Garratt

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For people named Garratt, see Garratt (surname)

A Garratt is a type of steam locomotive that is articulated in three parts. Its boiler is mounted on the centre frame, and two steam engines are mounted on separate frames, one on each end of the boiler. Because a Garratt locomotive has the wheel arrangement of two locomotives back to back, it is typically named "Double x," where x is a named arrangement. The 4-6-2 arrangement is called a Pacific, so a 4-6-2 + 2-6-4 Garratt is called a Double Pacific^{[citation needed]}.

Articulation permits larger locomotives to negotiate curves which might otherwise restrict large rigid framed locomotives. Many articulated designs aim to double the power of the largest conventional locomotives operating on their railways, thus eliminating the need for two locomotives and multiple crews.

The Garratt's main competition was the Mallet, however no railway that possessed Mallets and purchased Garratts ever purchased another Mallet ^[1].

Contents 1 Locomotive manufacture 1.1 The first Garratts 1.2 Darjeeling Himalayan Railway 1.3 First mainline class 1.4 Beyer-Garratt 1.5 Final Garratts constructed 2 Garratts around the world 2.1 The Australian Standard Garratt 3 Advantages of the Garratt concept 4 Disadvantages of the Garratt concept 5 Class-Specific Issues 6 Preservation 7 References 8 Web Sites

[edit] Locomotive manufacture

The Garratt articulated locomotive was developed by Herbert William Garratt, a British locomotive engineer who after a career with British colonial railways was for some time the New South Wales Railways' Inspecting Engineer based in London. He first applied for a patent on the idea in 1907, after observing articulated gun carriages^{[citation needed]}.

Garratt first approached Kitson & Co., but his idea was rejected, perhaps because that company were already committed to the Kitson-Meyer^{[citation needed]}. He then approached Beyer-Peacock, who were only marginally more interested^{[citation needed]}.

In 1907 Beyer-Peacock submitted a proposal for a 2' gauge 0-4-0+0-4-0 Garratt to the New South Wales Government Railway, which was not proceeded with. The following year a design for 2' gauge mallet was submitted in reply to an enquiry from the Tasmanian Government. This was followed with a submission for a Garratt based on, but a little heavier than, the New South Wales proposal. This proposal was accepted; two locomotives were built in 1909, and became the K class^[2].

[edit] The first Garratts

Contrary to Garratt's patent, the Tasmanian Railways insisted on a compound arrangement with cylinders facing inwards, in order to reduce the distance between both the main steam pipe and the high-pressure cylinders and the distance between the high-pressure and low-pressure cylinders^{[citation needed]}. Not only did this make the locomotive unnecessarily complicated, it also placed the high-pressure cylinders directly underneath the cabin, making the cabin uncomfortably hot, especially in summer^{[citation needed]}. The pattern was not repeated on succeeding Garratt designs. Only one more Garratt locomotive, again built by Beyer-Peacock, was produced with compound propulsion^{[citation needed]}.

Early design and construction difficulties involved the steam-tight flexible connections between the boiler unit and the power units. These were solved by Beyer-Peacock's designers after studying a description of the spherical steam joints used on a Fairlie locomotive built for the Ffestiniog Railway followed by a visit to the FR to observe these locomotives at work. ^[3]

[edit] Darjeeling Himalayan Railway

The third Garratt built was, like the first two, an 0-4-0 + 0-4-0 built in 1910 for the Darjeeling Himalayan Railway which became the DHR class "D". As with many early Garratt classes, this engine's dimensions and power were designed to be roughly equivalent to those of two of the line's existing 0-4-0T engines, although in practice it only achieved a 65% increase in loading^[4]. The "D" class was true to Garratt's patent, without compounding of the cylinders, and with the cylinders facing outwards. It also incorporated Beyer-Peacock's first improvement to the design, namely placing the engine unit pivot above the rear axle, rather than between the two axles, as Garratt specified^{[citation needed]}. This allowed the engine units of future Garratts to improve, and the design evolved into larger and more powerful locomotives. Although technically successful, the locomotive was was withdrawn in 1954^[5].

[edit] First mainline class

In 1911 Beyer-Peacock built six 2-6-0 + 0-6-2 Garratts for the West Australian railways. The locos designated M class,were followed by the Ms and later the Msa class. These were the first Garratts built for main line use, the first built in large numbers, and the first design to be repeated and developed^{[citation needed]}. They also formed the pattern locos for the Victorian Railways G class, and the Garratts supplied to Australian Portland Cement ^[1].

