Category Archives: Structures

Adding details and lighting to highway underpass

Finishing the highway underpass leading out of town. I added led lighting and safety railings, as I have made the sidewalks higher above the road surface.

strip light and connector

self adhesive LED strip light and connector

Here the railings have been added and some random trash added. (might add more later)

almost ready to install

almost ready to install         

View from road under the bridge showing lights, railing and a poster on the wall

Under the bridge

Under the bridge

Will add a wall surface from sidewalk to the Road before installing the underpass

 

 

Cast Concrete arch bridge

 

Picking back up on a much earlier post, I finally started casting my concrete arch hydrocal bridge in two halves.

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Wood & Sintra Mold

My waxed wood and sintra casting form

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Wood & Sintra mold showing thickness

Pouring hydrocal with steel rod reinforcements

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Pouring requires working quickly as Hydrocal sets fast

Leveling  to the face of the form

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Level as close to flat as possible

Exterior pieces of the form being removed

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Exterior parts remove easily

Casting removed from the mold and flipped over, with only the individual small arch pieces to be removed. These pieces have a 3 degree slope for ease of getting them out of the piece.     Still required a few knocks with a small hammer on each to remove!

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Casting lightly sanded at this point

First half cast, but I’ll add some detailing with a file, forming casting joints and other details, then cast the other half and place them back to back, with a spacer which is typical for this type of bridge, really two identical arches, connected at the top.

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Casting before final detailing

 

Pop-up access scenery sections

 

Having made 4 pop-up areas in my layout for access to track etc, I made foam plugs to sit on strips in the access holes to support the scenery, or town, or hill. The foam is light and  sturdy.

Layout of town on section

Layout of town on section

Here is the first section that will hold part of the town on my layout, in this case using a large sheet of styrene for the roads that lap over the joints of the plug to conceal it once settled into
the pop-up area.

Adding Styrene for roads and sidewalk

Adding Styrene for roads and sidewalk

Access area to be filled with section

Access area to be filled with section

I also put some large bolts that will be hidden inside removable buildings, that make it very easy to lift the section from the area.

Setting section in place

Setting section in place

Test fitting the soon to be town

Test fitting the soon to be town

A Test Casting

Shown here is a test casting, in Hydrocal, of a section of the concrete arch bridge. I wanted to test how the plaster would exit the mold. It was difficult, even in this small section, and even though I had built the mold with a 3 degree taper for the pieces forming the small enclosed arches. The outside pieces of the mold all are removable and that was fine, so I decided to make each of the individual small arch pieces separately removable, so one by one they can be eased out of the whole piece. Hopefully I will have a photo of a completed full casting sometime in the near future. I was pleased by the look of the piece and anxious to see a whole side intact!

Test section

Concrete Arch Bridge Test Sectional casting

Bridge Building

Designing my layout, I wanted to incorporate different types of bridges (I suppose that’s a thought of many model railroaders), but I wanted to design some of my own bridges in a freelanced but believable way. There are a number of concrete arch bridges in my area of NW Philadelphia including the Walnut Lane Bridge and the Henry Avenue Bridge, both Highway spans but seemingly constructed very similar to many railroad bridges of the same type. I also referred to the terrific book “Bridge and Trestle Handbook” by Paul Mallery to keep me building a basically sound engineered structure.

The Drawing shows my design for a concrete arch bridge to span a gorge that will be right in the front of my layout.
The photo shows the form I built to cast the bridge (actually half the bridge) as two castings back to back will form the bridge.
The form is made from Wood and sintra.

Bridge Drawing

Concrete Arch Bridge Drawing

casting mold

Arch Bridge casting mold

Bricks

Some thoughts on plastic model brick painting.
Working on some DPM kits I decided to dry brush brick faces after base painting the whole structure with a mortar color.
I think this does work pretty well but is very time consuming, if you are being careful not to get too much paint on the brush, so it does not run down into the mortar. I want to try some other methods including the Roberts Mortar, and see if it works as well and is quicker.
There also was an article in RMC or Model Railroader about washes of color for stone and brick, a short time ago that seemed really good, but I can’t seem to find it. Anybody remember an issue about this?

Dry Brushed Bricks

Dry Brushed Bricks