Presentation on theme: "Module 7: Basic Track – Part II"— Presentation transcript:
1 Module 7: Basic Track – Part II Introduce YourselfModule 7: Basic Track – Part IISpecial Trackwork
2 Module Objectives Recognize Complex Track Components Understand Their FunctionFamiliarity with TerminologyIn previous modules we examined the basic components of track and railway equipment, such as rail, ties fasteners and ballast, as well as the cars that use them.This module is designed to build upon that knowledge and:Demonstrate how those basic components are utilized to create more complex track components, commonly referred to as “Special Trackwork”,How the complex components function to permit trains to change tracks and cross other tracks and roadways, andFamiliarize ourselves with terminology used to identify sub parts of the special trackwork components.
3 Turnouts & Crossings Frog Switch Turnouts are often inaccurately referred to as switches. A turnout is a combination of a switch, a frog, the rails necessary to connect the switch and the frog, and a switch stand or switch machine for operating the switch. A turnout begins with the switch and ends with the Long ties beyond the frog. The purpose of a turnout is to permit engines and cars to pass from one track to another.Each turnout is identified as a number (e.g. # 10). The number of the turnout is determined by the ratio of the units of length for one unit of spread between the gage lines of the frog. The turnout # also determines the geometry of the many other dimensions of the turnout.Train movements through the turnouts are defined as Facing Point when the movement is from the switch points towards the Frog, and Trailing Point when the movement is from the frog towards the switch points.A crossing refers to the intersection of one railroad at grade with another. In some cases, the functions of both a crossing and a switch are combined to form a Slip Switch.Switch
4 Turnout Details-Switch BENTSTOCKRAILSTRAIGHT STOCK RAILSTRAIGHTSWITCH POINTDIVERGINGSWITCH POINTSWITCH HEELIntro SlideThe turnout is comprised of numerous parts. These next few slides will familiarize you with the terminology of the turnout parts and how the turnout functions to accomplish it’s purpose.A significant portion of the turnout parts comprise what is known as the switch. These are the moving parts that switch the train from one track to the next. While a turnout is designated by #, a switch is designated principally by the length between the points and the heel, and the geometry of the diverging switch point; straight or curved. There are numerous possible variations of switches and turnouts based on the combinations of component alternatives selected. While AREMA has recommended practices based on the type of use, each track owner has their own standards for specific situations. Detailed plans of all of the turnout parts can be found in the AREMA Portfolio. A few key diagrams, are included in this module.The switch diverts wheels from one track to the other and is delineated from the heel of switch to the point of switch.SWITCH RODSRAILBRACESSWITCHPLATESOPERATING RODHEAD BLOCK TIESSWITCH MACHINE
5 Switch Points AREMA Portfolio Plan 221 The switch consists of two switch or point rails connected by switch rods and operated as a unit. AREMA Portfolio plan 190 provides a more detailed illustration of the switch parts. The switch rails are of full rail section at one end, and are tapered to a ¼-in. or 1/8-in. point at the other end [PHOTO TOP RIGHT]. The tapered end is called the point of switch and the other end is called the heel of switch. The switch rails rest upon metal plates fastened to the ties.The theoretical point of switch is located ahead of the actual point of switch as the knife point edge would break off under train action. The actual point of switch is the practical end where the point is of nominal thickness at the tip. On railroad maps and surveys, this location is commonly noted as the “PS” or “HB” for the Head Block Tie on which the switch point is located.The approximate front 18” of the point is located below the top of the stock rail [POINT TO STOCK RAIL]. As the wheel moves along the stock rail, the wheel is gradually raised and transferred to the point. At that point, the point must now be rising higher than the stock rail to prevent the outside edge of the wheel from contacting the gage side of the stock rail and rolling the rail out. The beveled section of the point lies directly along the stock rail and at the point it begins to break away from the stock rail, it is a full section.Switch points can be a standard switch point (Photo Top Left), the end of which is tapered back and lays against the gage face of the stock rail or a Samson point, which is beveled back and fits against a beveled stock rail gage face – thus housing and protecting the point.The point of switch moves through a distance of about 5 inches, which is called the throw.Diverging switch points can either be straight or curved. The curved diverging points, shown on the details slide, reduce the angle between the switch point and the stock rail, permitting higher diverging speed. The hand of a switch point can be determined by standing at the tip end of the point and looking along its length: If switch clips are on the right side of the point, the point is a left hand switch point (and vice versa). The Switch Point details can be found in the AREMA Portfolio Plan 221.AREMA Portfolio Plan 221
6 Stock Rails Samson Undercut Stock rails are the outside rails in a switch that the points bear against. The stock rails are made of rail of the same weight and section as the switch point. The stock rail on the diverging side is bent [FRONT CENTER OF PHOTO TOP LEFT] so that a proper fit is maintained between the switch point and the stock rail, and to protect the point from wheel impact. The other stock rail is straight. In the case of an equilateral turnout, both stock rails are bent.Stock rails are either Samson, (called "undercut" when ordered), or standard. The beveled Samson stock rail allows the Samson point to tuck underneath the stock rail, thus protecting the point from impact. Samson and standard switch points and stock rails cannot be intermixed.Stock rails can be purchased pre-bent or as Universal, which require the use of a stock rail bender, a special hydraulic jack, to bend the stock rail. In addition to being bent, diverging Stock Rails must be straight or curved to match the diverging switch point.The Universal Samson stock rail (Photo Top Right) is beveled on opposite faces on either end.The Stock Rails are shown in the AREMA Portfolio with the appropriate switch detail.
