N Structure Kit SINGLE-TRACK ARCHED PRATT TRUSS BRIDGE
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N Structure Kit SINGLE-TRACK ARCHED PRATT TRUSS BRIDGE 933-3870 © 2018 Wm. K. Walthers, Inc., Milwaukee, WI 53218 I-933-3870 Printed In China 3 4 1 2 5 6 7 8 7 6 5 Thanks for purchasing this Cornerstone® kit. Please read these instructions and study the drawings before starting construction. All parts are styrene, so use compatible glue and paint to assemble and finish your model. To simplify installing your bridge in new or existing scenery, the following are available separately and you may wish to have them on hand before starting: bulk rail or a length of flexible track, Single-Track Concrete Bridge Piers (#933-3880 pkg(2) and Single-Track Concrete Bridge Abut- ments (#933-3881 pkg(2). While simple bridges had been around for centuries, railroads presented engineers with new challenges to design structures that could withstand the tremendous weight, vibration, pushing (compression) and pulling (tension) forces exerted by a moving train. Early spans were built of wood and later iron, and if a longer or sturdier design was needed, engineers turned to the truss. This triangular-shaped assembly strengthened the floor supports and distributed the stress and strain over a larger area. Many styles soon appeared, including the Pratt Truss developed by Thomas and Caleb Pratt in 1844, which used vertical posts and diagonal cross members sloping up and away from the middle, the opposite of most existing designs. The bigger and heavier locos and cars of the 19th and 20th centuries also demanded stronger and larger bridges, and many roads opted for all-steel Pratt through-truss bridges, used where clearance under the bridge was required. In the 1890s engineers introduced a variation of the design for longer spans, with curved top chords (actually straight sections joined at a slight angle) to strengthen the unsupported center. As the extra length of these designs also required extra height, the top chords were connected by a series of angled struts between panels and straight laterals at each vertical post. Tough and durable, many are still in daily railroad service. Typical of arched Pratt truss bridges built all over North America in the 20th century above roads, other rail lines and navigable waterways where maximum clearance was needed below the structure, your finished model will add a realistic touch to any layout. For additional products to complete your scene, see your participating hobby dealer, check out the latest Walthers Model Railroad Reference Book or visit us online at walthers.com. 1) Make one each left and right Truss Assembly; work on a flat surface and be sure all parts are straight during assembly. Align mounting pins and openings on each Truss Exterior (Left 1, Right 2) and Interior (Right 3, Left 4) halves at ends as shown. PLEASE NOTE: Locater pins on the four different sizes of Lower Lacings (5, 6, 7 & 8) are keyed to fit only as shown, you may however find it easier to install all of one part number before moving on to the next. Align tabs and angled edges between inset areas of truss assemblies as shown, and care- fully glue where parts meet. Repeat for second truss assembly.
Transcript of N Structure Kit SINGLE-TRACK ARCHED PRATT TRUSS BRIDGE
N Structure KitSINGLE-TRACK ARCHEDPRATT TRUSS BRIDGE
933-3870
© 2018 Wm. K. Walthers, Inc., Milwaukee, WI 53218 I-933-3870 Printed In China
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Thanks for purchasing this Cornerstone® kit. Please read these instructions and study the drawings before starting construction. All parts are styrene, so use compatible glue and paint to assemble and finish your model. To simplify installing your bridge in new or existing scenery, the following are available separately and you may wish to have them on hand before starting: bulk rail or a length of flexible track, Single-Track Concrete Bridge Piers (#933-3880 pkg(2) and Single-Track Concrete Bridge Abut-ments (#933-3881 pkg(2). While simple bridges had been around for centuries, railroads presented engineers with new challenges to design structures that could withstand the tremendous weight, vibration, pushing (compression) and pulling (tension) forces exerted by a moving train. Early spans were built of wood and later iron, and if a longer or sturdier design was needed, engineers turned to the truss. This triangular-shaped assembly strengthened the floor supports and distributed the stress and strain over a larger area. Many styles soon appeared, including the Pratt Truss developed by Thomas and Caleb Pratt in 1844, which used vertical posts and diagonal cross members sloping up and away from the middle, the opposite of most existing designs. The bigger and heavier locos and cars of the 19th and 20th centuries also demanded stronger and larger bridges, and many roads opted for all-steel Pratt through-truss bridges, used where clearance under the bridge was required. In the 1890s engineers introduced a variation of the design for longer spans, with curved top chords (actually straight sections joined at a slight angle) to strengthen the unsupported center. As the extra length of these designs also required extra height, the top chords were connected by a series of angled struts between panels and straight laterals at each vertical post. Tough and durable, many are still in daily railroad service. Typical of arched Pratt truss bridges built all over North America in the 20th century above roads, other rail lines and navigable waterways where maximum clearance was needed below the structure, your finished model will add a realistic touch to any layout. For additional products to complete your scene, see your participating hobby dealer, check out the latest Walthers Model Railroad Reference Book or visit us online at walthers.com.
1) Make one each left and right Truss Assembly; work on a flat surface and be sure all parts are straight during assembly. Align mounting pins and openings on each Truss Exterior (Left 1, Right 2) and Interior (Right 3, Left 4) halves at ends as shown. PLEASE NOTE: Locater pins on the four different sizes of Lower Lacings (5, 6, 7 & 8) are keyed to fit only as shown, you may however find it easier to install all of one part number before moving on to the next. Align tabs and angled edges between inset areas of truss assemblies as shown, and care-fully glue where parts meet. Repeat for second truss assembly.
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2) Support left and right Truss assemblies so they stand upright; note the correct placement and carefully align tabs on End Beams (2x 10) and Floor Beams (6x 11; be sure angle braces face upward as shown); with openings along each side of Truss assemblies and glue in place, keeping parts straight and level.
3) PLEASE NOTE: Make sure flat ends (straight, without notch) of Stringers (2x each 12, 13) face outward; slide openings on Stringers over End and Floor Beams as shown and glue where parts meet. 4) Carefully remove the X-shaped Left (19), and Right (20) Bottom Laterals; note the two half gussets meet in the middle as shown. Align raised tabs on Laterals with inset areas along bottoms of Truss assemblies and glue where parts meet. 5) PLEASE NOTE: To reduce damage in the event of a derailment, track on bridges features wider wooden ties and inside guardrails, which can be modeled in several ways. Decide what you’ll use and follow the appropriate steps; we suggest test-fitting your bridge first to determine final alignment of track. A) To use Flexible Track or Rail (each sold separately):Make sure Open Wooden Deck (2x 22) is centered side-to-side on the Stringers and glue in place. For bulk rail, or a section of flexible track with ties removed to fit, align rails along the outside mounting points and glue rails in place with CA. To model the guardrail, cut lengths of rail to fit, align on inside mounting points and glue in place with CA B) To use N Scale bridge track available separately from Micro Engineering Center Bridge Track (either Code 70 #255-11110 or Code 55 #255-11112 can be used) on Stringers and glue in place. 6) PLEASE NOTE: Carefully cut Large (2x 14) and Small Top Laterals (2x 15) from sprues; do not remove small mounting tabs on outside edges. Align tabs with rectangular mounting points on inside of trusses, and glue in place as shown. 7) Align raised tabs on bottom with openings at top of truss assemblies, and glue Center (16), Intermediate (2x 17) and End (2x 18) Top Chord/Struts in place as shown. 8) Align raised tabs on back of End Posts (2x 9) with openings in truss ends and glue in place. 9) Align open area on top of Bridge Shoes (4x 21) with tabs at corners of Bottom Laterals and glue where parts meet.
