The main feature of this exhibtion layout  is a working single track Bascule Bridge (a drawbridge with a counterweight – to be precise the bridge modelled is a single leaf through truss with an above-deck counterweight).
 
On either side of the bridge the double track main lines are combined into gauntlet track to run over the bridge. Gauntlet track refers to the where tracks converge onto a single roadbed and are interlaced without using  turnouts or points. A switch frog at each end allows the two tracks to overlap, and the four rails run parallel over the bridge on the same sleepers and separate again at the other end.

The signalling, bridge operation and track power supply are interlocked. This will makes operating the layout particularly interesting. It also means that trains can’t crash into each other on the bridge or fall into the water when the bridge is up.

The bascule bridge is adapted from the Walther's model and is over 70cm in length. The gauntlet track is hand laid in code 83 rail utilsing the frogs from No. 6 Shinohara turnouts. The other turnouts on the layout are Micro Engineering.



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PROTOTYPE & PERIOD MODELLED
Kelly River is a freelanced layout. It is not based upon a specific place in North America. We have combined a number of US prototype layout design elements such as a junction with an interlocking tower, the gauntlet track and our focal point, a railroad draw bridge.   We run trains from a variety of North American railroads from the 1940s through to the present day (not all at the same time).



GAUNTLET TRACK
Gauntlet track refers to the where tracks converge onto a single roadbed and are interlaced to pass over the bridge. Our research confirmed the use of gauntlet track on bascule bridges. A switch frog at each end allows the two tracks to overlap, and the four rails run parallel over the bridge on the same sleepers and separate again at the other end.

Gauntlet tracks are commonly used when a rail line's capacity is increased with the addition of an additional track, but cost or other factors prevent the widening of the bridges. Since there are no points or other moving parts on gauntlet track, a train operating on one of the tracks cannot be routed onto the other. Because two trains cannot use the gauntlet at the same time, scheduling and block signals must allow for this restriction.


BASCULE BRIDGE

A bascule bridge is a drawbridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing to provide clearance for boat traffic. Bascule is a French word for seesaw or balance, and bascule bridges operate along the same principle. They are the most common type of movable bridge because they open quickly and require relatively little energy to operate.

The bridge modelled is a single leaf through truss heel trunnion with an above-deck counterweight. A "heel-trunnion" bascule bridge is where the moveable leaf and counterweight each rotate around separate heels (called "trunnions").





Bascule bridge over the Duwamish River, Washington State, USA

 

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page last updated 03-10-2011


Pat KELLY 1951-2005