Alfred County Railway - Garratt 2-6-2+2-6-2
NGG16A N^os. 141 & 155

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Note: This page would not have been possible without the assistance of Nigel Day, Phil Girdlestone and Shaun McMahon. Nigel lent me a large number of slides and several black and white photographs taken by Shaun McMahon. These photographs form the bulk of the illustrations below. Shaun has also filled in many of the technical details for me. I also wish to record my thanks to Phil Girdlestone for allowing me to publish the information below, for checking it and suggesting improvements. That said any errors are my own.

As the final 8 NGG16s were the last steam locomotives supplied new to South African Railways and the last production batch of Garratt locomotives produced (to date) they are fairly well known. However there is always more to learn on a given subject so, as an authoritative introduction to the class, I have made an excellent article by Phil Girdlestone and Shaun McMahon available. This piece was written in 1994 when it was announced the NGG16s were preferred motive power for the soon to reopen Welsh Highland Railway. Click here to read it.

NGG16A 141 at Port Shepstone. 1998. © Nigel A.H. Day.

A read three-quarters view of 141 at Port Shepstone. On the rear of the coal bunker/water tanks are the sizeable oil reservoirs and the sand boxes. 1998. © Nigel A.H. Day.

In August 1989, under the direction of CME Phil Girdlestone, ACR completed the modification of NGG16 141 turning the locomotive into a NGG16A. This work had commenced in February 1988. In March 1990 155 was similarly outshopped. Both locomotives were modified at the Port Shepstone workshops on ACR. These locomotives had been selected as their boilers were in good condition and mechanically they did not require huge amounts of work.

The modification work carried out included:

• Gas Producer Combustion System;
• Lempor exhaust with a de laval blower;
• Kordina BETWEEN engine units, not between individual cylinders;
• Master Mechanics self cleaning type spark arrestor specially smoothed for low draught loss. Rounded char breakers were fitted;
• Lightweight, mutli-ringed, articulated piston valves;
• Valvegear alterations;
• Proportional feed mechanical lubrication;
• Extended mechanical lubrication, going from a 17 point feed to a 21 point feed;
• Roller bearings fitted to the eccentric cranks;
• Larger water tank opening to avoid precise "spotting" of the locomotive at water columns.

A rear view of 141's cab on the drivers side. Note the bottle of water and the movable seat both outside of the cab to help the water and the driver stay cool in the very hot operating conditions. The curve in the cabside is the accommodate the screw reverser handle. 1998. © Nigel A.H. Day.

Modified Garratt NGG16A 155 on shed at Port shepstone, ACR. April 1995 © Shaun McMahon

The Lempor diffuser section appears as the chimney above the smokebox. Attached to the top of the chimney is a final stage spark arrestor. See below for more details. November 1993. © Shaun McMahon

A wider shot than above giving a better idea of the scale of the chimney relative to the rest of the locomotive. The smokebox is painted with a heat resistant paint. Note the builders plate on the boiler cradle bottom right. 1998 © Nigel A.H. Day

The locomotives were equipped with a Kordina between the engine units but not between the individual cylinders. The Lempor nozzle attaches to the top surface, the hole for which had yet to be drilled when the photograph was taken. This item replaced the piece shown below. November 1993. © Shaun McMahon

This is the original blast pipe arrangement showing how the exhaust steam from each engine unit was joined. November 1993. © Shaun McMahon

This is the view down the diffuser and mixing chamber (chimney) to the Lempor nozzles on 155. Not all hardware is installed as this is a 2005 view with the loco partially dismantled for overhaul. © Sandstone Heritage Trust. Courtesy of Shaun McMahon

The Lempor nozzle on 155 with the De Laval blower nozzles at the base. The blower pipework is missing. Note that the nozzle sits on top of a section of the Master Mechanics type spark arrestor. Combustion gasses flow underneath the plate seen. © Sandstone Heritage Trust. Courtesy of Shaun McMahon

A different angle on 155's nozzle and dismantles spark arrestor. At the rear of the remaining spark arrestor plate would be a solid plate directing the combustion gases underneath and around the nozzle location. © Sandstone Heritage Trust. Courtesy of Shaun McMahon

The NGG16As were equipped with a low draught loss spark arrestor based on the Master Mechanics type. Sharp corners were removed from the arrestor to ease the gas flow. Here parts of this system can be seen, the rest is dismantled. With these parts removed the Lempor nozzles and the base of the mixing chamber can be seen along with the specially shaped entrance to the mixing chamber. November 1993. © Shaun McMahon

In addition to the spark arresting internal to the smokebox the locomotives were fitted with a final stage of mesh at the top of the diffuser. November 1993. © Shaun McMahon

Recently Shaun McMahon made the following comments to the webmaster on the spark arrestors fitted to the NGG16As:

"It should also be noted that the secondary arrestors as fitted to 141 and 155 came some years after the original modification. In the main this was due to the drought in that part of Natal province during 1991 and subsequent setting alight of farmers land next to the railway in the Paddock area. Around 1992 the secondary arrestors as seen in the photos on the chimney top were designed and fitted. These had "easy clean" swing top lids whereby you could undo the nut and bolt, lift the arrestor and bash it a few times so as to free the very fine particles that caused blockage, it was very rare for these to block up but not unknown. When running the carryover was akin to a shower of fine sand constantly falling on your head, but nothing hot, all black - no red embers. A standard 16 would go around throwing spark in a terrible way."

