AUTOMATIC CAR CLASSIFICATION
Automatic Control 1102
Distributed Computer Control System 1103
Automatic Switch Control 1103
Automatic Retarder Control 1104
Automatic Process Backup 1105
Control Console 1105
Car Retarders 1106
Electric Car Retarders 1106
Weight-Responsive Hydraulic Retarders 1107
Yard Switch Machines 1110
Model 6 Electric Switch Machine 1110
Speed-Frater Electric Switch Machine 1112
Generail Remote Control 1117
Yard Signals and Indicators 1117
Hump Signal 1117
Trimmer Signal 1117
Yard Track Indicator 1118
Yard Detecting Devices and Systems 1118
Closed Circuit TV 1118
Dragging Equipment Detector 1119
Broken Flange Detector 1119
Weigh Scale 1119
Car Clearance Detector 1119
Wheel Detector 1120
Weight Detector 1120
Distance to Couple 1121
Maintainer Test Panel 1121
The GRS car classification system provides an efficient, economical method of handling cars in classification yards of the gravity type (hump yards). The particular design of a GRS classification system varies from yard to yard, depending upon location, type and weight of cars to be handled, number of tracks, volume of classification work, etc., but basic elements in all installations are car retarders for controlling the speed of cars, and power-operated switches for routing cars to classification tracks. Although either or both of these elements, retarders and power switches, may be manually controlled, in modern yards they are automatically controlled in normal yard operation.
Figure 1101 shows a typical, modern car classification yard. The master retarders are located just below the crest of the hump, with group retarders on the tracks which lead to each group of classification tracks. This arrangement permits preliminary retardation of all cars by the master retarders, with final control at the group retarders.
Another - and more recent - retarder arrangement, called “tangent point retardation,” is characterized by the use of a retarder in each classification track. In addition, a master retarder may be used with tangent point retardation and, if needed, group retarders also. The decision to use the master and group retarder arrangement or an array including tangent point retardation is dependent on a railroad’s study of its particular needs at a specific yard.
rolling resistance of cars varies with type of car, condition of journals,
wheel wear, weight, temperature, wind conditions, etc., the grades in the yard
must ensure that the hardest rolling car will roll through the yard to the
desired position on a classification track. The retarders must control speeds
of the cars so that the freer rolling cars, which would otherwise acquire
excessive speed, are sufficiently slowed to enter the classification tracks at
With manual control of retarders and switches there are limits to the humping rates that can be achieved and to the number of classification tracks that can be handled. Large manual yards thus required two or even three operators, each in a separate tower. Apart from such limitations, manual control is also subject to switching errors and incorrect car speeds resulting from human factors like slow reaction time, diversion of attention, and fatigue.
To obtain the classification efficiency of large- scale yards, to minimize problems caused by human error, and to reduce manpower requirements, systems were developed which automated car routing and speed control. These systems are designated automatic switch control (ASC) and automatic retarder control (ARC).
In the first automatic switching systems, numbered pushbuttons were used to identify the classification track for each cut. Pushbutton entries for as many as four consecutive cuts approaching the hump were made by the hump conductor and stored in a relay “memory.” The memory followed the progress of each cut as switch detector circuits were occupied and lined up switches for the route required.
In the early automatic retarder control systems, radar units employing ultrahigh-frequency vacuum tubes were used to measure speed of cars in retarders. Data from the radars was fed to special- purpose vacuum-tube control units. Using analogs, such as voltage levels, for comparisons between actual speed and desired release speed, these devices actuated retarders to obtain the requisite release speed.
Automatic switch control and automatic retardercontrol continue to be basic to classification operations. But in modern yards these systems, implemented through digital computers, have capabilities far beyond tho offered by earlier systems. For example, instead of a switching mem Figur
1101. A typical automated car classification yard. Radar units are between the retarder rails.
that can store four routes, a digital computer can store switching information
for an entire train -
several trains. Instead of obtaining classification track information from
pushbuttons, the computer obtains it via suitable communication links from the
local electronic terminal information system (TIS), or even from railroad
operating centers hundreds of miles away.
