Track training 03082013

MBTA Standardized Track Training

CHAPTER ONE
TRACK STRUCTURE
ATTENTION VIEWERS

Chapter 1: Track Structure
The track structure for railroads consists basically of:
Subgrade Ballast Ties Rail Plates Spikes Splice BarsBolts
Track Structure

The two primary functions of the track structure
Support the Train Guide the Train
• The weight of the train is
transferred from the steel
wheels to the steel rail
• It is then distributed by the
beam action of the rail to several
cross-ties.
• The crossties further
redistribute the load, passing in
on to the ballast.
• Finally the ballast redistributes
the load again and passes it on
to the subballast and ground
Track Structure

HEAD
BASE
RUNNING SURFACE
SIDE
FILLET
WEB
The T-rail is the standard
for railroads in the
United States today.
T-rails vary in shape
(section) and weight
RAIL

RAIL

Almost all rail of standard 39’ length used to be
fastened together at joints by the use of joint bars
Today, (39’), the joints have been considerably
reduced by welding standard length rails together
into continuous strings
Joints and Continuous Welded Rail

With bolted rail, the joint bars are attached to the rail by
either 4 or 6 bolts. The rail is eventually battered down by this
repeated action
Four-hole joint bars are 24 inches long and six-hole bars are
36 inches long. Spacing of bolt holes in the rail and joint bars
often differ for each rail weight and section
Proper maintenance of joints is essential to prevent end
batter of rail, to provide support, and to give a smooth ride.
End batter is caused by the slight pounding action of car
wheels as they leave one rail and ride onto the next. The rails
are normally drilled at the mill.
Joints and Continuous Welded Rail

Holds the rail in
proper gage and
line.
Transmits the
train weight from
rail to ballast.
Distributes the train
weight over a larger
area
Provides a base to
which the rail can
be anchored.
Provides support
which distributes
the load & across
the roadbed and
under both rails .
Crossties
Crossties serve several important functions including the following:
Most wood crossties are treated with a preservative to
inhibit decay and insect attack. Average life of a tie is
about thirty years, but tie life expectancy varies due to
climatic conditions, damage and amount and type of
traffic.
Standard size crossties range from 6” x 8” to 7” x 9”
in cross section and 8’ to 8’6” in length. Longer
timbers 9’ to 22’ in length are used under switches.

GAGE
Gage of the track is the distance between the rails.
Standard gage today is 4’ 8 ½” measured from the inside
edge of one rail to the inside edge of another rail.
Gage widths have varied over the years ranging from 3
feet for narrow gage and up to six (6) feet for broad gage.
The origins of the 4’ 8 ½” gage width have been lost in
antiquity. Some people claim it was based on the Roman
Chariot.
Perhaps the most logical explanation is that since
railroads were a natural progression from the tramways,
and since the tramways had a gage of 4’ 8 ½” then, as a
matter of convenience, the railroads adopted the
tramway gage.

Chapter 2: Rail
Identification
Rail is described as steel rolled into a shape referred to as a
“Tee” configuration usually in thirty-nine (39) or seventy-eight
(78) foot lengths.
Some section names:
RE American Railroad Engineering &
Maintenance of Way Association
ASCE America Society of Civil Engineers
Rail is rolled into different sizes (dimension) and shapes or of
different weight and section

Identification
Chapter 2: Rail

Rail is identified by the upset letter and numbers hot stamped on the web of
the rail. The hot stamping shows the weight and section of the rail, cooling
and end hardening process, name of the manufacturer, mill location, and the
year and month the rail was rolled.
(Example: 132, RE, CC (or CII), BSCO, STEELTON, 1961, ////////)
Meaning:
132 - Weight of the rail per yard
RE - Rail Section (area in this case)
CC - Rail is control cooled
CH - Rail is control cooled and end
hardened
BSCO - Manufactured at Bethlehem Steel
Corporation
STEELTON - At Steelton Mill (in Steelton, PA)
1961 - Year Rolled
//////// - Month rolled (August)
OH - When shown means Open Hearth
(process of making steel)
Identification
Chapter 2: Rail

