nl-2011-05-spotlight

The SMARTT-swingbridge current version circa 2011 (note the stone viaduct)

Spotlight

on The Swing Bridge

by Raymond G. Potter

In my previous column on the train room, I touched upon the idea of a custom swing bridge (or swing-gate) as a method of entry into the layout. The swing bridge is definitely one of the SMARTT  features about which we get a lot of email, so I’d like to take a moment to elaborate on the concept, and explain how we can make access to the layout much easier.

 

The SMARTT  swing bridge earlier version circa 2001

 

Around-the-wall track plan designs are often the best use of the available space in which to create a most pleasing and interesting custom model railroad layout. Around-the-wall layouts have an interior aisle enabling viewers and operators to walk inside the perimeter of the layout to get “up close and personal” to otherwise inaccessible areas. Unless the track plan design has large bulging, turnarounds for all tracks on either end, the only way to access this space requires that somehow the viewer pass under or through operating tracks.

The easiest but least elegant solution is to “duck-under” the layout. This means bending down, or often even crawling on all fours on the floor to get in and out. Not the best way to work out! For most people who enjoy this hobby, “duck-unders” are not only inconvenient but often even painful. Layouts designed with this requirement are not even an option for them to consider, even if the track plan itself would benefit from such an approach, because of the technical skill involved.

 

The SMARTT-swingbridge current version circa 2011 (note the stone viaduct)

The SMARTT -swingbridge current version circa 2011 (note the stone viaduct)

 

A sometimes used workaround is a lift-out or hinged lift-up panel with tracks running across it. The problem here is that lift-outs are often heavy to handle and they are limited as to what track designs will function properly. They can especially be a problem with multiple tracks running on opposing grade angles or curves or with bridges on the section.

Another option if the track plan design calls for tracks running across an aisle is to make the tracks that must be crossed run high enough to pass under without stooping. This often requires complex helixes for which space may not be available or untenably steep grades.

The obvious solution to avoid any of these far-from-perfect choices is to use a “Dutch-door” style swing gate. The idea is not new, but its complexity can be intimidating. Precise track alignment is essential, and complex trackwork on the moving gate can be daunting for those without a precision fabrication skills.

Our SMARTT solution to the swing gate challenge makes “duck-unders” a relic of the past. Our unique “Dutch-door” design allows access into the interior aisles of the layout with the ease of passing through a garden gate. A SMARTT swing bridge door is a sophisticated, high precision device. It has fully operable track running on it, complete with matching scenery to maintain the look and feel of the layout’s style. Multiple tracks can run across the swing bridge depending upon the space and design.

Whether it’s one or several tracks, our swing bridge technology allows the use of curved track, tracks on grade – even opposing grades, scale model bridges on the gate, and even complex trackwork with double crossovers and the like.

One layout SMARTT built had a swing bridge designed to look like a curved double deck industrial steel bridge with a total of six tracks on it. Stone viaduct bridges are frequent swing bridge features.

The SMARTT industrial steel double decker swing bridge

The SMARTT industrial steel double decker swing bridge

 

Every swing bridge is custom designed to fit the layout. Since each train room is unique in the characteristics of its floor, we designed the swing bridge to be easily custom adjusted on-site to make ideal alignment achievable with minimum extra effort. The adjacent sides of the swing bridge are held in alignment by a threshold connecting them, making the swing bridge an integrated part of the overall layout. The swing bridge itself has a slide latch or bolt to secure it in the closed position. Upon final installation, the positions of the rail ends themselves are fine-tuned for maximum accuracy so that the transition from layout to bridge and back again is smooth and problem-free.

The swing bridge is electrically connected to the main line by an umbilical, meaning that there will be no loss of track power as the train crosses into the bridge area. For layouts using DCC or for O scale, the MTH DCS or Lionel TMCC systems, the electrical characteristics of the swing bridge are accounted for in the overall electrical design so that there is no diminishment of signal strength as the trains cross.

A frequent worry for modelers attempting to create this feature on their own is the possibility that a cherished locomotive could run off the end of a carelessly left-open swing bridge. SMARTT ’s electrical design makes this impossible by integrating a kill-switch that cuts power to the track on either side of the gate so that electrical power will shut off well before a train can ever reach the open section. This effect is only local to the bridge so that power continues everywhere else, and the user can enter and exit the layout while the train is running elsewhere with no loss of overall power.

Over the past 15 years, SMARTT has built a swing bridge into many of its custom layouts both big and small. Since every layout and circumstance is unique, it is vital that the swing bridge be designed at the start of the overall layout design process. For this reason, SMARTT cannot make swing bridges by themselves. There are just too many variables we would need to control to make the bridge bulletproof in its reliability.

If you’re considering having SMARTT build a layout and access is important to you, the SMARTT swing bridge is definitely the way to go.


from the May, 2011 SMARTT Newsletter

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