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A bridge so fast

The world's ultimate bridge building set is to be the star turn at Civils 98.

Throughout the show the Royal Engineers' Combat Engineer School will be giving demonstrations of how to build a 30m span tank-carrying bridge in as many minutes. Code named ABLE - that's Automotive Bridge Launching Equipment in plain English - the bridge building kit is the fully mechanised 1990s successor to the medium girder bridge which was developed from the original Bailey Bridge (NCE 10 March 1994).

In a preview laid on last week for NCE at the Gibraltar Barracks military training area it was clear that the only similarity with the familiar manhandleable lattice girder bridges was the expletives used to encourage the Sappers in their work. However, these are likely to be deleted from the family show to be put on for Civils 98 in the outside area adjacent to Hall 12 at the NEC.

Everything about ABLE is spectacular. The bridge is carried on three huge 8x8 Alvis Unipower transporters which reduce even the most steroid civilian off-road vehicles to puny bystanders. On arrival at the bridge site the lead vehicle deploys a launch rail - a modular aluminum boom with steel pinned connections - and lands it on the far bank.

As soon as the nose touches down the 10 man crew set to work craning the twin box section ramps of the first bridge module off the two support vehicles so they can be pinned together and rolled out under the launch rail. Successive deck modules are then lifted in, assembled and winched out over the gap. Finally, the crew carry in deck panels to fill the gap between the beams, fit low parapet sections which help to guide drivers across, and winch the launch rail back.

Military purpose of the bridging system is to give 'general support' and help maintain transport links behind a battle front. It is a major part of the BR90 'Bridging for the Nineties' equipment developed for the Army by Vickers. Special versions of ABLE can span up to 42m with a chain link reinforcement system attached to the beam soffits, or cross a 60m gap using intermediate support from a pontoon or pier and a special launching nose.

Time and manpower savings over its predecessor are spectacular. The team of 30 needed to assemble an equivalent medium girder bridge would be a quarter the way through their task when the 10 sappers manipulating ABLE had completed their bridge.

The system also includes two 'close support' bridges that can be deployed during a battle to span up to 12m with a simple twin box ramp and 24m with a pair of folding ramps which are hinged together.

Structural material of the bridges is almost exclusively high grade 232B aluminium alloy with stainless steel nosings bolted on to form the eyes of the most highly stressed site pinned connections. The 1m deep section spanning 32m is very lively but the large deflections under loads such as a Challenger tank are entirely as expected by its designers. There are 19 sets of ABLE and many more close support bridges deployed with the Royal Engineers.

As with all military equipment the hope is that its sole purpose will be training for an event that does not occur. But Major Mick Wood of 63 Training Support Squadron RE sees enormous potential for training to include projects such as disaster relief work where instant bridging can make all the difference in keeping emergency food supply routes open. The Civils 98 demonstrations will be part of 63 TSSRE training as is a demonstration of the system this month at a military exhibition in Malaysia.

ABLE is a revelation in what can be achieved with dedicated equipment. The team at Civils 98 led by top trainer Ian Stobbs hopes to achieve some record breaking build times and we will be hyping up the betting on the spot with NCE's daily magazine the Civils 98 Show Guide.

Mike Winney

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