The Dd Class is a 4-6-0 "Ten Wheeler" type of steam locomotive which ran on the Victorian Railways of Australia from 1902.
History[]
At the turn of the century, the VR's fleet consisted mostly of aging 4-4-0 and 0-6-0 designs, the former were the VR's express passenger locomotives (namely the Old A, New A and Aa Class locomotives). The Dd Class entered service in 1902 as a new express passenger locomotive class.
261 Dd Class locomotives were built across the world from various manufacturers in Australia, the United Kingdom and the United States.
The Dd Class was built with a saturated steam boiler and a Belpaire firebox. When they were first introduced, they has a very British like appearance (then again, so did most locomotives on the VR before then) with a low running plates with splashers above the wheels and a narrow cab. Later on they were rebuilt with higher running plates above the driving wheels and a wider cab of Canadian design, which would become standard features on future VR designs.
They continued their lives on top link passenger duties across Victoria until the the late 00 years where Victoria (like the rest of the world) saw a massive boom in traffic, thus massively increasing workloads, where the Dd found itself incapable of keeping up, thus in 1907 they were replaced by the larger and more powerful A2 Class 4-6-0's. Despite this, their axle loads allowed them to be relegated branchline duties, where they served well as branch line passenger locomotives for the next 50 years.
In 1914, to increase performance on their duties, the Dd's were refitted with superheated boilers as opposed to saturated boilers, which increased their tractive effort (along with all of the A2 Class locomotives, superheated boilers were to become standard on all future VR designs).
In 1922 a renumbering and reclassing of VR locos saw the class being divided into variants, the D1's being the original locos with saturated steam boilers, the D2's being the locomotives being the newer superheated steam boilers.
Withdrawals and scrapings of Dd's commenced as early as 1929 being rendered obsolete by larger and more powerful K Class and N Class 2-8-2 locomotives, with the saturated D1 Class being the first to go with 120 being scrapped by 1951. The remaining D1's being shunters, the D2's being suburban goods and branchline mixed traffic engines and the D3's being on branchline and mainline services. Until 1954 came the time for the Dd variants to be superseded by the J Class 2-8-0 and T Class Bo-Bo diesel locomotives on even brancline duties.
D3 Class[]
In 1922, the K Class 2-8-0's were introduced to handle branch line goods duties and had superior performance to any Dd variant, which led to several Dd's being refitted with new boilers based on that of the K Class engines in 1929, which was so successful that 94 Dd's were converted to D3's between 1929 and 1947.
Said upgrades increasing speed and power considerably, allowing for faster timetables as well as being more efficient than their original selves.
Dde tank engine[]
The Dd design was so successful than the design was adapted into a tank engine design known as the Dde Class 4-6-2T in 1908. This variant of the Dd was built due to increased traffic on Melbourne's suburban network and delays on electrification with the need for more powerful locomotives to replace the 19th century suburban passenger tank engines.
After electrification in 1919, the Dde's became redundant and two were converted to Dd tender engines.
In the 1920's, many Dde's were scrapped or relegated to shunters at suburban stations.
In 1929 the Dde's were re classed into the D4 Class after the reclassing of the Dd variants and were refitted with superheated boilers.
Preservation[]
A total of 17 locomotives have been preserved, with one of them operational.
- D2 604 (originally DD 557) is the only preserved original DD class (specifically a superheated variant), having being reclassified as a D1 and later a D2, but didn't receive a D3 rebuild and remained in its original form. It was withdrawn from VR service in 1956 and was sold to Australian Paper Manufacturers Ltd to replace a D1 locomotive they bought in the 1940s. It was finally reitred in 1960 and was allocated to the Newport Railway Museum where it now resides.
- D3 639 (formerly D3 658) was used on commissioner trains until it was replaced in this role by a Y class (EMD G6B) diesel electric locomotive. However, the locomotive had since October 1964 taken on a new role providing motive power for the ARHS 'Vintage Train' as the first 'Special Trains Vintage Engine', and continued in this popular role until deteriorated boiler condition saw it finally withdrawn from service in 1974. D3 639 was restored to operating condition in 1984 and was recommissioned into service by Prime Minister Bob Hawke on 17 November 1984. Since this date, it has continued in service hauling various rail enthusiast special trains under the owner of Steamrail.
- D3 635 is on display at the Newport Railway museum as the only preserved Baldwin example, with the remaining D3 classes being displays across Victoria.
- D4 268 (originally DDE 790) was the last D4 locomotive in service and was withdrawn in 1960, and allocated for preservation. It's now at the Newport Railway Museum as the only preserved D4.
Specifications[]
D1/D2[]
Weigh 96.3 tonnes with an axle load of 13.2 tonnes. The engine having two cylinders with an 18 inch bore by a 26 inch stroke (457 x 660 mm). The locomotive has a boiler pressure of 175 psi and has a tractive effort of 20,530 lbf. The firebox possesses a grate area of 21.2 square feet (1.97 m^2) Their driving wheels are 61 inches (1.55 meters) in diameter.
Their tenders are capable of holding 5.1 tonnes and 4220 gallons (19,200 litres) of water.
D3[]
Weigh 101.2 tonnes with an axle load of 13.9 tonnes. The bore of the engine's cylinders being increased by an inch compared to the original D1/D2 classes (19 inches or 483 mm) and the boiler pressure decreased by 5 psi (170 psi) with tractive effort increased to 22,600 lbf. The firebox possesses a grate area of 25 square feet (2.3 m^2).
D4[]
An axle load of 14.7 tonnes.
Their bunkers are capable of holding 2.8 tonnes of coal and their tanks capable of holding 1700 gallons (7700 litres) of water.
Trivia[]
- The Dd were the predecessor for all modern VR designs
- The Dd Class is notable for being the last class of locomotives built by Phoenix Foundry in Ballarat
Gallery[]
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