LNWR Webb Experiment Class

{{Use dmy dates|date=April 2017}}

{{Use British English|date=April 2017}}

{{Refimprove|date=May 2014}}

{{Infobox locomotive

|name = LNWR Experiment Class (Webb)

|image = LNWR engine No.301 Economist.jpg

|caption = No.301 Economist

|powertype = Steam

|designer = F. W. Webb

|builder = Crewe Works

|serialnumber = 2500, 2625–2628, 2669–2673, 2734–2753

|builddate = 1882–84

|totalproduction = 30

|whytetype = 2-(2-2)-0

|uicclass = 1AA n3v

|gauge = {{RailGauge|ussg}}

|leadingdiameter = {{convert|3|ft|6|in|m|3|abbr=on}}

|driverdiameter = {{convert|6|ft|6|in|m|3|abbr=on}}

|wheelbase =

|length =

|locoweight = {{convert|38|LT}}

|fueltype = Coal

|fuelcap =

|watercap =

|boiler =

|boilerpressure =

|firearea =

|totalsurface = {{convert|1083.5|sqft|m2|abbr=on}}

|cylindercount = Three: two high pressure outside, driving rear wheels; one low pressure inside, driving front drivers

|hpcylindersize = {{convert|13|x|24|in|mm|0|abbr=on}}

|lpcylindersize = {{convert|26|x|24|in|mm|0|abbr=on}}

|valvegear = Joy valve gear for HP, and slip-eccentric valve gear for LP.

|tractiveeffort =

|operator = London and North Western Railway

|operatorclass =

|fleetnumbers =

|withdrawndate = 1903–1904

|scrapdate = 1904–1905

|disposition = All scrapped

}}

The London and North Western Railway Experiment Class was a series of 30 three-cylinder 2-(2-2)-0 compound locomotives designed by Francis Webb for the London and North Western Railway between 1882 and 1884. They were Webb’s first large-scale experiment with a class of express compound locomotives, and the first engine was named accordingly. They were followed by a class of similar, but larger locomotives, that featured larger boilers and smaller driving wheels – the LNWR Dreadnought Class.

After Webb's retirement, his successor, George Whale, withdrew the Experiment class locomotives soon after he took up office in 1903.