74 min
- Source: Hot box
- Source: Hotbox
A hot box is the term used when an axle bearing overheats on a piece of railway rolling stock. The term is derived from the journal-bearing trucks used before the mid-20th century. The axle bearings were housed in a box that used oil-soaked rags or cotton (collectively called "packing") to reduce the friction of the axle against the truck frame. When the oil leaked or dried out, the bearings overheated, often starting a fire that could destroy the entire railroad car (and cars coupled to it) if not detected early enough.
The packing and bearing had to be regularly inspected by yard crews, and packing was often added at major stops. The journal bearing was replaceable, but if neglected, it would heat to a temperature where the babbitt bearing alloy would melt away, leaving the brass carrier riding on the steel axle, and result in a "taper journal". This would eventually lead to the axle fracturing and the car above falling onto the wheel, or failure of the taper journal, causing the side frame and journal box to fall below the level of the rails, either of which could cause a major derailment of the train. Train worker duties consisted partly of inspecting the train as it ran by, looking for smoke, sparks, or fire. They would then sound the audible report "All Black" to mean the train was not giving off any light energy that would indicate combustion or destruction of the wheel bearings. If the train worker saw "Red" or smoke, he would alert other crew members, or else make an emergency stop to the train to prevent further damage.
When this type of axle box was used, any diesel exhaust smells had to be tracked to their source, as a hot-box sometimes smells similar. Most of the larger railroads use defect detectors to scan passing trains for hot box conditions. Some of these detectors also have "automated mile posts" which send an automated radio signal to the train crew listing the train number, track number, number of axles on the train and train speed.
Modern ball, roller or tapered bearings can also overheat, but the likelihood of a roller bearing overheating is usually far smaller than with journal bearings. When modern bearings do fail, the balls or rollers and their races fail, generating heat which can ignite fires or be the ignition source of a dust explosion in grain, coal, sawdust, etc.
Gallery
Journal boxes and heat detectors
See also
Defect detector
1833 Hightstown rail accident (United States)
1943 Frankford Junction train wreck (United States)
1979 Mississauga train derailment (Canada)
1984 Summit tunnel fire (England)
2023 Ohio train derailment (United States)
References
Bibliography
Railway Age magazine April 1, 1957
Model Railroader 1980 May 62pp
Hotbox or hot box may refer to:
a hotbed (gardening) that is enclosed in a box with a glass or clear plastic lid
Hot box, an overheated journal box on a railroad car
Hot box (game), a half-court flying disc sport with a very small box-shaped scoring area
Hotbox (baseball), also known as the rundown, is a running/fielding/throwing drill in baseball training
Hot Box (appliance), an improvised appliance to heat up food, usually with incandescent light bulbs as the heat source
Hotbox (TV series), a Canadian sketch comedy show named for the marijuana/hash smoking practice
Box (torture), also called a hot box, a form of torture and penal punishment by imprisoning a person in an overheated room, cell or cage
A hotbox, a pressure washer accessory, powered by oil, gas or electricity, used to heat water before it is sprayed from the washer
Hotboxing, smoking marijuana or hashish in a small enclosed area, causing it to fill with smoke in order to maximize the effect
The Hot Box, a fictional nightclub from the musical Guys and Dolls
an enclosure used for beef aging
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