The High Bridge

3/9/21

Sometimes we have to engineer parts of the layout on the spot. We call an engineering meeting, evaluate the options, figure in the fix, and get to work. From time to time the fix is complicated enough that a drawing or sketch is in order. An example is where the top of the helix has to cross several tracks far below and, at the same time,  provide abutments for a bridge above. We couldn’t support it on normal risers so we had to use cantilevered stringers to support the sub-roadbed while leaving the lower level mainline untouched. We also wanted scenery  levels to be somewhat below track grade to provide room for a fill. Moreover, this piece provided the transition from the helix to the second level of the layout at Blodgett and vertical accuracy was a must. This required a sketch and some thought. 

George and Doug celebrate the fact that their construction matches almost exactly the required  elevation of the helix. Right under the level is where the  “high bridge” will go. 

The temporary “high bridge” launches out into  pace, sailing almost 100′ above the valley floor. Hugh donated this 1″ aluminum square tube many  years ago and it’s been waiting all this time for a place to star. Thank you, Hugh.  

Once completed and explained, Doug and George took the sketch and got right to work. They turned it into 3 dimensional reality in record time. As they neared completion, we began checking for level and plumb. This whole process took about 2 hours. As they dialed it in closer and closer, excitement built. We installed the temporary bridge, put a level on it, a nd,  HOTDANG !!, it was dead on. This was the culmination of  about 5 weeks work and will be a focal point for the  railroad. 

The high bridge provides us with some pretty neat things. At 48” (almost 400 HO feet) long and 12” (almost 100 HO feet) high it will be a dramatic scene.  It’s very satisfying to have calculated the helix to crossover itself 3 times, maintain 1.4% and 1.7% grades,  use 48” and 45” radius curves and arrive at precisely the height needed to match the existing height of the upper deck.  It’s close to the edge of the layout and will provide great photo  ops. It has a robust temporary structure so the mainline will operate during the time we take to build an actual bridge.  

The actual, on site, high quality, fully  dimensioned (with tolerances) sketch from which George and Doug worked their magic

DCC control boxes built by Gene ready for  installation. Also note the backdrop behind the yard being  installed 

Larry’s prototype tunnel with open front wall, rock backwall, and dark colors to enhance the  “tunnelism”. 

In his own shop, Gene built boxes which will support our DCC system. These boxes are designed to hang below the layout with shelves for booster, power supply, circuit breaker board with 4 breakers, and terminal strips for power districts. The large holes in the sides are for cooling air. They are very nicely built with dadoed and rabbeted joints. As soon as these are installed and bus wires run, trains can go!! 

Larry has begun experiments using various rock forming techniques to create a “back wall” to our helix “tunnel”. Right now he’s using Sculptamold layers with crumpled tin foil rock forms pressed into the wet plaster. An India ink wash will be applied to deepen crevasses and dry brushing with light grey will bring out highlights.

It is our intent to complete track laying on the helix next week. There are long pieces (18’-24’) laying loose on the helix cork right now. If you go by the club  to take a look, please be careful of the temporary track placement and high bridge. 

In general, the work is progressing very nicely and somewhat ahead of schedule. There are many other things happening we don’t have room for (or time to write about) this week – Patrick’s town development, the Eagle Cove barge slip, and an almost finished mainline. 

Doug demonstrates complicated and accurate cutting and sanding as he fabricates parts. We haven’t  figured out what this is but it sure looks good.