railway, Perth, Western Australia. Restored to traffic as from 10 May 2007. Exported from South Africa to Australia in 1985. |
| 133 | Owned by the Festiniog Railway Company. Acquired for potential use on the Welsh Highland Railway. Stored in the open at the Dinas station of the Welsh Highland Railway (Caernarfon). |
| 134 | Owned by the Festiniog Railway Company. Acquired for potential use on the Welsh Highland Railway. Dismantled for restoration to working order, with the components stored at the Dinas station of the Welsh Highland Railway (Caernarfon). |
| 135 | Owned by the Exmoor Steam Railway. In Store. |
| 146 | Owned by the Brecon Mountain Railway. In Store. |
[edit] The Otavi Railway HD Class Locomotives and the South African Railways NG5 Class
There were three HD class locomotives built by the German company Henschel & Sohn at their Kassel (Cassel at the time) works in 1911, builder's numbers 10720, 10721 and 10722. The HD locomotives had plate frames outside all the wheels. They were numbered 40, 41 and 42 in the Otavi Railway fleet. They came into SAR ownership in 1923 when the Otavi Railway was nationalised. Ex Otavi Railway locomotives had the prefix SW added to their existing numbers, which distinguished them from any SAR narrow gauge locomotives which carried the same number. It is not known if the SW prefix was actually displayed on the locomotives. Number 40 is believed to have been the last locomotive in steam on the narrow gauge Otavi Railway during September 1961, shortly before demolition of the line was completed. Number 40 was then placed on display at Usakos station. After the 1914-18 war Usakos had become the southern terminus of the narrow gauge. It was also where the railway's works were located. Number 41 was retained with the intention to display it in a museum in Windhoek. Number 41 was plinthed in 1960 at the Otjiwarongo station and was still there in August 2007. Number 42 was sold in 1962 to Chick Scrap Metals, along with all six 1922 built NG5s and 1916 built Baldwin NG10 pacific number 63.
The six NG5s were built in 1922 by Henschel & Sohn in Germany, with works numbers 18578 through to 18583, inclusive. The NG5s were built to the same general design as the HDs. They had slide valves instead of the piston valves used on the HDs. The driving wheel suspension arrangements also differed. They were numbered 71 to 76 in the SAR narrow gauge fleet, were ordered by SAR and were SAR property.
The following table details the Otavi Railway HD class locomotive and tender, and also the similar South African Railways NG5 locomotive and tender, from which the SAR NG15 class were developed.
The data in this table should be taken as indicative only and not as being 100% accurate. The published sources used differ on details, particularly regarding the boiler heating surfaces, and some of the heating surface area figures used here appear to be inconsistent.
| Feature | Details |
|---|---|
| Tractive effort, 75% boiler pressure | 73 kN (16,610 pounds) |
| Locomotive wheel arrangement | 2-8-2 |
| Tender wheel arrangement | two x four-wheel bogies |
| Locomotive weight, in full working order | 33.4 tonnes (32 tons 17 cwt or 73584 pounds) |
| Tender weight, in full working order | 26 tonnes (25 tons 11 3/4 cwt or 57316 pounds) |
| Length over buffers, locomotive + tender | 15170 mm (49 feet 9.25 inches) |
| Driving wheel diameter | 860 mm (2 feet 9.875 inches) |
| Cylinders | 2 |
| Cylinder dimensions, diameter x stroke | 400 mm x 450 mm (15.75 inches x 17.75 inches) |
| Valve gear | Unknown |
| Boiler pressure | 1180 kPa (171 pounds per square inch) |
| Grate area | 1.5 square metres (16 square feet) |
| Firebox | 6.3 square metres (68 square feet) |
| Tubes | 112 of 45 mm (1.75 inches) external diameter,
14 of 120 mm (4.71875) external diameter |
| Tubes heating surface | 77.3 square metres (832 square feet) |
| Superheater heating surface | 22.7 square metres (244 square feet) |
| Distance between tubeplates | 4000 mm (13 feet 1.5 inches) |
| Tender coal capacity | 2.9 tonnes (2 tons 17 cwt or 6384 pounds) |
| Tender water capacity | 13000 litres (2860 gallons) |
| Locomotive, leading and trailing wheel diameter | 550 mm (1 foot 9.65625 inches) |
| Tender wheel diameter | 520 mm (1 foot 8.5 inches) |
| Tender bogie wheelbase | 1000 mm (3 feet 3.375 inches) |
| Distance between tender bogie centres | 2500 mm (8 feet 2.375 inches) |
[edit] References
- "Namib Narrow Gauge", by S.M.Moir and H.Temple Crittenden. The Oakwood Press.
- "24 Inches Apart", by Sidney Moir. Janus Publishing, 1981.
- "The Locomotive in South Africa", by T.J.Espitalier and W.A.J.Day. South African Transport Services Museum, 1989.
- "The Kei Explorer 1989", South African Transport Services Museum and Railway Society of S.A.
- "The Steam Locomotive, A History", by David Ross. Tempus Publishing Limited, 2006.
- WHR Porthmadog NG15 Class
- SAR Steam 2ft 0in SAR Class NG15 Tender