[edit] Beyer-Garratt

Garratt licenced the British firm of Beyer-Peacock to build locomotives to his patent design^{[citation needed]}. As well as producing locomotives, Beyer-Peacock developed and marketed the design, licensing it to other builders. After the original Garratt patents expired in 1928, Beyer-Peacock continued to market Garratts under its own brand, Beyer-Garratt^{[citation needed]}. With continuing development and patent improvements, Beyer-Peacock maintained its leadership with the Garratt, and just under two-thirds of all Garratt locomotives (1023 of 1651) were built at Beyer-Peacock's Gorton Foundry^{[citation needed]}. The remainder were constructed by a number of licensees, as well as a small number by non-licensed builders. Garratts were built in Britain, France, Spain, Germany, Italy, Belgium, South Africa, Brazil, and Australia^{[citation needed]}.

[edit] Final Garratts constructed

The final Garratts were built in 1967-8. They were a group of 8 South African Railways NGG16 class, built for the 2 ft (610 mm) gauge. The order was placed with Beyer-Peacock, but as Beyer-Peacock was closing down, it subcontracted the order to the Hunslet Engine Company. Hunslet constructed most of these locomotives in South Africa through their South African subsidiary.^[1].

[edit] Garratts around the world

Garratt locomotives were exported to the world. Garratts were employed in Great Britain, Russia and Spain, where some five railway companies employed seven classes of Garratt locomotives. These included Spain's 1931 order for Central of Aragon Railway, employing six Double Pacific Garratts for fast passenger service. In Brazil, post-1927, the San Paulo Railway operated broad gauge 4-6-2 + 2-6-4 Garratts which ran passenger trains at 70 m.p.h.(The Great Book of Trains, pp. 144-145) In Algiers, a series of 30 French built 4-6-2 + 2-6-4 Garratts using Cossart motion gear operated until the civil war caused their withdrawal in 1951. These engines were streamlined fast runners and performed well in mountainous regions.(Ibid.)

The Rio Tinto Railway which possessed two Beyer-Garratts, used for hauling mineral trains of up to 2,000 tonnes downhill and 550 tonnes of empties uphill^{[citation needed]}.

The Garratt was most widely used in Africa^{[citation needed]}. The most powerful of all Garratts irrespective of gauge were the South African Railways' eight GL class locomotives of 1929-30, which delivered 78,650 lbs of tractive effort.(Last Stronghold of Steam, pp. 48-49) However, one claim suggests the largest and most powerful was the East African Railways, 59 Class garratt, 4-8-2 + 2-8-4s, which delived a tractive effort of 83,350 lbs.(Great Book of Trains, pp. 194-195) These 34 East African garratts had a large 70 sq ft grate and a reputation as the largest and most powerful of any steam locomotive in the world.(Ibid)

Garratts were also used in Asia, Australia and South America. No Garratts were ever introduced into service on North American railroads, the most common explanation being that American rail companies considered the Garratt's coal and water capacities unequal to their requirements ^[1].

British usage of Garratts was minimal. In the UK a single large Garratt (2-8-0+0-8-2, number 2395/69999 London and North Eastern Raiway Class 01) was built in 1925 for banking heavy coal trains on the Woodhead route^{[citation needed]}. A class of 33 2-6-0+0-6-2 locomotives were built for the London, Midland and Scottish Railway and several 0-4-0+0-4-0s were built for industrial use, one of which is preserved^{[citation needed]}. However, the Garratt design was ignored on British railways, as most goods trains were short and light, and operated on railways with broad curves and moderate grades compared with elsewhere in the world^{[citation needed]}.

The New South Wales Government Railways introduced the 4-8-4 + 4-8-4 AD60 Garratt in 1952, built by Beyer Peacock. The AD60 weighed 265 tonnes, with a 16 tonne axle loading. As delivered, the AD60 developed a tractive effort of 60,000lbs or 265 kN; though not as powerful as the South African Railways GMA/M 4-8-2 + 2-8-4 garratts of 1954, which developed a tractive effort of 60,700lbs or 270Kn).(Last Stronghold, pp. 50-51) Following modifications in 1958 to thirty AD60s, their tractive effort was increased to 63,016lbs.(Oberg, p. 200) In his book, Australian Locomotives (1975), author Leon Oberg cited that he witnessed, a 1220-tonne, double-headed, diesel freight failed on a 1 in 55 grade. An AD60 cleared the dead train from the section, pulling the entire load (now 1450 tonnes) up the grade without any wheel slip (Oberg, p.191)

