LT&SR 79 Class

{{Short description|4-4-2 tank locomotive class used by the London, Tilbury & Southend Railway}}

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

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

{{Infobox locomotive

|name = LT&SR 79 class

|powertype = Steam

|image = Bressingham Steam Museum and Gardens 15.jpg

|caption = Preserved LTSR 4-4-2T No. 80 Thundersley

|designer = Thomas Whitelegg

|builder = {{ubl|Robert Stephenson & Co. (4),|Nasmyth, Wilson & Co. (5),|Derby Works (30)}}

|serialnumber = {{ubl|RS 3366–3369,|NW 1448–1452}}

|builddate = 1909–1930

|totalproduction = 39

|whytetype = 4-4-2T

|uicclass = 2′B1 t

|gauge = {{RailGauge|ussg}}

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

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

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

|length = {{convert|39|ft|0|in|m|2|abbr=on}}

|wheelbase = {{convert|30|ft|9+1/2|in|m|2|abbr=on}}

|fueltype = Coal

|fuelcap = {{convert|2.75|LT}}

|watercap = {{convert|1800|impgal|abbr=on}}

|locoweight = {{convert|71.50|LT}}

|boilerpressure = {{convert|170|psi|MPa|2|abbr=on}}

|cylindercount = Two, outside

|cylindersize = {{convert|19|x|26|in|mm|0|abbr=on}}

|valvegear = Stephenson

|tractiveeffort = {{convert|17390|lbf|kN|1|abbr=on}}

|operator = {{ubl|LTSR|→MR|→LMS|→BR}}

|powerclass = MR/LMS/BR: 3P

|numinclass = 1 January 1923: 4
1 January 1948: 39

| locale = London Midland Region

|withdrawndate = 1951–1960

|disposition = One preserved, remainder scrapped

}}

The London, Tilbury and Southend Railway (LTSR) 79 Class is a class of 4-4-2T suburban tank engines. They were designed by Thomas Whitelegg, as a development of the earlier 37 Class. They could reach a top speed of 65 mph (105 km/h).{{cite book |title=Train: The Definitive Visual History |date=2014 |publisher=DK Publishing |isbn=978-1465436580 |page=97 |url=https://books.google.com/books?id=LrWBBAAAQBAJ |access-date=2 October 2020}}

The four locomotives ordered by the LTSR were numbered 79–82 and were named after places in Essex, near the LTSR route. After absorption by the Midland Railway in 1912, they were renumbered 2176–2179 and their names were removed. The Midland gave them the power classification 3P, and later continued construction; an order for 10 locomotives was delivered in 1923, just after grouping.