| Sri Lanka Railways class M1 | |
| Powertype: | Diesel-electric |
| Builder: | Brush Bagnall Traction |
| Serialnumber: | 3025–3049 |
| Builddate: | 1952 |
| Totalproduction: | 25 |
| Aarwheels: | A1A-A1A |
| Uicclass: | (A1A)(A1A) |
| Locoweight: | 88LT |
| Fueltype: | Diesel |
| Primemover: | Mirlees JS12VT |
| Enginetype: | V12, 4 stroke diesel |
| Poweroutput: | 10000NaN0 |
| Operator: | Ceylon Government Railway » Sri Lanka Railways |
| Operatorclass: | M1 |
| Fleetnumbers: | 539–563 |
| Firstrundate: | 1953–1956 |
| Withdrawndate: | 1983 |
| Notes: | Sources:[1] except where noted |
The M1 locomotive was a class of locomotives, used by Sri Lanka Railways, imported from 1953, and manufactured by Brush Bagnall Traction.
The locomotives weighed had a 10000NaN0 V12 Mirlees JS12VT four-stroke engine. The Sri Lanka railway had a fleet of 25 of these Class M1 locomotives which began introduction in 1953 and were removed from service from 1983.[2]
Locomotive number 560 is the subject of a restoration attempt.[3]
In the 1950s Sri Lankan Railways was seeking replacements for old rolling stock, routine replacement of which had been delayed by World War II. Specifications were for 25 locomotives with 750hp power at the wheel, available from 12mph upwards, and up to an altitude of 6200feet. The train was expected to be used for suburban trains centered on Colombo, as well as mail trains in the north of the country, and trains in hill areas: approximately requirements were for a vehicle capable of pulling 550LT at 18mph on a gradient of 1 in 44 (2.27%) on track with 5chain reverse curves; preferably within an 80LT locomotive weight on 6 axles (A1A-A1A). Several firms tendered for the contact; American suppliers were unable to enter a competitive bid due to the devaluation of both the rupee and British pound.
Brush offered a locomotive with 1000hp power, and a generator output of 625hp, capable of multiple working, and was awarded the contract. Five locomotives were supplied (deliveries beginning Jan. 1953) for operational testing – Brush had not been able to fully stress test the units in England due to an absence of a full scale test track.During testing engine overheating was found to be a serious problem on the steeply graded and curving mainline. Other issues requiring attention included fuel pump problems including air-locks, and bogie frame cracking. The electrical circuit for torque control was also modified.
The remaining twenty locomotives, with modifications required to resolve the issues found during testing were delivered from May 1954, at a rate of approximately 1 per month.