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Record: 71951 (21/04/2026)
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LNER Gresley "A4" Class 4-6-2
Class Types
| LNER Class |
A4 |
General
| Designer |
Sir Nigel Gresley |
| Introduced |
1935 |
| Grouping Company |
London and North Eastern Railway |
| Description (1957) |
Class A4 Gresley streamlined Pacifics. The original four engines (now 60014-7) were introduced in 1935 for working the 'Silver Jubilee', Britain's first high speed completely streamlined train. Additional engines were completed 1936-38 for other similar services and for general main line work. No. 60022, Mallard, holds the world's highest authenticated speed for steam, 126½ m. p. h. attained on a test run on 7 July, 1938. 6'8" wheels, 250 lbs. pressure, 3 cylinders, 18% X 26 ins. |
| Wheel Arrangement |
4-6-2 |
| Number Built as A4 |
35 |
| First in Service |
07/09/1935 |
| Last in Service |
05/09/1966 |
| Manufacturers |
|
| Orders |
|
|
|
|
Power
|
A4 |
A4/1 |
| Variant Introduced |
1935 |
1947 |
| Miscellaneous Differences |
|
Inside cylinder lined up to 17" in order to balance the power output at certain cut-off's against the outside cylinders. |
| Tractive Effort |
35,455lbs |
33,616lbs |
| Inside Cylinders |
18.5" x 26" (1 off) |
17" x 26" (1 off) |
| Inside Valves |
9"Piston |
As A4 |
| Inside Motion |
Walschaerts/Gresley |
As A4 |
| Outside Cylinders |
18.5" x 26" (2 off) |
As A4 |
| Outside Valves |
9"Piston |
As A4 |
| Outside Motion |
Walschaerts/Gresley |
As A4 |
Wheels
|
A4 |
A4/1 |
| Pony |
3' 2" |
As A4 |
| Drivers |
6' 8" |
As A4 |
| Truck |
3' 8" |
As A4 |
| Locomotive Wheelbase |
35' 9" |
As A4 |
| Tender Wheelbase |
16' |
As A4 |
| Total Wheelbase |
60' 105⁄8" |
As A4 |
| Descriptive Wheelbase |
6' 3" + 5' 6" + 7' 3" + 7' 3" + 9' 6" + (10' 1⅝") + 5' 3" + 5' 6" + 5' 3" = 60' 10⅝" |
As A4 |
Dimensions
|
A4 |
A4/1 |
| Length (over buffers) |
71' 03⁄8" |
As A4 |
| Weight (loco only) |
102t 19cwt |
As A4 |
| Adhesive Weight |
66t 0cwt |
As A4 |
| Maximum Axle Load |
22t 0cwt |
As A4 |
| Water Capacity |
5,000gal |
As A4 |
| Coal Capacity |
9t 0cwt |
As A4 |
Boiler & Firebox
|
A4 |
A4/1 |
| Boiler Diagram |
107 |
As A4 |
| Boiler Max Diameter |
6' 5" |
As A4 |
| Boiler Barrel Length |
17' 113⁄4" |
As A4 |
| Boiler Pressure |
250lbs |
As A4 |
| Boiler Pitch |
9' 41⁄2" |
As A4 |
| Firebox Type |
Belpaire |
As A4 |
| Firebox Length |
10' 53⁄4" |
As A4 |
| Firebox Grate Area |
41.25ft2 |
As A4 |
| Firebox Heating Surface |
231.2ft2 |
As A4 |
| Tube Number |
121 |
As A4 |
| Tube Diameter |
21⁄4" |
As A4 |
| Tube Area |
1281.4ft2 |
As A4 |
| Flue Elements |
43 |
As A4 |
| Flue Diameter |
51⁄4" |
As A4 |
| Flue Area |
1063.7ft2 |
As A4 |
| Total Evaporative Area |
2576.3ft2 |
As A4 |
| Superheater Elements |
43 |
As A4 |
| Superheater Element Diameter |
1.244" |
As A4 |
| Superheater Element Area |
748.9ft2 |
As A4 |
| Total Heating Area |
3325.2ft2 |
As A4 |
|
