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Questions and Answers
Which of the following describes a flat faced follower?
Which of the following describes a flat faced follower?
What distinguishes a hydraulic brake from other types of brakes?
What distinguishes a hydraulic brake from other types of brakes?
What role does the prime circle play in a roller follower setup?
What role does the prime circle play in a roller follower setup?
What is a key characteristic of an axial brake?
What is a key characteristic of an axial brake?
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In cam drives, what does the pitch point signify?
In cam drives, what does the pitch point signify?
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What is an advantage of a double shoe brake compared to a single shoe brake?
What is an advantage of a double shoe brake compared to a single shoe brake?
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Which of the following accurately describes the term 'slip' in belt drive systems?
Which of the following accurately describes the term 'slip' in belt drive systems?
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Which brake type is characterized as generating electricity during operation?
Which brake type is characterized as generating electricity during operation?
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Which type of follower uses a round surface for contact?
Which type of follower uses a round surface for contact?
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Which of the following classifications represent mechanical brakes?
Which of the following classifications represent mechanical brakes?
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Which of the following depicts the smallest circle that can be drawn to a cam profile?
Which of the following depicts the smallest circle that can be drawn to a cam profile?
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What term describes the circle that is tangent to the pitch curve in cam design?
What term describes the circle that is tangent to the pitch curve in cam design?
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Which classification of cam refers to a cam that is shaped like a disc?
Which classification of cam refers to a cam that is shaped like a disc?
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Which of the following factors does NOT affect power transmission in a belt drive?
Which of the following factors does NOT affect power transmission in a belt drive?
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In the context of brakes, which type relies on the flow of fluid for energy transformation?
In the context of brakes, which type relies on the flow of fluid for energy transformation?
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What type of follower moves in a back-and-forth motion?
What type of follower moves in a back-and-forth motion?
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Study Notes
Classifying Cams and Followers
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Cam Followers can be classified based on their surface in contact, motion, and path of motion.
- Surface in contact: Knife edge, roller, flat-faced, spherical.
- Motion: Reciprocating or translating, oscillating or rotating.
- Path of motion: Radial, off-set.
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Cams can be classified into two main categories:
- Radial or disc cam: The camshaft rotates, and the follower moves radially.
- Cylindrical cam: The camshaft rotates, and the follower moves in a plane parallel to the camshaft axis.
Internal Expanding Shoe Brake
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Working:
- The internal expanding shoe brake uses a hydraulic or mechanical system to push outward on brake shoes located within the brake drum.
- As the shoes expand, they create friction against the drum, slowing or stopping the rotation.
Classifying Brakes
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Brakes can be classified by the means used to transform the energy by the braking elements:
- Hydraulic brakes: Utilize a hydraulic system for braking force.
- Electric brakes: Employ electromagnetic methods for braking.
- Mechanical brakes: Rely on mechanical components for braking force.
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Mechanical Brakes can be categorized based on the direction of the acting force:
- Radial brakes: The braking force acts radially towards the center of rotation.
- Axial brakes: The braking force acts axially along the axis of rotation.
Advantages of Double Shoe Brake over Single Shoe Brake
- Increased braking torque: Double shoe brakes provide more braking force because they have two shoes acting on the drum.
- Balanced braking: The two shoes create opposing forces that balance each other, reducing uneven wear.
- Improved stability: Double shoe brakes contribute to greater stability in the braking system.
Belt Drive Advantages and Disadvantages
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Advantages:
- Simple design: Relatively easy to construct and maintain.
- Smooth operation: Provides a relatively smooth power transmission.
- Affordable: Generally a cost-effective method for power transfer.
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Disadvantages:
- Slippage: Can experience slippage, leading to power loss.
- Limited power transmission: Not suitable for high power applications.
- Limited speed ratio: Speed ratio limitations based on belt material.
Classifying Belt Drives
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Belt drives can be classified based on the type of belt used:
- Flat belts: Wide, flat belts.
- V-belts: Have a V-shaped cross-section.
- Round belts: Have a circular cross-section.
Cam Drive Terminology
- Base Circle: The smallest circle that can be drawn tangent to the cam profile.
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Prime Circle: The smallest circle drawn from the center of the cam that is tangent to the pitch curve.
- For knife edge and flat-faced followers, the prime circle and base circle coincide.
- For roller followers, the prime circle is larger than the base circle by the roller's radius.
- Pitch Point: The point on the pitch curve with the maximum pressure angle.
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Pitch Curve: The curve traced by the follower's trace point as it moves relative to the cam.
- For knife edge followers, the pitch curve and cam profile are identical.
- For roller followers, the pitch curve and cam profile are separated by the roller's radius.
Governor and Flywheel Difference
- Governor's function: Regulates the mean speed of an engine by controlling the fuel supply to counteract load variations.