For ARC, the speed and capacity of digital computers permit expansion of retarder control calculations to include more variables in more complex formulas, while still providing split-second retarder control. Thus modern ARC provides precision and flexibility that could not be achieved with analog devices. And, coupled with solid-state radar, these modern systems offer operating reliability not possible with vacuum-tube electronics.
The term digital computer” covers a wide range of devices differing in capability and cost. A computer can accomplish myriads of calculation and decision operations per second, but it must have exact instructions (a program) before it can function. The type of computer selected and the program created to achieve a specified result are critical elements in obtaining desired cost/benefit ratios.
Effective application of computers to automatic classification requires knowledge both of yard operations and of computer capabilities. Programs must recognize not only the engineering formulas applicable to rolling car behavior, but also the practical requirements of running a classification yard.
The GRS Distributed Computer Control System (DCS) was developed for optimum benefits in computer control of classification operations. Fundamental to DCS is the segregation of primary yard functions, and the development of computer programs to carry out these functions independently in very fast small computers (minicomputers). The number of computers used and the specific types chosen are determined to meet the individual needs of each yard. Figure 1102 shows diagrammatically the input, processing, and output relationships involved in a yard employing a distributed computer system.
For a typical yard, primary functional areas of the distributed computer system are automatic switching control and automatic retarder control. A third functional area is automatic process backup (PBU). The PBU function accepts and stores data used in ASC and ARC and provides ‘hot stand-
support. That is, PBU immediately substitutes for a failed primary ASC or ARC
function without disturbance of yard operations in progress.
The detailed computer programs required for automatic classification are prepared by GRS engineers who know yard operations and who are also familiar with the computers selected for the job. In addition, they recognize the required interfacing between the yard system and the railroad’s general data processing and communication network.
Automatic Switch Control
The automatic switch control function is first to deal with cars to be classified, since it handles information on trains arriving at the yard. This takes the form of a hump list, received via railroad communication links and stored for use when the train is humped. The hump list is a tabulation in train sequence of cars to be switched including car identification and the assigned classification tracks. As humping progresses, information on the next several cars approaching the crest and their track assignments is fed from the computer and displayed on a video display screen on the control console. Typically the display indicates details on the next ten cars that will reach the hump crest. The list advances in step with humping progress.
Information on cut progress after release at the hump is provided by outputs from wheel detectors, track circuits, and switch occupancy loop detectors. This information is received and analyzed by the ASC computer function, which generates properly timed commands for switch machine operations which route the cut to the specified track.
However, to accomplish this a great deal more is required than merely positioning switches normal and reverse. The following partial list gives some of the factors the computer deals with:
1. If yard personnel have indicated (by manual input) a track change for a particular car, change switching sequence for that car.
2. If yard personnel have indicated a track not available (full or blue flagged), reroute all cars listed for that track o a specified alternate track.
3. Check that each cut arrives at next switch within an anticipated time interval. If not, recognize possibility of stalled car in switching zone.
4. Check speeds of cars going to adjacent tracks to see if the following car will catch up with the lead car before the lead car clears the fouling area of the tracks involved, If so, route second car to same track as first car to avoid possible “corner” collision.
Figure 1102. Functional organization of distributed computer system.
Continuously check clearance track circuits of classification tracks. Reroute
cars away from any fouled tracks into fouling track until situation is cleared.
6. Verify that switches respond properly to position commands, i.e., are not blocked or otherwise defective.
7. Check agreement between switch detector circuits and occupancy loop indicators.
8. Provide pertinent data to the retarder control function and maintain the process backup function updated.
9. If discrepancies or failure are detected, alert yard personnel by appropriate alarms. Produce printout detailing nature of problem and put yard signals to stop when required.
Automatic Retarder Control
The first objective of the automatic retarder control function is to release cars from the master retarder at speeds which permit the desired humping rate and which allow sufficient spacing so that switches can operate between cars. The second
is to release each cut from the group or tangent point retarder at a speed
which will carry it to the coupling point on the assigned classification track.
