Tracked Hovercraft

It combined two British inventions, the hovercraft and the linear induction motor, in an effort to produce a train system that would provide 250 mph (400 km/h) inter-city service with lowered capital costs compared to other high-speed solutions.

It was noticed early on in the development of the hovercraft that the energy needed to lift a vehicle was directly related to the smoothness of the surface on which it travelled.

[1] This is the purpose of the skirt found on most hovercraft; it allows the fuselage to be some distance from the ground while keeping the air gap as small as possible.

[4] In 1960 several engineers at Christopher Cockerell's Hovercraft Development Ltd. in Hythe, Hampshire, began early studies on the hovertrain concept.

As the hovercraft had no strong contact with a running surface, propulsion was normally provided by an aircraft-like solution, typically a large propeller.

Their initial solution was a track shaped like an upside-down T, with the vertical portion consisting of a central concrete section with aluminium stator plates fixed on either side.

Their first design concept looked like the fuselage of an airliner with two decks, riding above the stator beam, with the LIM centred in the middle of the body.

A test rig of this layout was built at Hythe, which was filmed in operation by British Pathé in 1963, which also showed a model of the proposed full-sized version.

In spite of its light weight compared to conventional train sets, the Tracked Hovercraft operated at such high speeds that its passage induced vibration modes in the guideway that needed to be damped out.

[10] The train layout was redesigned with a box-like main girder, with a top-mounted reaction plate being used for the LIM, and the vertical sides of the guideway being used for centring.

[13] Although high-speed travel would require new lines to be laid, expensive ones, such a train could use existing rail infrastructure at lower speeds.

This would allow such a train to approach existing stations at lower speeds, greatly reducing capital costs of bringing the service into cities.

[14] NDRC was unsuccessful in raising new capital from the government and decided to put in £1 million from their own pre-assigned discretionary budget to start construction of a track, hoping that additional funding would be forthcoming from industry.

[16] Seeking to protect their investment, and finding little external funding, the NRDC decided to spin off the hovertrain group as Tracked Hovercraft Ltd. (THL).

They also decided to spool out the funding over four years, starting with a £1 million grant for a single prototype vehicle and a short portion of the test track.

By this time the French government had started providing major funding for Jean Bertin's Aérotrain project, which was substantially similar to the Tracked Hovercraft in concept.

Laithwaite, always described as persuasive, convinced the government that they were about to lose out on this burgeoning field of high-speed transit,[15] and eventually won £2 million in additional funding.

[19] Even without an outright failure, any mechanical motion in the plate due to the forces of the passing train could induce waves in the stator that travelled along with it.

Power pick-ups extended from the rear of the vertical wing-like surfaces on either side of the vehicle, and the sparks they threw during operation are easily visible on test runs.

The track was about 6 feet (1.8 m) off the ground, running along the earthworks between the Old Bedford River and the Counter Drain just to its north, between Earith and the Denver Sluice.

To gain some clarity, they formed an interdepartmental working party that studied several potential inter-city transit solutions on the London–Manchester and London–Glasgow routes.

In comparison, Tracked Hovercraft would not be ready for real-world testing until the late 1970s, and could not enter service until a completely new set of guideways had been constructed.

[28] Heseltine was accused by Airey Neave and others of earlier misleading the House of Commons when he stated that the government was still considering giving financial support to the hovertrain, when the decision to pull the plug must have already been taken by the cabinet.

[28] He called together the Select Committee on Science and Technology to examine the issue, but they were constantly frustrated in their efforts to obtain cabinet meeting reports.

One thing that did surface was that Hawker Siddeley and Tracked Hovercraft were in the process of entering a bid for the GO-Urban system in Toronto, Ontario.

[30] By that point Rohr, Inc. in the US were already experimenting with their own LIM arrangement of this sort on their ROMAG personal rapid transport system, and there were several German maglev efforts underway as well.

[32] The test track was removed, but several concrete footings project, at ground level, from a small pond beside the Counter Drain.