Beyer Peacock constructed the largest steam locomotive built in Europe, a 4-8-2+2-8-4 for Soviet Russia built as works order number 1176 in 1932. The locomotive gained the Russian Classification Ya.01 (Я.01). This massive machine was built to the Russian standard of 5 foot gauge and a loading gauge height of 17 feet. The locomotive underwent extensive testing and proved to be very able to operate in the extremely low temperatures due to specific measures to ensure adequate protection of the external plumbing between boiler and engine units. This may have been the lowest temperature operation of a Garratt type. The locomotive was used for a number of years for coal traffic in the Donbass region, but was never replicated. This decision appears to be a combination of unfamiliar maintenance processes and politics. (Locomotives, A.M.Bell) (Russian Steam Locomotives, LeFleming/Price)(Locomotives of Russia 1845 - 1955, V.A.Rakov). The Russians later went on to experiment with Mallet locomotives, the P34 2-6-6-2 and the P38 2-8-8-4^{[citation needed]}.

[edit] The Australian Standard Garratt

The narrow gauge (3 ft 6 in (1067 mm)) Australian Standard Garratt (ASG) of 1943, a 4-8-2+2-8-4 locomotive was designed and constructed in Australia during the crisis days of World War Two immediately following the bombing of Darwin in 1942. A more detailed comment is in the Australian Standard Garratt

[edit] Advantages of the Garratt concept

The principal benefit of the Garratt design is that the boiler and firebox unit are slung between the two engine units. This frees the boiler and firebox from the size constraints imposed where they are placed over the frames and running gear, as in conventional designs and other articulateds such as Mallets. Garratts can have a boiler with a greater diameter, which increases heating area and aids the production of steam. The boiler can also be shorter than other designs with the same heating area. In some loco designs, the boiler is so long almost no heating of the water occurs at the smokebox end of the boiler. A larger firebox promotes more efficient combustion of fuel and also increases the heat available to the boiler^{[citation needed]}.

Garratts enjoy an advantage over the Mallet system, because of the geometry of the design; Hollingworth and Cooke suggested that when swinging around curves the boiler and cab unit move inward 'like a bowstring in the bow of a curve' and this reduces the centrifugal force that would overturn a normal locomotive and which inturn permits fast running. In the Mallet's design, the forward articulated unit tends to throw out as the loco rounds curves. (The Great Book of Trains, pp.144-145). While most Garratts were designed for freight or mixed traffic, there were a number of passenger Garratt classes. A Garratt holds the world speed record for an articulated locomotive^{[citation needed]}.

Garratts have several advantages when used on light and narrow gauge railways. They are tank locomotives, thus eliminating the need for expensive turntables or wyes. They don’t need to be run through to terminals increasing operational flexibility. Because the engine units are separated by the boiler unit, the weight of the locomotive is split over the two units. Therefore they can run over bridges that might not be able to support conventional or Mallet locomotives of similar weight^{[citation needed]}.

According to Hollingsworth & Cook, whilst most conventional locomotives have reached their maximum in 'critical dimensions', the garratt's potential has 'still some way to go', with larger [driving] wheels, larger boilers and greater power output still achievable. p.145)

[edit] Disadvantages of the Garratt concept

The major disadvantage of a Garratt (shared with all tank engines) is that the tractive weight reduces as the water is used from the front tank and coal from the rear bunker. As the weight on the wheels reduces slipping occurs. To reduce wheel slippage, a wagon containing water was attached behind the garratt, and this practice also permitted the engine to operate over longer distances^{[citation needed]}. The weight of the water in the locomotive's tank and weight of coal in the bunker (necessary for the factor of adhesion) was predicted in advance, and this problem was not normally an operational issue^{[citation needed]}.

Another disadvantage, when compared with two separate locomotives, is that both power units are controlled by one regulator, thus if one power unit slipped the steam to both was reduced as the driver tried to control the slip^{[citation needed]}.

The Garratt had an identified safety problem in Western Australia when operating through a narrow-profile single-track tunnel. Should a Garratt stall in a narrow tunnel the crew could be trapped, since there was no route forward or backwards past the hot cylinders. A normal engine has hot cylinders at one end, and there is always an escape route at the other end. Two crew members died in Western Australia in the 1940s when an Australian Standard Garratt stalled in the state's only tunnel, the Swan View Tunnel.

[edit] Class-Specific Issues

Garratt locomotives sometimes exceeded the operational capacities of the railways on which they operated.