At the coupling point, residual speed should assure positive coupling while
holding impact to an acceptably low level. The two objectives are interrelated,
since entering speed at the group or tangent point retarder is a function of
release speed from the master retarder. Automatic retarder control achieves these
objectives by computing how cars will behave as they roll down the hump and
into the classification tracks. The computation is based on many factors. Some
of these are related to the cars, such as weight, rollability, and frontal area
(bulkhead). Other factors relate specifically to the designated classification
tracks: grade and curvature, and distance to coupling. Still other
considerations relate to operating environment such as temperature and wind
Inputs specifying all these parameters are accepted by the ARC computer function. By inserting this data in formulas defined by the ARC program, the computer derives optimum release speed
OUTPUTS FOR PRIMARY CONTROLOUTPUTS
DATA TO ANALYSES
TERM INFO OF SYSTEM
RERO KEEPING & PERFORMANCE ANALYSIS OUTPUTS
each cut. It compares this value with the actual speed indicated by radar, then
controls the retarder to obtain the desired speed.
Efficient automatic retarder control involves substantially more than opening retarders when radar indicates correct speed. For example, retardation should be distributed through the length of the retarder to equalize shoe wear. A further objective is to minimize the number of movements of the retarder mechanism, to save energy, reduce wear, and extend intervals between maintenance.
Performance verification is also included. Actual leaving speed is compared with computed optimum speed. If actual speed differs by more than one mph from optimum, a printout is produced which identifies the car by initial and serial number, and indicates the retarder involved.
Automatic Process Backup
Automatic process backup is implemented by an independent minicomputer. This accepts digital data relating to both ASC and ARC. It is thus always ready to take over ASC or ARC functions.
An important area of the DCS is inclusion of means for detection of failure in the primary computer functions. When a failure is detected, switch- over to PBU is automatic and essentially instantaneous without loss of control or information. Occurrence of switchover and the reasons are recorded by printout.
Typically PBU computer capacity is such that additional functions are possible. For example, statistical analyses of yard performance may be made, operating on data gathered by ASC and ARC and passed along to PBU. Analytical reports are valuable in fine-tuning the control system when it is installed, and in subsequent adjustment of yard parameters that may change with time and yard use.
The control console in an automatic yard, Figure 1103, serves as the yard nerve center. It is usually installed in the yard tower, in an office with an overall view of the yard. The console has indicating lights and video displays which provide information on factors related to yard operation, systems status, and equipment condition. In addition, it includes controls which permit yard personnel to initiate changes and to correct system operation if circumstances require. Consoles are custom designed for each yard hence differ in detail but typically include the major features discussed below.
As indicated by Figure 1104, a plan of the switching layout at the hump end of the yard is shown on the console panel. Panel lights on the track diagram, adjacent to switch levers, indicate actual switch position and the next switch position requested for cars enroute to classification tracks. Passage of cars through switch detector zones is indicated by a white light in the barrel of the switch lever. Occupancy lights beyond the last switch show car movement through clearance track circuits.
Switch control levers, when aligned with the diagram, have priority over automatic switching and position switches as indicated by the lever position. Turning the switch lever away from the track diagram places the switch under automatic control. Failure of a switch to line as required, under either manual or automatic control, sounds an audible alarm and is indicated by a flashing red display in the barrel of the switch lever.
Retarder control levers are located on the diagram at positions corresponding to the locations of the retarders. These levers have a control position for each position of the associated retarders.
Control console in modern digital computer automated yard.
lever to a control position causes the retarder to respond accordingly. Manual
control has priority over automatic control. For automatic control, the lever
is moved to an additional panel position designated for that purpose.
Indicating lights adjacent to the retarder control levers light each time the
retarder mechanism changes position.
Yard signal control is accomplished by two panel levers provided for that purpose. Adjacent lights repeat the aspects displayed. Control circuits are interlocked to prevent display of conflicting aspects, regardless of lever positions.
Additional panel lights report a variety of auxiliary information. Examples of these are radar function, cut length, car weight class, and status of various power systems. Other indications are included as required by the individual installation. Similarly, supplementary controls related to power supply and other functions are included as needed.
In addition to panel lights, video display units provide alpha-numeric display for hump lists and similar text data.