Protection against stray sparks was also given alongside the secondary air (over fire air) inlets in the firebox sides. November 1993. © Shaun McMahon

The over fire air holes as viewed from the inside of the firebox. Note the swirl inducers within the holes designed to help gas mixing in the firebox. November 1993.© Shaun McMahon

A 2005 view inside 155's firebox with the combustion arch and swirl inducers in the over fire air holes removed. As can be seen the over fire air holes have taken the place of stays. © Sandstone Heritage Trust. Courtesy of Shaun McMahon

With the external spark arrestors not in place but the fire lit the swirl plates are clearly visible. 1998. © Nigel A.H. Day

The outer view of the over fire air holes on 155 again clearly showing how they have directly replaced stays. In effect they act as hollow stays. © Sandstone Heritage Trust. Courtesy of Shaun McMahon

The NGG16As were fitted with the best practice grate. As shown on the Red Devil pin hole grate sections perform extremely well. This view shows the rear-most section on 155 in 2005. © Sandstone Heritage Trust. Courtesy of Shaun McMahon

On the right as the original NGG16 type ring retainer equipped with 4 wide rings (not fitted) whilst on the left is an experimental 8 iron ring version trailed on 155. 141 was fitted with a 7 bronze ring version and retained them whilst in service. The use of extra rings provides greater steam tightness and a lower specific bearing pressure. November 1993. © Shaun McMahon

The red rod running in front of the cylinder is the revised drive arrangement to the mechanical lubricator. This drive, from the top of the combination level provided a proportional oil feed. The mechanical lubrication was increased and was "between the rings" on the piston valves. There was one such arrangement per engine unit. 1998 © Nigel A.H. Day

This view looking to the end of the engine unit clearly shows the mechanical lubricator drive from the combination lever. Note that the bearing on the drive rod is a roller bearing. Why would it be otherwise in this days and age ? That said the bearings used were recycled from SAR 3'6" GMA/M type Garratt locomotives built between 1953 and 1958. 1998. © Nigel A.H. Day

This cover covers the site of the drifting valves removed during the modification. The 3 prominent brass fittings are high pressure terminal check valves on the mechanical lubrication feed providing "between the rings" lubrication of the piston valves, 1 for each head, and a feed to the piston. 1998. © Nigel A.H.Day

"Vryloop in Middelstand - Drift in Mid Gear" A clear instruction to the driver! With the removal of drifting valves and the provision of a drifting steam supply to maintain positive pressure in the steam chests it was possible to do away with the tradition of drifting in anything other than mid gear. An explanation why this is a good idea was kindly provided by Phil Girdlestone: "The reason for mid gear drifting (with air and by pass valves removed) is to create a positive valvechest pressure to prevent gases and solid particles being sucked down the blast pipe. With the very thin admission edge lips of the valves it also gave the advantage that all valve rings were pressed towards the exhaust side face of the ring grooves. This could be seen as these faces were polished and the steam side of the groove had a light coating of carbon. You can see a faint line on the pressure gauges at 400kPa, this was meant to indicate the minimum pressure for this condition to be achieved." November 1993. © Shaun McMahon

A general view of 141 in Port Shepstone shed. 1998. © Nigel A.H. Day

The fireman's view forward on 141. 1998. © Nigel A.H.Day

ACR Assistant CME Shaun McMahon (right) discusses the performance of 141 with ACR's senior driver George van Niekerk. On this very hot day (mid 30s °C) Shaun was the locomotive's fireman due to a shortage of operating staff. 1998. © Nigel A.H.Day

NGG16A 155 out and about on the ACR. March 19 1996. © P.F.Bagshawe, Courtesy of Shaun McMahon

Taking water the South African way. Such a system is less than ideal. To reduce the oxygen content of the water it is best to use a submerged hose thus limiting the waters ability to mix with the air. However as 141 & 155 were given what has become known as 'Porta Treatment' the effects of this type of refilling would have been reduced considerably. 1998. © Nigel A.H.Day

141 also included a little bit of Wales.... 1998. © Nigel Day

And the results of this work ?

• 25% reduction in coal consumption;
• 90% availability and utilisation achieved with 141 in conducive conditions, conditions which sadly did not exist on ACR very often! This was also severely effected by the inherent problems in the design;
• Modification costs recouped within 12 months.

Based on the great success achieved with 141 and 155 plans existed to build a new type of Garratt - classified as NGG17 - thus taking advantage of starting with a clean sheet of paper and not being stuck with inherent weaknesses in the NGG16s. Sadly changed circumstances on South Africa saw this project shelved. Both CME Phil Girdlestone and Assistant Mechanical Engineer Shaun McMahon have now moved on to pastures new. ACR as it was in the 1990's is no more, I believe Spoornet are now back in charge as of August 03 2004. So I wonder what the future now holds for this railway ?

A replica numberplate from 155 is now on display at Estación del Fin del Mundo, Ushuaia reflecting Shaun McMahon's involvement with both the NGG16As and FCAF. January 21 2004

141 came out of service in mid 1998 when the boiler ticket expired. Since that date it has been dumped at Port Shepstone. It is reported that the chimney has rusted off.... 155, which continued in service for longer, has now moved to the Sandstone Estates near Ficksburg. See http://www.sandstone-estates.com. This locomotive is currently out of service but it is hoped to return it to service in modified format in the not to distant future.

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