Section 14 - Satsop River Bridge - Part 1

Its time to layout the Satsop River section. The layout design given and druthers of this section is indentified in Station 14 Satsop River.

Design Elements

 This section consists of eight layout design elements:

1. A darkened cloudy sky suggesting inclement weather is approaching. 
2. A mid distant tree line and visible riverbank.
3. A shallow river with significant sand and gravel on the river bottom and sides.
4. A 5 bent wood trestle and a wood abutment. 
5. Two 16 panel plate girder bridges
6. Two 10 panel plate girder bridges
7. 4 unique piers 
8. A concrete abutment for one of the 16 panel bridges.

In addition I added two additional layout design elements to reflect the logging operations that occurred in the area prior to the time period modeled: 

1. A 26 inch curved spur at the right (south) end of the module connecting to the Polson Canyon Module formerly OPLC Camp 7 that was closed in 1932.
2. A 26 inch curved leg wye at the left (north) end of the module connecting to the Basalt Module, formerly OPLC Camp 9 that was closed and the site leased to Basalt Sand and Gravel. 

Section Construction

See the WWSL section construction reference page for the construction technique. 

As this section is a river scene I have modified the construction technique. Instead of using the two 1x3 girders on the bottom of the section, I need a solid bottom on the section for the riverbed. The 1x3 girders are replaced by a 2 foot by 8 foot piece of plywood 3/4 inches thick. The two ends of the section are cut out to permit attachment of the section electrical connectors and section interface bolts. 

 The remainder of the section is built per WWSL construction standards.

Scenery Design Considerations

1. The backdrop available for the Satsop River Bridge Section is 22 inches in height. With the bridge height at approximately 4 inches, and the roadway centered at 12 inches on the module, a 45 degree angle would suggest that the background trees painted on the backdrop could be 8 to 12 inches in height. This would then allow 10 inches of cloud/sky. Rainclouds would cover about 5 inches of this cloud sky space.

2. The background land mass can be observed both in the picture and on the module. I am using styrofoam insulation, and the smallest thickness of foam is 1/2 inch thick. This is a good height for the edge of the distant river bank, and an additional two and half inches in height three inches deep from the backdrop will give sufficient room for a line of trees and shrubs adding depth to the backdrop painted trees, and several inches of depth to plant the trees without them falling over.

3. The river will be approximately centered on the module and will disappear to the right rear. The river bank will be a slow rise to the left and a fill embankment to the right. The river bottom is composed of a large number of various sized stones and gravel. I have from a previous layout about 2 gallons of bluish grey kitty litter than can be readily sifted for size and placed appropriately. A shallow pour of properly tinted resin will round out the overall look and feel of the module.

ROW Design Considerations 

The most critical design considerations on this section is the length of the bridge. With only 96 inches of linear space to model two curved legs, two river banks and and 5 bridges, something has to be compressed. 

First I looked at the two curved legs. At Basalt, the 26 inch radius curve needs to connect to a tangent track located 10 inches from the front fascia. That means that 16 inches of space is needed on this section for the north wye design element. At Polson Canyon, the 26 inch radius curve needs to connect to a tangent track located 16 inches from the front fascia. This means that 10 inches of space is needed on this section for the south main line and the abandoned spur track. A total of approximately 26 inches is needed for the curved main line components. That leaves us with 70 inches of tangent mainline track for the five bridges. See Satsop River Bridge N5 for the baseline construction details.

4. I pulled up a construction diagram of a timber trestle built by the Southern Pacific.  That diagram has each bent a distance of 15 feet apart. In HO scale that's a bit less than 2 inches per bent. Five bents and a wood abutment is about 10 inches. See Satsop River Bridge N5a for construction details.

5. I am planning to kitbatch the plate girder bridges. I have eight Atlas Thru Plate Girder Bridges, six of them have 10 identically spaced steel plates, the other two have 10 steel plates of different widths. I chose to use two of the 10 panel bridges to represent the 16 panel bridges. This is a 38% selective  compression of the bridge scene. All i need to do is shorten the height of the two bridges by approximately 1/3rd. Total length of those two bridges will be 18 inches. See Satsop River Bridge N5b for construction details.

6. Using the selective compression percentage above, I will need to add (rounded up) 4 panels to each of the two 10 panel bridges to represent the 20 (modeled 14) paneled panel plate girder bridges. Total length of those two bridges will be 25 inches. See Satsop River Bridge N5b for construction details.

7. There are 4 interesting piers to be constructed. Three are wood pile bents, one is a steel pile bent. They will have to be kitbatched. See Satsop River Bridge N5c for construction details.

8. The concrete abutment will have to be designed to reflect the dimensions of the embankment constructed. See Satsop River Bridge N5d for construction details.

Adding all those bridge lengths gets me to about 53 (18+25+10) inches, with a leeway of about 17 inches for  'off the bridge tangent track' leading into the curves at each end.

Laying out Right of Way

I am not going to go into great detail about putting down the roadbed lines. See the Right of Way Reference Page  for the details if you haven't had the fun to do it before. 

Essentially you're going to follow this process: 

1. Lay out the main line. I centered it at the 12 inch line.
   
2. Lay out the transition template line.
   
3. Lay out the main line curves. Layout the abandoned wye and spur curves. 
4. Lay out the bridge template, the length of the bridge and adjust as necessary.
5. Lay out the south embankment leading to the bridges. 
6. Locate the abutments and piers (to include heights).
7. Layout the sloped river bank on the north side of the river.
   

Because this section ties into both the Section 15 - Basalt and the Section 13 - Polson Canyon, some layout of those sections will need to be done at the same time, primarily the main line locator at Basalt (10 inches from the fascia) and the northernmost Polson Canyon curve (16 inches from the fascia ).  

In the next blog (Section 14 - Satsop River Bridge Module - Part 2) I will discuss the Landform Design Considerations.