Hovertrain
The concept aims to eliminate rolling resistance and allow very high performance, while also simplifying the infrastructure needed to lay new lines.
Hovertrains were seen as a relatively low-risk and low-cost way to develop high-speed inter-city train service, in an era when conventional rail seemed stuck to speeds around 140 mph (230 km/h) or less.
Although the hovertrains still had reduced infrastructure costs compared to the APT and similar designs like the TGV, in practice this was offset by their need for entirely new lines.
Conventional wheeled trains could run at low speed on existing lines, greatly reducing capital expenditures in urban areas.
Originally developed at General Motors as an automated guideway transit system, GM was forced to divest the design as part of an antitrust ruling.
One of the earliest hovertrain concepts predates hovercraft by decades; in the early 1930s Andrew Kucher, an engineer at Ford, came up with the idea of using compressed air to provide lift as a form of lubrication.
The Levapad required extremely flat surfaces to work on, either metal plates, or as originally intended, the very smooth concrete of a factory floor.
[2] What was lacking from all of them was a suitable way to move the vehicles forward – since the whole idea of the hovertrain concept was to eliminate any physical contact with the running surface, especially wheels, some sort of contact-less thrust would have to be provided.
There were various proposals using air ducted from the lift fans, propeller, or even jet engines,[4] but none of these could approach the efficiency of an electric motor powering a wheel.
At about the same time, Eric Laithwaite was building the first practical linear induction motors (LIMs), which, prior to his efforts, had been limited to "toy" systems.
A LIM can be built in several different ways, but in its simplest form it consists of an active portion on the vehicle corresponding to the windings on a conventional motor, and a metal plate on the tracks acting as the stator.
The LIM concept sparked considerable interest in the transportation world, as it offered a way to make an electric motor with no moving parts and no physical contact, which could greatly reduce maintenance needs.
The amount of air that is lost though this mechanism is dependent on vehicle speed, surface roughness and the total area of the lift pads.
However, these locomotives weighed 80 tons,[vague] much of it constituted by the voltage control and conversion equipment, whereas the Tracked Hovercraft design was intended to be a very lightweight vehicle.
The German government, in particular, was funding several different passive and active systems in order to explore which of the proposed solutions made the most sense.
By the mid 1970s, several of these projects had progressed to about the same point as the hovertrains, yet appeared to have none of their disadvantages—high sound levels, blown dirt and higher energy use than initially expected.
The earliest examples of serious hovertrain proposals come, unsurprisingly, from Christopher Cockerell's group, organized in Hythe, Hampshire as Hovercraft Development Ltd. As early as 1960 their engineers were experimenting with the hovertrain concept, and by 1963 had developed a test-bed system about the size of a tractor-trailer that ran for short distances on a concrete pad with a central vertical surface that provided directional control.
A small model of their proposal shows a train that looks like the fuselage of a narrow-body airliner running on a monorail track shaped like an upside-down "T".
During this same period, British Rail was working on an extensive study project that was suggesting that the hunting problems seen on existing trains could be addressed through development of suitable suspension systems.
In the meantime, the Hythe team had no funds for the full-scale test system they were proposing, and complained at Hovershow that the French would be taking the lead in hovertrain development.
A combination of factors, including Laithwaite's persuasiveness and Bertin's successes in France, quickly gained the company government funding.
[19] A combination of the total lack of interest on BR's part, and infighting between the various high-speed efforts, prompted the formation of an independent review board that heavily favored APT.
This success garnered funding for the addition of a Turbomeca Marboré turbojet engine taken from a Fouga Magister, which powered it to 345 km/h (214 mph) on 1 November 1967.
Several newer prototypes of ever-larger size followed, culminating in the I-80, a 44-seat vehicle powered by two turboshaft engines driving a single shrouded propeller.
As part of the High Speed Ground Transportation Act of 1965, the Federal Railway Administration (FRA) received funds to develop a series of high-speed trains.
In December 1969, the DOT selected and purchased a large parcel of land outside Pueblo, Colorado, and built the High Speed Ground Test Center (HSGTC) for the various programs.
Once the track was ready, linear induction motor, vehicle power systems, and rail dynamics testing progressed and by October 1972, a speed of 187.9 mph (302.4 km/h) was achieved.
[25] The second stage of the TACV project was a hovercraft testbed initially powered by turbofan engines, the Tracked Air Cushion Research Vehicle (TACRV).
[22] Although Grumman's efforts got the majority of the funding in the TACV project, ensuring the construction of 22 miles (35 km) of track, the reaction rails for the LIM propulsion were never installed.
[24] The third stage of the TACV project was a complete LIM-powered hovertrain with passenger seating, the Urban Tracked Air Cushion Vehicle (UTACV).
