BUILDING RGS BRIDGE 45-B

By Bob Hyman

UPDATED: 02/07/02. This is an updated version of the previous article of the same title.

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Abstract

This is a "how-to" article for building a highly detailed model of one of the most famous high line bridges on the Rio Grande Southern railroad. A section on jigs and molds gives valuable information for making and using these handy tools that simplify model bridge building. The article contains very detailed step-by-step instructions for preparing plans, fabricating the various sub-assemblies, and assembling the completed trestle. Some of the drawings contained in the article are drawn to scale and can be used as templates for making various components. The tips and techniques clearly explained in this article will provide the modeler with valuable information for building this and other RGS trestles.

Introduction

Bridge 45-B was located on the Ophir Loop, just south of the depot. It crossed the Howard Fork of the San Miguel River on a 24-degree curve and 2% grade. No other curve on the RGS was tighter, although the curve at the upper end of Trout Lake at Bridge 51-A was just as tight. Bridge 45-B was unique in that it had a pedestrian walkway beside the track on the inside edge of the curve.

The original bridge was 112 feet long and 24 feet high. It consisted of eight bents placed sixteen feet on centers. In 1919 the bridge was reported as108 feet in length. This corresponds to the timeframe (1914-1918) when the other Ophir trestle, Bridge 45-A, and several of the other high line bridges were extensively modified.

The modification to Bridge 45-B shortened the distance between the last two bents (#7 and #8) to twelve feet. This is probably also when the pedestrian walkway was added, the concrete foundation was placed under bent #4, and the guard rails moved from the inside to the outside of the running rails. Judging from photographs of the bridge after it was modified, it does not appear that the end panel between bents #7 and #8 was actually shortened. I think that another bent (call it Bent #8A for reference) was simply added between bents #7 and #8. The pedestrian walkway ended at the new bent #8A.

My completed model represents Bridge 45-B as it would have appeared in the 1939 timeframe. This model is applicable for most RGS layouts from the 1920’s through the end of operations. The hand railing on the pedestrian walkway was repaired several times over the years, and looks slightly different in various photographs.

Part 1. Prototype Trestle Construction

Stringers

The bridge engineers had to make some adjustments when building a bridge on a curve this sharp. The three 8" x 18" stringers that made up each of the bridge beams were staggered and spanned two panels each, just as they were for most trestles. However, they were not parallel, as they would be in a tangent (straight) trestle.

Figure 1 - Curved Trestle Stringer Arrangement

On a 24-degree curved trestle like bridge 45-B, the center stringer of each beam was angled. To accommodate this arrangement, the beams were about 36 inches wide and were spaced only a foot apart. This resulted in a total deck width of about 84 inches when measured from the outside edge of one beam to the outside edge of the other beam. With the beams resting on the tops of the 14-foot long bent caps, this resulted in about 42 inches of exposed cap on each side of the beams at bents #1, #3, #5, #7, #8, and #8A. On bents #2, #4 and #6, the exposed portion of the bent cap on the outside curve side would be slightly greater than 42 inches and the exposed portion on the inside curve side would be slightly less than 42 inches (approximately a six inch difference.) The 9-foot long bridge ties overhung the beams by an average of twelve inches on each side.

Tie Placement

The 8" x 8" x 9’ bridge ties were laid 12 inches center to center, which is typical for RGS trestles. This results in a 4-inch spacing between the ties. The ties were not perpendicular to the beams; they were laid perpendicular to a chord drawn between the midpoints of each bent cap. The track centerline also passes through these same midpoints. Viewed from above with the ties in place, the trestle deck appears to be constructed of seven straight segments, with angled joints above each of the bent caps.

