Garratt locomotive
[2] A large firebox and its unrestricted air supply also allowed the Garratt to operate with poor-quality fuel without reducing steaming capacity.
A French-built Algerian Railways Garratt holds the world speed record for an articulated locomotive at 132 kilometres per hour (82 mph).
Nock wrote,[6] the Garratt type holds several advantages over the Mallet type:This [the Mallet] was so designed to provide a very large engine unit, to be managed by a single crew, but to spread the dead weight over many axles and thus avoid excessive loads on the track and under-line bridges, and at the same time retain flexibility of wheelbase to facilitate operation on severely curved sections of line.
The Mallet, having driving-wheel units beneath the boiler, retains the limitation in dimensions inherent in the orthodox type of steam locomotive, while the immense length of some of these machines is itself a handicap.
It could be kept short, and of large diameter, which is the best possible form for securing a high rate of evaporation.Although at the end of the steam locomotive era, most conventional steam locomotives had reached their maximum in "critical dimensions", the Garratt still had potential for further development, with larger driving wheels, larger boilers, and greater output still achievable.
Of these, the closest was the Union Garratt, a type originally prompted by the perceived necessity for a rigid connection between a bunker or tender and a firebox fed by a mechanical stoker.
[9][page needed] In 1907, Beyer, Peacock and Company submitted a proposal for a 2 ft (610 mm) gauge 0-4-0+0-4-0 Garratt to the New South Wales Government Railways, which was not proceeded with.
[13] The latter feature made the locomotive unnecessarily complicated and placed the high-pressure cylinders directly underneath the cab, making it uncomfortably hot for the crew on the rare days when Tasmania's West Coast Range was warm.
[18][note 4] The final built to a Beyer-Peacock design, in 1967–1968, were eight 2 ft (610 mm) gauge South African Railways Class NG G16 locomotives.
[9][page needed] The Garratt was most widely used in Africa:[9][page needed] large numbers were in South Africa, Rhodesia (now Zimbabwe) and Algeria, and smaller numbers in Angola, Congo, Ghana, Ivory Coast, Kenya, Libya, Madagascar, Mozambique, Nigeria, Senegal, Sierra Leone, Sudan, Uganda and Zaïre.
The East African Railways 4-8-2+2-8-4 59 class Garratts were the largest and most powerful steam locomotives to run on metre gauge, having a large 70-square-foot (6.5-square-metre) grate and a tractive effort of 83,350 pounds-force (370.76 kilonewtons).
[20] The Royal State Railway of Siam acquired 8 Garratts built by the German company Henschel during 1929–1937 for heavy freight duties in the Pak Chong highland areas.
[34] The Australian Standard Garratt (ASG) was designed in Australia as an emergency measure during World War II, when demand on 1067 mm (3 ft 6 in) narrow-gauge railways could not be met by the available stock of locomotives.
A royal commission convened in 1946 to investigate the locomotives, whose deficiencies had caused enginemen to go on strike, concluded: "It is obvious when one analyses the evidence that the new Australian Standard Garratt has put up a poor performance.
[45] Oberg wrote he witnessed an AD60 clear a dead 1220-tonne double-headed diesel freight (total weight 1450 tonnes) from a 1 in 55 grade without wheel slip.
The locomotives were ordered in 1951 from Beyer, Peacock & Company, when there was a need for more and bigger motive power to haul the heavy ore trains on the 1,067 mm (3 ft 6 in) narrow-gauge line between Broken Hill and Port Pirie.
The company subsequently subcontracted the order, with main specifications identical to those of the notable 60th class of the East African Railways, to Société Franco-Belge, its European associate based in Raismes.
[50] Their eight cylinders proved a nightmare to maintain, and after several fatal and disastrous derailments in the late 1920s, mainly due to inadequate trackwork, they were withdrawn and scrapped.
[citation needed] Beyer, Peacock built three 4-6-2+2-6-4 NZR G class locomotives in 1928, which were too powerful for the system and had complicated valve mechanisms.
Spain had a varied collection of Garratts from most builders; Beyer, Peacock themselves only building a pair of 3 ft 6 in (1,067 mm) 2-6-2+2-6-2s for Rio Tinto in 1929.
Also on the metre gauge, the Ferrocarril de la Robla bought two pairs of 2-6-2+2-6-2s, the first from Hanomag of Germany in 1929, the second from Babcock & Wilcox of Bilbao in 1931.
It underwent extensive testing and proved to be very able to operate in extremely low temperatures, due to adequate protection of the external plumbing between boiler and engine units.
This reluctance was reportedly based on a concern that tractive effort and factor of adhesion would suffer as the weight of water and fuel over the driving wheels diminished.
[citation needed] The British-owned 5 ft 6 in (1,676 mm) gauge Buenos Aires Great Southern Railway operated twelve Garratt 4-8-2+2-8-4 oil-fired locomotives, numbers 4851–4862, built by Beyer, Peacock in 1929.
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.
Finally, in 2019 it was decided to move the locomotive to the Statfold Barn Railway in Central England on a ten year loan with two boiler overhauls in the agreement.
Both locomotives are managed by ARMF, a non-profit organisation which also holds the only main line repair workshop for historical railway vehicles on broad gauge network.
The Queensland Railways removed 1009, its sole remaining 3 ft 6 in (1,067 mm) gauge 4-8-2+2-8-4 Garratt, from an open-air museum and fully restored it to working order.
In December 2007, Zimbabwe class 14A Garratt number 509, overhauled in Bulawayo was offloaded in New Zealand for operational preservation by the Mainline Steam trust.
[citation needed] In September 2018, South Eastern Zone of Indian Railways made a successful trial run of a Beyer-Garratt numbered 811 from Kharagpur.