In New Zealand the Beyer-Garratt built 4-6-2+2-6-4 NZR G class locomotives were too powerful for the drawgear then used in New Zealand, and short crossing sidings made it impractical to haul the largest loads the locomotives were capable of^{[citation needed]}.

The smooth operation at speed of the early Tasmanian M class 4-4-2+2-4-4 locomotives resulted in drivers exceeding speed limits, and subsequent unacceptable levels of derailment. This led to these locomotives' early withdrawal^{[citation needed]}.

[edit] Preservation

Around 250 Garratts exist today. While many are stored or dumped in various stages of disrepair, more than 100 are preserved in museum collections or on heritage railway operations. Operating Garratt locomotives can be found in Europe, Africa, India and Australia. ^[6]

A single Hanomag-built narrow gauge example in Texas, United States was auctioned in 2000^{[citation needed]}.

The first Garratt locomotive, the K class of the North-East Dundas Tramway has been preserved. After the line closed in 1929 the locomotives were put up for sale. K1 was purchased by Beyer-Peacock in 1947 for their museum. Subsequent investigation has found the preserved loco has parts from both original engines. including the boiler from K2. When Beyer-Peacock ceased trading, the locomotive was sold to the Ffestiniog Railway, who initially proposed to cut it down to meet their loading gauge. For a number of years it was on loan to the National Railway Museum and exhibited in York. In 1995 it was removed from York to commence restoration in Birmingham. It was returned to Wales in 2000 where restoration was continued at the Ffestiniog Railway workshops at Boston Lodge. It was fitted with a new boiler and restored to full running order on the Welsh Highland Railway in September 2006. The Welsh Highland Railway owns several former South African NGG16 class Garrats, and so now operates both the first and last Garratts construced by Beyer-Peacock^[7].

Several Australian Garratts have been restored to operating condition. G 42, formerly used on the Victorian Railways narrow gauge lines, now works regularly on the Puffing Billy Railway in the Dandenong Ranges outside Melbourne^{[citation needed]}. The Queensland Railways removed its sole remaining 3' 6" (1066mm) gauge 4-8-2+2-8-4 Garratt from an open air museum and fully restored the locomotive (No. 1009) to working order. During 2006 the engine received a major overhaul prior to resumption of service^{[citation needed]}.

In South Africa, a restored mainline 3' 6" (1066mm) gauge GMAM class Garratt, No.4079, operates as a tourist attraction and was used in 2006 on a special Rovos Rail tour. At Pietermaritzburg in KwaZulu-Natal a 2' (610mm) narrow gauge Garratt is operational on a short tourist line^{[citation needed]}.

[edit] References

1. ^ ^{a b c d} Durrant, A.E. (1981). Garratt Locomotives of the World. David & Charles. ISBN 0-7153-7641-1. 
2. ^ Belbin, B., Browning, J, & McKillop, B. K1 Steams Again in Light Rails No. 193, Feb 2007, p.4
3. ^ Rolt L.T.C., A Hunslet Hundred David & Charles, Dawlish, 1964, (page 66) quoted by Tom Rolt from Edgar Alcock regarding his time at Beyer Peacock's.
4. ^ Hughes, Hugh, 1994. Indian Locomotives Part 3 Narrow Gauge 1865-1940. Continental Railway Circle, Kenton. ISBN 0952165503. p.37.
5. ^ Hughes, Hugh, 1994. Indian Locomotives Part 3 Narrow Gauge 1865-1940. Continental Railway Circle, Kenton. ISBN 0952165503. p.37.
6. ^ Hamilton, G. Surviving Garratt Locomotives accessed 5th March 2007
7. ^ Belbin, B., Browning, J, & McKillop, B. K1 Steams Again in Light Rails No. 193, Feb 2007, pp.6-7

• Butlin, S.J. Australia in the War of 1939-1945: Vol 111, War Ecomony 1939-1942. Australian War Memorial, Canberra, 1961.
• Hollingsworth, Brian. & Cook, Arthur. The Great Book of Trains, 1987, Lifetime Distributors, ISBN 0-86101-919-9
• South African Government, South Africa - Last Stronghold of Steam, Johannesburg, 1978. ISBN 0-949934-24-0

[edit] Web Sites

• A Complete List of All Garratt Locomotives, Gavin Hamilton
• K1 The World's First Garratt, Ben Fisher
• Karamoja,a Kenya-Uganda Garratt Locomotive, garrattmaker
• K1 class Garratt,
• Herbert William Garratt.
• Illustrations of Garratts.