During POH & ROH, striker casting wear plate should be replaced as per Railway Board's letter.

During POH, knuckle, CBC lock, rotary lock lift assembly, bearing piece, yoke pin support plate liner and shank wear plate should be replaced.

The report recommended strictly checking and enhancing replacement of knuckles, knuckle pivot pin, lock, lock lifter with toggle, yoke pin, operating handle and bearing piece during maintenance.

Uncoupling cases were mainly due to lock defective/broken, lock lifting arrangement defective, knuckle worn out/defective and operating handle/bearing bracket defective.

A press of 40 tonnes is required to dismantle Mark-50 draft gear.

When plate clearance reduces to zero, the draft gear loses its effectiveness to cushion and some parts will start wearing on the housing, causing considerable damage.

Plate clearance is a built-in wear life gauge that indicates the total surface wear of the friction components in Mark-50 draft gear.

The alternative method is to place the stuck draft gear in front of a wall and give sledge hammer blows with 8-10 kg hammer on top front, side fronts, edges and rear wall.

First move another wagon against the coupler, forcing follower and draft gear against rear stops before any other action.

The warning clearly states: WEAR SAFETY EQUIPMENT INCLUDING HARD HAT, SAFETY GLASSES, SAFETY SHOES, GLOVES AND BODY PROTECTION.

The internal spring forces in a fully stuck Mark-50 draft gear are between 11,000 kg and 23,000 kg.

A fully stuck draft gear has components of the friction clutch jammed and flush with the open end of the housing. A large gap would appear at front or rear stops.

In a partially stuck draft gear, the draft gear is loose in the pocket and the draft gear travel will be less than 82.55 mm (3-1/4").

The internal spring forces in a normal fully released Mark 50 draft gear will be from 7,000 kg to 10,000 kg.

A normally released draft gear has the follower plate against the front lugs, the housing against the rear lugs, and components fully returned to neutral position.

Preferable shielding for root run is 75% Argon and 25% CO2 gas.

MIG welding with AWS A5.18-69 class E70S-1B, 1.14 mm diameter, 100,000 psi tensile wire is used for root run.

The housing is to be cut to a length of 463.6 mm ± 1.6 mm (18-1/4" ± 1/16").

Rubber pads must be returned to minimum free height of 61 mm within one minute after load is released.

Wedge and shoes are to be shot-peened to remove rust and dirt before assembly. Shot-peening also allows better visual examination.

To function properly, every part of the assembly must be free of oil, grease and moisture.

Bore taper should be smooth and any concavity must not exceed 0.8 mm (1/32").

The inside friction bore walls must be worn symmetrical and the wall thickness must not be less than 20.6 mm (13/16").

Shoes to be reused must have no wear more than 0.8 mm (1/32") on any friction surface.

A 200 tonnes vertical open gap press, assembly block, and assembly ring are required to remove shoes and wedge from RF-361 draft gear.

A loose clutch normally means that there is either a defective rubber springs package or excessive wear has taken place on the cylinder bore friction surfaces.

RF-361 draft gear requires complete reconditioning only if the gear has loose clutch components (shoes & wedges), a broken housing, or a cracked weld at the rear wall.

The performance efficiency of RF-361 draft gear is 36.6%.

The performance efficiency of MK-50 draft gear is 69.0%.

At present, three types of high capacity draft gears are in service: MK-50, RF-361, and MINER SL-76.

Bogie wagons manufactured prior to 1984-85 were fitted with HR-40-I or MF-400-I IR draft gears, but these are being replaced with high capacity draft gears progressively.

The draft capacity of HT coupler is 36% higher than standard coupler due to higher yield strength of knuckle.

The ultimate tensile strength of Grade 'B' coupler body (for Grade 'C' knuckle) is 290t, while for Grade 'E' coupler body it is 408t.

When using Gauge No. 8, if the gap is more than 3.2 mm at "B", it indicates combined wear of lock at knuckle contacting surface and engagement surface with coupler body, so lock must be renewed.

Gauge No. 7 checks the anti-creep lug (bridge) of rotary lever. If gauge is not mating properly, renew the rotary lever.

Ineffective anti-creep can lead to unintentional uncoupling, which is a major cause of train partings.

Gauge No. 6 checks the bottom anti-creep. If there is a gap between gauge and bottom lifter, renew the bottom lifter as anti-creep is ineffective.

Gauge No. 5 (Knuckle pivot gauge) checks for excessive wear at the locking face of the knuckle. If the gauge passes vertically, knuckle must be renewed.

During knuckle nose wear check, if "E" passes, it indicates excessive knuckle nose wear and the knuckle must be renewed.

When using Gauge No. 4 for knuckle check, if "D" touches, the knuckle is stretched and must be renewed.

When applying Gauge No. 3, if "A" is in contact and "B" or "C" touches, renew the coupler body as the guard arm is distorted.

If after replacing knuckle, pin and lock, Gauge No. 2 still passes, the coupler body must be renewed because the guard arm is expanded.

If Gauge No. 1 passes, renew knuckle, knuckle pin and lock. After replacement, if Gauge No. 2 passes, renew the coupler body.

To remove draft gear from yoke, compress the gear by means of screw and insert two pre-shortners, then release screw and remove draft gear.

To remove tight gear, first apply cross key through front of yoke, then apply screw and turn until gear is loose in the wagon pocket.

Draft gears shall be inspected at every POH of the wagon, irrespective of the amount of free slack existing.

Free slack is determined by first sledging the coupler back solid and measuring clearance, then prying coupler out and measuring again. The difference is the free slack.

When the knuckle does not move freely, first grind the top face of "top pulling lug" and "lock face" of knuckle in position.

The lock position is indicated by the toggle, which is clearly visible below the coupler head.

In transition CBC, coupler body with shank is longer and is provided with an arrangement to fit clevis with the help of clevis pin.