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Flyda urban mass transit

John Emanuel of technology transfer specialists Pax Consultants takes a look back at the technology behind Flyda, a metro system with minimised infrastructure costs, which is now in the public domain.

Cutting capital costs

You would think that a technology that claimed to cut the capital cost of building new transit lines in cities by up to 60% or more, with commensurate reductions in environmental impact, and with potential service benefits, would have been an immediate success.

Initially conceived and patented by Commander Francis Perrot in the 1980s and further developed in co-operation with a number of major consulting engineers and large civil and mechanical engineering groups, Perrot’s company Flyda Ltd could not endure the long time scales in metro commissioning and is no longer in business. So now the Flyda technology is in the public domain, freely available to all.

Perrot’s insight was to focus on infrastructure construction, by far the greatest source of costs and environmental impact in new transit line provision. Project budgets at that time indicated that some 80% of the total capital costs were spent on tunnels, bridges and elevated tracks and stations. How could these be minimised?

A first simple strategy was to operate frequent smaller, lower axle weight, automated trains, rather than infrequent larger trains, to meet capacity requirements. Tunnels, bridges and elevated tracks can all then be smaller, cheaper and easier on the environment. Modern computer control systems make this easier than was the case in the 1980s.

The second strategy was to further reduce the bridge and elevated track size, weight and cost by using a high narrow stiff beam construction and cantilevering the up-train from one side and the down-train from the other, dispensing with the usual deck – rather like a monorail track but providing two tracks rather than just the one. Bridges of this type are much smaller and cheaper than conventional bridges and can be ‘installed’ rather than ‘constructed’ with far less disruption. With an emergency footpath down the centre, elevated tracks can be on the scale of a footbridge rather than a railway bridge.

Smaller, more environmentally friendly elevated tracks in many cases can also come closer to the downtown area acceptably, for example down the centre of an existing highway, thus reducing the amount of costly tunnelling needed.

Wheels on the roof

The challenge was to devise vehicle configurations that would allow coupled trains to transfer seamlessly from a tunnel in the city centre, to elevated cantilever track in the near suburbs, and at grade further out. The trains also had to operate safely through junctions.

Perrot’s solution was simple, wonderfully ingenious, and counter-intuitive. In addition to the driven wheels under the vehicle he positioned extra wheels on both sides of the vehicle roofs. In tunnel and at grade the trains ran on the lower wheels. However, on cantilever, the vehicles’ weight was carried on the lower wheels, the upper wheels securing the vehicles to the top of the track.

All that remained to be determined was the switching mechanism. Avoiding moving parts on the tracks, Perrot put yet other wheels on the roof – the computer controlled pivotable ‘track selection wheels’. These could be positioned, left or right, to select the desired track as the train transfers from ground support to cantilever and back.

Matching capacity to demand

A third strategy, already in use but easier to facilitate in a new metro line, was to balance capacity across a system. Typically in the centre of a city high-capacity trains and high-capacity stations are required. Further out, there are fewer riders so stations can be smaller. Flyda’s vehicles travelled in coupled trains but could also travel independently. Thus a 16-car train in the city centre could split at a junction into two eight-car trains further out and, theoretically, into four-car, two-car, and eventually one-car trains in the distant suburbs. Smaller trains in the suburbs, requiring smaller stations, reduce costs or allow the transit system to serve a wider community.

Flyda spent about $1m in the early 1980s on engineering design work on the tracks, vehicles and control system. In joint bids with leading UK civil and mechanical engineering contractors, Flyda made preliminary offers for a number of schemes in the UK and North America.

Flyda technology uses entirely conventional components – wheels, motors, brakes, concrete, steel, etc – no magnetic levitation, air cushions or other exotic or expensive elements.

This technology offers potential opportunities to urban mass transit authorities, and to civil, mechanical and electrical contractors, to build and use urban mass transit systems at half or less the capital cost of conventional systems, with far lower environmental impact and superior passenger service.

The challenge is to build the first one!

John D Emanuel was a Director of Flyda Ltd for a period in the 1980s. A more detailed article on Flyda can be found here: www.railtechnologymagazine.com/Rail-Industry-Focus-/Page-2/flyda-mass-transit-systems