7 Switch Plates AREMA Portfolio Plan 223 The Switch Plates [VERTICAL CIRCLES] provide two functions. One, they are milled to enable the stock rail to set lower than the point. The second function of the turnout plates is to provide a lubricated bearing surface for the plates to slide on.The front plates [BLUE CIRCLES] are known as gage plates and are continuous between the two stock rails. Maintaining perfect gage is critical immediately ahead of, and at the point of switch. These plates are often numbered as the 0 and No. 1 plates.Two styles of switch plates are commonly used. The uniform riser plates are milled exactly the same thickness for the stock rail. Specialty plates are used behind the heel to return the rail to its original elevation. For through bolted heel blocks a specialty heel casting is required to maintain the elevation difference between point and stock rail. The graduated riser plates run–off the elevation ahead of the heel block through plates of varying thickness at the stock rail seat.For either style of plates, tie spacing is critical. The plates are numbered and their order must not be mixed. Other specialty plates are used at the heel block, under the frog and guard rails as well.The Switch Plate details can be found in the AREMA Portfolio Plan 223.Click on the photos to return to the Master Turnout slide.AREMA Portfolio Plan 223
8 Rail Braces AREMA Portfolio Plan 223 WEDGE The outside braces [BLACK CIRCLE]support the stock rail from moving out under the applied load of wheel bearing against the switch point and stock rail. There are many styles of braces in use. The braces depicted in the photo are adjustable and are known as Security Braces. A tapered and serrated wedge [BLACK ARROW] is driven between a stop welded to the switch plate and the brace. A cover plate with cap nuts serves to keep the assembly in place. Repetitive train action tends to loosen the wedges and they must be periodically tightened. Over-driving of the wedge can tip the stock rail inward so that it is not properly seated in the plates.An older style of brace is the rigid non-adjustable brace. The brace base is spiked through the plate into the tie. With time, the timbers become spike killed and the brace is no longer secure.The Rail Brace details can be found in the AREMA Portfolio Plan 223.WEDGEAREMA Portfolio Plan 223
9 Head Block TimberThe head block timber are typically in the neighborhood of 17’ in length. The hand throw switch stand or powered switch machine are fastened to the ends of the switch timber. It is imperative that this timber be in good condition, so that lost motion in the throw of the switch not occur because of movement of the machine or switch stand about the timbers. The lost motion could translate into a gap opening up between the point and the stock rail, with the wheel flange splitting the switch.These ties must be kept tamped up as well. Otherwise, the point will tend to hang and under a train can be struck by a following wheel as the stock rail deflects downward.
