Train Dynamics
Knowledge of different forces which were developed on loco and load during train working and train handling is called train dynamics.
Importance-
• It reduce train parting cases
• It reduce train stalling cases
• Fuel oil saving
Definition –
Tractive effort - The rotating force developed on wheel of loco motive which tends to pull the load. Tractive effort is different for different locomotives.
Adhesion - That grip which the wheels have on the rail dependent upon weight, track condition and weather conditions.
Draft Force - Force required for pulling other attached coupler / wagon is called draft force. Pulling of the other wagon starts only after complete extension of the couplers attached together.
Buff Force - Force required for pushing other attached coupler / wagon is called buff force. Pushing of the other wagon starts only after complete compression of couplers attached together.
Slack - Slack movement is the free play in the draw gear and in some draft gear.
There are two kinds of slacks -
1. Free Slack - Free slack is the clearance with in the draw gear which can run-in or run-out without compressing the draft gear. Free slack can be as high as one inch between two couplings of the vehicle.
2. Spring Slack - spring slack is the additional amount of movement that can occur after the free slack movement is finished and when draft gear is compressed and which then rebounds and drives all slack in opposite direction. Spring slack for conventional draft gear can amount to approximately 5 inches per vehicle when fully compressed.
Run-In - It occurs when a rear portion of a train is traveling faster than a forward portion of a train. Run-in may be a combination of slack movement and spring slack dependent upon the forces generated.
Run-Out - When a rear portion of a train is traveling slower than a forward portion of a train. Run-out may also be a combination of slack movement and spring slack dependent upon the forces generate
Coupler Breakages - The coupler fatigue depends on how many times it has undergone stress & strain during the train travel. The frequent run-in & run-out of wagons (coupler compressions & extensions) with heavy slack speeds increases the coupler fatigue. Thus it is evident that controlled run-in / run-out / slack movement can reduce coupler fatigue.
Jerk - It can be felt when sudden changes on coupler force takes place either from Draft force to Buff force or Buff force to Draft force.
Lurch - It can be felt when sudden changes in track gradient from level to down & then up (due to track defect).
Different gradients
Train Parting - Train parting is a common unusual occurrence affecting the train movement. There are number of contributing factors towards train parting such as poor driving technique, inadequate maintenance, material failure, improper marshalling, loco troubles, etc.
Reason of Train Parting
1. If the Tractive force exceeds the tensile strength of the coupling system.
2. If any coupling gets opened or works out.
3. If any coupling gets uncouple due to excessive buffer height/ difference in rail level.
Out of the above 3 situation the first one is related to wrong driving technique adopted by loco pilots, provided there is no material failure.
Reason of Tractive Effort Exceeds the Tensile Strength
1. Due to sudden notching up.
2. Sudden application of brakes from rear.
3. Notching up with out proper recreation of vacuum/ air.
Procedure of opening the throttle
1. Advance the throttle with pause of 10 sec
2. Keep watch on load meter
3. Advance the throttle after observing the load meter, its needle should be stable
Note- With the above sudden increase of tensile force can be avoid and also possibility of load parting.
Jerk - Following reasons are for sudden increasing/decreasing of Tractive force
1. Poor driving technique
2. Loco failure like power ground, wheel slip, sudden stopping of engine etc.
3. Brake application from rear
Reason of jerks developed by loco pilot
1. Sudden notching
2. Sudden braking
3. Sudden power cut off
Procedure of avoiding the jerk at the time of train starting
1. All coupling should be intact properly
2. Ensure adequate amount of BP/Vacuum in train and brake should be in release condition
3. After opening 1st notch wait for 10 sec to stabilize load meter then release SA9
a) For starting on up gradient with full load open the notch accordingly then release the loco brake to avoid wheel slip