On the opposite side of the rail web cold stamped inset letters
and numerals are shown. This is commonly called the heat
number.
(Example: CH 2900065 B 6)
Meaning:
CH - Control Cooled and End Hardened
290 - Heat Number (can also identify the type of
furnace)
065 - Heat Number, the number representing a
furnace loading(charge) of metal. Each
loading consecutively numbered.
B -The second rail produced (rolled) down
from the top of an ingot. Either the second
rail is rolled from the first bloom or first rail
from the second bloom. (See Figure 2-2)
6 -This rail was rolled out of the sixth ingot of
the heat.
Identification
Chapter 2: Rail

Manufacture of Rail
There are three (3) basic types of heating used for steel
made today in the United States:
Open Hearth
Basic Oxygen
Electric
Steel mills generally manufacture rail metal by the
Open Hearth (OH) process.
Chapter 2: Rail

Furnaces are charged with
scrap metal, lime stone,
and or molten pig iron to
produce rail steel
The molten metal is
tapped (poured) from the
furnace into the huge
ladle
The molten steel is then
poured into ingot molds
This cavity (pipe) end of
the rail is visually
inspected
Manufacture of Rail
Chapter 2: Rail

Procedure
During the rolling process
this cavity, or most of it, is
rolled (pressed) together
resulting in usable steel
As the metal cools in the
ingot mold, there is a
shrinkage cavity formed in
the center of the ingot from
the top downward
The rail bloom is further
cut back until the defect
disappears
As the ingot cools, the
metal shrinks (contracts)
and the ingot mold is
removed
Manufacture of Rail
Chapter 2: Rail

Once mold is stripped from ingot,
mills move the red hot ingot directly
to rail mill for immediate rolling.
After the rolling process the hot
rolled rail moves to the hot saw and
is sawed into 39’ lengths
The rail then goes to the hot bed
and cools to about 800 F
The rail is then moved to the
control cooling boxes (cars),
covered and further cooled for
about 10 hours
Rail is processed through the
finishing mills for straightening,
end milling, and final inspection
to acceptance.
Manufacture of Rail
Chapter 2: Rail

Hold rail in
proper gage
and line
Transmit the
train weight
from rail to
ballast
Distribute the
train weight
over a larger
area
Provides
base to which
the rail can be
anchored to
prevent the rail
from moving
Provide support
to distributes
the load across
the roadbed and
under the rails
allows
adjustments to
be made in
track line and
surface
Chapter 3: Crossties
Use
Crossties serve several important functions:
1. The Crosstie must
be strong enough
to support this
weight
2. Hold the rail in
proper gage
3. Withstand outward
forces and;
4. Transmit the load
to the ballast.

Wood Ties
• Provide elasticity of support to the
track structure, are easily worked
and have relatively long life
• Decay, fire, derailments and wear
from heavier loads can
significantly reduce the life of a tie
or destroy it entirely
• Exposure to wet conditions reduces
tie life
• Many varieties of wood can be used
for ties, including both hardwoods and
softwoods. **The MBTA uses mostly
oak timber ties
• Regardless of the type of wood used,
the tie should be free from large splits,
numerous knots, and obvious decay

Wood Ties
Ties are graded by size to allow the larger ones to be sorted for
use in tracks carrying heavier and faster traffic. Practically all
railroads use the same grading system shown as follows:
**The MBTA uses ties that are 7” x 9” in section, and 8’-6” long, for
standard track. Longer ties are used in turnouts.
Grade of Crosstie
1 6” thick x 6” wide (top)
2 6” 6” thick x 7” wide (top)
3a 7” thick x 7” wide top (8” wide through body)
4 7” 7” thick x 8” wide (top)

Anti-Splitting Devices
Due to the natural tendency of wood to split, the practice of
applying anti-splitting devices into the ends of the tie has been
used for many years

Treatment (wood)
Wood, unless it is protected, will be
destroyed by insects, ice, and decay. To
extend the life of wood ties, ties are treated
with a preservative
Creosote is a primary ingredient in most of
the preservatives used to treat ties and
timber
Species that are hard to treat or have very
little sapwood are run through a machine
where the surfaces receive hundreds of
knife cuts. This is called incising.