10 Switch HeelThe heel of the switch is the pivot point for the switch points. The heel [BLACK CIRCLES] is a solid block, commonly used for points 16’-6” in length or shorter, through bolted between the point and stock rail. This block connects the closure and lead rails to the point and stock rails. The heel block is provided with a pair of bars, one of which is straight and the other bent to allow the point to move. Thimbles are included in the point end of the heel for insertion of the bolts, which provides latitude for movement.Longer points, shown in the above photo, commonly use a floating heel block, which is bolted only to the switch point. The long point moves as a result of the lever arm provided by the switch stand or switch machine against the remainder of the point fully spiked to the ties behind the heel. The floating heel block acts as a stop for the point in the closed position as it butts up against the stock rail.The distance between the gage lines of the main track and of the turnout at the heel of the switch rails [Black ARROWS] is called the heel spread and varies from 5-1/2 to 6-1/4 in. The angle between the gage lines of the switch rail and of the main track rail is called the switch angle, s, and is computed from the equationSin s = [heel spread (h) – width of switch point (p)] / [length of point (l)]Ahead of the heel block on each side are one or more stops, commonly called cusps [BLACK AROWS]. These are attached to the switch points, immediately ahead of the Heel Blocks, and provide positive support from the stock rail.SPREAD
11 Vertical SMJ RodsThe primary purpose of the switch rods is to maintain the proper spacing of the points such that each point when thrown is properly fitted against its respective stock rail. The properly adjusted rods cause the thrown point to contact the stock rail at each stop or cusp. The number of switch rods in use are reflective of the length of the points and the number of the turnout.Rod length may be adjustable through a serrated adjustable bolted clamp, in the center of the rod, as shown in the SMJ vertical rods [PHOTO TOP LEFT]. In the case of the horizontal rods [PHOTO TOP RIGHT], adjustment of length takes place via adjustable transit clips at the ends of the rods, which are bolted to the switch point. For Power Switches this adjustment is performed by the Signal Department, while hand throw switches are maintained by the track department.It is critical that sufficient space be provided between the inside face of the open point and the stock rail [HIGHLIGHT OPEN POINT]. the back edge of the wheel might strike the open point as the wheel traverses along the stock rail. Proper adjustment of the switch rods will ensure that this happens.The Switch Rod details can be found in the AREMA Portfolio 222.The adjustable clamps are circled.
12 Horizontal Rods The adjustable clips are circled. Typically, on hand throw switches the Maintenance of Way forces are responsible for adjusting the switch. On power operated switches the Signal forces are responsible for adjusting the switch.
13 Operating/Throw Rod No. 1 Rod Basket Operating Rod Front Rod Connecting rods are also called the operating or throw rod. The connecting rod connects the front switch rod to the switch stand. It may be attached by an adjustable connection (called a clevis) to the crank eye in the bottom of the switch stand and (by a rigid connection) to the front switch rod.There are different types of connecting rods - some are adjustable, some are not. They come in a variety of lengths depending on their use and the type of switch stand being used. For a switch to be in proper adjustment, the points must fit tightly against the stock rail when thrown in both positions. It should not be possible to lock the switch stand up with an obstruction more than ¼” thick placed between the point and stock rail at the No. 1 rod. The throw of the switch can be adjusted by lengthening or shortening the connecting rod at the same time as the crank eye on the bottom of the switch stand is lengthened or shortened. Switches equipped with non-adjustable throw rods and fixed length crank eyes can only be adjusted by changing the rod position on the transit clip or repositioning the switch stand.On a power switch [PHOTO ABOVE], the throw or operating rod is attached to a barrel shaped basket which is connected to the No. 1 switch rod. Adjustment of the lock nuts to either side of the basket enables adjustment of the switch throw. An additional rod coming out of the switch machine and attached to the front rod is the Lock Rod. Through the internal mechanism of the switch machine, this prevents movement of the points once the switch is in proper correspondence and a proceed signal is provided.For hand throw switches, the switch may be protected by a point detector rod which electrically checks to ensure that the point is thrown and in the closed position. This rod is typically of light construction and is connected to a switch circuit controller. The point detector rod does not provide locking protection.BasketOperating RodFront Rod
