Reefsteamers
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100 Years of Susan, the 12 AR

 A detailed report of the 100 year old Lady "Susan", a big thank to our brilliant writer Mr. Lee Gates, enjoy the read

Class 12AR No.1535 ‘Susan’ is Reefsteamers’ grand old lady at 100 years of age.  She presently (as of 2019) has the triple distinction of being the last surviving SAR Class 12AR type locomotive; being Reefsteamers’ oldest operating locomotive and is also the oldest locomotive of any kind still operating on an active main line in South Africa.  Susan the 12AR also has the engineering distinction of possessing the last working ‘Loubser Boiler.’

‘Susan’ weights 101 tons, pulling a 67 ton tender and has 14 wheels.  She has four small wheels in front on a pivoted bogie, eight coupled driving wheels and two smaller pivoted wheels supporting the firebox.  This makes Susan the 12AR a 4-8-2, which is known as the ‘Mountain’ wheel configuration.

‘Susan’ was originally built as a Class 12A by North British (Glasgow, Scotland) in 1919 and shipped to South Africa.  The brand-new locomotive first entered traffic on 15 March 1920.

The original Class 12s, from which the Class 12As originated, were the first new class ordered by the then-new South African Railways.  Designed by D.A. Hendrie, the Class 12s were the largest non-articulated Cape Gauge (3ft 6in) locomotive in Africa (and possibly the world) at the time.  The Class 12 was a simple locomotive being essentially a larger version of the already successful Class 3B. The Class 3s were themselves based on Natal Government Railways Class 4-8-0 Class Bs; of which 6 which were modified to 4-8-2 for passenger service in 1906 and became the first 4-8-2 ‘Mountain’ type tender locomotives in the world.

The early Class 12s thus already have quite a lineage, and the 4-8-2 ‘Mountain’ wheel arrangement they sported would go on to become the most common wheel configuration on the South African Railways. The Class 12s were originally designed for heavy coal haulage from Witbank to Germiston, to supply coal to the young and rapidly growing Johannesburg on the Witwatersrand.  To help with the traction but keep the locomotive a reasonable length, the eight x 51 inch drivers wheels were specifically mounted to be as close as possible.  This meant the brake hangars had to be redesigned and mounted outside the wheels which was quite unusual at the time.  They were a successful design and were able to haul 1400 ton coal trains.

Hendrie then designed the Class 12A as an upgraded Class 12 with larger cylinders (2ft diameter), better valve porting and an improved boiler with a distinctive square-topped Belpaire firebox, and a combustion chamber.  The combination of a Belpaire Firebox and combustion chamber is a rarity in locomotive design, making the 12As unusual engines. The slightly heavier Class 12A locomotives worked alongside the original Class 12s in coal service.  Our Little Susie was the 15th such Class 12A locomotive built in the first batch of 20.  Between 1919 and 1929, 67 Class 12As were built in 5 batches by 2 different manufacturers (North British and Henschel & Sohn).

Built in 1919, the 12A 1535 was originally supplied with Cape Government Railways Johnson Link-and-Pin couplers which had been in use since 1873.  The USA-pattern AAR knuckle coupler she now wears as a 12AR was a later addition. The 12s and the 12As were successful locomotives.  However, the 12As cost more than the 12s to maintain though due to their more complicated boilers. In the mid 1930’s, the then-aging Class 12s and the derivative 12As came under CME A.G. Watson’s nation-wide reboilering program which was implemented to reduce repair time and spares stocks.  However, none of Watson’s seven standard boiler designs would fit.  It was a ‘Goldilocks problem’ with the Watson Standard no. 2 series being too small, while the no. 3 series were too large.  After experiments with two locomotives, a unique boiler design (Designed by CME Dr. Kobus Loubser) was applied to 42 Class 12As.  The new boilers were larger, but of simpler construction.  These 'kettles' became known as ‘Loubser Boilers.’

The new boiler also incorporated a three-bobbin Melesco regulator and super-heater system, and a pair of ross pop safety valves replacing the old dual Ramsbottom set.  The feedwater system was replumbed and changed to a top entry system via a dual clack valve box.   The new extended smokebox also gained a self-cleaning system with spark arresters.  A new roomier cab was also fitted (even though the original cabs were already larger than typical for the time), but retained running board doors. The latter is a feature which is absent on the larger SAR locomotives due to their wider fireboxes. However, the running boards and sand boxes remained unchanged. - With the new boilers fitted, the letter ‘R’ was suffixed to the locomotive class designations. The upgraded Class 12As became the Class 12ARs. - The then-25 year old 12A No.1535 was pulled into the works to receive her new boiler and upgrade in 1944 and became the Class 12AR 1535.  She was placed back into service on 16 April 1947.