Curve Radius

Bridge engineers use basic trigonometry to layout prototype curves. They reference curves using a term called "Degree of Curvature". To convert degree of curvature into an actual curve radius, simply take the sine of ½ the degree of curvature and divide it into 50 feet. The result will be the prototype radius in feet. To find the model radius, just multiply the prototype radius by the scale. The 24-degree curve of the prototype represents an actual curve radius of about 240 feet. My model trestle is built in S Scale (1:64) and scales out to a 45-inch radius. In the case of Bridge 45-B in S Scale, the computation is as follows:

	Sine of 12° = 0.208 (rounded to three decimal positions)
	50 feet / 0.208 = 240 feet (rounded to nearest foot)
	240 feet x 1/64 = 3.75 feet or 45 inches

Panel Configuration

The portion of a trestle between two bents is called a panel. Bridge 45-B was composed of eight bents (nine, if you count bent #8A) and seven panels. Since the number of panels is uneven, the beam configuration does not appear perfectly symmetrical when viewed from the sides. The odd panel was at panel #7 on the south or uphill end of the trestle (toward Rico), between bents #7 and #8.

Figure 2 - Panel Configuration

When viewed from the side, the trestle appears to have three equal 32-foot beams between bents #1 and #3, between bents #3 and #5, and between bents #5 and #7. The odd panel appears as a 16-foot beam between bents #7 and #8. Of course this is only how the beams look from the outside; the middle stringer in each beam is staggered between bents #2 and #4, between bents #4 and #6, and between bents #6 and #8, with the short middle stringer between bents #1 and #2.

Pedestrian Walkway

The supports for the walkway consisted of twenty-eight 4" x 8" x 12’ timbers placed between the ties at every fourth tie, starting at bent #1 and ending at bent #8A. They extended out about four feet past the tie ends on the inside of the curve. Three 3" x 12" floorboards were nailed to the 4" x 8" supports to form the walkway. The vertical handrail posts were four foot lengths of 3" x 6". The horizontal railings were a combination of 3" x 12" and 3" x 6" boards. A 3" x 6" cap ran along the tops of the posts.

Figures #3 and #4 show how the walkway was attached to the trestle. The stringers that form the beams of the deck are visible between the ties for reference. On the actual trestle, the beams were covered with #22 galvanized sheet metal and the individual stringers would not be visible. Also, note how the ends of the walkway support timbers were butted up against, but did not extend under, the guard timbers on the outside edge of the trestle.

Figure 3 - Pedestrian Walkway Cross-Section View

Figure 4 - Pedestrian Walkway Overhead View

Bents

On a straight or mildly curved trestle, the two vertical posts within each bent were typically spaced 36" center-to-center. On Bridge 45-B, the two vertical posts of each bent were spaced 48" center-to-center, probably due to the wider beams. This causes the trestle to have a short, squat appearance when compared to other bridges. Like most curved trestles, the angled posts of each bent were 3 in 12 batter. This means they spread 3 inches for every foot of height.

One other difference was the bent caps; on 45-B they were 12" x 12" x 14’ as opposed to the normal 12" x 14" x 14’. Other than these unique differences, Bridge 45-B followed typical RGS bridge building practices: 12" x 12" posts and sills, 3" x 12" diagonal cross bracing, 8" x 8" x 9’ bridge ties, and notched 5" x 8" guard timbers.

The bents in Bridge 45-B were all single-story. Bents #1, #8, and #8A did not contain any posts. All bents except bent #4 rested on timber footings made from 3-foot lengths of leftover 12" x 12" post material. Bent #4 rested on a concrete footing. The following figures show Bents #1 through #8A.

Figure 5 - Bent #1

Figure 6 - Bent #2

Figure 7 - Bent #3

Figure 8 - Bent #4

Figure 9 - Bent #5

Figure 10 - Bent #6

Figure 11 - Bent #7

Figure 12 - Bent #8A

Figure 13 - Bent #8

Part 2. Model Trestle Construction

Note: Any scale dimensions given in this section are for an S Scale model. Where prototype dimensions are given, the equivalent model dimensions are sometimes shown in parentheses for clarity.

Material Preparation

You will need the following sizes of scale timbers:

	8" x 18" Stringers
	12" x 12" Caps, Posts, Sills, Footings
	3" x 12" Cross Bracing, Walkway Floor Boards, Walkway Railing
	3" x 6" Walkway Railing, Walkway Posts
	4" x 8" Walkway Supports
	5" x 8" Guard Timbers
	8" x 8" Ties
	4” x 12” Dump Boards

Prepare the materials as explained in steps 1 through 5.

