Anatomy of a Module

by Bob Hyman

Part 1 – Module Specifications

Introduction

This is the first installment of a six-part "cyber-clinic" that will cover the design and fabrication of a portable Sn3 module from start to finish. My goal is to complete the module prior to the next Sn3 Symposium at St. Louis, and to present a clinic on its construction at that time. I will document the progress with photographs and clinic updates on this site as I go along. In this initial part, I have established the overall module theme, defined the major scenic elements, determined physical size and weight constraints for the module, and established a set of design factors that will guide me during its construction.

Module Theme

The module will represent a portion of the Rio Grande Southern “Highline” above Ophir, Colorado as it appeared in the late 1930's time frame. It will include bridges 46-A, 46-B, and 46-C in their entirety. This dramatic section of the highline was visually exciting and much photographed. These three bridges were located very close together. The total distance from the start of bridge 46-A to the end of bridge 46-C was less than 500 actual feet.

Major Scenic Elements

The primary focal points on the module will be the three timber trestles, bridges 46-A, 46-B and 46-C. The rocky mountainside traversed by the roadbed and bridges will slope dramatically from the rear to the front of the module. All concrete and stonework abutments and bent foundations will be accurately modeled and placed into the rugged terrain.

Module Size

The module will represent an actual 512-foot long by 128-foot wide section of the Highline. This scales out to an eight-foot long by two-foot wide module (sixteen square feet).

Track Segments and Electrical Wiring

The track will climb on a ruling 3% grade from left to right, as it runs across bridges 46-A and 46-B and out onto bridge 46-C. This section of the track will be tangent. Halfway across bridge 46-C, the grade will drop to 2.75% and the track will begin a gentle 6.5 degree curve to the left. The curve and reduced grade will continue to the end of the module. The module will include the following track segments:

Module Track Segments
Segment	Length
Segment	Prototype (ft.)	Module (ft.)	Module (in.)
LEFT	13	0.203125	2.4375
46-A	62	0.96875	11.625
GAP	152	2.375	28.5
46-B	102	1.59375	19.125
GAP	19	0.296875	3.5625
46-C	151	2.359375	28.3125
RIGHT	13	0.203125	2.4375
Total	512	8	96

Track Segments:

	All track segments on the module shall be wired as a single continuous block.
	An electrical switching mechanism shall be provided to disable power to at least one rail of segments LEFT and RIGHT to prevent a locomotive from inadvertently running off the ends of the module when adjacent mating modules are not connected.
	All track segments on the module shall utilize code 55 rail for running rails and code 40 rail for guard rails.

Electrical Wiring:

	Power wiring shall consist of 12AWG (minimum) insulated solid copper bus wires running the length of the module. Bus wire insulation shall be red for the front-most bus wire and black for the rear-most bus wire.
	Suitable wiring connectors shall be provided beneath the module at each end to facilitate electrical connection of the bus wires to adjacent mating modules.
	Feeder wiring shall consist of 18AWG (minimum) insulated solid copper wires. The insulation color of the feeder wires shall match the insulation color of the bus wires.
	Feeder wiring shall connect the red bus wire to the front-most rail and the black bus wire to the rear-most rail.
	Feeder wires shall be soldered to the bus wires and the rails at thirty-six inch (maximum) intervals.
	Soldered connections between the bus wires and the feeder wires shall be covered with electrical tape, heat shrink tubing, or equivalent insulation material.
	Rail joints shall not be utilized for power conduction. Each individual section of rail shall be connected to a bus wire by at least one feeder wire.

Design Factors

The primary design factors for this module will be size, weight, strength, durability, storage life, ease of transportation, safety, accuracy of the modeled scene, and cost.

Size:

The completed module shall not exceed ninety-six inches in length, twenty-four inches in width, and thirty-six inches in height (48 cubic feet maximum).

The module shall fit within an enclosed storage and transporting case not to exceed ninety-eight inches in length, twenty-six inches in width, and thirty-eight inches in height.

Weight:

The completed module shall not weigh in excess of one pound per cubic foot (forty-eight pounds maximum).

The combined module and storage case shall not weigh more than one hundred pounds.

Strength:

The completed module shall be capable of standing without distortion (flexing, bending or sagging) when removed from the storage case and supported only at module ends for indefinite periods of time.