14 Switch Machine/Stand Dual Control Switch Machine Switch Stand Hand Throw Switch Stands There are a variety of switch stands in use. Typically, high stand switch stands are used in main line applications, whereas the ground throw stands [PHOTO TOP RIGHT] are used in industry or yard applications. Automatic switch stands are used to enable the stand to line when points are trailed through from either route. Main line switch stands are equipped with a target that is colored green when the switch is lined for the normal route and red if the switch is reversed. Yard switches equipped with targets are usually green for the normal route and yellow for the reverse route.Spring Switch This is a hand throw switch equipped with a spring mechanism instead of a rigid connecting rod. It is often called a mechanical switchman because the points return to normal position after the passage of each wheel. It is designed to allow trailing point movements from the diverging route without having to stop and reset the switch. The spring switch - switch stands must be bolted to the ties and be of the rigid type. The spring switch is typically provided with a target marked “SS” or other designation.Power Switch A power switch is an electrically powered machine that lines the switch. Some power switches are known as dual control switches. Dual control power switches (Photo Top Left) can be operated either by hand, using the hand throw lever, or remotely by the dispatcher.Dual Control Switch MachineSwitch Stand
15 Turnout Details-Frog FROG CURVED CLOSURE RAIL GUARD RAIL STRAIGHT CLOSURE RAILCURVEDLEAD RAILStraight Lead RailTurnouts are typically delivered today in paneled sections for field assembly. Behind the Switch, which may be delivered in 1 or more panels, are the Center Panels, consisting of the lead and closure rails, and the frog panel.The closure rail runs from the heel of switch (the pivot point) to the toe of frog (the joint at the front end of the frog). And finally the frog section contains the frog and guard rails. Special components are located in each of these two sections.We will look at the key components of these turnout panels.SWITCH TIMBER
16 Closure Rail Curved Lead Rail Straight Lead Rail Curved Closure Rail The closure rail are technically the two rails that connect the heel joint to the two toe rails of the frog – one curved and one straight. The outside two rails that the guard rails are secured to are known as the lead rails – one curved and one straight. The entire section of the turnout between heel and toe of frog is often called the closure rail section.The curved closure rail provides the connecting curve between the switch points and the frog. Its radius must be such that no superelevation is required to offset the effects of centrifugal force for a wheel traversing the turnout at designated speed. Obviously, the higher the diverging speed, the larger the required curve radius must be and the longer the closure rail section required.Turnouts equipped with uniform riser switch plates require specialty plates in the closure rail section to run-off the elevation that raised the point higher than the stock rail. Some railways utilize specialty plates called hook-twin tie plates with forged lugs that fit over the base of the rail throughout the entire closure rail section.The very nature of the closure rail section invites high lateral loads. Premium elastic fasteners are often used in heavy haul territory to minimize gage spreading under load.Curved Lead RailStraight Lead RailCurved Closure RailStraight Closure Rail
17 Frog Types Rail Bound Manganese Bolted Rigid Self Guarded Spring Rail Moveable PointFlange BearingPOINTA frog is a device at the intersection of two running rails to permit the flange of a wheel moving along one rail to cross the other rail. Turnout frogs may be classified as rigid frogs or spring-rail frogs. Both types of frogs are generally made with straight gage lines, except those used on street railways and specialty ordered curved frogs used in high curvature. Curved frogs are very undesirable, particularly for heavy car loadings.The point of the frog is machined off from the true or theoretical point to where the spread is 1/2“, referred to as the actual point of frog or “PF”. The distance “P”, between the actual frog point and the theoretical point (intersection of gage lines), equals the width of the blunt point multiplied by the frog number i.e., (1/2 N).The frog used in a turnout determines the number of the turnout. e.g.: # 10 turnout uses a number 10 frog, # 12 uses a number 12 frog. To find the number of the frog: Utilizing a tape measure, find the location behind the point of frog, on straight track, where the spread between the gauge lines equals an even increment of inches. Starting at that point, measure along the gauge line to the location where the spread between gauge lines equals one inch more than that previously measured. The distance in inches between the two locations where the gauge spread differed by one-inch equals the frog number. When measuring the frog number, particularly in a light rail line that may use special or ½ size frogs, one must take care to insure that both gage lines are straight. Measuring through a curve will create an error in your calculation. On freight railroads, where only a few sizes of even number frogs are in use, the same measurement can be made with a rudimentary instrument, such as a stick. Selecting a location where the spread of the gage lines equal the length of the stick, measure back towards the point of frog. The number of full increments of the measuring device from the initial point to the point of the frog is the frog number.Key frog components consist of:The frog point – a separation between the two flangeways.The frog tread - the surfaces that the wheels ride on ahead and at the point of frog.The flangeway - gap that permits the wheel flange to move without contact as it traverses across the frog.The toe is the front or narrow end of the frog, at the top of this photo, and the heel is the rear or wide end, at the bottom of this photo.TREADFLANGEWAY