Step 1. Obtain and Prepare the Wood

After you have purchased or cut the required sizes of timbers, you need to prepare the wood. Distress, age, paint, stain, weather, or otherwise "doctor" the wood according to your preferred method. No one seems to agree on the best method but here's how I did mine:

	First, I rubbed the surfaces of each timber lengthwise with a file card to add grain texture. The file card is a stiff, short-bristled, wire brush used to clean files. It is sometimes called a file cleaner.
	Then I stained each timber with Minwax brand water-based wood stain; Colonial Pine color. I brushed on the full strength stain, allowed it to dry for a few minutes, then wiped the timbers with a damp rag to remove the excess. At this stage the timbers will be a nice, soft brown color.

Note: For items where multiple, identical-sized, short lengths are required (like the ties or foundation timber blocks), I cut the pieces to length and stain them all at once by dipping rather than brushing. This saves me the bother of touching-up the cut ends later. You will need 113 ties (8" x 8" x 9') and 144 foundation timber blocks (12" x 12" x 3'.) When dipping, I thin the stain about 50 /50 with tap water. Rather than wiping each individual piece with a rag, I simply take the stained pieces and rinse them under running water to remove the excess stain. Shake off the excess water, place the pieces in a large paper bag, then shake the bag to remove the surface moisture and to keep the pieces from sticking together. Empty the damp pieces from the bag onto a paper towel, and microwave them at high heat for about 30 seconds to 1 minute, or until they are slightly warm to the touch. Spread them out on a piece of newspaper and they will dry quickly.

Next I brushed each timber with a coat of A-West "Weather-It" to tone down the brown color and add blackish gray surface highlights.

Note: Again, for the small pieces, I used the dip, shake and "nuke" method.

	During assembly, after cutting the various sized timbers to the required lengths, I touched-up any unstained cut edges before gluing them together.
	Finally, after the major components such as the bents and deck were assembled, I brushed on a solution of India ink in alcohol (about 25 drops per ounce.) The ink ran into the cracks and crevices of the timbers scratched by the file card and accentuated the simulated grain texture.

Step 2. Prepare the Sheet Metal Pieces

You will need material for the #22 galvanized sheet metal flashing that goes between the bridge beams and the ties, and also on the exposed bent caps. I used Avery #6873 white shipping labels for color laser printers and copiers. These labels are 2” x 3 ¾” each. Eight labels are on each 8.5” x 11” page. You can also use regular white 20-pound bond typing paper. Color print or paint the paper pieces with rust and grays shades. The advantage of using the shipping labels is that they are a “peel-and-stick” item. If you use plain paper, you will need to glue the paper to the wood with Elmer’s White glue or equivalent. Use whatever material you feel most comfortable with to duplicate the sheet metal.

	Make 14 strips 3' wide x 17' long (9/16" x 3 3/16".) You will use these for the flashing between the beams and the ties.
	Make 18 strips 18" wide x 52" long (9/32" x 13/16"). You will use these to cover the exposed bent caps.

Step 3. Fabricate the Concrete Foundation for Bent #4

Bent #4 rests on a concrete footing. I made mine from plaster, poured into a mold made from strip wood. This allowed the wood grain from the mold to appear on the concrete, just as on the prototype. Here are the dimensions of the concrete footing:

Figure 14 - Bent #4 Concrete Foundation

Note: The mold and directions for its use are described in the JIGS AND MOLDS section of this article.

Step 4. Obtain and Prepare the Rails

You will need two pieces each of code 40 and code 55 rail. These typically come in 3-foot sections. The code 40 rail represents the 30# guard rails. The code 55 rail represents the 57# running rail.

Note: If you would rather use larger rail sizes, you can go up to code 70 for the running rails and code 55 for the guard rails without looking too much out-of-scale. Just remember to keep the relative size differences between the running rails and guard rails.

