The Ophir Loop Modules

 By Bob Hyman

 UPDATED: 10/03/2001

Notes:

To download this handout document in Portable Document File (.pdf) format, just click here: The Ophir Loop Modules.pdf (208K Bytes). 

Introduction

Like many NG modelers, I love the look and feel of the Ophir Loop area of the Rio Grande Southern Railroad.  To me, it embodies exactly what NG railroading is all about.  For several years, I have jokingly said that I model the RGS from Bridge 45A to 45B.  Actually, there is a lot of truth to that, and as a matter of fact, that is what this article is about.  Those of you who have seen my Bridge 45A diorama know that I try to model as accurately to scale as possible.  The Ophir Loop is one of those prototype areas that can actually be modeled to scale.  The problem is -- after you have built the loop area to scale, what can you do with it?  Here is my solution to that dilemma.

Overview

The Ophir Loop Modules are a series of eleven Sn³ modular dioramas than can be combined to form an operating layout representing the Ophir Loop area of the RGS.  When connected, the modules occupy a 12’ x 20’ area, or roughly the size of a single-stall garage.  Overall minimum radius is 36”; most viewable track is of 39” minimum radius or larger.  Maximum grade is 3%.  The purpose of these modules is as follows:

All modules are constructed using the common module concept of module framework construction.  This concept is described in my clinic Modular Framing For Dioramas and Layouts.  If you are not familiar with this framing concept, just click on the clinic title to go directly to the clinic. The concept revolves around the use of common triangular-shaped elements that are assembled into the required module configurations.

To view the figures in this article, click on the thumbnail images.  To return to this HTML page after viewing the figures, click the BACK button on your browser.

  Figure 1 is a schematic diagram representing the track layout contained on the Ophir Loop modules OL1 through OL11.  Solid lines represent viewable track and dashed lines represent hidden track. The points indicated by the letters A through AF are used throughout this handout to indicate transitions from one module to another or significant points within a module.  All locations north of Bridge 45A are considered to be “lowline”.  All locations south of Bridge 45B are considered to be “highline”.  All locations between Bridges 45A and 45B are considered to be the “Ophir Loop area”. 

Bridges 45A and 45B, and the area between them, are contained on modules OL5 through OL8.  This portion is modeled in exact scale to the prototype, including scale grades, curves, and distances between features and structures.  Minimum radius in this area is 45” (24-degree prototype curve).

Modules OL3, OL4, OL10, and OL11 represent the approaches to the immediate Loop area from the north and south and contain the Ophir Loop passing siding.  This portion utilizes considerable compression of features, but still captures the essential feeling of the area.  Minimum radius in this area is 39”. The only visible non-prototypical track is the branch on module OL10 that leaves the Ophir Loop passing siding at switch AD   This track was necessary to provide for a continuous-run capability.

Modules OL1 and OL2 contain the hidden helix tracks and associated interface tracks.  The helix arrangement consists of four concentric circles of 45”, 42”, 39” and 36” radii.  The function of these tracks is to:

1. increase by 18” the vertical separation between the highline and lowline tracks where they enter/leave the Ophir Loop Modules at points M and N,
2. provide a continuous run capability for the Ophir Loop area by interconnecting the lowline with the highline, and 
3. provide three separate hidden passing sidings.

  Figure 2 shows how the eleven modules are interconnected.  Following the module interconnect diagram, detailed descriptions and individual drawings are provided for each of the eleven modules. Note: The scale of the drawings for the individual modules varies to allow the drawings to be placed as close as possible to the their text descriptions.

The Modules

OL1 – Helix Module

  Module OL1s is a large 8’ x 8’ octagonal shaped module containing the highline helix, the lowline helix, and the continuous run helix.  All track on the module is hidden. The module is composed of twenty-four basic triangles.  Provisions are included for separating the module into two 4’ x 8’ sections for shipment, if required.

Lowline Helix.  This helix consists of a 270-degree loop (3/4 circle) of the 45” and 42” circles plus associated tangent lead-ins.  It provides a 6” climb in elevation for the lowline track, and includes a hidden passing siding.  The track enters from Module OL2 at point A on a 3% ascending grade coming up from the Butterfly area, passes through facing point switch B where the hidden siding begins, continues on a steady 2.25% - 2.5% ascending grade clockwise through the helix curves, passes through trailing point switch C where the hidden siding ends, passes through trailing point switch D where it is joined by the continuous run helix track coming from the Ophir Loop area, and exits to Module OL2 at point E where it returns to the ruling 3% ascending grade up to the Ophir Loop area.