A bank of panel pushbuttons, labeled by function, enables the hump foreman to communicate various commands and decisions to the classifica tio
Included are numbered buttons for manual selection of classification track
More detailed input is available via the console keyboard which functions as an input terminal to the system computers. Using the keyboard, detailed alpha-numeric information may be communicated, as for correction or revision of a hump list stored in the computer.
Electric Car Retarders
The GRS car retarder, Figure 1105, is a rail brake, electrically controlled, by means of which the speed of cars rolling down to the classification tracks may be regulated, either automatically or manually. The braking effect of the retarder is obtained by means of heat-treated alloy steel shoes mounted on each side of the rails, as shown in simplified form for one rail, in Figure 1106. A reversible motor and an associated gear train (part of the mechanism shown in Figure 1107) rotate the drive gear. Counterclockwise rotation of the drive gear moves the shoes toward edh other, as shown
AUXILIARY INDICATION LIGHTS POWEN BUSSES, LONG CUT. ETCI
Figure 1104. Typical layout, control console panel.
Figure 1105. Electric car retarder.
by the arrows adjacent to the shoes in Figure 1106. Clockwise rotation separates the shoes. To obtain retardation, the shoes are positioned so that the space between them is less than the thickness of a car wheel. When a wheel moves between the shoes, the shoes are forced apart against the compression of the spring. The resultant frictional forces between the shoes and the car wheel serve to retard the car.
The amount of retardation obtained depends upon the position of the retarder shoes when there is no wheel between them. The closer together in their original position, the more the spring is com Figur
1106. Simplified diagram of linkage to position retarder shoes. Shown for one rail.
when the shoes are separated to car-wheel width, and the greater the braking
force exerted by the retarder.
The retarder mechanism usually provides several positions of the shoes, for various degrees of retardation, and an open position in which the shoes do not touch the wheels. With both master and group retarders in the maximum closed position, a car can be stopped and held in the group retarder.
As shown in Figures 1106 and 1107, a combination of fixed and floating pivots is used to adjust the spacing between shoes, an arrangement which makes the pressure exerted by the shoes equal on both inside and outside surfaces of the wheel. This equalized shoe pressure gives a high average pressure without exceeding the maximum allowable pressure, the point at which a car wheel is lifted. Equalized shoe pressure, regardless of variations in wheel thickness and spacing of wheels on axles, thus permits maximum retardation effect.
Figure 1106 also shows the toggle action which occurs between the toggle crank and the operating bar as the shoes are closed. As a result of this high mechanical advantage, only moderate torque is required of the drive motor, even when compressing the springs directly, as when the retarder is adjusted to a higher degree of retardation with a car in the retarder.
Articulation of the beams which support the retarder shoes permits adjacent springs to share the retardation load and at the same time eliminates the possibility of binding caused by variations in track level. The GRS retarder readily adapts itself to considerable vertical misalignment in the track, and, in fact, is frequently installed on vertical curves. Articulation provides the additional advantage that any number of retarder units may be assembled in line to produce a continuous retarding surface with most economical use of track space.
GRS electric retarders are available in two models, the Type El and the Type E160. They are basically similar except that the Type E160 is for use where very heavy cars must be controlled, up to 160 tons with wheel diametrs of 38 inches. Retarders are available in units of 51/2 feet of rail length. As many as eight operating sections of retarder may be operated from one mechanism.
Weight-Responsive Hydraulic Retarders
The Types El and E160 electric car retarders are commonly furnished as master and group retarders for handling substantial amounts of traffic. Weight-responsive hydraulic retarders, Figure 1108, either Type F4 or F5, may be used as master and as group retarders in low volume yards where
cars are not usually encountered. They are ideal for use as skating retarders,
to hold cars at the ends of classification tracks. Also, where cars must be
spotted precisely, at loading chutes for example, weight-responsive hydraulic
retarders furnish an effective means of controlling car movements.