Paint the rail a rusty-brown color. (I used weathered rail so I wouldn't have to bother painting it.)

Step 5. Obtain and Prepare the NBW Castings

	Obtain and paint 56 NBW castings for the beams. I used Grandt Line, HO Scale #5099 (3" Nut & 4 1/2" Washer). In S scale, this represents a 2 1/4" Nut & 3 3/8" Washer.
	Obtain and paint 74 NBW casting for the guard timbers. I used Grandt Line, O Scale #62 (7/8" Nut & 2" Washer.) In S scale, this represent a 1 1/8" Nut & 2 5/8" Washer.
	I painted mine a dark earth color, and then weathered them with rust while they were still attached to the sprues.

Deck Plans

The easiest method for assembling a trestle is to mount scale plans on a flat surface and to build the trestle directly on the plans. You will need two versions of the deck plan; one in normal view (viewed from above) and the other in reversed view (viewed from below.) You will need two copies of the reversed view and one copy of the normal view. Draw the plan as explained in steps 6 through 11. This will result in a reversed view plan.

Step 6. Layout the Track Centerline and Bent Positions #1 - #8

Figure 15 - Track Centerline Drawn and Bent Positions #1 Through #8 Marked

	Begin by laying out the 45-inch (240-foot) radius arc that will represent the track centerline.
	Mark the arc at eight points in 3-inch (16-foot) increments.
	Label the marks as Bent #1 through Bent #8 going from right to left.

Step 7. Layout the Chords and Bent Position #8A

Figure 16 - Chords Drawn and Bent Position #8A Marked

	Draw reference lines between adjoining marks on the arc to locate the seven panel chords. These chords should be exactly 3 inches (16 feet) long.
	On the panel chord between the marks for Bent #7 and #8, measure ¾" (4-feet) from the mark for Bent #8 and make another mark. Label this mark as #8A.
	Draw reference lines between the marks for Bents #1 and #3, Bents #3 and #5, and Bents #5 and #7 to locate the exterior stringer chords. These chords should be slightly less than 6 inches (32 feet) long.
	Draw reference lines between the marks for Bents #2 and #4, Bents #4 and #6, and Bents #6 and #8 to locate the interior stringer chords. These chords should be slightly less than 6 inches (32 feet) long.

Step 8. Layout the Bent Cap Positions and the Tie End Lines

Figure 17 - Bent Cap Positions and Tie End Lines Drawn

	Lay a straightedge between the arc center point and the mark for Bent #1 and draw a reference line through the mark, extending 1 5/16" (seven feet) on either side of the arc. Repeat for remaining eight marks. These reference lines represent the centerlines of the 2 5/8" (14-foot) bent caps. They will also be the cut line for all stringers that end at bents #2 through #7.
	Draw the outlines of the bent caps sides by drawing lines parallel to each of the nine bent cap centerlines and spaced 3/32" (6-inches) on either side. Connect the ends of the side lines to outline the bent cap positions.
	Next draw reference lines parallel to the seven panel chords and spaced 27/32" (4 1/2 feet) on each side. These lines represent the ends of the 1 11/16" (9-foot) ties.

Step 9. Locate the Long Interior Stringers

Figure 18 - Long Exterior Stringers Drawn

	Each beam is composed of three stringers: two exterior stringers and one interior stringer.
	The exterior stringer on the outside of the beam (the side facing the tie ends) is called the outer exterior stringer.
	The exterior stringer on the inside edge of the beam (side facing the other beam) is called the inner exterior stringer.
	The inner exterior stringers are always 3/16" (1 foot) apart.
	To locate the long inner exterior stringers, draw lines parallel to the exterior stringer chord and spaced 3/32" (6-inches) on either side. Now draw another set of lines parallel to the exterior stringer chord and spaced 7/32" (14-inches) on either side. These sets of parallel lines locate the edges of the 1/8" (8-inch) wide inner long exterior stringers.
	The outer exterior stringers are always spaced 5/16" (20-inches) from the inner exterior stringers. To locate the long outer exterior stringers, draw lines parallel to the exterior stringer chord and spaced 17/32" (34-inches) on either side. Now draw another set of lines parallel to the exterior stringer chord and spaced 21/32" (42-inches) on either side. These sets of parallel lines locate the edges of the 1/8" (8-inch) wide long outer exterior stringers.
	These stringers end at the centerlines of bent caps #7, #5, and #3, and at the right edge of bent cap #1.