18 AREMA Portfolio Plans 612 to 691 Rail Bound ManganeseINSERTReferred to as RBM frog.This is a heavy-duty frog used on mainlines because of its durability. The insert is made of a one-piece manganese casting. Lengths of machined rail or binder rails are bolted to the insert.[HIGHLIGHT JOINTS BETWEEN THE CASTING, BINDER RAILS AND REGULAR RAILS]RBM Frog details can be found in the AREMA Portfolio Plans 612 to 691.BINDER RAILSAREMA Portfolio Plans 612 to 691
19 AREMA Portfolio Plans 320-390 Bolted Rigid FrogsGUARD RAILBolted Rigid Frogs [PHOTO TOP LEFT] are made of machined rail bolted together. They are cheap to make and are used primarily in yards and secondary lines. They are designated as right or left hand. The straight route side of the bolted rigid frog point is continuous, whereas the diverging side of the frog point is milled to intersect the straight side frog point rail – hence the need to differentiate the hand of the frog by diverging side.. This is highlighted in the Milling Detail slide. Bolted rigid frogs are primarily relegated to yards and branch lines. Replacement with a RBM frog is the norm when frog changeout is due.Bolted Rigid Frogs details can be found in the AREMA Portfolio PlansSelf guarded bolted rigid frogs [PHOTO TOP RIGHT] contain an outside guard to trap the wheel. They are relegated primarily to light duty yards and leads.GUARD RAILSelf Guarded FrogAREMA Portfolio Plans
20 Bolted Frog Milling CONTINUOUS RAIL MILLED RAIL In this frog, the straight side and continuous rail are on the right, with the milled end is on the left as can be seen at the circled joint.MILLED RAIL
21 Self Guarded Frogs AREMA Portfolio Plan 671 SOLID CASTING The Solid Manganese Self-Guarded Frog, pictured here, also called SMSG has a built-in guard rail to prevent wheels from mis-routing. Thus, conventional guard rails are not required. SMSG frogs are supplied either with plates as part of the casting or utilize hook twin plates [CIRCLE] to secure the frog to the switch ties. SMSG frogs are normally limited to yard use primarily because of the resultant impact that the guarding face would suffer at higher speeds. They are not recommend for use in main line trackage with speeds over 20 MPH.Most Self Guarded Frogs are of the solid manganese insert [ARROW] construction, although some older frogs without the manganese inserts will be encountered.SMSG Frogs details can be found in the AREMA Portfolio Plan 671.SOLIDCASTINGAREMA Portfolio Plan 671
22 AREMA Portfolio Plans 401 to 490 Spring Rail FrogsHORNHOLDDOWNHOUSINGThe spring frog provides continuous support for the wheel as it transits through the frog flangeway. This frog has a moveable wing rail. The wing rail is held closed by a spring assembly. The wing rail is restrained vertically by horns and holddown housing which permit a maximum of ¼” of upward movement. The guardrail pulls the wheels over, forcing the wing to open on the diverging side. The wing rail springs closed again after the wheels are through. Spring frogs are supplied as either right or left hand. To determine the hand of a spring frog, stand at the rigid wing end, facing the frog; the side the moveable wing is on indicates left or right.The spring frog is used for trackage with predominate main line traffic, especially high-speed movements, because there is less pounding and a smoother ride. The disadvantage is that it requires more maintenance than conventional frogs. Recent advancements in spring frog design have eliminated some of the rigorous maintenance needed to keep a spring frog functional.Spring Rail Frog details can be found in the AREMA Portfolio Plans 401 to 490.SPRINGWING RAILAREMA Portfolio Plans 401 to 490
23 Moveable Point Frog MOVEABLE POINT KNUCKLE RAIL Movable point frogs are used in locations where the crossing angle between two sets of tracks is less than 14-degrees 15-minutes. The excessively long throat created by using conventional crossing diamond frogs would be impractical to maintain and to guard. A movable point frog consists of a pair of movable center point rails. The free points face each other a few inches apart where each pair may be alternately operated against two knuckle rails kinked to a point between the free ends of the movable points. The closed movable point, thereby maintains the flangeway.The pictured location is a crossing diamond frog lined for through movement on the tangent track. Other applications are:High-speed, high-number turnouts – utilize a single movable point frog in order to gain the benefits of the continuous flangeway.Slip switches - utilize a movable point frog s due to the multiple routes. These are described latter.
