Design and Fabrication of Vacuum Brake system

The design and fabrication of a braking system is a difficult task. The application of brakes using vacuum in automobiles is a more difficult task in the initial stages of the work. But it has been successfully proved that such brake application is possible with the fail-safe condition. While implementing this idea on a heavy vehicle, it is better to replace the manually operated directional control valve with solenoid operated directional control valve to reduce driver effort and also it will work like a brake pedal switch. In this project, you will design and fabricate a vacuum braking system for a Train.

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A vehicle brake is used to slow down a moving vehicle by converting its Kinetic energy into heat. The basic hydraulic system, most commonly used, usually has six main stages. The brake pedal, the brake boost (vacuum servo), the master cylinder, the apportioning valves and finally the road wheel brakes themselves. The vacuum brake system has been used by people for many years, in place of the air brake as it is, fail-safe. Pneumatic braking systems use compressed air as the force used to push blocks on to wheels. The vacuum brake system is controlled through a brake pipe connecting a brake valve in the driver's cab with braking equipment on the vehicle. A vacuum is created in the pipe by an ejector or exhaust. The ejector removes atmospheric pressure from the brake pipe to create the vacuum using steam on a steam locomotive, or an exhausted, using electric power on other types of train. With no vacuum, the brake is fully applied. The vacuum in the brake pipe is created and maintained by a motor-driven exhauster. The exhauster has two speeds, high speed and low speed. The high speed is switched in to create a vacuum and thus release the brakes. Slow speed is used to keep the vacuum at the required level to maintain brake release. Vacuum against small leaks in the brake pipe is maintained by it.

Project Description:

• Driver’s Brake Valve: It is the mean by which the driver controls the brake. The brake valve will have (at least) the following positions: "Release", "Running", "Lap" and "Brake On". There may also be a "Neutral" or "Shut Down" position, which locks the valve out of use. The "Release" position connects the exhauster to the brake pipe and switches the exhauster to full speed. This raises the vacuum in the brake pipe as quickly as possible to get a release. In the "Running" position, the exhauster keeps running but at its slow speed. This ensures that the vacuum is maintained against any small leaks or losses in the brake pipe, connections, and hoses. "Lap" is used to shut off the connection between the exhauster and the brake pipe to close off the connection to the atmosphere after a brake application has been made. It can be used to provide a partial release as well as a partial application, something not possible with the original forms of air brake. "Brake On" closes off the connection to the exhauster and opens the brake pipe to atmosphere. The vacuum is reduced as air rushes in. Some brake valves were fitted with an "Emergency" position. Its operation was the same as the "Brake On" position, except that the opening to the atmosphere was larger to give a quicker application.

• Vacuum Brake System: A vacuum brake is a type of brake that works by atmospheric pressure acting on a piston in a vacuum cylinder. It is operated by a vacuum taken from the intake manifold or carburetor at a point just above the throttle valve.

Project Implementation:

1. At 1st design the complete mechanism of a vacuum braking system using any solid modelling software. While designing consider the following criteria,
• Availability of materials.
• Suitability of the material for the required components.
• Suitability of the material for the desired working conditions.
• Cost of the material and Design.
• The strength of your structure.
2. After the completion of 3D modelling of vacuum braking system, you have to perform the structural analysis part on that material which is to be used in the vacuum braking system. The goals of the structural analysis are to visualize the stress distribution, load application, deformation under static loads and validate the methodology used.
3. Then after performing structural analysis, fabricate the system by joining various elements of the braking system.

Project Brief: With the successful completion of the project you can observe that depressing the brake pedal opens a valve between the power cylinder, which contains a piston, and the intake manifold to which the power cylinder is connected. When you apply the brakes, air is exhausted from the cylinder head of the piston. At the same time, atmospheric pressure acts on the rear side of the piston to exert a powerful pull on the rod attached to the piston. When the brake valve is closed, the chamber ahead of the piston is shut off from the intake manifold and is opened to the atmosphere. The pressure is then the same on both sides of the piston; therefore, no pull is exerted upon the pull rod. The brakes are released and the piston returned to its original position in the power cylinder by the brake shoe return springs.

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Software requirements:

1. CATIA: This is one of the popular solid modelling software made by Dassault System. You will use this software to design your machine structure.
2. ANSYS: You will be needing ANSYS software to perform structural analysis and visualize the result.

• Workshop equipments

• Mechanical
• manufacturing
• braking system
• catia
• ANSYS
• design
• Analysis

Design and Fabrication of Vacuum Brake system