Types F4and F5 retarders, Figure 1109, employ the lever principle to apply braking force to the car wheels in proportion to car weight. All cars having the same wheel diameter and characteristics receive the same braking effect. Type F4 retarder inner levers are power operated in the closed direction by hydraulic rams which close the shoe rails against the car wheels. Hydraulic rams in the F5 retarder similarly power the levers to the closing position and also provide for power operation in the open direction. Thus the F5 can release a car faster than the F4.
Two hydraulic systems are available. For handling lightweight cars or for such applications as
a low-pressure, pump-driven (either directly or through an accumulator)
hydraulic system is available. A high-pressure, pump-driven hydraulic system is
available for handling any weight cars in such applications as hump, group, and
tangent point retarder control.
The pump, oil reservoir, and valving are housed near the retarder; the accumulator is mounted adjacent to the retarder. Each pump is tailored to the particular application. Its size depends upon the number of hydraulic rams, operating pressure, and desired response time for a sequence of operations.
Manual or automatic control opens or closes a solenoid valve, which, in turn, regulates the flow of fluid to orfrom the hydraulic rams.
As shown in Figure 1109, the hydraulic rams move the shoe rails to the operating position, thus applying braking force to the car wheels. The sequence of operation is as follows:
In the closed position (A), the shoe rails are closer together than the narrowest car wheel. The wheels of a car entering the retarder (B) spread the shoe rails, thereby forcing the inner and outer levers to lift the running rail.
The downward force of the car wheels, exerted upon the running rail, is transmitted through the knuckle joint to the levers and consequently to the shoe rail. Thus, braking force to the car wheels is in proportion to the car’s weight.
The rams of the Type F5 retarder are hydraulically opened (C). This allows the inner levers to drop, thus widening the separation between the braking surfaces and releasing the car wheels quickly. The rams of the Type F4 are not hydraulically opened. In the open position, hydraulic pressure to the rams is releaséd, allowing the inner
LEVER SPRING CROSS BAR STEEL TIE
Figure 1107. Cross section of type E retarder.
ire 1108. Type F4 weight-responsive hydraulic retarder.
Figure 1109. Types F4 and F5 retarders, sequence of operation: closed (A), operating position (B), and open (C). Arrows in (B) indicate lines for force during retarder operation. Arrow in (C) indicates line of force for power operation direction for the Type F5 retarder only.
to lower. Thus, the separation between the braking surfaces is widened, and the
car wheels run free.
YARD SWITCH MACHINES
Model 6 Electric Switch Machine
Switch machines that are used in switching cars into classification tracks must operate quickly and must be trailabte. The Model 6 switch machine, Figure 1110, is specifically designed for use in car classification. It operates in as little as 0.6 second and is fully trailable.
The motor-control contacts, Figure 1111A, located in spaces 1A, 2A, 3A, and 4A, and 5B, 6B, 7B, and 8B, are operated by two cams on the outside of the main gear.
indicate when the main gear reaches its full stroke position - either normal or
The point-detection contacts, located in spaces 7A, 8A, 1B, and 2B, are operated by a three-position cam on the sector, Figure 1112. The contacts indicate when the throw bar is in its full stroke position - either normal or reverse.
Point-detection contact 2B is connected in series with correspondence contact 6A-3B to ensure that the position of the main gear is in correspendence with the position of the throw bar (“normal”) before an indication is given. Contact 7A is connected in series with correspondence contact 5A-4B to ensure that the position of the main gear is in correspondence with the position of the throw bar (“reverse”) before an indication is given.
Figures 1111 A-C show the electrical operation of the Model 6. Figure 1111A shows conditions just as the machine has completed its stroke. The motor armature, still spinning, is being dynamically snubbed (circuit shown in blue). Resistance is sometimes inserted in the CW lead to reduce the snub-
The correspondence contacts, located in spaces 5A, 6A, 3B, and 4B, are also operated by the cams on the outside of the main gear. These con-
Figure 1110. Model 6 electric switch machine.
BY MOTOR CONTACTS
Figure 1111 a. Model 6 switch machine circuit, in “normal” position. Blue shows motor shunt circuit.