b) To start on down gradient 1st release the loco brake then notching
4. Do not take traction immediately after releasing of dynamic brake.
Procedure of avoiding the jerk on run
1. Update the section road knowledge
2. Advance the throttle with pause
3. Do not open the throttle suddenly and do not apply brake suddenly
4. Apply gradual braking
5. Ensure load is fully released before opening the throttle after application of brakes.
6. Do not apply/release dynamic brakes suddenly.
7. Reduce the notch during wheel slip on up gradient.
8. Keep healthy communication with Guard/Banker loco Pilot.
9. Banker loco pilot open the notch first while starting the train.
Procedure of avoiding the jerk on stopping
1. Apply gradual braking.
2. Apply loco brakes after stand still.
3. Try to stop the train in released condition.
4. Try to stop the train on notches on up gradient (if required) and apply the loco brake after stopping then bring the throttle on idle.
5. Avoid to couple screw coupling load with multiple unit.
Train Handling Method
It is a technique to handle the train operation, it vary person to person. Regarding train operation some guide lines are given below –
Loco Pilot should keep in mind –
1. Load hauling (Tractive effort)
2. Draft force (Draw bar pull)
3. slackness in load
4. Brake power
5. Geographical condition of rail track
6. Fuel saving
7. Punctuality
On A Level Section
A) Starting of train from level section
1. Keep train brakes in released condition.
2. Take first notch and simultaneously release SA-9.
3. Wait for few seconds until the load meter reading stops increasing and
begin to reduce.
4. Advance throttle to notch 2 and again note load meter indication as in (3).
5. If necessary, advance the throttle to 3 or 4 notches but always wait for a few second {as in (3)} between each notch position.
6. When the train is in a stretched condition and in motion, slowly advance the throttle as required {as in (3)} for achieving maximum speed of the train.
B) Negotiating level section
1. After achieving maximum speed, maintain it by increasing / decreasing the notch.
2. Avoid frequent changing in notches as this develops slack in the train.
C) Stopping of train in level section
1. At a sufficient distance in advance of point of slowing, ease the throttle notch by notch for the slack to adjust to a bunched condition.
2. Coasting to be done for some distance before braking.
3. Apply Dynamic / train or both brakes as required
4. As the train comes to stop apply SA-9(loco brakes).
On up Gradient
A) Starting procedure in ascending (up) grade Assuming train brakes are applied
1. Move throttle to take 3 or 4 notches (Keep watch on load meter)
2. Release SA-9 (loco brake)
3. Gradually release A9 (train brake)
4. Wait for few seconds until the load meter reading stops increasing and begin to reduce.
5. Advance throttle, wait for few second as (4) for achieving maximum speed.
B) Negotiating ascending grade
1. Before arriving up gradient, take sufficient momentum of train.
2. Take maximum notches as you reach to the crest (end point of up gradient)
3. Reduce notches after 3/4 of the entire train comes on level track.
4. Maintain maximum speed.
C) Stopping of train in ascending grade
1. At a sufficient distance in advance of point of stopping, ease the throttle notch by notch to allow speed to reduce naturally due to the grade.
2. Stop the train on notches.
3. Apply SA-9 (loco brake)
4. Apply A9 (train brake) to avoid roll back of train.
On Down Gradient
A) Starting of train in descending (down) grade Assuming train brakes & loco brakes are applied
1. Release loco brakes first then release train brakes.
2. Allow train to move slowly until entire train is moving.
3. Pickup & maintain the maximum speed.
4. If necessary use Train / dynamic brake to avoid over speeding.
B) Negotiating descending grade
1. Start reducing notches after passing 1/4th of entire train in the down gradient.
2. Use dynamic/Train brakes to avoid over speeding.
3. Before ending the down gradient train should be in released condition & there should be margin in speed to take few notches.