It is important to remember that the preservative does not penetrate
completely through the tie or timber, only about ¼”
Thus, rough handling, reshaping or old spike holes can expose
the untreated wood to decay fungus, wood destroying insects
and moisture which will cause early failure of the timber
All holes should he plugged and all exposed areas treated with
preservative
Some railroads, including the MBTA order their ties with spike
holes pre-bored prior to treatment
Treatment (wood)

Concrete Ties
• Concrete then installed on the Ashmont
Line are still in service though
• Concrete ties are pre-cut and made
with 7000 psi concrete
• The typical railroad concrete tie is 780
lbs while the transit version is 680 lbs
• MBTA has had some bad experiences
with concrete on the commuter rail
system due to chemical reaction
between the concrete and aggregate
• There are two types, monoblock and
dual block. Dual block are made of
separate cement blocks, one under
each rail, connected by a steel bar.
Monoblock concrete ties are one
continuous beam

Tie Spacing
Timber ties on MBTA
Commuter Rail
standard track, are
spaced at 191/2”.
Transit timber ties are
spaced at 24”
Concrete ties are
spaced at 24” for
commuter rails
and 30” for
transit.
Switch ties will
have varied
spacing due to the
nature of the switch
hardware they
support.

Direct Fixation

CHAPTER FOUR
OTHER TRACK MATERIAL

There are 3 types of joint
bars in use
Insulating
Joint
Compromise
Joint (step
bars)
Standard
Track Joint
(splice bars)
Chapter 4: Other Track Material
Joint Bars, Bolts, and Nut Locks

Tie Plates
Tie Plates
Functions
Form a seat for the rail
Enable the weight to be
distributed over a larger area
to reduce tie cutting &
abrasive effects of the loads
Provide better holding power
for the spikes and help hold
the track gage
The size of tie plates ranges from 7” x 10 ¼” to 7¾” x 15 ½”
depending on the width of the base of the rail

The MBTA uses so called “double shoulder” tie plates. These
plates have two shoulders, one on each side of the rail seat
• The double shoulder plates must be designed for each
specific weight of rail
• All double shoulder plates are punched with square or round
holes to hold a maximum of 8 spikes or screw spikes
respectively
• When a rail is properly seated in a plate, lateral movement is
restrained which helps hold the track in gage
Tie Plates

Track Spikes
The track spike stands alone as the one item of track fastening
that hasn’t changed a great deal over many years of railroad
constructions and maintenance in the United States
They are generally 6 inches
long, ¾ inch square and 1 ¼
inches wide across the head
Spikes are made of soft (ductile)
metal because if they were brittle
they would break when driven or
fracture when stressed under
traffic conditions
They weigh about 10 ounces
each and are shipped in metal
containers with approximately
240 spikes per container

All spikes are driven straight down with the extended head end
facing the rail. Spikes driven against or at the base of the rail are
called rail holding spikes. Other spikes driven in the plate holes are
called plate holding spikes or anchor spikes
Track Spikes
LEGEND
Indicates Rail holding Spikes In all Cases
• 1st Plate Holding Spike (Where Only One is Required).
• 2nd Plate Holding Spike (Where Two Are Required).
• Use Additional Spike Holed, if specs require it
SPIKE APPLICATION WITHIN
JOINT BAR LIMITS
SPIKE APPLICATION OF RAIL AND
PLATE HOLDING SPIKES
(TANGENT AND CURVED TRACK)
Rail holding spikes shall have
approximately ¼” clearance between
underside of head and top of base of rail
Spiking on bridges and trenches
shall be the same as for
Standard Ballasted Track

Pandrol Clip Fasteners

Concrete Tie Fastening
Standard track spikes or screws cannot be used
for fastening rail to concrete tiers
The type of rail fastening utilized for concrete ties is
a shoulder inserted into the tie concrete when wet
at the pre cast plant

Rail Anchors
• Rail anchors are devices that retard expansion and
contraction of rail, on any movement or slippage of
the rail through the ties plate
• They are used on either side of the tie, which is
called box anchoring
• Contact with banded clips, the anchoring is
accomplished by the vertical face of the clips on the
top of the rail base providing about 2000lbs of
longitudinal resistance

Rail Anchors

Derails
• Derails are used as a last resort to prevent a run-
away car from causing great damage, by moving
into the path of an incoming train
• Derails actually derail the car under the
assumption that the cost of re-railing one car is
less than clearing a massive wreck the loose car
could cause if it ran into another train
• There are three main types, the hinges on sliding
derails used in freight sidings, and the switch point
derails commonly associated with moveable bridge
and track crossings at interlocking

