2-8-2+2-8-2

{{Short description|Locomotive wheel arrangement}}

{{Infobox steam wheel arrangement

| name = 2-8-2+2-8-2 (Double Mikado)

| image = WheelArrangement 2-8-2+2-8-2.svg

| alt = Diagram of one small leading wheel, four large driving wheels joined by a coupling rod, two small trailing wheels, four large driving wheels joined by a coupling rod, and one small leading wheel

| caption =

| image2 = Class GE no. 2274.jpg

| alt2 =

| caption2 = SAR Class GE, c. 1966

| hatnote =

| UIC/Germany/Italy= 1D1+1D1, 1'D1'+1'D1'

| French/Spanish = 141+141

| Turkish = 46+46

| Swiss = 4/6+4/6, 8/12 from 1920s

| Russian = 1-4-1+1-4-1

| date = 1924

| country = South Africa

| locomotive = SAR Class GE

| railway = South African Railways

| designer = Beyer, Peacock & Company

| builder = Beyer, Peacock & Company

| evolvedfrom =

| evolvedto =

| mainbenefit =

| maindrawback =

| date2 =

| country2 =

| locomotive2 =

| railway2 =

| designer2 =

| builder2 =

| evolvedfrom2 =

| evolvedto2 =

| mainbenefit2 =

| maindrawback2 =

| date3 =

| country3 =

| locomotive3 =

| railway3 =

| designer3 =

| builder3 =

| evolvedfrom3 =

| evolvedto3 =

| mainbenefit3 =

| maindrawback3 =

}}

Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a {{nowrap|2-8-2+2-8-2}} is an articulated locomotive using a pair of {{nowrap|2-8-2}} power units back to back, with the boiler and cab suspended between them. The 2-8-2 wheel arrangement has a single pair of leading wheels in a leading truck, followed by four coupled pairs of driving wheels and a pair of trailing wheels in a trailing truck. Since the 2-8-2 type was known as Mikado, the corresponding Garratt and Modified Fairlie types were usually known as Double Mikado.

Overview

The 2-8-2+2-8-2 wheel arrangement was used by Garratt and Modified Fairlie locomotives.

=Garratt locomotives=

The Double Mikado was the fourth most common Garratt type, with 144 examples constructed, 114 built by Garratt patent owner Beyer, Peacock & Company and 30 built by others under license. Only 10, six for Chile and four for Peru, were built to {{RailGauge|4ft8.5in|al=on|allk=on}}. Ninety were built to {{Track gauge|Cape|allk=on}} for a number of different African railways. For Spain, sixteen were built to {{Track gauge|1672mm|lk=on}} gauge.

class="wikitable collapsible collapsed sortable" style="margin:0.5em auto; font-size:100%;text-align:center"

|+2-8-2+2-8-2 Garratt production list – All manufacturers {{Garratt Builders B}}{{Garratt Builders O}}

Gauge

!Railway

!Class

!Works no.

!Units

!Year

!Builder

{{sort|1000|{{TrackGauge|1000 mm|disp=1|lk=on}}}}

|C.F. Franco Ethiopien & Libya

|

|1371-1376

|6

|1939

|Ansaldo, Italy

{{sort|1000|{{TrackGauge|1000 mm|disp=1|lk=on}}}}

|War Department, India/Burma

|

|7122-7135

|14

|1944

|Beyer, Peacock & Company

{{sort|1000|{{TrackGauge|1000 mm|disp=1|lk=on}}}}

|Royal State Railways of Thailand

|

|21618-21623

|6

|1929

|Henschel & Son

{{sort|1000|{{TrackGauge|1000 mm|disp=1|lk=on}}}}

|Royal State Railways of Thailand

|

|23109-23110

|2

|1936

|Henschel & Son

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|Sierra Leone Development Corporation

|

|6786

|1

|1937

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|Sierra Leone Development Corporation

|

|6842

|1

|1937

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|South African Railways

|GE

|6193-6198

|6

|1924

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|South African Railways

|GE

|6339-6348

|10

|1927

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|Rhodesia Railways

|

|6562-6569

|8

|1929-30

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|South African Railways

|GE

|6716-6717

|2

|1930

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|Sierra Leone Development Corporation

|

|6726-6727

|2

|1931

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|Rhodesia Railways

|

|6877-6882

|6

|1938

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|Rhodesia Railways

|

|6899-6904

|6

|1937

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|War Department, Congo/Gold Coast/Rhodesia