BY MOTOR CONTACTS
Figure 1111 b. Model 6 switch machine circuit, starting to move toward “reverse.”
current if snubbing is too abrupt. The red part of the circuit shows how the
switch machine position is detected by the RWP and NWP relays.
Figure 1112 shows the cam (blue) and sector (red) mechanism that permits the Model 6 to be trailed without damage. When the wheels of a car trailing the switch force the switch rail away from the stock rail, the motion is transmitted to the throw bar. The sector (red) is thus forced to move, but the cam (blue) is locked in place by the position of the main gear roller (not shown) within the internal cam surface. The force on the sector causes the spring loaded sector roller to move out of its notch in the sector, thus allowing the throw bar and sector to move without motion of the cam. The next power operation causes the cam and sector to return to their normal positional relationship.
When the switch points are obstructed, the action is similar, except that the throw bar cannot move, thus the sector remains stationary and the cam moves, allowing the machine gearing to complete its cycle of operation, but the machine does not complete its stroke. The points snap back against the stock rail. The point detector contacts will not operate to close in the position toward which the machine was called. In either case, the switch points remain opposite to the called-for
until the called position is changed. Thus after the points have been trailed
or obstructed the call must be changed twice to move the points.
Figure 1113 shows how switches in the automatic switching system are protected by loop detectors. If track circuits were used, they would have to be long enough so that a car could not span a circuit. As compared to loop detectors, the track circuits would require more space between switches. This would decrease the maximum rate at which cars can be put through the system.
Speed-FraterTM Electric Switch Machine
The Speed-Frater, Figure 1114, is for general - receiving, departure, and industrial - yard use wherever a fast-acting, non-interlocked switch machine will save time and train delays. It is not for use in classifying cars. The previously described Model 6 is designed for best performance in that kind of service. The Speed-Frater is a very simple machine. It operates on 115 or 230 volts a.c. It can be trailed without damage, it has a built-in hand- throw lever, and it is fast - operating in under a second at rated voltage. The basic Speed-Frater (without the optional automatic restoration feature) is reversible in midstroke if an obstruction is encountered. When equipped with the automatic
Figure 111 ic. Model 6 switch machine circuit, in “reverse” position. Blue shows motor shunt circuit.
/ DETECTOR CONTACTS
Figure 1112. Cam and sector mechanism which makes Model 6 switch machine trailable.
Figure 1113. Switches in an automatic switching system are protected by loop presence detectors, as shown here schematically.
OPERATED BY ROLLER ON MAIN GEAR
ENGAGES THROW BAR
J. THROW BAR
DIRECTION OF TRAILING FORCE
SPRINGS WHICH FORCE ROLLER INTO NOTCH
CONTACT IS OPEN WHEN CAR IS ON LOOP
feature, the Speed-Frater automatically reverses in midstroke and returns the
points to their original position if an obstruction is encountered. Contacts
are included to indicate machine position remotely. Optionally available are
indicator lights, built into the cover as shown.
The single-phase motor, Figure 1115, has a start winding and a run winding. Both are energized for starting the motor to produce the required torque. A capacitor, located on top of the motor and connected in series with the start winding, produces the required phase shift to initiate armature rotation. When the motor reaches a predetermined speed, a built-in centrifugal switch opens the start winding, and the motor continues to operate on the run winding only.
An adjustable overload torque limiter and sprocket are fastened to the output shaft of the gear-head motor. A chain connects this sprocket to the large sprocket, which drives the switch
Figure 1114. Speed-Frater electric switch machine.
TORQUE LIMITER AND SMALL SPROCKET
Speed-Frater with cover open.
mechanism and cam. The cam actuates point detector contacts, SW1 and SW2,
•Before the large sprocket reaches the end of its travel, a cross pin in the sprocket actuates one of the limit switches SW3 or SW4, Figure 11 16a, which de-energizes the appropriate contactor and also closes the contacts used in the correspondence circuits. Dropping of the contactor opens the motor circuit. The cross pin then comes up against a positive stop, and the torque limiter slips slightly to allow the motor to come to a smooth stop.