Bumping Posts
• Bumping Posts are placed at the ends of tracks to
prevent cars from rolling off the end of the track
• They cannot stop a speeding train, only very slowly
moving cars
• Other end-track devices involve wheel stops,
concrete blocks, or a pile of fill which reduces
damage to the car if hit
• Piston bumpers are used at North and South
Stations to absorb a slow speed strike, presumably
up to 15 mph

Chapter 5: Grade Crossings
Grade Crossings are used to
allow automobile traffic to cross
over tracks
Crossings must be designed for good
drainage. If the track is in a grade, the
uphill side becomes a dam that holds
water and causes deterioration. Track
drains on the uphill side freely alleviate
this problem.
This pattern is most seen on the Green
Line surface road medians where the
tracks are on a grade.
General Information

Chapter 6: Turnouts
Turnouts or switches are track structures that
allow trains to move from one track to another
They consist of various rails, plates, braces,
rods and other fixtures to allow for the
mechanical transfer of a train from one track
to another
General Information

General Information
Chapter 6: Turnouts
Guard Rail
Guard Rail

Turnouts are designated
as left or right, equilateral,
or curved
If a person stands at the
switch end of a turnout
and looks toward the frog,
the turnout is right if the
diverging route turns to the
person’s right, and left if it
turns to the person’s left
General Information
Chapter 6: Turnouts

• Turnouts can be thrown manually or by use of a
switch machine
• A terminology commonly used for powered switches is
to designate the two routes as either “normal” or
“reverse.”
• It is important to know how to “read” a switch
• Reading a switch is determining what route it is set for
just by looking at the mechanical setting of the switch
points
General Information
Chapter 6: Turnouts

With respect to terminology, moving
over the turnout in the direction from
the switch points to the frog is called a
“facing point” move
Moving in a direction over the turnout
from the frog toward the switch points
is called a “trailing point” move
General Information
Chapter 6: Turnouts

Size Designation
Turnout sizes are designated by either the curved radius of
the curved route, or the frog number
Transit turnouts can be: 50’
75’
100’
150’
200’
250’
Turnouts on the Red, Orange, and Blue lines are as small
as 150’ radius and the smallest on the Green line are 50’
Chapter 6: Turnouts

• Beyond 250’, the designation of a turnout changes to a
number system related to the frog angle, the smallest being a
No. 5, which is close to a 250’ CR turnout
Size Designation
• The smallest turnouts on railroads are either
No. 7’s or 8”s
• The smallest prescribed on the MBTA commuter rail
system is the No.8
• The terminal tracks outside of South Station are
filled with No. 8’s
• However in new MBTA work, No 10’s are the smallest an
are used for industrial sidings coming off the main track,
while No. 15’s and 20’s are common for use in the main
line track for crossovers and sidings
Chapter 6: Turnouts

Size Designation
No. 6
No. 8
No. 20
Chapter 6: Turnouts

Size Designation
The number of the turnout refers to the frog number
that designates a characteristic of the geometry of
the frog angle
The frog number is defined by AREMA as ½
COT (1/2(frog angle))
This system makes it easy to determine the frog
number in the field
Chapter 6: Turnouts

The ½” Point of Frog (PF)
In plans and drawings of frogs, a dimension called the ½” point of frog is
often shown, rather than the theoretical point of frog
Chapter 6: Turnouts

Point of Intersection (PI) and Point of Switch (PS)
A critical construction point of a turnout is the point of intersection, from which
the point of switch, and the ½” point of frog are measured
The point of intersection, or the PI, is the point where the tangent extension of the
centerline of the diverging route intersects the track centerline of the main route
The point of switch, or PS, is the physical end of the switch point rails, and
the ½” point of frog, or PF, is as discussed in the previous paragraph
Chapter 6: Turnouts