25 Frog Details AREMA Portfolio Plan 618-89 The above is a sample of an AREMA Frog Layout diagram. Note it is specific to the Frog #, as well as the style – RBM – weight, [RIGHT HAND CORNER]. The plan also provides a bill of material of tie plates [LOWER LEFT]. The Notes provide references to other related plans[LOWER RIGHT]The Portfolio Plan number references the plan date, in this case While not updated often, be sure you are using the most current plan.AREMA Portfolio Plan
26 Turnout Size and Speed 2” 3” 9” Turnout size is ratio of length to spread measured at the frog:2”3”9”Number 9The higher the ratio, the smaller the angle, thus the higher the speed.General rule of thumb:Double the size and round off to get the speed through the turnout(straight move speed is not affected on a tangential turnout)
27 Purpose of the Guard Rail Not all turnouts require guard rails: self-guarded frogs, moveable point frogs
28 AREMA Portfolio Plans 502 to 590 Frog Guard RailsGuard rails are used to prevent mis-routing and derailing at the frog point and to prevent wheels from striking the frog point. They may be of either the adjustable [PHOTO TOP LEFT] or non-adjustable type [PHOTO TOP RIGHT AND BOTTOM RIGHT]. The guard rail captures the back of the flange on the wheel opposite the frog and guides the other wheel through the throat opening of the frog. Thus, the mid-point of the guard rail must be positioned ahead of the frog point to ensure that the wheel is properly tracking when it reaches the throat of the frog from either direction.The non-adjustable guard rail is secured directly to the running rail with fixed castings. On the adjustable guard rail, end castings are located at each end of the guard rail. An adjustable separator block along with the end castings are used to space the flangeway opening initially at 1-7/8 inches. As the outside flange of the wheel abrades away the gage face of the guard rail, this dimension will increase. The FRA sets limits defined by the guard face and guard check [PHOTO BOTTOM LEFT] dimensions to ensure that the wheel is properly contained through the frog flangeway.Guard rails are supplied in different lengths as specified by the railway’s standard plan. They use a variety of plates, which must be spiked on each end, plus spiked between running rail and guard rail.The Guard Rail details can be found in the AREMA Portfolio Plans 502 to 590.AREMA Portfolio Plans 502 to 590
29 Switch Ties AREMA Portfolio Plan 912 Timber Concrete Steel Timber switch ties [PHOTO TOP LEFT] are commonly hardwood species, usually provided in either 6" or 12" increments beginning at 9'-0" up to 23'-0" in length. Nominal cross-section dimension is 7" x 9", although larger ties are specified by some railways. Switch timber can also be provided in concrete [PHOTO TOP LEFT] or steel [PHOTO BOTTOM].Turnout Switch Tie Layout details can be found in the AREMA Portfolio Plan 912 and many railways have standardized plans for the switch tie layout for the turnouts utilized on their property. The two switch ties under the switch mechanism are called head block ties. The ties under the heel block assembly are called heel block ties and those under the frog are called frog ties.The condition of the switch timber is critical to the integrity of the turnout. Spike killed head block ties can permit lost motion when the switch lever or switch machine is thrown. Defective ties under the point section will permit stock rail movement when a wheel traversing the point bears up against the stock rail. Poor timber support under the heel will cause the heel to deflect downward, thus raising the front of the point up above the stock rail where it can be struck by the next advancing set of wheels. Poor ties under the closure rail will lead to wide gage in the diverging moves due to the lateral forces present there. Poor ties under the frog and guard rails will lead to frog movement or breakage. A wheel traversing the open frog flangeway could climb the frog point, thereby causing a derailment.TimberConcreteAREMA PortfolioPlan 912Steel
30 Turnout Types Lateral Equilateral Lap Slip Switches Turnouts can be categorized into four groupings:Lateral turnouts,Equilateral Turnouts,Lap Turnouts, andSlip switchesWe will look at each turnout type and typical applications, The decision to utilize a specific turnout should be reviewed with each client, based on their standards.
31 AREMA Portfolio Plans 910 and 920 Lateral TurnoutsLateral turnouts have one straight side and one curved side, commonly referred to as the diverging side. Lateral turnouts are defined as right hand when the diverging track runs to the right and left hand when the diverging track runs to the left when facing the turnout from the point side. The above photo is a left hand turnout.The size of the turnout determines the sharpness of the curve in the diverging side. Except for very high speed operations, there is no restriction on speed through the straight side, however speed through the diverging side is limited by the resultant curvature through the switch points and turnout curve. Each railroad has its own standards for allowable speeds through the diverging side of the turnout. Curve speed restrictions are discussed in later modules.Because of the speed restriction, lateral turnouts are typically aligned to provide straight moves for the predominant traffic route and the diverging side to the lesser used route. There are situations where other factors, such as staging, space, and geometry restrictions, requiring the turnout be designed to accommodate the primary move at line speed through the diverging side, while a secondary move is made at a lesser speed through the straight side.Some railway and AREMA switch plans utilize a curved switch point on the diverging side and a curved stock rail on the straight side in lieu of straight switch points and a straight and bent stock rail. The curvature is consistent with the curvature through the closure rails vs. the switch angle produced by straight points followed by the curve through the closure rail. Use of a curved switch instead of a straight switch enables a slight increase in speed through the diverging route or a small decrease in the lead length (Distance from point of switch to actual point of frog).Layout plans for Straight and Curved Switches are shown on AREMA Portfolio Plans 910 and 920 respectively.AREMA Portfolio Plans 910 and 920
32 Equilateral TurnoutsIn an Equilateral Turnout, both routes curve or diverge as opposed to only one route diverging in the lateral turnout. With no straight side, half the curvature is on each side of the turnout, providing for a flatter curve and a higher diverging speed than a lateral turnout of the same number.The most typical use of an equilateral turnout is at the end of double track territory, where two tracks go to one, and the traffic and speeds are substantially equal. They may also be used where:Congestion or geometry will not accommodate a lateral turnout of sufficient length to provide the desired diverging speed, orWhere one track accommodates a high speed while the other accommodates a significantly higher tonnage, such as the juncture of freight and passenger mains.