Step 10. Locate the Long Interior Stringers

Figure 19 - Long Interior Stringers Drawn

	The long interior stringers of each beam alternate back and forth; touching the outer exterior stringer at one bent and the inner exterior stringer at the next.
	To locate the long interior stringers, draw lines parallel to the interior stringer chord and spaced 5/16" (20-inches) on either side. Now draw another set of lines parallel to the interior stringer chord and spaced 7/16" (28-inches) on either side. These sets of parallel lines locate the edges of the 1/8" (8-inch) wide long interior stringers.
	These stringers end at the centerlines of bent caps #6, #4, and #2, and at the left edge of bent cap #8.

Step 11. Locate the Short Stringers at Trestle Ends

Figure 20 - Short Stringers Drawn

The short stringers at either end of the trestle are parallel to the panel chords.

On the Bent #8 end of the bridge, the short stringers are the four exterior stringers.

On the Bent #1 end of the bridge, the short stringers are the two interior stringers.

To locate the short inner exterior stringers at the left (Bent #8) end of the trestle:

Draw lines parallel to the panel chord between bents 7 and 8 spaced 3/32" (6-inches) on either side.

Now draw another set of lines parallel to the panel chord between bents #7 and #8 spaced 7/32" (14-inches) on either side.

These sets of parallel lines locate the edges of the 1/8" (8-inch) wide short inner exterior stringers.

The short inner exterior stringers end at the left edge of bent cap #8 and the centerline of bent cap #7.

To locate the short outer exterior stringers at the left (Bent #8) end of the trestle:

Draw lines parallel to the panel chord between bents #7 and #8 spaced 17/32" (34-inches) on either side.

Now draw another set of lines parallel to the panel chord between bents #7 and #8 spaced 21/32" (42-inches) on either side.

These sets of parallel lines locate the edges of the 1/8" (8-inch) wide short outer exterior stringers.

The short outer exterior stringers end at the left edge of bent cap #8 and the centerline of bent cap #7.

To locate the short interior stringers at the right (Bent #1) end of the trestle:

Draw lines parallel to the panel chord between bents 1 and 2 spaced 5/16" (20-inches) on either side.

Now draw another set of lines parallel to the panel chord between bents #1 and #2 spaced 7/16" (28-inches) on either side.

These sets of parallel lines locate the edges of the 1/8" (8-inch) wide short interior stringers.

The short interior stringers end at the centerline of bent cap #2 and the right edge of bent cap #1.

The deck plan is now complete. Make a copy of the plan and label it as "REVERSED VIEW PLAN."

Make a mirror image copy of the plan and label it as "NORMAL VIEW PLAN."

Deck Assembly

Assemble the bridge deck as explained in steps 12 through 15.

Step 12. Cut and Assemble the Stringers Into Beams

	Attach the original reversed view copy of the deck plan to a flat work surface. I used masking tape to attach the corners of the plan onto piece of smooth 1/4" hardboard.
	Cut a 1/8" x 9/32" (8" x 18") stringer to fit over each stringer in the plan, using the appropriate position of the angle cut jig.

Note: The angle cut jig and directions for its use are described in the JIGS AND MOLDS section of this article.

Drill #71 holes in the outer exterior stringer of each beam to accept the NBW castings.

Notes: The NBW positioning jig and directions for its use are described in the JIGS AND MOLDS section of this article. You can also drill holes for NBW castings on the inner exterior stringers if desired. These inside NBW castings would be almost impossible to see on the completed trestle. I left them off on my model. If you decide to add them, you will need an additional 56 #5099 NBW castings.

