Garratt (locomotive)
The Garratt design is a special design of steam locomotives with two separate engine units that are connected by a bridge frame that supports the steam boiler and driver's cab .
The name Garratt goes back to the engineer Herbert William Garratt , who developed this type of locomotive together with Beyer, Peacock & Co. in Manchester . The first Garratt, the TGR K class of the Tasmanian Government Railways , was 1909 for the North-East Dundas Tramway in Tasmania delivered. 1704 Garrrat locomotives were built worldwide, 1124 of them for Africa alone .
technical features
The Garratt steam locomotive was developed with the requirement to provide enough tractive power for heavy trains on routes with a light superstructure and tight curves, as is typically the case with narrow-gauge railways . For this purpose, Garratts were built with two separate chassis , each with its own steam engine . The front landing gear was mounted under a frame in front with a water tank, the rear undercarriage under the rear tender with another water tank and the fuel tank. The boiler, including the driver's cab , was supported on a bridge-like frame with its ends on pivot pins on the two undercarriages. Because of this construction method and because of the deep boiler position that it promotes, the boiler and fire box can be designed completely freely and without hindrance from drive wheels and frame components, with regard to thermal and maintenance properties:
- Large diameter, numerous and narrow heating pipes in the superheater
- Deep fire box with freely accessible ash box
- Straight boiler walls on all sides , thus advantages in production and maintenance
- Low meter load due to the bridge frame
The Mallet and Meyer types have a comparatively disadvantage in terms of these features. The problem with Garratt machines is access to the smoke chamber and the boiler tubes because of the water box on the front drive, so either the water box is provided with a niche for swiveling out the smoke chamber door or there is a sufficiently large distance between the boiler and the front water tank. The line view of the staff is also restricted due to the construction.
Due to the particularly favorable and thermally effective boiler construction of the Garratt design, which is also possible in particular with narrow clearance profiles , as well as the favorable distribution of the vehicle's mass over many axles and a great length, and last but not least the excellent running properties compared to other joint constructions, the Construction of extremely powerful machines with low axle loads possible. They particularly proved themselves on the routes in the former African colonies that were built with little effort . Disadvantages are the necessary movable steam lines and the frictional load that fluctuates during operation, which does not occur in this form in standard design locomotives with tender.
The success of the Garratts led Beyer-Peacock to plan Super Garratts with a pair of mallet engines under each tender. The patent was granted, but the machines never got beyond the planning phase.
Areas of application
Garratt locomotives were particularly common in Africa, Asia , Australia, and Brazil .
In Europe , there was only a large number of different Garratt designs in use in Spain . After all, 33 Garratt locomotives were used from 1930 by the London, Midland and Scottish Railway (LMS) under the designation LMS Beyer Garratt in heavy freight traffic. Together with a single example that Sir Nigel Gresley had built for the London and North Eastern Railway (LNER) in 1925, the locomotives were used by British Railways until the mid-1950s.
The main producer was Beyer, Peacock & Co., which explains the frequently used name Beyer-Garratt. They were also built by other manufacturers under license or after the patent expired. a. at Henschel & Sohn in Kassel , Cockerill-Sambre in Liège , Euskalduna and Babcock & Wilcox in Spain.
Today Garratts are mainly used on museum railways . In Europe, the Welsh Highland Railway in particular is known for its stock of three to four Garratts taken over from South Africa and Tasmania, and in Switzerland the Schinznacher Baumschulbahn , whose Garratt locomotive was available as an LGB model. The state railways of Zimbabwe are still using a few examples commercially in shunting operations . The Ferrocarril Austral Fueguino on Tierra del Fuego has two 500 mm narrow-gauge Garratts of the FCAF class KM, newly built in 1994 and 2006, in operation.
literature
- Anthony E. Durrant: Garratt Locomotives of the World . Birkhäuser Verlag ISBN 3-7643-1481-8
Web links
- A Complete list of Garratt Locomotives (English)
Individual evidence
- ^ A b Thomas Franke: Garratts in Zimbabwe. Resurrection . In: Lok Magazin . No. 7 , 2014, p. 55 .
- ↑ LNER Encyclopedia: The U1 Garratt ('The Wath Banker') , accessed June 5, 2019