The new ‘Loubser Boiler’ led to the distinctive look of the 42 new Class 12ARs, with a large 6ft dia. boiler and the long smokebox overhang at the front.   Looking from the side, the long boiler looks even bigger over the close-set driving wheels.  The Class 12AR gained 2 inches in height to 13 feet tall, but stayed the same weight at 101 Tons.  However, the different boiler design was actually slightly LIGHTER and shifted the weight backwards, imposing a 17.6 ton axle load on the 3rd and 4th driver axle. (On most 4-8-2 locomotives, the heaviest axle load is on the 2nd driver axle, which is the main driver axle driven by the con rods.)  To help balance the load and retain their weight for traction, the 12ARs were fitted with heavy trim weights right at the front end.   Those extra weights can be seen from the outside today as a distinctive heavy casting above the very front wheels and they angle inwards towards the frames at 45 degrees.

The ex-Class 12As also lost the combustion chambers and ran instead with an extra ‘course’ in the boiler and with the resulting longer boiler tubes.  The active heating surface of the 12AR was actually slightly LESS than the old 12A design.  The new boiler was designed more to maintain a thermal reserve rather than for quick steam raising.  The crews actually preferred the old 12As for easy steam raising, although the maintenance costs were higher with the previous complicated firebox arrangement and non-standard parts.

With some irony, the ‘standard’ Loubser-designed boiler fitted to the 12AR was never fitted to any other locomotive, due to the unusual close-wheeled proportions inherited from the original design brief.  A shorter version of the boiler with one course eliminated, was fitted to an eight-coupled shunting locomotive, the type S1. Being a 0-8-0 shunter, the S1 also had close-coupled driver wheels, so the choice made sense.

The 44 reboilered 12AR locomotives served alongside more modern locomotives in the steam hubs of South Africa.  They performed dedicated heavy haulage work until 1972.  From 1972 to 1985, the 12ARs spread out over South Africa and put those oversized boilers to good use!  It is during this era that the No.1535 locomotive first received the name ‘Susan.’

In their later days, they were very useful, simple and robust shunters until displaced by the bigger Class 15CAs.  A famous brace of 3 ‘super-shine’ Class 12ARs operated in Kaserne, South of Johannesburg.  The Witwatersrand Class 12ARs were based in several sub-sheds but the medium overhauls were all performed at the Germiston 15M Shops which Reefsteamers operates today.  Unlike many other retired locomotives, no Class 12ARs were sold into mining or industrial service, which is one reason why No.1535 ‘Susan’ is the last survivor.  (Many mining locomotives outlasted those on the railways, albeit in poor condition or dumped.)

In her last SAR years, No.1535 ‘Susan’ worked as the Germiston Station pilot (Displacing 12R No.1947 ‘Rosie’, who is also under our care) and was always fairly well looked after.  Unlike most of the world’s steam locomotives which survived into preservation, 12AR 1535 ‘Susan’ was never formally retired and thus was never actually restored from stripped, scrap or abandoned condition.

Still owned by Spoornet (and in revenue service) and operated by Spoornet Crews,  ‘Susan’ the 12AR  began hauling heritage trains from the mid-1980s onwards.  She hauled heritage trains and specials throughout the late 1980’s and participated in the last Great Steam Festival in 1991.  In 1993, she was briefly named ‘Little Foot’ at Magaliesburg by the then-Sports Minister, after one of the hominid fossils in the nearby Cradle of Humankind.  However, the name reverted back to ‘Susan’ shortly afterwards.

When Spoornet officially stopped steam operations in 1992, Susan the 12AR was deemed surplus to requirements and was NOT selected to go to the National Collection for preservation.  Still owned by Spoornet, the now-surplus ‘Susan’ was moved to the Millsite (Krugersdorp) Depot from where she would operate for a few more years.  Susan’ occasionally revisited the Germiston Depot (Closed 1992), which was by then abandoned and being stripped, except for the 15M workshops where the then-new Reefsteamers were.

Based at Millsite (Krugersdorp) and still operated by Spoornet crews, Susan was chartered by various local parties, such as RSSA.  In 1996, Spoornet (As a part of SATS) closed down the last few steam workshops, including the Millsite shops.  They would no longer support steam repairs, infrastructure or provide crews to operate the engines. Skills and experience became harder to come by and Susan the 12AR started developing some mechanical problems.

