HO Layout Construction Details
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HO Layout Construction Details |
The Association predecessor, the San Diego Model Railroad Club, became one of the charter members
of the San Diego Model Railroad Museum in 1980, and planning began on permanent layouts.
The new HO layout was planned to include:
Construction began in April 1982 at the peninsula containing Coyote Wells and
Plaster City. By this time the logging branch had faded from the plans, and the
minimum radius was the norm. Construction using flex track on homasote over
laminated spline sub-roadbed built from Coyote Wells to the Hipass wye by 1984.
In the next year track reached Valle Redondo and a temporary loop. What looked
fine on paper was turning out to not be operationally sound. By 1990 large
portions of the mainline had been redesigned to increase the radius and improve
the grade. At the formation of the Association, 99 percent of the track work is
complete.
From the outset, benchwork has been constructed from member-built I-beams. Lighter
and stronger than L-girder construction, I-beams are versatile enough to build
complex shapes quickly. Sub-roadbed began as laminated spline, but this was later
abandoned in favor of cookie-cutter 3/4 inch plywood. Likewise, the homasote roadbed
proved undesireable in the San Diego 15% to 99% humidity levels. Only a tiny fraction
of original roadbed and flex track exists. Today 5/16" pine strips are nailed
and glued to the plywood, then planed smooth in preparation for wood profile ties.
Visible track is mostly hand-laid code 100, with some code 83, on the standard gauge.
Code 70 is used for the narrow gauge and dual gauge section. The larger rail sizes
have been helpful extending rail lifetime. Operations are now 6 days a week. As layout construction progressed, construction practices improved, and the first
layers of hydrocal hardshell brought the layout to life. It is hard to imagine that
those first barren tracks are now part of the rich scenic vistas you see today. The empty room First benchwork I-beam details The route through Carriso Gorge Electrical Systems
The San Diego Model Railroad Association HO layout is large and complex
and operation skill levels of members and visitors cover a wide
area. For these and other reasons, Digital Command Control (DCC)
is used, but analog DC and block section are retained. This means there is great flexibility in
operations, depending of operator desires. Usually it is all DCC or all analog
DC, but it is possible to operate portions with each system simultaneously. For
example, the HO main line can be DCC, but the narrow gauge analog DC. Hardshell and Scenery
The current hardshell consists of foot long nylon stucco netting
strips dipped into a thin mixture of Hydrocal, which fills the mesh
holes. This is then placed on a wadded paper form and successive
layers built up criss-cross to a thickness of about ½".
At this time the underlying paper is removed leaving an extremely
strong hardshell which is smooth on the bottom. Rock castings are
then applied, and additional Hydrocal is used to form soil erosions
and to fill in between rock castings. In some cases blending is
performed before the Hydrocal hardens.
Logos copyright ©SDMRRA, NMRA
See the initial design criteria in the standards
section of this web site.
Each control panel on the layout has at least three local DC throttles
capable of sustained load up to 5 amps. Circuit breakers are
provided for short circuit protection, and each throttle has
meters for both voltage and current. Block selection is accomplished
with toggle switch banks, with the lefthandmost active switch (if
more than one toggle is "up") being the controlling
throttle. In addition, the lowest priority toggle is oriented
east-west (center off) and allows that block to be remoted to the
next panel. Entire panels can be bypassed in this manner if short
handed, or cascaded panels may be controlled from a distant
location.
DC Throttles are manufactured by association members, with the heavy electronics
mounted under the layout, and the hand-held controller a small,
light weight, box tethered with telephone coil-cord. Failures
are easily replaced with spares, and members can trouble shoot
problems by swapping controllers, cords, etc. without any tools.
The layout is common rail (except the branch line and narrow gauge
areas) with all buss wiring 14 AWG stranded wire. Track feeders are
20 AWG stranded, limited length. All connections use barrier strip
terminal blocks and crimp terminal lugs. In line wire splices are
not allowed. All wiring is color coded for easy trouble shooting.
Switch machines are PFM slow motion with feedback LED indication
wiring. There are no hand-throw turnouts on the layout. We have
close to 300 switch machines in daily operation, and failure
rates of 1 machine every couple of years. Some gear lubrication
is required periodically for heavily used switch
machines.
Cuts and blasted rock areas are generally performed using the
crumpled aluminum foil method. The roughness is determined by
the surrounding topography. Initial coloring is a diluted Rit
fabric dye mixture sprayed on with trigger bottles. The color
lightens over time, so it is hard to overdo the dye process.
Foil cuts can be seen in the photo gallery at Encanto, and also
at the stock pens near Valle Redondo.
Vegetation is arid or semi-arid and in photographs does not seem
to be present unless extreme closeups are used. Rose Canyon is
one of the few green areas, being next to the Pacific Coast. The
other end of the spectrum are Carriso Gorge and the desert sands
around Plaster City. El Centro greens up with irrigated fields,
but fallow ground is still barren desert.
This page is under construction. Visit us again.
HO Layout Standards page.
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HO Carriso Gorge Exhibit page