Highline Helix.  This helix consists of a 720-degree loop (2 circles) of the 39” and 36” circles.  It provides for a 12” climb in elevation for the highline track, and includes a hidden passing siding.  The track enters from Module OL4 at point I on a 3% ascending grade, coming up from the Ophir Loop area, passes through facing point switch J where the hidden passing siding begins, continues on a steady 2.45% - 2.65% ascending grade counter-clockwise through the helix curves, passes through trailing point switch K where the hidden passing siding ends, and exits to Module OL2 at point L where it returns to the ruling 3% ascending grade up the highline towards the first highline bridge (Bridge 46A).

Continuous Run Helix.  This helix consists of a 720-degree loop (2 circles) of the 39” and 36” circles.  It provides for a 12” descent in elevation for the continuous run track, and includes a hidden passing siding.  This track enters at point H on a 3% ascending grade, coming up from a facing point switch on the highline siding on Module OL10 just south of Bridge 45B and just prior to the north end of the highline passing siding.  The track levels and then begins a steady 2.45% - 2.65% descent.  This helix occupies the 39” radius circle position for the first 360-degrees, passes through facing point switch G where the hidden passing siding begins, passes through trailing point switch F where the hidden passing siding ends, and then levels and begins a 2.25% ascent before connecting to the lowline helix at trailing point switch D.

OL2 – Helix Interface Module

  Module OL2 is a  small 2’ x 4’ rectangular shaped module composed of four basic triangles and containing interface tracks for three of the five entrances/exits to helix module OL1.  There are three separate track segments on the module; all are hidden.  Points where the tracks enter/exit the module are identified with the letters N, A, E, O, L, and M.  The track segments are identified as track N-A, track E-O, and track L-M.  

Track N-A (lowline) coming upgrade from the Butterfly area enters the module at point N, climbs across the module on a steady 2.25% grade, and exits to module OL1 at point A.  Track E-O (lowline) enters the module at point E from module OL1, climbs across the module on a steady 2.25% grade, and exits to module OL3 at point O.  Track E-O is approximately 6 inches above track N-A at the intersection point.  Track L-M (highline) enters the module at point L, climbs across the module at a steady 3% grade, and exits to the Highline at point M.  Track L-M is approximately 12 inches above track E-O at the intersection point.

OL3 – Lowline Transition Module

   Module OL3 is a hexagonal-shaped module composed of six basic triangles.  There is one track segment on the module; it is entirely visible.  Points where the track enters/exits the module are identified with the letters O and P.  The track segment is identified as track O-P.

Track O-P (lowline) coming upgrade from module OL2 enters the module at point O, climbs across the module on a steady 3% grade, and exits to module OL4 at point P.

OL4 – The Narrows Module

  Module OL4 is a corner module composed of seven basic triangle.  The module contains segments of both the lowline and the highline.  There are four track segments on the module.  Points where the tracks enter/exit the module are identified with the letters P, Q, R, S, and I.  There is one switch on the module at point T.  The track segments are identified as track P-Q,  track R-T, track S-T, and track T-I.

Track P-Q (lowline) coming upgrade from module OL3 enters the module at point P, climbs across the module on a steady 3% grade, and exits to module OL5 at point Q.  Track R-T (highline main) coming upgrade from module OL11 enters the module at point R on a 3.0% grade and 48” radius curve and terminates at the left (tangent) leg of switch T.  Track S-T (highline siding) coming upgrade from module OL11 enters the module at point S on a 3.0% grade and 46” radius curve and terminates at the right (curved) leg of switch T.  Track T-I (highline) is a short segment from the points of switch T continuing upgrade on a 3.0% grade to point I where it leaves the module.

OL5 – Bridge 45A Module

  Module OL5 is a 2’ x 8’ rectangular module composed of eight basic triangles.  It contains Bridge 45A in its entirety.  There is one track segment on the module; it is entirely visible.  Points where the track enters/exits the module are identified with the letters Q and U.  The track segment is identified as track Q-U.