	Touch-up any unstained cut edges of the stringers.
	Glue the stringers to each other and to the plan with small drops of Elmer's wood glue. The deck is constructed upside down, so the surface of the stringers glued to the plan will eventually be covered by the sheet metal flashing and the ties.
	After the stringers are assembled into completed beams, slide a razor blade between the plan and the beams. Discard the plan.
	Sand the surface of the beams smooth to remove any glue or paper residue.
	Add NBW castings to the beams at each bent position in the previously drilled holes.

Step 13. Add the Sheet Metal flashing to the Beams

	Attach the normal view copy of the deck plan to the work surface.
	Glue the beams onto the plan with small drops of Elmer's wood glue at each end bent location.
	Starting at the left (Bent #1) end of the beams, glue 9/16" x 3 3/16" strips of simulated sheet metal flashing to the tops of the beams. Trim the strip ends at the Bent #3, #5, and #7 centerlines. Trim the last pieces at the right (Bent #8) end of the beams.

Step 14. Add the Ties, guard Timbers, and Walkway Supports

	First, glue ties to the beams directly above bent caps #1 through #8 (not at Bent #8A.) These eight ties are aligned parallel with, and centered over, the bent caps and fit between the tie end reference lines on the plan.
	Next, fabricate fourteen guard timbers using the notch jig.

Note: The notch jig and directions for making guard timbers are described in the JIGS AND MOLDS section of this article.

	Touch-up any unstained cut edges and notches of the guard timbers.
	Then, fabricate seven tie / guard timber sub-assemblies using the tie positioning jig.

Note: The tie positioning jig and directions for making the tie / guard timber sub-assemblies are described in the JIGS AND MOLDS section of this article.

	Starting with panel #7, and working back towards the left end of the trestle, test fit the panels on the beams. The lap joints should meet directly over the ties previously glued to the beams above the bent caps.
	Carefully trim the excess material from the lap joint areas where the guard timbers meet. Touch-up any trimmed edges of the guard timbers with stain.
	Glue the tie / guard timber sub-assembly onto the beams using the tie end reference lines on the plans as a guide.
	As you glue on each panel, add the pedestrian walkway support timbers that are next to tie #1/17 directly above bent caps #1 - #7. These support timbers are parallel with, and on the right side of, ties #1/17.
	At the lap joints where the panels connect (bents #2 - #7), at the tie#1 end of panel #1 (bent #1), and at the tie #17 end of panel #7 (bent #8), drill sixteen #71 holes in the guard timbers for the NBW castings. Drill the holes completely through the guard timbers and ties.
	Add sixteen #62 NBW castings to the holes in the guard timbers.

Note: The sixteen corresponding NBW castings beneath the ties will be added after the deck is removed from the plan.

Step 15. Add the Rails

	Add code 55 running rails and code 40 guard rails.
	The running rails are located 9/32" (18") on either side of the track centerline.
	The guard rails are located approximately halfway between the running rails and the guard timbers.
	Use your preferred method for attaching rail to the ties. I used micro-sized spikes on each side of the rails above every bent position.
	Cut the running rail lengths to extend a minimum of six inches beyond the trestle deck so that the rail joints will not be near the ends of the trestle. I used the full 36-inch length rails, overhanging the ends approximately equally on either side.
	Cut the guard rails at approximately 2 ½ to 3 inches beyond the ends of the trestle. The guard rails extend onto approximately eight ties at both approaches and flare slightly outward at both ends.
	Remove the deck from the plan by sliding a razor blade between the plan and the beams. Discard the plan.
	Remove any glue or paper residue from the bottoms of the beams.
	Add sixteen #62 NBW casting to the holes in the bottom ends of ties 1/17 at each bent position, corresponding to the sixteen #62 NBW castings above.

Trestle Assembly

Assemble the trestle as explained in steps 16 through 19.

Step 16. Fabricate and Add the Bents

Fabricate the nine bents using the angle cut jig and bent jigs.

Note: The angle cut jig and bent jigs and directions for making the bents are described in the JIGS AND MOLDS section of this article.

Lightly sand the tops of the bent caps at an 88.854 degree angle using the bent attachment jig.

