NZR UD class

{{Short description|Class of 2 New Zealand 4-6-0 locomotives}} {{Use New Zealand English|date=July 2024}} {{Use dmy dates|date=April 2022}} {{DISPLAYTITLE:NZR U{{sup|D}} class}} {{Infobox locomotive | name = NZR UD class | powertype = Steam | image = Ud Class steam locomotive, New Zealand Railways no 464, 4-6-0 type ATLIB 257728.png | caption = Ud Class no 464 between 1909 and 1929 | builder = [[Baldwin Locomotive Works]] | serialnumber = | buildmodel = | builddate = 1904 | totalproduction = 2 | whytetype = [[4-6-0]] | uicclass = | gauge = {{track gauge|3ft6in}} | trucks = | leadingdiameter = | driverdiameter = {{convert|58|in|0|abbr=on}} | wheelbase = | length = | weightondrivers = {{convert|29.2|LT|t ST|abbr=on}}{{sfn|Cassells|1994|p=169}} | locoweight = {{convert|39.5|LT|t ST|abbr=on}} | tenderweight = {{convert|27.4|LT|t ST|abbr=on}} | locotenderweight = | fueltype = [[Coal]] | fuelcap = | watercap = {{convert|2400|impgal|abbr=on}} | tendercap = {{convert|5|LT|t ST|abbr=on}} | enginetype = | displacement = | cylindercount = 2 | cylindersize = {{convert|16.5|x|22|in|0|abbr=on}} | valvegear = [[Stephenson valve gear|Stephenson]] | maxspeed = | poweroutput = | firearea = {{convert|16.5|sqft|abbr=on}} | boilerpressure = {{convert|185|psi|kPa|0|abbr=on}} | totalsurface = {{convert|1095|sqft|m2|abbr=on}} | tractiveeffort = {{convert|15280|lbf|kN|abbr=on}} | factorofadhesion = | locobrakes = | trainbrakes = | safety = | operatorclass = | officialname = | firstrundate = | lastrundate = | retiredate = 1929 | nicknames = | numinclass = 2 | locale = | disposition = }}

The '''NZR U{{sup|D}} class''' was a class of two [[4-6-0]] [[steam locomotive]]s built by the [[Baldwin Locomotive Works]] in 1904 for the [[Wellington and Manawatu Railway Company]]. When that company was nationalised in 1908, they passed into the ownership of the [[New Zealand Railways Department|New Zealand Railways]] and received the designation U{{sup|D}}.{{sfn|Palmer|Stewart|1965|p=98}}

== Introduction == The two locomotives were the final new [[locomotive|motive power]] ordered by the independent Wellington and Manawatu Railway Company.{{sfn|Palmer|Stewart|1965|p=98}}

==Specification== Weighing {{convert|39.5|LT|t ST}} with a [[Tender (rail)|tender]] of {{convert|27.4|LT|t ST}}, they could haul express trains easily at {{convert|50|mph|0}} on track that was flat or only a light grade. The {{convert|58|in|0}} coupled driving wheels were large for the period, {{sfn|Palmer|Stewart|1965|p=98}} and were the largest to run in New Zealand.{{sfn|Cassells|1994|p=108}}{{sfn|Hoy|1972|p=70}} Their working steam pressure was {{convert|185|psi|0}}, and they had {{convert|16.5|in|0}} [[diameter]] cylinders with {{convert|22|in|0}} [[Stroke (engine)|piston strokes]].

The handsome UD locomotives were more than capable of making up lost time, with mile-a-minute runs recalled with pride by Manawatu railway employees.{{sfn|Palmer|Stewart|1965|p=98}} Due to their power, the locomotives were capable of hauling mail trains without the need for a banking locomotive from Paekakariki south to Pukerua Bay,{{sfn|Cassells|1994|p=122}} and were used principally on mail trains north of Paekakariki.{{sfn|Cassells|1994|p=108}}

==Withdrawal== Although they were fast and powerful, the UD locomotives were unable to survive a programme of standardisation undertaken between 1925 and 1935 to eliminate small locomotive classes that were costly to maintain in favour of large, homogeneous types that provided economies of scale. They were written off in 1929.

== References == ===Citations=== {{reflist}}

===Bibliography=== {{refbegin}} * {{cite book|title=Uncommon Carrier - The History of the Wellington & Manawatu Railway Company, 1882-1908|last1=Cassells|first1=KR (Ken) |year=1994|publisher=[[New Zealand Railway and Locomotive Society]]|ISBN=0908573634}} *{{cite book | last = Hoy | first = Douglas | title = West of the Tararuas: An Illustrated History of the Wellington and Manawatu Railway Co | publisher = Southern Press | date = 1972 | location = Dunedin }} * {{NZR Steam Locomotive}} * {{Palmer & Stewart}} * {{When Steam Was King}} {{refend}}

==External links== *[https://kura.aucklandlibraries.govt.nz/digital/collection/photos/id/195531 Photo of 1910 derailment] at [[Koputaroa railway station|Koputaroa]]

{{DEFAULTSORT:Nzr Ud Class}} [[Category:Steam locomotives of New Zealand|UD class]] [[Category:3 ft 6 in gauge locomotives of New Zealand]] [[Category:4-6-0 locomotives]] [[Category:2′C n2 locomotives]] [[Category:Baldwin locomotives]] [[Category:Scrapped locomotives]] [[Category:Railway locomotives introduced in 1904]]