Track Q-U coming upgrade from module OL3 enters the module at point Q and the grade decreases to 2.87% as the track goes onto the tangent portion of Bridge 45-A.  At the junction of the tangent and curved portions of the bridge, the grade decreases to 2.37%.  The track continues to the end of the bridge and exits to module OL6 at point U.

OL6 – Lower Ophir Loop Module

  Module OL6 is composed of five basic triangles.  There are three track segments on the module. Points where the tracks enter/exit the module are identified as U, W, and X.  The track segments are identified as track U-V, track V-W, and track V-X.  There is one switch on the module at point V.  Both legs of the switch are curved.

Track U-V coming upgrade from module OL5 enters the module at point U on a 2.37% grade and 48” radius and ends at facing point switch V.  Track V-W (main) continues on the left leg of switch V on a steady 2.37% grade and 48” radius to module OL7.  Track V-X (spur) continues on the right leg of switch V on a decreasing uphill grade and 36” minimum radius.  It approaches a level grade at point X where it exits to module OL7.

OL7 – Middle Ophir Loop Module

  Module OL7 is a small 2’ x 4’ rectangular shaped module composed of four basic triangles.  There are two separate track segments on the module.  Points where the tracks enter/exit the module are identified with the letters W, X, and Z.  Point Y identifies where radius and grade change. Point AA identifies where a track segment ends on the module.  The track segments are identified as track W-Z and X-AA.

Track W-Z (main) coming upgrade from the module OL6 enters the module at point W, climbs across the module on a steady 2.37% grade and 48” radius to point Y where it changes to a 2.2%grade and 45” radius, and exits to module OL8 at point Z.  Track X-AA (spur) enters the module at point X from module OL6, continues across the module on an approximately level grade, and ends at point AA.

OL8 – Upper Ophir Loop Module

  Module OL7 is composed of seven basic triangles.  There is one track segment on the module.  Points where the track enters/exits the module are identified with the letters Z and AB.  The track segment is identified as track Z-AB.

Track Z-AB coming upgrade from module OL7 enters the module at point Z, climbs across the module on a steady 2.2% grade and 45” radius, and exits to module OL10 at point AB.  This module contain Bridge 45B in its entirety.

OL9 – Upper Ophir Loop Extension Module

  Module OL9 is a shelf-type scenic filler module composed of three basic triangles.  It contains no track segments.

OL10 – Lower Highline Siding

  Module OL10 is a corner module composed of a basic hexagon plus one additional basic triangle.  There are a total of seven basic triangles.  There are five separate track segments on the module.  Points where the tracks enter/exit the module are identified with the letters AB, AE, AF, and H.  There are two switches on the module at points AC and AD.  The track segments are identified as track AB-AC, track AC-AE, track AC-AD, track AD-AF, and track AD-H.

Track AB-AC (highline) coming upgrade from module OL8 enters the module at point AB on a 2.2% grade and 45” radius.  It terminates at the points of switch AC.  Both legs of switch AC are curved.  Track AC-AE (highline main) continues on the right leg of switch on a 2.2% climb and 43” radius, gradually increasing to a 3.0% climb by the time it reaches point AE where it leaves the module.  Track AC-AD (highline siding) continues on the left leg of switch AC on a 2.2% climb and 45” radius.  It terminates at the points of switch AD.  Switch AD is a wye-shaped switch.  Track AD-AF (highline siding) continues on the right leg of the switch on a 2.2% climb and 45” radius, gradually increasing to a 3.0% climb by the time it reaches point AF where it leaves the module.  Track AD-H (continuous run track) continues on the left leg of switch on a 2.2% climb and 36” radius gradually decreasing to an approximately level grade at point H where it leaves the module.

OL11 – Middle Highline Siding Module

  Module OL11 is a shelf-type module composed of three basic triangles.  It contains two track segments.  Points where the tracks enter/exit the module are identified with the letters AE, AF, R, and S.  The track segments are identified as track AE-R and track AF-S.

Track AE-R (highline main) coming upgrade from module OL10 enters the module at point AE on a 3.0% grade.  It curves to the left on a wide (approximately 48”) radius curve to point R where it leaves the module.  Track AF-S (highline siding) coming upgrade from module OL10 enters the module at point AF.  It curves to the left on a wide (approximately 46”) radius curve to point S where it leaves the module.