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Erik C Lindgren posted:

I'm blushing Matt 

oh it's completely prototype and a complete story line behind it. When I get time I will elaborate. 


Thank you 

Makes me want to revisit a spot on the old Redlands Loop where the ATSF line paralled the SP line to Crafton. There were two small bridges across a creek -- one a full wooden trestle (ATSF) and the other more modern for the SP line (probably wood with concrete footings. The ATSF trestle is a ruin but is still there; all that's left of the SP bridge is the footings.

Eric....I have that same through plate girder bridge but in black.   What a beautiful model!    I've talked to Peter through that famous auction site about doing these with square end girders, and he is going to look into possibly doing these at some point in time........   Please keep us posted with pictures as you make progress in your project.

Erik and i discussed some ideas and he made a sketch (above) and i set out to design and build the modules to support it.  Comments were made about prototype accuracy,  so Erik did some research.  Guess we didn't miss it by much judging from the photos he found.  Stay tuned,  there may be a 3rd rail in the picture yet!  Prototype: Alamosa/Antinito line of the D&RGW,  San Luis valley branch.

AGHRMatt posted:


Do you have any photos of the framing under the foam in the bridge module set? I'm curious how the foam is supported.

I responded to John for you he will likely show you what's involved in the design. 

This is from his article about the engineering earlier last year:

Lightweight Module Construction

A little history here will explain why this type of module construction came to be. Forty years ago N Trak was breaking a lot of new ground with the idea of modular layouts. They could be set up and displayed in many venues previously unavailable, like shopping malls. The hobby shop with the layout in the front window was getting rare and shopping malls were the the new meccas of retail trade. A lot of modeler got their start with these groups.

My club at the time was building a HO layout based on Marin County railroads in an old dairy barn. We decided to build a modular layout to display at the county fair. Construction was based on the N Trak standards, 1x4s with 1/2” plywood top. Sturdy but not very light. Legs were an issue as it was difficult to prevent swaying when they were leaned upon without getting involved with a lot of bracing. I even drilled lightning holes in th 1x4 crossmembers (actually 1/2”x4” plywood) in an effort to cut some weight. Later the 2x2” legs were replaced with 3/4” EMT conduit with angle braces to improve stability. Both efforts were marginal improvements.

My next effort was based on 1/4” plywood. Sides and ends were laminated with extra plys where the strength was needed. Legs were folding 2x2s. Not bad, it was lighter and easier to set up but still not quite right.

With my move to Colorado and switching to 1/4” scale came the opportunity to start over. Everything module effort to date had multiple toos problems:
too heavy
too fragile
too difficult to set up

Experimenting with a portable F scale layout introduced some new ideas. First to go was the legs, simple sawhorses under the joints replaced attached legs. Set up time was dramatically reduced. Next to go was the bolts/C clamps tyeing the modules together.





to continue about construction of modules:

We use spring clamps w/ locating dowels between sections,  quick and easy.

Actual module is 2" insulation extruded foam (not white beaded stuff) that comes in pink or blue,  depending on manufacturer.  Default module width is 22".  Beam strength is provided by 2 3/4" strip of 5mm underlayment plywood on each side.  End boards a 3/4" lumber to provide strength for dowels & clamps.  Stringers of 3/4x3/4 wood are used about every 12" to control sag between sides.  This is where the 2 3/4" side depth comes from.  Titebond used for wood/wood joints,  foam/wood joints are secured w/ our secret ingredient, Gorilla glue!  This results in a bonded structure that resists twisting and bending.  A 5' module will support my weight in the middle (165#) with very little sag.  A bare module weights appox 5#.  #12 bare copper busses are strung under the track for feeders,  SAE 4 prong plugs (trailer connectors) connect each module.  Two Pony 2404 or equivalent spring clamps grip lower lip at joints where a lightweight sawhorse supports the joint. 

Two plywood boxes (24x24x40") were added to the center of each side of our 9x35' layout for added stability.  A casual bump doesn't phase it.  They also serve as control stands and power centers.  A fixed clamp joins two modules on top and electrical connectors tie into the buss.

We will work on making a video of the construction process.  Construction time is about an hour of actual work,  added time for glues to set.  Assembly is done on a fixture to insure squareness and assist clamping.  Further questions can be submitted to our website:,  contact us form.

Setup time for 16 modules is about an hour for one person,  longer with help.  Track ends at module edge,  rails are soldered to screws or nails in the sub-roadbed (spline).  This method has been in service for over a year (5 shows) w/o any problems.





Showing the authenticity in these fine brass bridge models. 


Timber supports will be in place of the red painted piers in this photo. 


Flex track laid in place for reference only  

John johnson has begun the track work phase of the bridges. We ordered Mt Albert bridge ties and other lumber for the project. 

Bill of Materials 

MA335P24 8x14 will double up for 14x14 pile cap 
MA342P24 10x18 stringers 
MA319P24 3x12 sway bracing 
MA322P24 4x8 guard timber 
MA324P24 4x12 shoring timbers 

MA382 8x8x10' bridge ties (500) 

Dowels will suffice for the bridge piling. 

We continue .... 



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Last edited by Erik C Lindgren

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