NZR UB class

{{Use New Zealand English|date=July 2024}}

{{Use dmy dates|date=July 2019}}

{{DISPLAYTITLE:NZR U^B class}}

{{Infobox locomotive

| name = NZR U^B class

| powertype = Steam

| image = UB locomotive NZ (cropped).jpg

| alt =

| caption = U^B class in the United States, prior to being delivered to New Zealand. The locomotive was renumbered no. 371 by NZR. A P Godber Collection, Alexander Turnbull Library

| designer =

| builder = Baldwin Locomotive Works (20),

Brooks Locomotive Works (1), Richmond Locomotive Works (1)

| ordernumber =

| serialnumber =

| buildmodel =

| builddate = 1898, 1901

| totalproduction = 22

| rebuilder =

| rebuilddate =

| numberrebuilt =

| whytetype = 4-6-0

| uicclass =

| gauge = {{RailGauge|3ft6in|lk=on}}

| leadingdiameter =

| driverdiameter = {{convert|49.125|in|m|3|abbr=on}}

| trailingdiameter =

| minimumcurve =

| wheelbase =

| length =

| width =

| height =

| axleload =

| weightondrivers = {{convert|26.4|LT|t ST|1|abbr=off}}

| locoweight =

| tenderweight =

| locotenderweight = {{convert|57.8|LT|t ST|1|abbr=off}}

| tendertype =

| fueltype = Coal

| fuelcap =

| watercap =

| tendercap =

| sandcap =

| boiler =

| boilerpressure = {{convert|175|lbf/in2|kPa|0|abbr=on}} (1898)
{{convert|200|psi|kPa|0|abbr=on}} (1901)

| feedwaterheater =

| firearea = {{convert|16|sqft|m2|abbr=on}}

| tubearea =

| fluearea =

| tubesandflues =

| fireboxarea =

| totalsurface = {{convert|1324|sqft|m2|abbr=on}}

| superheatertype =

| superheaterarea =

| cylindercount = Two, outside

| cylindersize = {{convert|16|x|20|in|mm|0|abbr=on}}

| frontcylindersize=

| rearcylindersize =

| hpcylindersize =

| lpcylindersize =

| valvegear =

| valvetype =

| valvetravel =

| valvelap =

| valvelead =

| transmission =

| maxspeed =

| poweroutput =

| tractiveeffort = {{convert|14590|lbf|kN|2|abbr=on}} (1898)
{{convert|16670|lbf|kN|2|abbr=on}} (1901)

| factorofadhesion =

| trainheating =

| locobrakes =

| locobrakeforce =

| trainbrakes =

| safety =

| operator = NZR

| operatorclass =

| powerclass =

| numinclass =

| fleetnumbers =

| officialname =

| nicknames =

| axleloadclass =

| locale =

| deliverydate =

| firstrundate =

| lastrundate =

| retiredate =

| withdrawndate =

| preservedunits =

| restoredate =

| scrapdate =

| currentowner =

| disposition = Withdrawn

| notes =

}}

The NZR U^B class were a series of Ten Wheelers built by American manufacturers for New Zealand Railways (NZR) around the start of the twentieth century. Two batches were built by Baldwin in 1898 and 1901 (ten each).{{sfn|Palmer|Stewart|1965|p=65}} The earlier batch of engines had slide valves and inside Stephenson motion, the later had piston valves and Walschaerts valve gear, as well as a higher boiler pressure.

File:Ub class steam locomotive 328, 4-6-0 type. ATLIB 277681.png