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Questions and Answers
What does BMBS stand for?
What does BMBS stand for?
Bogie Mounted Brake System
What type of brake system is the BMBS?
What type of brake system is the BMBS?
The BMBS is designed to be fitted on any type of bogie.
The BMBS is designed to be fitted on any type of bogie.
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What is the diameter of the pneumatic Brake Cylinder used in BMBS?
What is the diameter of the pneumatic Brake Cylinder used in BMBS?
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What is the thickness of the brake shoes used in BMBS?
What is the thickness of the brake shoes used in BMBS?
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What does the integral double-acting slack adjuster in the BMBS provide?
What does the integral double-acting slack adjuster in the BMBS provide?
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What are the two types of brake cylinders used in BMBS?
What are the two types of brake cylinders used in BMBS?
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The BMBS is designed to reduce the shoe and wheel wear.
The BMBS is designed to reduce the shoe and wheel wear.
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What is the purpose of the APM device in BMBS?
What is the purpose of the APM device in BMBS?
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APDs are only used on the pins of the bogie rigging, not on the brake cylinder.
APDs are only used on the pins of the bogie rigging, not on the brake cylinder.
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What type of weld is used for APDs on the primary and secondary brake beams?
What type of weld is used for APDs on the primary and secondary brake beams?
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The BMBS is designed to be a drop-in fit system.
The BMBS is designed to be a drop-in fit system.
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Study Notes
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.
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