Point of Intersection (PI) and Point of Switch (PS)
The equivalent radii of turnouts with number designations, actual lead,
length of tie bed, and speeds are as follows, based on AREMA standards:
Notice that the higher the turnout
number, the greater the length
and speed
*Speed depends on whether
straight or curved switch points
are used. It is higher for curved
points
Chapter 6: Turnouts
Turnout No. Curved Radius Actual Lead Length of Tie Bed Speed*
No.5 177.80’ 42’-6 1/2” 60’-11” 2 mph
No. 6 258.57’ 47’-6” 69’-8” 13-15 mph
No. 8 487.28’ 68’-0” 97’-8” 19-20 mph
No. 10 779.39’ 78’-9” 115-11” 20-25 mph
No. 12 1104.63’ 96’-8” 141’-4” 27-29 mph
No. 15 1720.77’ 126’-4 ½” 182’-3” 36-38 mph
No. 20 3289.29’ 151’-11 ½” 226’-7” 36-50 mph
1

Turnout Components
Turnout
Components
Include
Switch
Points Stock
Rails
Closure
Rails
Frogs
Switch
Tie
Plates
Braces
Heel
Blocks
Switch
Rods
Rail
Restraint
Guard
Rails
Switch
Ties
Chapter 6: Turnouts

CHAPTER SEVEN
TRACK ALIGNMENT & CURVATURE

Simple Curves
The primary purpose of any curve is to provide the required change in
direction in a form best suited to the operating conditions
• A simple curve is a segment of
a circle having a constant
radius and length
• The tangent touches the
circumference (on the circle)
at only one point, the point of
tangency
• At this point the radius of
the circle and the tangent
are at right angles (90 )
Chapter 7: Track Alignment and Curvature

If two or more simple curves of different degree of sharpness are joined
together without a tangent section between them, it is a compound curve
PC
PCC
PC
PC = Point of Curvature
PCC= Pointof Compound
Curvature
Compound Curves

Spiral curves having constantly changing radii are used to provide a gradual
transition between a curve and its tangents, or between two or more simple
curves to form a compound curve
TS
0 + 00
SC
1 + 00
CS
3 + 00
ST
4 + 00
Direction of increasing
Stationing
TC - Tangent of Spiral
SC – Spiral to Curve
CS – Curveto Spiral
ST – Spiral to Tangent
Spiral Curves

1. A curve or is defined by its radius
2. For most railroad curves, the radius is so large that the
center of the curve is inaccessible in the field, and
although it is necessary for computation purposes, it is not
used in field work
3. Instead, the degree of curvature is used to define
railroad curvature
There are two definitions of degree of curve
Chord definition Arc definition
Spiral Curves

Chord definition – The
degree of curve is equal to
the central angle subtended
by a 100 foot chord
Arc definition – The degree of
curve is equal to the central
angle subtended by a 100
foot arc
Curve Definition

Vertical Curves
• Where different grade lines meet, the change from one
grade to another must be gradual
• To accomplish this gradual change in elevation requires
the use of some type of curve
• For horizontal alignment, a simple curve of constant
radius, supplemented with spirals, is generally used
• In the vertical plane (profile), the constant radius curve does
not provide the gradual transition required for smooth
operation
• Consequently, parabolic curves are used to
accomplish a gradual change in grades

Parabolic curves as compared to a simple curve of constant radius
deviate from grade line gradually, providing a smooth transition
A parabolic curve plotted on a coordinate axis would appear as
shown below:
Vertical Curves

The following basic equation is used for calculating vertical parabolic curves:
G1 = - Grade No. 1 in %.
G2 = - Grade No. 2 in %
L = - Length of Curve = No. of 100ft. stations measured horizontally.
2a = - Rate of change of adjacent chords, and is a constant that has
been established through usage. The maximum value of “2a” in
general practice has been established at 0.05 ft. per 100ft. for
sag curves, and 0.10 ft. per 100ft. for crest (summit) curves on
high speed main tracks. These values of “2a” are frequently
doubled for main and secondary tracks of lesser speeds thereby
permitting shorter and sharper vertical curves.
2a = 100 (G2 – G1)
L
Vertical Curves

CHAPTER EIGHT
TRACK SURFACE AND SUPERELEVATION

Chapter 8: Track Surface and Superelevation
Track Surface
Commonly used to describe the smoothness of track
Technically, it is the height relation of opposite rails to each
other in profile and cross level
Cross level is the difference in elevation at the top of the rail
measured at right angles to the track
Proper track surface is attained when the rails are at the
same height throughout their length or when the elevation
changes uniformly
General Information

General Information

High Rail
Low Rail
Superelevation
SUPERELEVATED TRACK
TANGENT TRACK
General Information