|

|7057-7074

|18

|1943

|Beyer, Peacock & Company

{{sort|1067|{{TrackGauge|3 ft 6 in|disp=1}}}}

|Rhodesia Railways

|

|7498-7527

|30

|1953

|Beyer, Peacock & Company

{{sort|1435|{{TrackGauge|4ft8.5in|disp=1|lk=on}}}}

|Central of Peru

|

|6731

|1

|1931

|Beyer, Peacock & Company

{{sort|1435|{{TrackGauge|4ft8.5in|disp=1|lk=on}}}}

|Nitrate Railways, Chile

|

|6291-6293

|3

|1926

|Beyer, Peacock & Company

{{sort|1435|{{TrackGauge|4ft8.5in|disp=1|lk=on}}}}

|Nitrate Railways, Chile

|

|6481-6483

|3

|1928

|Beyer, Peacock & Company

{{sort|1435|{{TrackGauge|4ft8.5in|disp=1|lk=on}}}}

|Central of Peru

|

|6626-6628

|3

|1930

|Beyer, Peacock & Company

{{sort|1676|{{TrackGauge|5 ft 6 in|disp=1|lk=on}}}}

|Central of Aragon, Spain

|

|402-407

|6

|1931

|Babcock & Wilcox, Spain

{{sort|1676|{{TrackGauge|5 ft 6 in|disp=1|lk=on}}}}

|Renfe, Spain

|

|730-739

|10

|1960

|Babcock & Wilcox, Spain

=Modified Fairlie locomotives=

The South African Railways (SAR), where the Modified Fairlie concept was conceived as a possible alternative to the Garratt, was the only user. The Modified Fairlie was essentially an adaptation of the Kitson-Meyer concept. It was similar in appearance to a Garratt, but with the boiler, cab, coal and water bunkers all mounted on a single rigid frame which pivoted on the engine units, with the pivot centers located approximately at the centre of the rigid wheelbase of each engine unit. In the Garratt design, by comparison, the coal and water bunkers are mounted directly on the engine units and swivel with them, while the boiler, firebox and cab are mounted on a rigid frame which is suspended between the two engine units.{{Holland-Vol 2|pages=43-45, 52-53}}{{Paxton-Bourne|pages=12, 91, 98}}The Fairlie locomotive

Usage

=South Africa=

Between 1925 and 1931, the SAR placed eighteen {{Track gauge|Cape|allk=on}} Class GE Garratts in service, all built by Beyer, Peacock & Company between 1924 and 1930. The first six entered service in 1925 and proved so successful that a second order for ten was placed in 1926. Another two locomotives entered service in 1931. All of them had Belpaire fireboxes, plate frames, Walschaerts valve gear and were superheated. The locomotive was an enlargement of the Class GD 2-6-2+2-6-2 Double Prairie and was designed as a heavy goods locomotive for use on light {{convert|60|lb/yd|kg/m|0|abbr=off}} rail. They were the first eight-coupled Garratts to be built for the SAR and, on a tractive effort basis at the time of their introduction, they were the most powerful locomotives operating on light track in Africa and the Southern Hemisphere.South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended{{Durrant-Twilight|pages=31-32, 111}}

File:SAR Class HF 1386 (2-8-2+2-8-2).jpg no. 1386, c. 1950]]

In 1927, the SAR placed ten Class HF Modified Fairlie Double Mikados in service, followed by an eleventh one in 1928. The locomotive was designed by the SAR under the direction of Colonel F.R. Collins DSO, SAR Chief Mechanical Engineer from 1922 to 1929, and was built by Henschel & Son in 1926 and 1927, hence the designation of Class HF for "Henschel Fairlie". Designed for mainline work, it was the Modified Fairlie equivalent of the Class GE Garratt which was similar in both size and mechanical respects. It had Walschaerts valve gear, a bar frame and was superheated, with a round-topped firebox.Henschel-Lieferliste (Henschel & Son works list), compiled by Dietmar Stresow

The Class HF proved to be a powerful locomotive, but it was less successful than its Garratt equivalent. The pivot bearings were subject to quite rapid wear since they carried a considerable additional load compared to those on the Garratt, as a result of the water and coal bunkers which were mounted on the main frame instead of on the engine units. This resulted in increased maintenance and, as a consequence, increased operating cost. No more locomotives of the Modified Fairlie design were acquired by the SAR.

References

{{Reflist}}