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| Overall view of Conrail clearance
detector in New Jersey. |
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Close up of sensor on pole for a clearance
detector. |
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Conrail equipment cabinet housing electronics
and radio equipment (note small antenna for radio transceiver).
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Details West 235-900 Detectors, Hot Box
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Details West 235-905 Detectors, Dragging
Equipment |
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Details West 235-908 Electric Relay Cabinets,
5 x 7' |
By M. R. Snell
One of the trackside icons of modern railroading is the defect
detector. Known by various names such as HBD (Hot Box Detector) or
DED (Dragging Equipment Detector), detectors can monitor one or more
mechanical conditions on passing trains, thus making them an invaluable
tool for railroads. With fewer employees on the ground to observe
passing trains, these detectors are the eyes and ears of today's railroads.
The first detectors simply employed a trackside display of lights
and a digital readout to alert the crew in the caboose of a problem
with their train. With the advances in technology and the elimination
of the caboose prerecorded messages are delivered via radio to the
train crew. These messages usually start out by identifying the railroad,
the location, and whether or not a defect is present. Other information
may include the number of axles, the train speed, and the outside
temperature.
On my own HO scale Conrail New Jersey Division I felt a necessity
to include such a detector, as they are as much a part of the railroad
landscape as signals and tracks. Modeling the actual physical plant
of the detectors is fairly easy utilizing castings available from
Details West. The real challenge lied in the audible part.
Hotbox and Dragging Equipment Detectors
Modeling the physical plant of a standard HBD-DED is fairly straightforward
using Details West castings #235-900 for the hotbox detector, #235-905
for the dragging equipment detector, and #235-908 for the instrument
shed which houses the electronics.
Install the castings as per the instructions, omitting the pole style
signals. On most prototype installations the dragging equipment hardware
is a rusty oxide brown and the hotbox hardware is silver. The instrument
shed should be placed within sight distance of the installation, several
feet off the track.
Turning attention to the audio, I was able to put the prerecorded
detector message onto a sound module (with the help of George Solovay
from Innovative Train Technology) with a speaker mounted under the
detector. The prerecorded detector message is tripped by a track shunt.
When locomotive wheels cross over the shunt the push button circuit
is closed and the sound module will be activated.
To cut the shunt into the track you must first cut and isolate a 1.5"
section of rail. After the cuts are made, isolate the section using
strip styrene, glue in with CA type cement, and then file to match
the contour of the rail. In the opposite rail now you will need to
cut and isolate another section. This section should be slightly offset
from the first. If it is directly opposite then any lighted car or
resistive wheelset shall close the circuit and you will receive multiple
activations of the sound module. The isolated sections should be of
a distance that the front left wheel of a four-axle diesel truck should
sit on the first isolated section and the rear right wheel of the
same truck should sit in the opposite section. Allowing for a little
play the shunt will be activated by both four- and six-axle diesel
locomotives.
Once the sections are isolated, solder one wire to each rail and run
these through the roadbed. These connect to the push button terminals
on the sound module. The speaker should be installed under the layout
in the area of the defect detector.
To add diversity to operations in addition to the standard "no
defects" message if you wish to add a "hotbox" or "dragging
equipment" message simply add a second set of wires to the shunt
and use a second module with the defect message.
For use of a second message, rather than connecting the speaker directly
to the module instead connect the speaker and DPDT toggle. The upper
and lower positions of the DPDT toggle should connect to the speaker
outputs on the modules and the center connection to the speaker itself.
Mount the toggle on a dispatcher's panel or elsewhere on the layout
and this will enable you to choose from either message.
Clearance Detectors
The second type of detector is the "clearance detector."
With the advent of double stacks these have been appearing more frequently
throughout the country along lines with obstructions such as low bridges.
Placed well ahead of the obstruction they instantly alert the train
crew and dispatcher of the height problem.
Clearance detectors are usually just two poles parallel with each
other, one on each side of the tracks. On the top is a sensor that
reads from pole to pole. When the beam is broken it activates the
detector with a clearance defect message. With the lack of a clearance
defect the detector usually remains silent.
To model this installation cut 2 sections of hollow aluminum or brass
tubing. Cut a small piece of styrene and file to the contour of the
sensor. The concrete bases that the poles are mounted in may be added
using round styrene or castings.
In order to activate the module mount an infrared sensor in either
the poles or in adjacent scenery. The sensor's electric "eyes"
should be aimed at each other and at the height you wish the detector
to activate at. A train of excess height will break the beam and thus
set off the circuit.
The connections to the module are similar to those used for the HBD-DED
but will vary dependent upon the infrared module you choose and it's
specific wiring configuration.
Getting The Message
The audible messages transmitted for each type of detector vary from
railroad to railroad. There are several sources and ways to record
and create messages.
The first method is to find a detector along the line you model and
take a scanner and a tape recorder. Place the scanner and recorder
in a quiet area, such as inside a car, and simply record the detector
announcement.
The second way is via the Internet. Several websites offer amateur
recordings of talking defect detectors. I have listed two sites in
particular at the end of this article.
The third option is to use a computer-generated voice to make your
own recordings. Some word processors for Mac and for PC's have the
option to read aloud text. Once you get the message tweaked to your
liking, you can make a recording of it.
While most detectors are specific to list car counts and train speeds
with a little editing of the recordings you can successfully tailor
the recordings to fit your specific situation. One example is Conrail
detectors. On my railroad I have added the detector near the town
of New Market. The actual recording I have is "CONRAIL - NEW
MARKET, NEW JERSEY - NO DEFECTS - TOTAL AXLE COUNT... 4-7-6 - TRAIN
SPEED... 4-3 - OVER" With a little editing you can reduce this
to "CONRAIL - NEW MARKET, NEW JERSEY - NO DEFECTS - OVER"
and thus making the message accurate for any passing train.
Conclusion
This has proven to be an interesting and unique feature of my railroad
and has added an interesting operational feature as well while being
a minor investment. You can easily recreate the same effects on your
home layout, while adding to the modern railroad atmosphere!
Resources
Innovative Train Technology
PO Box 5042
West Hills CA 91308
(818) 992-6124
Details West
235-900 Detectors, Hot Box
235-905 Detectors, Dragging Equipment
235-908 Electric Relay Cabinets, 5 x 7'
Detector Audio
sites
http://kickitup.railfan.net/html/mult/wave_dd.html
http://www.mainline.railfan.net/wave/
Matt
Snell, 35, born and raised in northern New Jersey, the basis for
his HO scale Conrail New Jersey Division, is a dockworker currently
residing in Milford, Ohio. Matt has been a model railroader and a
railfan since age 12 and is currently married, "with goldfish
and trains." |
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