The following table shows the maximum allowable variations in profile,
elevations, and cross level for safe passage of trains
Track Surface Condition
Class of Track – Maximum Speeds
1
F- 10
P- 15
2
F- 25
P- 30
3
F- 40
P- 60
4
F- 60
P- 80
5
F- 70
P- 90
6
F- 70
P- 100
The runoff in any 31 feet of track at the
end of a raise may not be more
than………………….
The deviation from the uniform profile on
either rail at the mid-ordinate of a 62- foot
chord may not be more
than……………..........
Deviation from designated elevation on
spirals may not be more
than…………………
Variation in cross level on spirals in any
31 feet may not be more
than…………………….
Uniform deviation from zero cross level at
any point on tangent or from designated
elevation on curves between spirals may
not be more
than…………………………………………
…….
The difference in cross level between any
two points less than 62- feet apart on
tangents and curves between spirals may
not be more
than……………………...............................
......
3-1/2”
3”
1-3/4”
2”
3”
3”
3”
2-3/4”
1- 1/2”
1-3/4”
2”
2”
2”
2-1/4”
1-1/4”
1-1/4”
1-3/4”
1-3/4”
1-1/2”
2”
1”
1”
1-1/4”
1-1/4”
1”
1-1/4”
3/4”
3/4”
1”
1”
1/2”
1/2”
1/2”
1/2”
1/2”
5/8”
General Information

A curved section of track is superelevated when the vertical
distance or height of the outer rail is above the inner rail
On curved sections of track, superelevations counteract the
centrifugal force which tends to keep cars going in a straight line
away from the curve
For perfect equilibrium, the amount of superelevation will exactly
balance the centrifugal force
It has been found that by introducing less elevation in a curve than
that which produces equilibrium increases the weight on the high
rail, improves ride comfort, and reduces rocking of equipment
Superelevation

R = 5730. E can be shown to be equal to:
D
E = 0.0007 V²D or V² = E .
0.0007 D
Superelevation
Where: E = amount of superelevation to achieve equilibrium in inches
V = Velocity (speed) in MPEE, D = degree of curve in degrees

To provide structural support for
the track, holding it in good line
and surface
To distribute the load evenly to the
subballast and subgrade and thus
help to provide stability
Provide for drainage
Chapter 9: BALLAST
Purpose
Ballast in railroad terminology is durable granular material placed between
the crosstie and the sub ballast to hold the track in line and grade
The primary purposes of ballast are:

BALLAST
SUBBALLAST SUBGRADE
BALLAST SECTION
Chapter 9: BALLAST
Purpose

Types of Ballast
MBTA uses crushed granite for ballast in its track.
It is quarried locally. MBTA normally uses AREMA
No. 4 ballast
Stone ballast (particularly trap rock) is most suited to
heavy service. Railroads attempt to buy the best
stone ballast available for use in heavy service tracks
Chapter 9: BALLAST

Functions of Ballast
In discussing the functions of ballast, the first three items, support,
distribution of load, and stability should be handled as one subject. A
standard ballast section for a double track system is shown below:
Chapter 9: BALLAST

Ballast Failure
Pumping ties is a condition where the roadbed has become
unstable and when a train passes over the section, the ties are
pushed down forcing water out from under them
A pumping situation may also indicate an unstable subgrade
brought about by too much water in it
The excess water may be a result of dirty (fouled) ballast,
inadequate surface drainage, high ground water table or
capillary action
The ballast and sub ballast material is then forced down in-to the
subgrade and the subgrade material works its way up through the
ballast
Pumping begins when water accumulates under the tie and is
forced out by the train pushing the tie down, carrying with it the
smallest particles of soil
Chapter 9: BALLAST

Ballast Testing
In general, ballast shall be composed of angular fragments, reasonably
uniform in quality and having specified durability and wear-resistant
qualities
These tests for compliance are made by special inspectors and
laboratory technicians; however, some knowledge of these procedures is
necessary for quality field work
Remember, the basic objective is to obtain a material which will support
the loads, provide stability, and be free draining
Chapter 9: BALLAST
Sieve Analysis
Absorption
Soundness
Abrasion
Cementing Value
Typical laboratory tests for determining the quality of ballasts include:

Field Inspection
In-transit shaking of a car of ballast may cause some separation of various
sizes of aggregate
Ballast should be inspected for conformance to specifications as it is
unloaded
Size No.
(See
Note 1)
Nominal
Size
Square
Opening
Percent Passing
3” 2 ½” 2” 1 ½” 1” ¾” ½” 3/8’ No. 4 No. 8
24 2 ½” – ¾” 100 80-100 25-60 0-10 0-5 - -- -
25 2 ½” – 3/8” 100 80-100 60-85 50-70 25-50 - 5-20 0-10 0-3 -
3 2” – 1” - 100 95-100 35-70 0-15 - 0-5 - - -
4A 2” – ¾” - 100 90-100 60-90 10-35 0-10 - 0-3 - -
4 1 ½” – ¾” - - 100 90-100 20-55 0-15 - 0-5 - -
5 1” – 3/8” - - - 100 90-100 40-75 15-35 0-15 0-5 -
57 1” – No. 4 - - - 100 90-100 - 25-60 - 0-10 0-5
Note 1: Gradation Numbers 24, 25, 3, 4A and 4 are main line ballast materials. Gradation Numbers 5
and 57 are yard ballast materials.
Table of Recommended Ballast Gradations
Chapter 9: BALLAST

Subballast
Subballast is defined as any material of a superior character, which
can be spread on top of the finished subgrade, between the subgrade
and the topballast, to provide better drainage, prevent upheaval by
frost, and better distribute the load over the roadbed
The Subballast is:
• Six (6) inches or more thick
• helps to spread the load over the subgrade
Subballast material should be placed entirely over the roadbed cross
section
Some typical subballast materials are Compacted gravel at 100%
compaction
Chapter 9: BALLAST

Chapter 10: RAIL WELDING
Welded Rail Joints
Thermite Process
Rail end
preparation
Setting the
weld gap
Universal
clamp
application
Applying and
luting the
molds
Placing
Thermit®
portion into
the crucible
Preheating
the rail ends
Ignition and
pouring of
Thermit®
steel
Demolding
Shearing of
excess head
metal
Rough
grinding
Final
Grinding

Electrifying the two opposing rails and then pushing them
together to create a huge short circuit that produces
enough heat to melt the rails so they fuse into one another
After being fused, they are sheared, grounded and
subsequently tested
The strings roll from the welder right into an
awaiting welded rail train comprised of flat cars with
racks of rollers
The train of rails then delivers the rails to the site
where individual rails are rolled off the train and
onto the track
Electric Flash Butt Welds
Electric flash butt welding is mostly used in a rail shop
where long strings are being fabricated
The Flash Butt Weld works by:

• The flash butt weld, or shop weld, is desirable because it is
comprised of the parent rail steel material
• Rails of different sections can be welded together in a
shop and brought to the field as a 19’ plug to connect rails
of different sections without the need for compromise joints
• Portable flash butt weld plants can be erected in the field.
This allows for smaller strings to be made in areas for which
a rail train is impractical and the transportation of long
strings over roadways by truck is impossible
• Oxyacetylene welding is another method of welding rail
strings. In this case, the rail ends are flame heated to the
melting point and then pushed together in the same
manner as described above for electric flash butt welding
Electric Flash Butt Welds

Laying Welded Rail
In laying the rail, it is heated to the
desired temperature using a rail
heater. Rail thermometers are used
to monitor the rail temperature
Once it reaches the desired
temperature, also known as the
neutral temperature, it is clipped
into place
The rail will then be field
welded to the next rail and
the process continues
Sometimes, after the track has been resurfaced, it will be unclipped
and re-stressed because the surfacing process may have disturbed
the track enough to require re-stressing and re-anchoring

Expansion of Welded Rail on Bridges
On bridges where the rail is fastened to ties directly attached to the
bridge, or on direct fixation deck bridges, welded rail is anchored
differently
This is accomplished in a few ways
Anchoring the rail in the middle of the bridge only for about 100
feet, and then use so-called zero toe load fasteners on the rails
on either side of it over the remaining length of the bridge
Anchoring the rail on the outside of one end of the bridge, use
zero toe load fasteners over the entire length of the bridge, and
then employ Conley joints on the opposite end of the bridge
OR

Track training 03082013

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