Sunday, October 30, 2022

Section 14 - Satsop River Bridge - Part 2

In the last blog (Section 14 - Satsop River Bridge - Part 1) I identified the layout design elements of the Satsop River Bridge Module and laid out the roadway lines. 

In this blog I am identifying the scenery construction concept and laying out the landforms.

As a refresher, here are the scenery 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 sloped bank on the north side of the river.
  5. An embankment on the south side of the river.

Scenery Design Considerations

Background. 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.

Once the bridges were build and temporarily placed I can shape the river and the river banks, adding foam as necessary to reach the bridge abutments. 

Mid-ground.

The river will be approximately centered on the module and will disappear to the right rear. The base of the river will be the 3/4" plywood base. The river bank will be a slow rise to the left and a fill embankment to the right, and a background land mass. 

Background land mass.  My initial plan was to use only extruded polystyrene insulation but realized that should I have to move the section, the mid-distant land mass would break loose. I have chosen instead to use a 1/8 " luan panel to anchor the landmass. The panel is sized to the height of the riverbank on both sides (approximately 4 inches) and about 6 foot long.. It is anchored to the benchwork with L shaped anchors. The riverbank will be 1/2 inch thick polystyrene . 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 base 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. See 5.5.7 Three Dimensional Backgrounds for construction details.

North river bank. The north river bank (left) is a natural occurring slope. I found a picture of the timber trestle bridge being used by the Mount Rainier Scenic Railroad. The slope is essentially flat for quite a distance. I will selectively compress the distance and create a greater slope. The 2 inch polystyrene is cut at about a 20 degree angle to model the slope with the base reflecting the effects of erosion caused by the occasional high river in spring. Building the trestle in advance is indicated in order to locate and cut in.the north abutment, and locate and place the trestle piles. 

South river bank.  The south river bank (right) is a man-made embankment. The AREA standard for an embankment is a 60 degree angle from the edge of the roadbed to the river bottom. I'm cheating a little bit by cutting the foam terrain on the backside of the embankment to a sharper slope while the visible side is AREA standard. See 4.1.1.2 Embankments for construction details. Using to total length of the bridge complex, I will locate the south abutment and cut it in. Pieces of polystyrene and expanding foam will complete the basic land form.

Foreground

This section's foreground is the Satsop River. The river bottom is to be gravel strewn. I have two gravel sources: 1) an unknown brand of gray kitty litter, and  2) a bag of Quikcrete general purpose paver mix. I am not sure yet what product will be ultimately used, probably both - the kitty litter for the water covered gravel bottom, the paver mix for the dry rock shoreline.

The critical piece of river construction will be the location of the bridge piers. A wood footprint of each pier type will be constructed and temporarily screwed into the section base from below. 

The water product is also undetermined. I have not poured a river yet, and am not sure whether epoxy, decoupage resin, or a Woodland Scenics product will be right for the river. It all depends on how the gravel bottom looks (dark and wet enough to pass as gravel).  The river's edge is a continuation of that product at double to triple thickness (depending on the distance from the river's edge. 

Because this is a wide shallow waterway, I am using stream construction techniques. See Streams for construction details.

Ground Cover

1. All land forms will be initially covered with will be covered with sculptamold. 

Soil color is to be determined based on the Northern Division Overview color scheme.

2 Far ground cover

3 Near ground cover

Vegetation

 Far land form Sparce tree line with some indication of previous logging activities 

Near land form - ground cover, shrubs, small trees


Other scenery aspects will be discussed in Section 14 - Satsop River Bridge - Part 3.

Sunday, October 16, 2022

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.

Layout Design Elements

The Satsop River section adjoins the Basalt Sand and Gravel section to the north and the Polson Canyon section to the south. This section has of eight layout design elements: (from backdrop to fascia):

  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.
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.


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. 
  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 ).  .

Laying the track.  The 1st (North) Division is WWSL Medium Profile Roadway. See 4.2.11.2  Modeling Technique for Medium Profile Roadway for details. 

See 4.2.3 Straight Track and 4.2.4 Curves for construction details.

Laying out the Structures 

There are no major structures on this section.

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