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Proto
- Modeling
Info |
Track Feeder Wires
LIRR Track wiring 07/25/09
Greenport
Photo: Al Castelli |
Transition Rail joiner
LIRR 03/09/1972 Richmond Hill
Photo: Robert B. Dunnet
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LIRR Frog 1/2019 Frank W. Sutera |
LIRR Switch Machine Gershow Recycling, Medford turnout 2021
Photo/Archive: Gregory Nelson |
Motor Truck 3rd rail pick-up shoe MU-MP54A #1595
c. 1930 Archive: Dave Keller |
DM30 truck 3rd rail shoe
Photo/Archive: Mike Boland |
Bonding Jumpers
provide a sure electrical connection between the two sections of rail. The
3rd rail return and signal track circuits use the running rails. the joint
bar is deemed not a significant enough connection for the circuits, so there
is that bonding jumper. Very likely this is temporary, and will no longer be
necessary when the rail joint is replaced by welding the two rail sections
together.
In the
days before welded rail you'd see a few smaller gage uninsulated wires
bonded by weld to both sections of the rail rather than the clamp you see in
that photo. The bonds carry power for two purposes.
In electrified territory, the rails provide the return path to the
substation for the 750 volts. That path is also provided through the ground,
or the earth. While the ground will easily provide a return path, the rails
do it better and assuring their continuity with good bonding reduces current
losses and protects buried utility pipes from corrosion caused when they
become a path to stray power. Rail bonds in electrified territory are very
thick, to accommodate the high propulsion current loads.
On non-electrified track, thinner bonds are used, and the only power path is
signal current, which is generally low voltage and amperage. Each signal
"block" is a segment of track, separated from the next block by insulated
rail joints. The insulated joints are made with a fiber or plastic sleeve
between the rail ends and connecting bars. Signal power, generally from a
battery, is fed into the rails at one end of the block and is received by an
electromagnet relay at the other end. In this manner, a broken rail or bond
anywhere in the block can be detected. When an axle shunts the two rails, it
shorts out the battery, deactivating the electromagnet. The relay "drops,"
displaying the proper signal aspect in the adjacent blocks.
A broken track wire generally causes a Stop and Proceed Signal aspect to be
displayed (which means Stop, then Proceed at Restricted Speed). By the very
definition of Restricted Speed, it contains wording which indicates that the
person operating the train, among other things (immediately reduce speed,
watch for crossing protection not working, etc.), should be looking out for
a broken rail. Robert Myers |
| ROW
- Roadbed by
David S.
Rose |
|
 Think
about the engineering challenge faced by running miles of narrow ribbons
of steel track on top of the ground: they are subject to heat expansion
and contraction, ground movement and vibration, precipitation buildup from
rough weather, and weed and plant growth from underneath. Now keep in mind
that while 99% of the time they are just sitting there unburdened, the
remaining 1% they are subject to moving loads as heavy as 1,000,000 pounds
(the weight of a Union Pacific Big Boy locomotive and its tender).
Put all this together, and you have yourself a really, really interesting
problem that was first solved nearly 200 years ago, and hasn't been
significantly improved since!
The crushed stones
are what is known as ballast. Their purpose is to hold the wooden cross
ties in place, which in turn hold the rails in place. |
|
 The
answer is to start with the bare ground, and then build up a foundation to
raise the track high enough so it won't get flooded. On top of the
foundation, you deposit a load of crushed stone (the ballast). On top of the
stone, you lay down (perpendicular to the direction of the track) a line of
wooden beams on 19.5 inch centers, 8 1/2 feet long, 9 inches wide and 7
inches thick, weighing about 200 pounds...3,249 of them per mile. You then
continue to dump crushed stone all around the beams. The sharp edges of the
stone make it difficult for them to slide over each other (in the way that
smooth, round pebbles would), thus effectively locking them in place. |
|
Think
about the engineering challenge faced by running miles of narrow ribbons
of steel track on top of the ground: they are subject to heat expansion
and contraction, ground movement and vibration, precipitation buildup from
rough weather, and weed and plant growth from underneath. Now keep in mind
that while 99% of the time they are just sitting there unburdened, the
remaining 1% they are subject to moving loads as heavy as 1,000,000 pounds
(the weight of a Union Pacific Big Boy locomotive and its tender).
Put all this together, and you have yourself a really, really interesting
problem that was first solved nearly 200 years ago, and hasn't been
significantly improved since!
The answer is to start with the bare ground, and then build up a
foundation to raise the track high enough so it won't get flooded. On top
of the foundation, you deposit a load of crushed stone (the ballast). On
top of the stone, you lay down (perpendicular to the direction of the
track) a line of wooden beams on 19.5 inch centers, 8 1/2 feet long, 9
inches wide and 7 inches thick, weighing about 200 pounds...3,249 of them
per mile. You then continue to dump crushed stone all around the beams.
The sharp edges of the stone make it difficult for them to slide over each
other (in the way that smooth, round pebbles would), thus effectively
locking them in place.
Note: There are
approximately 689,974,000 ties in the United States, supporting 212,000
miles of railroad track. In 2011 the major US railroads replaced a total
of 15,063,539 ties. 14,148,012 of them were new and made of wood; 544,652
were second-hand wood ties; and 370,875 were new ties made of something
other than wood. Old ties are recycled for use in landscaping, turned into
pellet fuel, or burned in co-generation plants to provide electricity. |
|
 Next,
you bring in hot-rolled steel rails, historically 39' long in the US
(because they were carried to the site in 40' gondola cars), but
increasingly now 78', and lay them on top of the ties, end to end. They
used to be joined by bolting on an extra piece of steel (called a
"fishplate") across the side of the joint, but today are usually
continuously welded end-to-end.
|
|
 It
would seem that you could just nail them or bolt them down to the ties,
but that won't work. The non-trivial movement caused by heat expansion and
contraction along the length of the rail would cause it to break or buckle
if any of it were fixed in place. So instead, the rails are attached to
the sleepers by clips or anchors, which hold them down but allow them to
move longitudinally as they expand or contract.
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|
 In
the event you have lighter weight rail to be connected to heaver weight rail
the use of a transition rail fishplate is utilized as seen in this photo on
the LIRR. Here we had the replacement of a turnout on the mainline in
Calverton, NY using heaver rail with the existing Grumman spur trackage.
Modelers
can duplicate this via the use of a flattened rail joiner under the smaller
code track joined to the larger code.
Photo: Tom Collins
|
So
there you have it: a centuries old process that is extremely effective at
facilitating the movement of people and material over thousands of
miles...even though nothing is permanently attached to the ground with a
fixed connection!
The ballast distributes the load of the ties (which in turn bear the load
of the train on the track, held by clips) across the foundation, allows
for ground movement, thermal expansion and weight variance, allow rain and
snow to drain through the track, and inhibit the growth of weeds and
vegetation that would quickly take over the track. |
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What's New
Last Updated:
04/28/2023
