65 Tracked Hovercraft E Edwards Feb 2017
At our meeting in February Eddy Edwards presented an account of his research into the development of the so called ‘Tracked Hovercraft’. This was an attempt to produce a high speed transport system linking the major UK cities using vehicles travelling at 200 to 300 mph on dedicated tracks.
To reduce the friction losses encountered in normal rail systems a group of engineers working with Christopher Cockerell on the development of marine hovercraft came up with the idea of applying the hover principal to vehicles travelling on a ground based track system. The early studies of such a system started in 1960 but it was soon realised that a major problem would be the selection of a suitable power source. Fortunately at the time Professor Eric Laithwaite was heavily involved in the development of the linear induction motor (LIM) which provided a propulsive force through the interaction of a magnetic field and an external conductor. In the case of the Tracked Hovercraft the magnetic field would be generated in the vehicle and the external conductor would be a metal plate fixed to the full length of the track. These two concepts were combined to develop a 6 ft long model which by 1966 was able to run successfully on a 600 ft long circular track. In order to progress the development of a full-sized prototype a government funded company called ‘Tracked Hovercraft Ltd.’ was formed in 1967 to develop both the vehicle and the necessary test track. After a long search for a suitable site a 20 mile long straight strip of land between the Old Bedford River and the Counter Drain and stretching from Earith and Denver Lock was acquired. A new workshop, including a hangar to house the test vehicle, was built at Earith and administration and R and D offices set up in Ditton Walk, Cambridge. The construction of a low level length of track using 75 ft precast rectangular concrete box beams began at Earith in 1969 and by 1970 one mile had been completed. The precast beams were manufactured at Stamford and were delivered by train to Huntingdon and then by road to Earith. At the same time construction started at Sutton Gault on a high level track with the 50 ton beams being supported about 30 ft above the ground on precast concrete frames. Unfortunately there were a number of accidents during construction and doubts were raised about the adequacy of the foundations and all work on track construction had stopped by 1971 to allow a review of the track design and construction to be carried out. Meanwhile the design of the prototype vehicle, named RTV31, had been completed and manufacture started at Vickers Armstrong at Swindon. The completed shell was delivered by road to Earith in 1971 where it was fitted out with the electro-magnetic equipment and the compressors to provide the cushions of air to support the vehicle and keep it on the track. In addition control equipment and extensive monitoring equipment to record the performance of the vehicle and it’s various pieces of equipment were added. Electric power was taken from live metal rails attached to the sides of the beams through metal shoes suspended on rods attached to the vehicle; it was reported that the vehicle emitted an impressive shower of sparks as it sped along the track. The first public demonstration of the vehicle took place at the end of 1971 when it reached a speed of 12 mph. After a number of modifications a speed of 72 mph was achieved in August 1972 followed by a speed of 107 mph in January 1973. This was the highest speed which could be attained with the limitations of having only one mile of track available and with the need to have sufficient distance to bring the vehicle safely to rest. In February 1973 the government abandoned the project and all work on the vehicle and the track stopped. The prototype vehicle RTV31 eventually found a home at the Railworld Museum in Peterborough where it is displayed sitting on one of the concrete track beams. The workshop and hangar at Earith are still in existence but all that remains of the track are a few concrete plinths near Sutton Gault. Pictures of the vehicle in motion and shots of some of the construction work can be seen in a video available on www.ousewashes.org.uk by clicking on Ouse News and scrolling down to item 15.