Unfortunately, she was prone to developing hot bearings on the front bogie axles and had problems with the steam-powered reverser.  Susan the 12AR was laid aside as unreliable after inexperienced repair attempts were made at Millsite Depot (Krugersdorp) and was leased to Reefsteamers in 2003.  ‘Susan’ had come back home to Germiston.  During this time, due to bureaucracy and politics, the last of Susan’s sisters was scrapped at Germiston.  She thus became the very last one of her kind.

From now on, ‘Susan’ the 12AR No.1535 would be repaired by Reefsteamers volunteers.  We sorted out the problems, which included piston cups that were installed back-to-front in the reverser’s steam cylinder!   
In the earlier years of Reefsteamers service, the tender was updated with roller bearing axles.  The ugly 1960s dual-sealed beam headlamp was retrofitted to a classic Golden Glow headlamp, which she bears today.   The neat yellow cab-side pinstriping and the ‘Germiston’ heralds that she bears to this day were hand painted by a Reefsteamers volunteer in classic sign-writer style.  

The repaired and upgraded Class 12AR went on to provide reliable service.  She ran her first Reefsteamers long distance tour in 2005, which was the Bethal Potato Festival.  ‘Susan’ also took part in another Reefsteamers landmark – the first SAR Steam Tours long distance train in Nov. 2013.

These days she goes well and is capable of about 100kph even with her small goods engine-sized wheels.  (Of course, we do stick to speed limits.)   The ‘little’ 12AR performed well until 2006 when she broke a bissell truck spring hangar.  This coincided with a 3-year boiler certificate renewal, so she stood idle in the workshops for 3 years alongside with then-incomplete Class 15F No.3046.  With 7 new boiler tubes, valve & piston overhaul, and the bronze valve gear bearings upgraded to synthetic Vesconite, she was restored to steam in March 2009.  She was also the last Reefsteamers locomotive ever to receive graphite paint on the smokebox, before we switched to black etching primer as a standard.

'Susan’ has since become Reefsteamers’ favourite locomotive for day trips.  The modified Vesconite valve gear was a great success.  She is a sure-footed ‘little’ engine and with a nearly 18 ton axle load, she can handle our trains on gradients that would cause the bigger engines to slip.  Designed to haul heavy coal trains, the Reefsteamers passenger train is a light load by comparison. Because of her classic open lines and old-fashioned look, she is also very popular amongst the photo community.

12AR 1535 is also an ideal training platform with her relatively narrow but forgiving firebox and simple controls.  Susan the 12AR is also an economical engine to run, sometimes with coal savings of R8500 and more over the dramatic 15F type for a 196km round-trip Magaliesburg run.

In 2016, ‘Susan’ was fitted with PFTE Ball valves and extended kick levers for the injector sets.  She is the only steam locomotive in S.A. so fitted, but we plan to modify the rest of them. There are also long-term plans to fit a mechanical lubricator to the locomotive.

The boiler presently serving on 12AR 1535 is NOT the original ‘standard’ boiler with which the locomotive was converted.  Commissioned in 1955, it was showing evidence of wasting (Thinning) in the lower part of the front tube sheet.  We arrested the thinning with a careful cleaning and washing regime after every trip – now a Reefsteamers standard for all our locomotives.  The new cleaning regime brought us 6 more years of service but by 2013, it was thought that we would eventually have to take the 12AR out of service for major boiler repairs.  Considering the funding, man-power and equipment needed, it might have meant permanent retiring of the locomotive and plinthing as a display piece.

When ‘Susan’s’ fourth Reefsteamers boiler certificate expired in 2016, the Boiler Inspector mandated that the front tube plate be repaired or replaced.  

It took many months to draft formal plans for repairs and welding of that tube sheet, and to submit designs for approval to the boiler inspector.  The repair was authorised and was completed in July 2017; and did not require dismounting of the boiler or removal of the smokebox.  Thus, ‘Susan’ the 12AR 1535 is STILL in service for her 100 year birthday and has also proven that a welded tube plate repair is viable, which might benefit other preserved steam locomotives in South Africa.

‘Susan’ was formally renamed in 2018 to … ‘Susan.’   The renaming rights were owned by the late Anthony John Hammill and the identical ‘Susan’ name references his wife.  Hamill passed away in the same year the locomotive’s name was secured.