What is Sentinel 7109?

Manufactured by the Sentinel Waggon Works at Shrewsbury in 1927, Sentinel 7109 is a balanced, double-engined, single-geared, industrial steam locomotive.

Sentinel 7109 (Joyce) in 1964 (photo C Verrall)

Weighing 28 tons, it is a steam locomotive with a pair of transverse engines at the front and a vertical water-tubed boiler at the rear in the cab. It uses both gears and chains to transfer the drive to the axles. Unlike later Sentinel locos, it has only a single gear ratio.

Its central section houses a four inch thick cast-iron water tank to provide ballast as well as hold water. Whatever the water level in the tank, the weight distribution remains the same and so the loco is balanced front to rear. Some Sentinel loco designs had the tank at one end and so were only balanced at one particular water level!

7109 was the first of eight pre-war locomotives of this type. Test results gave sufficient confidence for two similar units to be purchased by the Somerset & Dorset Joint Railway Company for use at Radstock. It is being restored at Midsomer Norton station, about a mile or so from Radstock, and so it is in as good a location as any to trigger memories of the once familiar Radstock Sentinels.

Sentinel Waggon Works Building in November 2009

The "Sentinel"