33 Lap Turnouts AREMA Portfolio Plan 925-02 Lap Turnouts, much as they sound, are turnouts in which part of the next turnout overlaps the first turnout. They contain two sets of switch points and three different frogs, allowing the closure rails of the second turnout to cross the first turnout. Lap Turnouts require special plates due to the proximity of multiple rails to each other. The Section View [LOWER LEFT] shows the second switch positioned between the other running rails.Lap turnouts are used when maximum track lengths and minimum clearance points are required – for example in yards. These should be avoided when possible, as their maintenance is not compatible with modern production equipment, along with many other reasons.AREMA Portfolio Plan
34 AREMA Portfolio Plans 818 to 836 Double Slip SwitchDouble slips, pictured above, are only used in locations where space is limited such as older large passenger terminals and urban interlockings. Movement in four different directions, two through movements and two diverging movements, can occur. Single slips limit movement to 3 directions, with one diverging movement.However, maintenance requirements are considerably more than a conventional turnout, and a slip switch should be the design of last resort.Slip Switch layout details can be found in the AREMA Portfolio Plans 818 to 836.AREMA Portfolio Plans 818 to 836
35 Turnout Geometry AREMA Portfolio Plan 910-12 PLAN VIEW The AREMA plan shown provides geometry details in tabular form. Some railroads have their own standards, that represent minor variations on the above dimensions. Most are leftover from predecessor companies and other constraints limit the ability to upgrade to a standard layout.The controlling dimension for utilizing an AREMA standard turnout is the “Lead” shown as “4”.[KEEP THIS SLIDE AS AN ODD NUMBERED SLIDE SO THAT IT AND THE TABLE ARE ON THE SAME HANDOUT]PLAN VIEWAREMA Portfolio Plan
36 Turnout Geometry Data AREMA Portfolio Plan 910-12 This fragment table is part of the previous diagram. The Frog numbers are in the left column, and then repeated again towards the center. The circled numbers across the top correspond with the dimensions shown on the plan view. Some railroads have their own standards, that represent minor variations on the above dimensions. Most are leftover from predecessor companies and other constraints limit the ability to upgrade to a standard layout.The controlling dimension for utilizing an AREMA standard turnout is the “Lead” shown as “4”.[KEEP THIS SLIDE AS AN even NUMBERED SLIDE SO THAT IT AND THE DIAGRAM ARE ON THE SAME HANDOUT]AREMA Portfolio Plan
37 Crossings Railroad Crossing Road Crossing Two tracks crossing each other, sometimes referred to as a “Railroad Crossing At Grade”. The combined hardware is a “Diamond”.Road CrossingWhere a railroad and highway cross at grade. Also called an “At-Grade Crossing” or “Highway/Rail Intersection”There are two principal types of crossings, that are frequently confused.