4. Advance throttle only up to load meter reading starts increasing to avoid high buff force.
5. Advance throttle further to maintain maximum speed.
C) Stopping of train in descending grade
1. Reduce the speed by using Train / dynamic brakes.
2. Train brakes should not be completely released to avoid roll down of train.
3. Apply Loco Brakes.
On Undulating Gradient
A) Starting of train in undulating gradient
1. Apply SA-9 fully, advance the throttle to notch 1 and observe load meter increase.
2. Gradually release SA-9 until locomotive begins to move.
3. After a few seconds pause, advance the throttle to notch 2 and observe load meter. Before advancing throttle further, wait for load meter reading to reduce.
B) Negotiating undulating gradient
1. The most reliable procedure is to reduce speed & power prior to entering the series of undulating grades & to operate at a constant speed throughout the undulating area by throttle manipulation. Concentrate upon the location of the rear end of the train, traction amperage, speed and pull of the train.
2. Reduce power on approach to the undulating grades.
3. Concentrate on the location of the rear end of the train.
4. Increase power when the locomotive approaches an ascending (up) grade.
5. Decrease power when the locomotive approaches to descending (down) grade.
6. Maintain a uniform speed throughout the undulating grade section.
C) Stopping the train in undulating gradient
In undulating grade, stopping procedure of the train should be followed as per ascending or descending grade, where the train has to stop during running. On Hump (Knoll) & Cresting Gradient
A) Starting of train on a hump or cresting grade There are no special requirements for starting on a hump or cresting grade. The starting procedure is the same as for starting the train on an ascending (up) grade.
B) Negotiating Hump (knoll) gradient
1. Approach the hump with reduced power thus providing margin for power increase and for stretching the train as the locomotive starts up the hump. Increase power, if possible, to avoid bunching the slack at the leading end and maintain this stretch condition until the locomotive reaches the crest of the hump.
2. As the locomotive passes the hump, and starts to pickup the speed the draw gear will tend to stretch out. To keep slack action to a minimum, reduce power to keep speed constant.
3. Keeps the slack action to a minimum by throttle manipulation to suit loading on the train and the grade.
C) Stopping of train on a crest grade
1. Avoid draw gear stresses: - Take all efforts to avoid stopping of train on a cresting grade, for which the Loco Pilot must have a good knowledge of the location of all cresting grade. A stop of a train on a cresting grade can lead to excessive draw gear stress on the wagon at the crest while attempting to restart the train.
Reducing draw gear stresses:- If a stop has to accomplish, do so in accordance with the stopping procedures for descending grades. When stopping on a cresting grade, always ensure that the brake application used to stop the train is the lightest possible thereby reducing draw gear forces particularly on the apex of the crest.
On Sag or Dip Gradient
A) Starting of train from sag or dip gradient
1. Advance throttle to notch 1st and note the increase of current on the oad meter. Release SA-9 (loco brakes) and wait for the release of the locomotive brakes.
2. After a pause advance the throttle and again observe the load meter. If necessary advance the throttle to position 3rd or 4th notch.
3. If acceleration is too rapid, reduce notches 1 or more. When the complete train is in a stretched condition & in motion, slowly advance the load meter as required.
B) Negotiating sag or dip gradient
1. In order to control slack when moving through sag or dip, the train speed must be allowed to reduce before the train moves into the sag or dip & throttle manipulation used to negotiate the sag or dip gradient. This can be achieved by reducing power & speed before reaching such areas.
2. Continue to reduce power to prevent speed increase as the head portion of the train begins descending in to the sag.
3. Just before the leading portion of the train reaches the ascending grade, begin to advance notches gradually.
4. Continue to advance the throttle on one notch at a time until the rear portion of the train approaches the base of the sag or dip.
5. Reduce power as the rear portion of the train starts on the ascending grade of the sag or dip thereby permitting slack to adjust gradually.
C) Stopping the train in sag or dip
1. In advance of the sag or dip, apply A-9 brakes to minimum reduction & engage dynamic brakes.
2. As the brakes gets effective apply A-9 further up to full service.
3. As the speed decrease below 5 KMPH release dynamic brakes as well as A-9.
4. Apply SA-9.
