Defect Detectors
Background
Electronic Defect Detectors have been installed at strategic positions along railways for many years. The purpose of these systems is to automatically detect potentially dangerous failures in passing trains. The detectors transmit a voice synthesized alarm message over the railroad radio frequency to inform the train crew of a defect. Reported failures/problems include:
- Excessively hot journals or bearings
- Excessively hot wheels
- Out of round wheels
- Clearance problems - car or load is too high/wide
- Equipment that is dragging along the rails
Twisted Trains has developed a Model Train Hot Box Detector so hobbyists can incorporate this important but overlooked aspect of railroad infrastructure into their layouts.
Hot Box Detectors
These trackside detectors locate overheated journals on moving trains prior to bearing failure. Overheated journals, i.e., hot boxes, occur when inadequate wheel bearing lubrication or mechanical flaws cause significant increase in bearing friction which, in turn, causes the wheel bearing temperature to increase. When the bearing temperature rises to an abnormally high level, bearing failure results. Such failures are a major cause of derailments, endangering life, destroying property, and resulting in costly delays.
Hot box detectors use infrared sensors that are focused at the wheel axles on both rails. As the train passes the detector, the temperature of each wheel bearing is measured. If either the absolute temperature of a bearing, or the temperature difference between two bearings on the same axle, exceeds a preset threshold then a radio mounted in a track-side enclosure transmits a beep over the radio. After the train completely passes the sensor, a "talker" will annunciate a message over the radio to inform the train crew of the axle number of each defect. When a train passes without problem, the talker transmits a "no defect" message over the radio. Some detectors report additional information such as:
- Train speed
- Number of axles
- Total length of the train
- Ambient temperature
After a hot box or equipment defect alarm is announced, the train crew will usually stop the train and perform an inspection to determine the cause of the problem. The crew will notify the dispatcher of the problem and how much delay they experienced.
More Information
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Matt Snell's excellent page provides background on defect detectors and modeling them.
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www.railroad.net |
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Trains.com maintains an active forum for train enthusiasts and experts. Click on the link to view an informative thread on the topic of hot box detectors.
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www.classictoytrains.com |
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Mike Yuha's recordings of Wisconsin Central, CP, UP and BNSF defect detector annunciations. One recording is of an integrity failure - a failure of the detector itself.
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www.mikeyuhas.org |
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The railfan.net hosts numerous railroading enthusiast sites. Of particular interest are these pages containing large collections of actual defect detector annunciation audio recordings.
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kickitup.railfan.net
mainline.railfan.net
ohiorr.railfan.net |
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John Peterson has collected a variety of defect detector annunciations and has posted them on his site.
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www.alabamarailfan.com |
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The Live Railroad Radio Communications site is an excellent place to learn more about the railroad radio communications infrastructure.
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www.railroadradio.net |
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Railway Track and Structures published this informative article on novel railway defect detectors.
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www.rtands.com |
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This is a link to a page in a 1989 safety manual for the John Galt Line Railroad Company containing interesting information about types of detectors, what crews are required to do during inspections, and actions they are expected to take after locating a defect.
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mostgraveconcern.com |
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Gary See has compiled a collection of maintenance manuals, some of which cover hot box detectors (Harmon, Servo).
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gsee.sdf-us.org |
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