Untitled Quiz

Bogie Mounted Brake System (BMBS) for Freight Stock

• BMBS has been introduced for freight stock, recently
• Air Brake freight stocks with BMBS on Indian railways use single pipe/twin pipe graduated release air brake systems
• Air brake system with BMBS is the most efficient and reliable braking system used for heavy and long trains at high speeds

Description of BMBS

• BMBS equipment includes a transversely mounted pneumatic brake cylinder (10" diameter)
• The system has a self-contained, double-acting slack adjuster
• It consists of two brake beams, two bell crank levers and interconnecting push rods
• A mechanical model with two flexible handbrake cables is available
• High friction brake shoes (K-type) are used on CASNUB type bogies

Working Description of BMBS

• During application, air is introduced into the brake cylinder, forcing the piston outwards along the ram assembly
• The brake cylinder extends equally on both sides
• This extension of the brake cylinder causes the rotation of the bell crank levers around their pivot, pushing the push rod towards the secondary beam
• The movement of the secondary brake beam applies force to the wheels
• Simultaneously, the primary brake beam and its related levers and brake cylinder move toward the wheels, applying force to the wheels

Some Other Features

• The brake cylinder is mounted parallel to the brake beams
• The parallelogram design increases efficiency and aligns braking forces with wheels, which reduces wear
• The system delivers optimal braking performance while minimizing weight
• The system can be easily fitted on any standard CASNUB bogie without modifications

To achieve uniform wheel loading

• Loads are applied to the ends of the brake beam, instead of the center
• IR standard 58 mm thick K type brake blocks are used
• A replaceable brake head design permits the reuse of the brake beam in the case of brake head damage

The Push Rods

• Positioned under the bolster
• This positioning increases track clearance

The Brake Cylinder

• Contains an integral double acting slack adjuster, maintaining a constant piston stroke (56 mm)
• The adjuster compensates for up to 500 mm of combined shoe and wheel wear (192 mm shoe, 188 mm wheel)
• All cylinders are equipped with an automatic piston stroke indicator

The Hand Brake System

• Uses two steel hand brake cables, providing a flexible and lightweight interface to the hand brake actuator
• Shoe wear helps extend turn-around time between wagon maintenance intervals
• An automatic pressure modification (APM) device enables two-stage braking (empty/loaded conditions)

Working Principle of BMBS with APM Valve

• The brake system on wagons with BMBS is a single/twin pipe graduated release system with automatic two stage braking
• Wagons have an Automatic Pressure Modification (APM) device to accommodate higher brake power during loaded conditions
• Empty conditions have a pressure of 2.2 ± 0.25 kg/cm², while the pressure for loaded conditions is 3.8 ± 0.1 kg/cm²

Changeover Mechanism

• An APM mechanism on the under-frame and side frame of the bogie is responsible for pressure changeover
• The mechanism activates at a pre-determined wagon weight change
• This mechanism changes the pressure going to the brake cylinder from 2.2 ± 0.25 kg/cm² to 3.8 ± 0.1 kg/cm² during transitions between empty and loaded conditions

Reduction of BP Pressure

• The AR pressure reduction positions the DV to connect the BC and APM device, applying the brake
• For empty conditions, the output pressure is 2.2 ± 0.25 kg/cm²
• For loaded conditions, the output pressure is 3.8 ± 0.1 kg/cm²

During Full Service Brake Application

• A reduction of 1.3 to 1.6 kg/cm² in brake pipe pressure leads to a maximum brake cylinder pressure of 3.8 ± 0.1 kg/cm² for loaded conditions and 2.2 ± 0.25 kg/cm² for empty conditions
• Further reduction in brake pipe pressure has no impact on brake cylinder pressure

Distributor Valve

• The DV used with BMBS has different application and release chokes to achieve specific timings
• Choke sizes (1.42 mm application, 1.52 mm release) are for KE Version DV
• The DV has a "BMBS" nameplate on the choke cover

Brake Cylinder with Built-in Double Acting Slack Adjuster

• The brake cylinder receives pneumatic pressure from AR (after regulation) via the distributor valve and APM device
• Develops mechanical brake power through outward piston movement with the ram assembly

The Built-in Slack Adjuster

• Compensates for brake block wear during application through equivalent pay-out
• A pry bar is used to pay in between brake shoe and wheel, then the rigging is pushed in
• The actuator keeps moving until all slack is taken care of, ensuring sufficient brake force delivery on the wheels

Brake Cylinder Indicator

• Shows "APPLIED" or "RELEASED" condition
• Avoid hitting the indicator, as it may retract slowly and damage

Brake Cylinder Slack Adjustment

• Has a slack adjustment of 500 mm, compensating for 48 mm of brake block wear (which reduces the diameter from 1000 mm to 906 mm) and 47 mm of wheel wear
• Two types: with and without hand brake cables

APM Device

• Interposed between the bogie and wagon side frames of CASNUB bogies
• Designed for automatic changeover of 2-stage load braking (for empty/loaded conditions)
• Limits the BC pressure coming from the distributor valve for both empty conditions (2.2 ± 0.25 kg/cm²) and loaded conditions (3.8 ± 0.1 kg/cm²)

Sensor Arm of the APM Device

• Comes down only during brake application for sensing.

Complete Movement of the Sensor Point

• 104 mm
• 80 mm for loaded zones and balance for empty zones
• Deflection from tare weight to changeover is added to 80 mm to provide full sensor point movement.
• Gap between sensor point and bogie surface is measured at the point where the sensor point touches the side frame; must be in the middle of the side frame

Indicator for Empty/Loaded Condition

• An indicator shows either empty (orange color) with brake cylinder pressure of 2.2 ± 0.25 kg/cm² or loaded condition
• Quick-connect socket to pressure gauge

Procedure for Changing Brake Blocks

• Easy, fast process after brake release
• Pry bar is used to move back brake block, creating space for new blocks between brake head and wheel
• Beam moved across side pockets to create more gap
• Brake block keys removed and replaced, new blocks secured with keys.

Anti-Pilferage Devices (APDs)

• Used to prevent theft or removal of various parts of the system

Maintenance Items

• Bogie rigging, Brake Beams, Bell Cranks, Levers, Push Rods, Brake Cylinder, APM Device, Hand Brake Rigging

Dos & Don'ts for BMBS

• Procedures for proper fitment, maintenance, and use of the system.
• Specific do's and don'ts for bogie rigging, brake cylinder, APM device, piping layout and handbrake arrangement.