Sentinel 4wVBT

George

The unorthodox vertical boilered steam locos built by Sentinel in Shrewsbury are a much under-rated loco. Whereas in a traditional locomotive the cylinders have to be fairly large to overcome the fact that they are driving directly to the wheels, in a Sentinel, a "steam engine" is an independent twin cylinder unit with its own cam and crankshafts, more reminiscent of an internal combustion engine. The crankshaft then drives through a cold-change 2-speed gearbox and duplex chains to the axles. The vertical boiler too, is the reverse of the traditional boiler. Whereas in horizontal boiler locos, the fire gases pass through tubes in the water space, in a Sentinel, the boiler comprises two concentric "barrels" which surround the fire with water, but as the gases naturally rise, they pass through water-filled tubes that criss-cross the central passage ensuring that as much heat as possible is transferred to the water. Late on in  development - at much the same time that Rolls-Royce bought Sentinel - a 3-pass system was developed whereby the cold water from the tank was passed through 3 heat exchangers - the first taking heat from exhaust steam, and the second and third on flues from the vertical boiler. The result, in the words of one Sentinel employee, was that "it made steam before the water entered the boiler" and in May 1957 a 200hp Sentinel steamer, on test on the Shropshire & Montgomeryshire (then still under Army control and used regularly by Sentinel for loco testing) turned in boiler efficiency figures well in the upper 90%s.  Within three months of those tests, Rolls-Royce had terminated steam loco development.

Later sold to a member of the Rutland Railway Museum, a start was made, collecting parts that had been misplaced or stolen whilst at SYR. A change in circumstances forced its sale and Andrew bought the loco and moved it to Elsecar (where it is seen just prior to being unloaded). Some preliminary stripping was carried out to determine the extent of superstructure replacement required. Andrew had made the decisoon, in June/July 2010, that since he could see no likelihood of making an early start on "George" that he would put it up for sale (through Heritage Transport Supplies Ltd - 01509 219725).