Figure 1116a shows a Speed-Frater circuit with the switch machine in its normal position. The green switch indicator lamps are lighted, BX24 is applied to external indication circuit NWE, and restoration relay CP is energized with BX115 on
The NX115-BX115 energy shown must be from the same a-c circuit. The machine is controlled by pole changing the energy on RW and NW. The BX24 for the indication circuits may be another voltage if desired.
Figure 1116b shows RW and NW polechanged relative to their energization in Figure 1116a. This calls the machine to operate toward reverse by picking up reverse contactor CR.
normal operating time, relay CP is maintained energized by its
As soon as the motor starting switch opens, resistance Ri is put in series with the coil of contactor CR. The value of Ri is such that CR can be maintained in its picked up position, but should the machine now be called reverse there would not be enough voltage to operate contactor CL and reverse the motor until the motor slowed down sufficiently to allow the motor starting contacts to close. This protects the motor.
During midstroke, all point detector and limit switches, SW1-4, are in their normally closed positions. This prevents the lighting of the switch indicator lamp units or the energization of indication circuit RWE or NWE. Note also that both contactors must be in their de-energized positions before energy can be put on RWE or NWE.
At the end of a stroke, all contacts SW1-4 reverse from the positions they held at the start of the stroke. Thus when the switch machine is at its reverse position, limit switch contact SW4 opens the RW circuit. This de-energizes contactor CR and opens the energy supply to the motor.
Figure 1116c shows the circuit when the switch points are obstructed while the machine is operat Figur
11 16a. Speed-Frater circuit, switch machine at rest in normal position.
• NDICATI ONCIRCUIT AND INDICAROE LURED CIRCUIT
Figure 111 6c. Speed-Frater circuit with CP de-energized, CL picked up, and the motor starting switch closed to operate. The machine back to its normal position.
Figure 1116b. Speed-Frater circuit, shown just as contactor CR picks up and motor starts to operate switch machine reverse.
toward, for example, reverse. CP has timed out and dropped. With CP contact 1-4
closed and limit switch SW4 contact iNC closed, BX115 is applied to both sides
of contactor CR, shunting it out, and it drops. Reverse contactor CL is
energized from NX1 15 on NW as shown. As soon as the motor has been slowed down
enough to allow the motor starting switch to close, the motor will operate to
return the switch machine to its normal position.
Now RW-NW must be pole changed to put
BX1 15 on NW through SW3 contact 2N0 to pick up
CP through its contact 8-5 and diode Dl to NX1 15.
Once CP is up, resistor R3 is put in series with CP
coil to reduce the current through CP windings.
GenerailTM Remote Control
An inductive (wireless) control system, GenerailTM, makes it possible to remote control a SpeedFrater switch machine from a light, compact, belt- carried transmitter. The.Generail system is shown in a simplified diagram, Figure 1117. Besides the man-portable transmitter, there are weatherproof receiving coils, one at each approach to the switch. The coils are cable connected to a receiver and control box, which is mounted near the SpeedFrater.
The transmitter is battery operated. The receiver operates on 120 volts a.c. Transmission is inductive, short range (about twelve feet from transmitter to receiving coil) and no licensing is required. The Generail remote control system is also readily adaptable to controlling practically any two-position device. The normal and reverse control relays can be arranged to pick up for 150
or to pick up and stay up until an opposite command is received. To control a
SpeedFrater, for example, the call must stay for the duration of the throw - about one second.
YARD SIGNALS AND INDICATORS Hump Signal
The hump signal, Figure 1118, directs the hump engineman in pushing the cars up the hump. Commonly, the hump signal can show any of four aspects:
Flashing red, red
over red, or other
In modern yards, hump engines are equipped with radio transmitted automatic controls, governed by the yard computer. The hump signal functions as a standby.
The trimmer signal, Figure 1119, has two aspects, as follows:
Hump and trimmer signals are often mounted on the same mast, Figure 1118. Normally, the control of these signals is interlocked so that both cannot be cleared at the same time.
NORMAL RE LAY
RECEIVING CO IL
Figure 1117. Block diagram of Generail remote control system.
