Sri Lanka Railways class M1
M1 No.560
Type and origin Power type Diesel-electric Builder Brush Bagnall Traction Serial number 3025–3049[1] Build date 1952[1] Total produced 25[1]
Specifications Configuration: ​  • AAR A1A-A1A  • UIC (A1A)(A1A) Gauge 5 ft 6 in (1,676 mm) Loco weight 88 long tons (89 t; 99 short tons) Fuel type Diesel Prime mover Mirlees JS12VT[2] Engine type V12, 4 stroke diesel[2]
Performance figures Power output 1,000 hp (746 kW)
Career Operators Ceylon Government Railway » Sri Lanka Railways Class M1 Numbers 539–563[1] First run 1953–1956 Withdrawn 1983
Sources:[3] 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 88 long tons (89 t) had a 1,000 hp (746 kW) 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.^[4]

Introduction

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 750 hp (559 kW) power at the wheel, available from 12 mph (19 km/h) upwards, and up to an altitude of 6,200 ft (1,900 m).^[5] 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 550 long tons (560 t; 620 short tons) at 18 mph (29 km/h) on a gradient of 1 in 44 (2.27%) on track with 5-chain (330 ft; 101 m) reverse curves; preferably within an 80 long tons (81 t; 90 short tons) 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.^[6]

Brush offered a locomotive with 1,000 hp (746 kW) power, and a generator output of 625 hp (466 kW), capable of multiple working,^[7] and was awarded the contract.^[5] 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 5 ft 6 in (1,676 mm) 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.^[8]

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.^[9]