Durability:

The completed module and storage case shall not be adversely affected or damaged by any vibration experienced while being transported in a cargo-type vehicle over paved highways under normal driving conditions.

Storage Life:

The module, when enclosed within its storage case, shall be capable of withstanding extended storage (up to one year) in a typical unheated, non air-conditioned garage environment subject to prolonged temperatures from 32 degrees to 120 degrees Fahrenheit and relative humidity from 10 percent to 90 percent, non-condensing, without noticeable warping, distortion, or deterioration.

Materials utilized in the module shall not be adversely affected by exposure to direct sunlight, artificial lighting (fluorescent or incandescent) or absence of light for extended periods during display or storage.

The module and its storage case shall be treated to resist rodent and insect infestation.

Materials utilized shall be resistant to mold, mildew, or other organic fungal growth.

Ease of Transportation:

The module shall be capable of being installed into or removed from its storage case by two persons without the aid of hoists or mechanical lifts.

The module shall be easily moved, carried, or otherwise transported by two persons without the aid of wheeled carts or other mechanical devices.

The module, when in its storage case, shall fit within an enclosed standard 5-foot by 8-foot cargo-type trailer.

The storage case shall be water-proofed as necessary to provide protection from moisture penetration during trailer loading or unloading activities in inclement weather.

The storage case shall be capable of being opened or closed without the use of special tools (common hand tools only.)

Safety:

The module shall not utilize any substance identified as “Hazardous Material” or “Toxic Material” by 29 CFR 1910.1200 (Federal Regulations - Safety and Health Standards - General Industry - Hazcom Standard.)

Material Safety Data Sheets (MSDS) shall be obtained from the manufacturer or retailer for all chemical products utilized in the construction of the module including adhesives, solvents, foam products, and paints. The information and directions provided in the MSDS shall be strictly followed when utilizing such chemical products.

Any construction materials subject to formaldehyde out-gassing (such as particle board) or materials that utilize cyanide or arsenic compounds for preservatives (such as pressure-treated lumber) are expressly prohibited.

All hand-holds, lift points, corners and exposed surfaces shall be free from sharp edges and splinters.

Any unusual center of gravity conditions or top-heavy conditions shall be clearly identified on the module and/or storage case.

If any two-part expanding polyurethane foams or epoxy materials are utilized during construction, the materials shall undergo sufficient curing time as specified on material container labels or MSDS before the module is placed into the storage case.

Accuracy of Modeled Scene:

The module shall accurately represent the prototype scene in regards to scale feature dimensions (height, width, and length), including prototype grades and curves.

Rendering of modeled rock, soil, concrete, stonework and vegetation colors and textures shall be based on photographic interpretation of the prototype scene using readily available modeling techniques and scenic materials.

Cost

The total cost of materials utilized in the construction of the module and its storage case shall not exceed two hundred and fifty dollars ($250.00.)

Construction Methods, Sources, and Required Skill Levels

	The module framework and storage case shall be fabricated using readily available construction materials that can be obtained at local hardware, home improvement, or lumber stores.
	Use of metal hardware (screws, nails, nuts, bolts, washers, etc.) shall be minimized to the greatest extent possible.
	Adhesives and construction materials shall be selected on the basis of weight, strength, moisture resistance, and chemical stability over the projected storage temperature and humidity range.
	Scenic materials and hobby supplies utilized shall be selected from those readily available to the general public through local retail hobby shops and/or mail order.
	Construction materials and fabrication techniques selected shall not preclude the building of this module by a person possessing average modeling skills with access to standard shop and hobby tools. Check back later for future installments of this clinic: [Dates in brackets are my current schedule estimates] Part 2 - Structural Framework - truss girders, web plates, fascia panels, risers, spline roadbed [April] Part 3 - Trestle Construction - bridges 46-A, 46-B, and 46-C, abutments, piers and foundations [July] Part 4 - Track Installation - trestle installation, gaps and lead-ins, wiring [August] Part 5 - Scenery - geodesic "skin", foam rock castings, talus slopes, soil, vegetation, ground covers, trees [November] Part 6 - Final Touches - trim, exterior finish, storage case [December]