Figure 1119. The trimmer signal faces down into the classification track area.
order to save time between humping trains, the hump conductor can clear the
hump signal to green while the trimmer signal is yellow. This means that the
trimmer engine can work while the next train is being pushed toward the hump.
There is, however, an approach track circuit to the hump signal. If the trimmer
signal is yellow when the train occupies the approach, the hump signal
automatically goes to red.
Yard Track Indicator
The yard track indicator, Figure 1120, displays the receiving yard track number to an entering train.
YARD DETECTING DEVICES AND
Closed Circuit TV
Television cameras, Figure 1121, fixed along the wayside and equipped with lighting for night use, are focused on each car coming into the yard. Monitors in the yard office provide a ready means of checking actual car numbers against advance consists.
Figure 1118. A hump signal directs the hump engineman.
Figure 1120. Yard track indicator.
Dragging Equipment Detector
Before the cars start down the hump, they pass over a dragging equipment detector, Figure 1122. Any dragging equipment actuates the detector, opening its normally closed contact. This alerts the hump office, and the affected car can then be routed to a repair track.
Broken Flange Detector
Like the dragging equipment detector, the broken flange detector, Figure 1123, helps to identify cars with defects that need correction. Fingers on the detectors “feel” the circumference of each wheel flange as it passes over them. A gap in a flange would leave a finger undisturbed. This would cause an alarm to be transmitted to the control off ice so the car could be routed to a repair track.
Each car is weighed as it approaches the hump by passing over a weigh-in-motion scale, Figure 1124. These weights are recorded automatically and are used for determining the motive power requirements for trains leaving the yard as well as for billing purposes.
Car Clearance Detector
A strategically placed array of light transmitters and photocells, Figure 1125, can be used to check each car to detect any unusual dimensions, such as might cause difficulties at tunnels or under- passes. Such devices can also detect “high bulk-
yard. head” cars, which have unusually high wind re Figur
1121. Television camera location at entrance to
e 1122. Dragging equipment detector on approach to hump.
a factor which the computer can utilize in determining release speeds from the
Magnetic wheel detectors, Figure 1126, are used to detect the instant a car enters a rollability test section and the instant it leaves the section. Timing the interval between these events gives the computer an indication of the rolling characteristics of the car. Other types of magnetic wheel detectors also detect direction. They are used to detect, for example, when a car, or a cut, enters and leaves a retarder or a ioop detector protecting a switch.
Car weight is an important factor in establishing accurate automatic control of retardation. As each car passes over the weight detector, Figure 1127, its weight classification - light, medium, heavy, or extra heavy - is determined for use by the computer.
Figure 1124. The weigh scale is in approach to the master retarder. Note switch to bypass weigh rails.
Distance to Couple
An important factor in determining correct release speed is the distance the car must roll to the coupling point. This information is provided by the distance-to-couple system.
Distance-to-couple is determined by measuring the impedance of the selected classification track, from the clearance point to the nearest axle of the car which last entered the track. A regulated a-c voltage is applied to the track and the resulting current flow measured. The greater the track current the lower the track impedance. Track impedance increases with increasing distance to the point of shunt. Low impedance thus indicates short distance to coupling, and high impedance indicates the opposite.
To eliminate the effect of rr(oving cars, two measurements are made within a short interval. If these differ the distance to the shunt is changing, hence the last car is still moving. When this occurs the automatic systems are programmed to estimate distance to coupling on the basis of previous information on the track.
Maintainer Test Panel
A busy yard may operate around the clock, and
system availability must be extremely high if delays
are to be avoided. Not only must inherent reli Figur
1125. An array of lights and photocells checks for out-of-clearance cars.
Figure 1126. Magnetic wheel detector.
.. . .
be high, but time to test the system and to correct any problem that does occur
must be minimal. The maintainer test panel, Figure 1128, is an important aid in
realizing this objective.
The test panel, located in an equipment room, displays information on the status and performance of system functions. It also provides for simulating operation. By observing system performance indicated on the panel, both during normal yard operation and under simulated conditions, the maintainer can rapidly complete routine checks or diagnose the cause of improper operation.
Figure 1127. Weight detector.
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Figure 1128. Typical maintainer test panel.