Note: The bent attachment jig and directions for its use are described in the JIGS AND MOLDS section of this article.

	Attach the second reversed view copy of the deck plan to the work surface.
	Position the deck onto the plan and secure with masking tape or weights.
	Glue the bents to the underside of the beams at the indicated bent positions with the bents leaning toward the north or downhill end of the trestle (the Bent #1 end toward Ridgway.) Use the bent attachment jig to insure the bents are leaning at the proper 88.854 degree angle.

Step 17. Add the Bent Footings

Add timber bent footings to bents #1 through #3 and #5 through #8A and the concrete footing to bent #4.

Note: If desired, the concrete footing can be left off until the trestle is ready to be installed in final position.

Remove the trestle from the plan and discard the plan.

Step 18. Add the Bent Cap Sheet Metal

Figure 21 - Bent Cap Sheet Metal Arrangement

	Temporarily support the trestle in an upright position by placing supports under the various height bents.
	Glue a piece of sheet metal to the exposed portion of each bent cap as shown.
	The piece should cover the top of the cap and extend down the vertical edges about 1/32" (2").
	The piece should be cut to the length of the exposed bent cap plus about 1/16" (4") so that about 1/32" (2") extends up the side of the beam and down over the end of the cap.

Step 19. Add the Dump Boards Behind Bents #1 and #8

Note: Dump boards were located at most trestle abutments (end bents) to keep the earth fill in place. These dump board were usually made from leftover scraps of bridge timbers or heavy planks. Since they were in constant contact with the ground, they tended to rot quickly and were generally replaced at least once during the life of a bridge. For the dump boards on my model, I used scrap pieces of 4” x 12” timbers.

	There are four dump boards on Bent #1 and three dump boards on Bent #8. Refer to Figure 5 and Figure 13 for details.
	Cut the dump boards to length so that the lowest board extends approximately one foot beyond the bent footing on either side.
	The next higher board is two feet shorter than the one below it, so that the outer edges of the dump boards have a stair-step appearance.

Step 20. Add the Pedestrian Walkway

Note: Over the years, there were various handrail configurations, and possibly some floorboard changes as well. Several photographs show only 27 handrail posts. No photographs clearly show the actual south end (uphill or Rico end) of the pedestrian walkway.

Add the floor boards to the pedestrian walkway support timbers as follows:

Carefully cut-to-fit three 3" x 12" floor board to fit at each segment of the deck corresponding to panels #1 through #7 of the tie / guard timber sub-assemblies.

The angle for the cut ends is 88.0898 degrees or position #2 on your angle cut jig, unless otherwise noted.

Touch-up the cut edges with stain.

On panels #2 through #6, the ends of the floorboards meet at the support timber closest to bent caps #2 – #7.

On panel #1, the left ends of the floorboards extend to the left edge of bent cap #1 and have perpendicular end cuts.

On panel #7 the right ends of the floor boards extend to the right edge of the right-most walkway support timber and have perpendicular end cuts.

After you have glued the floorboards to the walkway support timbers, use a needle to impress nail holes at each support timber.

Add the handrail posts as follows:

Cut twenty-eight pieces of handrail posts, each 3" x 6" x 4’.

Touch-up the cut edges with stain.

Glue a post to each walkway support timber flush against the outer floorboard. The posts go on the right (Bent #8) side of the support timbers.

After you have glued the posts to the walkway support timbers, use a needle to impress nail holes at the bottom of the post at each support timber.

Add the bottom railings as follows:

Carefully cut-to-fit seven 3" x 12" bottom railings, one per segment.

Touch-up the cut edges with stain.

Glue the bottom railings to the inside of the handrail posts, just touching or about an inch (1/64") above the floorboards.

After you have glued the bottom railings to the handrail posts, use a needle to impress nail holes in the rails at each post.

Add the center and top railings as follows:

Carefully cut-to-fit fourteen 3" x 6" center and top railings, one of each per segment.

Touch-up the cut edges with stain.

Glue the top railings to the inside of the handrail posts, with the tops of the railing level with the tops of the posts.

