DEFINITION
DRAWGEAR
The actual coupling between locomotive and wagon, and wagon to wagon.
DRAFTGEAR : The impact absorbing apparatus whereby the drawgear is attached to the locomotive or wagon.
TRAIN AS ELASTIC MASS:
There are two kinds of slacks:
1. Free Slack : Free slack is the clearance with in the drawgear which can run-in or run-out without compressing the draftgear. 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 draftgear 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.
Therefore there is a sizeable potential movement within a train between the front and rear as illustrated below:
It is very much essential to control the run-in / runout slack movements because the destructive force or shock increases with square of the speed. When a wagon at a speed of 5 KMPH hits or draws a wagon running at 3 KMPH (speed difference 2 Free Slack Spring Slack. KMPH) creates a shock 4 times that of 1 KMPH speed difference. Similarly,
at 3 KMPH speed difference impact will be 9 times that of 1 KMPH. at 4 KMPH speed difference impact will be 16 times that of 1 KMPH.
RUN-IN: When a rear section of a train is travelling faster than a forward section 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 section of a train is travelling slower than a forward section of a train. Run-out may also be a combination of slack movement and spring slack dependent upon the forces generated.
BREAK-IN-TWO / COUPLER BRAKAGES : The life of a coupler depends on how much less fatigue it has gained. The more the fatigue the less will be the remaining life of the coupler. 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. The less number of times run-in to run-out and run-out to run-in occurs the less will be the shock on the couplers & coupler fatigue.
ADHESION: That grip which the wheels have on the rail dependent upon weight, track condition and weather conditions.
ENERGY CONSUMPTION: Consumption of electricity by a locomotive for moving train from one location to another location. Unit of electric energy is Kwh.
TONNE KM/KWH: Load hauled by a loco for a length of one Kilometer on consumption of one unit of electricity.
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 feel when sudden changes in track gradient from level to down & then up (due to track defect).
