This article appeared in the Summer 1971 (Issue #24) edition of the Kent Archaeological Review.
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A Brennan Torpedo Station at Cliffe Fort.
Cliffe Fort (TQ 707767) on the south bank of the River Thames about 6½ Km east of Gravesend, is perhaps not a very inspiring example of one of the standard pattern Royal Commission forts of the 1860's, 76 of which were built in Britain, three of them at the mouth of the Thames. Yet what is different about it, is that it contains, unfortunately in bad condition, a very rare surviving example of a Brennan Torpedo Station.
In the second half of the 19th century, Louis Brennan (1852-1932), inventor of the monorail form of transport, pioneered a new type of shore-based torpedo system for use against warships and other maritime craft of any potential enemy. This particular system allowed the torpedo to operate usefully only from a fixed base and being unsuitable for launching from ships was not adopted by the Royal Navy. However, it was tried by the Army's Corps of Royal Engineers and formed a feature of harbour defence for some years. Under Brennan himself, a factory for the production of this weapon was set up at St Mary's Barracks, Brompton (later moved through other temporary accommodation to Gillingham) and in about 1885 one of the handful of his experimental torpedo stations in Britain was built at Cliffe Fort. The station's location in one of the forward batteries of the Thames defences was well chosen to cover the river where it turns into Gravesend Reach. It consisted of two sets of launching rails, which still remain today, sloping down into the river in separate launching bays. The rails lead down from a space between the casemate battery and the open battery. One of the magazines was adapted for use as a servicing area and in the root is a loading slit through which the torpedoes were raised and conditioned for either launching bay.
The motive power of the Brennan torpedo is quite interesting, for its driving force was actually provided from the land. Two drums of piano-wire were mounted in the torpedo itself and were connected to a steam winch in the fort. The torpedo was launched down the rail on top of a small carriage which separated at the last moment when the weapon entered the river. The steam winch immediately began to unwind at high speed the wires off the torpedo drums which through gears turned a pair of contra-rotating propellers in the stern and sufficient power was developed to force the weapon through the water. A continual unwinding of these wires off the torpedo drums on to other drums on the steam winch was necessary to provide propulsion right up to the moment of impact. Maximum range was about 2,750 metres and speed could be varied to 32 Kilometres per hour.
The aiming principle of the Brennan torpedo had something in common with the modern wire-guided anti-tank missile, for the unwinding wires were also used for steering, which was facilitated by varying the speed of one of the drums in the weapon which then reacted mechanically on an adjustable rudder, thus guiding the high explosive Warhead on to the target. An above-water indicator in the form of a telescopic mast with flag was fixed to the torpedo. This aided the operator to sight the weapon on to the target and enabled the steering system to be used to the best advantage. The torpedo ran at about 3 metres below water level and depth keeping was maintained by a pendulum/hydrostat system of a similar type to the one used in the famous Whitehead Torpedo.
Had war forced the Cliffe Brennan Torpedo Station into an operational role it would have been part of a defensive network which covered the Thames estuary and co-ordinated with the Medway defences through the medium of Slough Point Fort. The river channels of the Thames would probably have been mined and the Brennan Torpedo Station would have fired through gaps in the minefield.
The Government discontinued the Brennan torpedo long before the First World War but Brennan went on to do further work in weapons research.
Although gutted, to a military researcher the Brennan Torpedo Station at Cliffe Fort is worth renovating in itself, but it is doubtful whether the cost of preservation could be justified. Fortunately it is not threatened by imminent destruction, but there is the possibility of industrial development in the area at some time in the future. A photographic record has been made and a plan is being prepared.