Glue the center railings to the inside of the handrail posts approximately halfway between the top railings and the bottom railings.

After you have glued the top and center railings to the handrail posts, use a needle to impress nail holes in the center and top rails at each post.

Add the railing caps as follows:

Carefully cut-to-fit seven 3" x 6" railing caps, one per segment.

Touch-up the cut edges with stain.

Glue the railing caps to the handrail posts, on the post tops and flush with the inside edge of the top railing.

After you have glued the railing caps to the handrail posts, use a needle to impress nail holes in the railing caps at each post.

Brush the pedestrian walkway with an India ink / alcohol solution (about 25 drops per ounce) to highlight the grain detail and nail head indentations.

Step 21. Add the Step-down at the Upper End of the Pedestrian Walkway

Note: No photographs clearly show the actual south end (uphill or Rico end) of the pedestrian walkway. In most photographs taken from this end of the bridge, either a large shrub or a locomotive blocks the view. Some photographs indicate a possible step-down at this end with the walkway railing angling downward similar to a staircase handrail. In any case, use your own judgment and feel free to deviate from my directions if you desire.

	If desired, add a step-down at the upper (Rico) end of the pedestrian walkway. I fabricated mine using leftover pieces of 3” x 12” boards from the pedestrian walkway floorboard material.
	The step-down consists of two four-foot wide steps, each with a 12-inch step and rise.
	The steps are supported on pieces of 4” x 12” dump boards mounted behind bents #8 and #8A.
	The step arrangement is shown in the following figure. The handrail for the steps is omitted from the figure for clarity, but is similar to the walkway handrail.

Figure 22 - Step-down at Upper End of Pedestrian Walkway

Part 3. Jigs and Molds

General Information

Several types of jigs and one mold were used to simplify construction of the model. These items can be fabricated from various types of material such as wood, acrylic (Plexiglas), or metal. Most of the jigs were used with my Dremel 4" table saw to cut the various timber pieces. The jigs and molds that I used to build the model of Bridge 45-B are described in this section of the article.

I use .093-inch thick Plexiglas as the backing material for most of my jigs. It is available at most home improvement stores (Lowe's, Home Depot, etc.) and comes in various size pieces (8" x 10", 11" x 14", and larger.) For most S-scale jigs, the 8" x 10" size is about right.

For jigs that slide in the slots on my table saw, such as the angle cut jig and bent jig, I start by gluing a strip of Plexiglas to the bottom of the Plexiglas sheet. This strip is the width of the slot in the table saw, and will align the jig so that it slides across the table of the saw in the same position every time. I glue the strip a little further from the edge of the sheet than the actual distance from the blade to the slot. After the glue is dry, I run the jig through the saw blade. This will trim the edge of the jig precisely. This edge of the jig will always be the "cut line". At his stage, I refer to the jig as a "jig blank".

Note: You can make jig blanks for either side of your table saw, depending on if you are left-handed or right-handed. On my Dremel table saw, the blanks are not interchangeable -- the slots are not quite the same distance from the blade on the left and right. My personal preference is to make my jigs to slide in the right side slot to the right of the blade. The plans shown for the various jigs are drawn accordingly.

To make a specific jig, I glue my paper plans onto the Plexiglas jig blank with spray adhesive or a glue stick. I align the "cut line" of the plan with edge of the jig blank that touches the saw blade. The cut line of the plan should just touch the blade as you slide the jig through the saw. I glue small blocks of wood to the paper plan with Elmer's Wood Glue as required to hold the pieces being fabricated. When I no longer need the jig, I can peel the paper plan from the Plexiglas, clean the adhesive residue from the surface, and re-use the jig blank with another plan.

Angle Cut Jig

Description

The angle cut jig has four positions. Starting from the top the positions are used to cut:

	90 degrees - All perpendicular end cuts
	88.0898 degrees - Walkway floorboard angled end cuts
	86.1796 degrees - Long stringer end cuts (both ends) and short stringer end cuts (at Bent #2 end and Bent #7 end)
	75.9638 degrees - 3 in 12 batter bent post end cuts