38 AREMA Portfolio Plans 700 to 793 Railroad CrossingA railway crossing, commonly called a diamond is a device used at the intersection of two tracks. It consists of four frogs and the necessary connecting rails. Any one of the frogs is a crossing frog. The crossing angle is the angle between the centerline of the tracks at their point of intersection.Crossings are designated as single curve, double curve, or straight, according to one, both, or neither of the tracks being curved. Crossings are usually made of rolled rails or manganese castings fitted together. When the crossing angle is greater than about 25°, the various pieces are cut to fit against each other and are united by filler blocks and heavy straps well bolted. This is frequently termed solid construction.For angles under about 25°, regular frog point construction is used, and such crossings are termed frog crossings versus a crossing frog. The end frogs [ARROWS] of a frog crossing are similar to a standard rigid frog in that there is a single point on which the wheels run. The middle frogs, however, have two running points and are therefore frequently termed "double-pointed frogs.”Crossings also require special tie layouts, as the ends of the ties would overlap, or leave unsupported track sections, if a standard track tie pattern was used.Crossing Frog details and Tie Layouts can be found in the AREMA Portfolio Plans 700 to 793.AREMA Portfolio Plans 700 to 793
40 Crossovers AREMA Portfolio Plan 912 Typically, a Crossover [ARROW] can be considered as two same number turnouts, connected by a short section of track, with minor limitations. The track between the two frogs follows the frog angle, and typically is straight. For typical track centers, the timber layout for 1/2 of the crossover is different from that of a turnout. Some railroads use turnout ties that span both parallel tracks in the section between frogs. Other railroads spread the parallel tracks so the crossover more closely resembles two complete turnouts, so that the turnout ties do not conflict with the track ties of the connecting track. Like the turnout ties, Crossover Tie Layout details can be found in the AREMA Portfolio Plan Many railways have standardized plans for the tie layout for the crossovers utilized on their property.Sometimes there is no clear distinction between a Crossover and a Connection Track. A crossover typically is the connection between parallel tracks at normal track spacing. There are numerous variations where:The connected tracks may be at a slight skew with a curve in the connecting track.The connected tracks may be separated by a considerable distance. The track between the turnouts may be curved to close the distance between the tracks more quickly, or cross other tracks.The Turnouts may be of different number with a curve in the connecting trackThe Turnouts may be of different hand, connecting the diverging side of one turnout with the straight side of the other turnout.Two turnouts on parallel tracks that allow trains to cross over from one track to the otherAREMA Portfolio Plan 912
41 Hump Yard RetardersPicture of BNSF’s Argentine Yard in Kansas City, KS. Shot taken from master retarder.
42 Derails AREMA Portfolio Plan 213 SWITCH POINT HINGED SLIDING SLIDING The purpose of the derail is to keep tracks free of unsecured rolling stock. When properly placed and in the derailing position, the derail will guide the wheels off the track. This prevents unintentional movement of rolling stock from fouling the main line.The derail is left in the derailing position whether or not there are cars occupying the track. Derails are designated as right hand or left hand for derailing in the desired direction. The engineer must select the appropriate model of derail on the basis of the rail section to be utilized. An under-sized derail will not properly cover the rail head and may not derail the car as intended. An over-sized derail may be damaged because of inadequate support.There are several different types of derails. They include:Hinged derails [PHOTO TOP LEFT], which are manually applied. The derail is rotated in a vertical semicircle to move the derail on or off the rail.Sliding derails [PHOTOS BOTTOM LEFT & RIGHT] are mounted on two switch ties and are operated by a switch stand. The stand on the right is connected to a circuit controller, indicating the position of the derail to the signal system.Switch point derails (PHOTO TOP RIGHT) are used at special locations such as steep gradients or where the possibility of high-speed movement, for example at movable bridges, could knock a hinged or sliding derail off the rail, rather than derailing the movement. These derails come in single - pictured here and double point configurations. The derail details are similar to those of a turnout switch of the same size and are shown in AREMA Portfolio Plan 213.SLIDINGSLIDINGAREMA Portfolio Plan 213
43 Bridge Trackwork SLIDING JOINT MITER RAILS IINNER GUARD RAILS Whenever track is to be opened and closed at frequent intervals, it will be costly and cumbersome to use regular joint bars.Miter rails [PHOTO TOP LEFT] allow easy opening of track at drawbridges and swing spans. Each rail of a track is cut through on a long angle and planed to make a neat overlapping fit of the mitred ends. The rail fits in a special shoe and is locked in place. The rail on each side of the mitered cut must be well enclosed to maintain a very small gap between the mitered rail ends [CIRCLE] to allow proper opening and closing of the joint structure.The purpose of a sliding joint [PHOTO TOP RIGHT] is to accommodate the longitudinal expansion and contraction of the rail on long open decked bridges. Rail anchors are not typically used on open decked bridges because of the damage done to the softwood bridge ties. The sliding joint [CIRCLE] accommodates the thermal expansion produced by enabling the beveled rail ends to move but yet still maintain the continuity of the running rail. This looks much like a self guarded frog.The purpose of installing bridge guard rails [BOTTOM PHOTO] is to keep derailed equipment from falling off an overpass or deck of a bridge, striking the sides of a structure, or piling up in a tunnel. Typically, the inner guard rail will be a lighter T-rail section, spiked directly to the ties, which does not extend to the height of the running rail. Tie plates are not used. The outside guard rails are usually timber members.SLIDING JOINTMITER RAILSIINNER GUARD RAILSOUTER GUARD RAILS
44 QUESTIONS? Authors: Joseph E. Riley, P.E. Bob Kimicata, P.E. Federal Railroad Administration(202)Bob Kimicata, P.E.Kimicata Rail Consulting(847)Arthur Charrow, P.E.BNSF Railway(817)Acknowledgements