- Flywheel's function: Stores energy during the power stroke and releases it to smooth out the engine speed during the other strokes, ensuring a more consistent rotational speed.
Belt Drive: Slip and Creep
- Slip: Occurs when there is relative motion between the belt and the pulley due to insufficient friction. This results in power loss.
- Creep: A phenomenon where the belt continuously moves slightly relative to the pulleys even when they are rotating at a constant speed. This results in slight speed variation.
Differential Gearbox
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Construction: Consists of a central differential gear and two side gears.
- Side gears are connected to the drive shafts of the wheels.
- The differential gear is connected to the input shaft.
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Working: Allows for different wheel speeds when turning.
- When turning, one wheel travels a shorter distance than the other, relying on the differential to adjust and provide the necessary speed difference.
Initial Tension in Belt Drive
- Initial Tension: The tension applied to the belt when the system is at rest.
- Purpose: Ensures that the belt remains in contact with the pulleys and prevents slippage.
- Factors Affecting Initial Tension: Belt material, pulley diameters, power transmission requirements.
Factors Affecting Power Transmission in Belt Drive
- Belt material: Friction coefficient, strength, and elasticity.
- Pulley diameter: Size influences the belt's speed and power transmission capability.
- Belt tension: Too loose = slippage; too tight = excessive wear.
- Centrifugal force: High speed can lead to belt tension loss due to centrifugal force.
- Belt length and alignment: Proper length and alignment are crucial for smooth operation.
Governor and Flywheel Functions
- Governor: Regulates the engine's speed by adjusting fuel delivery to maintain a consistent speed despite varying loads.
- Flywheel: Stores energy from the power stroke and releases it during other strokes, smoothing out the engine's rotational speed.
Cam and Follower Classification
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Follower Classification
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Surface in Contact
- Knife edge follower
- Roller follower
- Flat faced or mushroom follower
- Spherical faced follower
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Motion of Follower
- Reciprocating or translating follower
- Oscillating or rotating follower
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Path of Motion of Follower
- Radial follower
- Off-set follower
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Surface in Contact
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Cam Classification
- Radial or disc cam
- Cylindrical cam
Internal Expanding Shoe Brake
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Working
- The internal expanding shoe brake uses a hydraulic or mechanical actuator to push the brake shoes outwards against the drum.
- The friction between the shoes and the drum creates a braking force that slows down the rotating drum.
- The brake shoes are usually lined with a high-friction material for better braking performance.
Brake Classification
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Classification by Energy Transformation
- Hydraulic Brakes: Use pumps or hydrodynamic brakes and fluid agitators
- Electric Brakes: Use generators and eddy current brakes
- Mechanical Brakes: Use mechanical means to apply braking force
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Mechanical Brakes by Force Direction
- Radial brakes
- Axial brakes
Advantages of Double Shoe Brake Over Single Shoe Brake
- Increased Braking Force: Double shoe brakes provide a larger contact area with the drum, resulting in a higher braking force.
- Improved Stability and Uniformity: The symmetrical arrangement of the shoes reduces uneven wear and improves the overall stability of the braking system.
Advantages and Disadvantages of Belt Drives
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Advantages of Belt Drives:
- Flexibility: Belt drives can handle misalignment and provide a smooth power transmission.
- Quiet Operation: Belt drives are generally quieter than gear drives.
- Low Maintenance: Belt drives typically require less maintenance compared to other power transmission systems.
- Shock Absorption: Belts can absorb shock loads and reduce vibrations in the system.
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Disadvantages of Belt Drives:
- Slippage: Belts can slip under high loads, leading to power loss.
- Limited Speed: Belt drives have a limited speed range compared to other power transmission systems.
- Limited Torque Capacity: Belt drives may not be suitable for high torque applications.
Belt Drive Classification
- Open Belt Drive: The belt runs over two pulleys mounted on shafts in the same direction.
- Cross Belt Drive: The belt runs over two pulleys mounted on shafts rotating in opposite directions.
- V-Belt Drive: The belt has a V-shaped cross-section that fits into corresponding grooves on the pulleys.
- Timing Belt Drive: The belt has teeth that engage with teeth on the pulleys, ensuring precise timing and eliminating slippage.
Cam Drive Terminology
- Base Circle: The smallest circle that can be drawn tangent to the cam profile.
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Prime Circle: The smallest circle that can be drawn from the center of the cam, tangent to the pitch curve.
- For knife edge and flat face followers, the prime circle and base circle coincide.
- For roller followers, the prime circle is larger than the base circle by the radius of the roller.
- Pitch Point: The point on the pitch curve where the pressure angle is maximum.
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Pitch Curve: The path traced by the follower's trace point as it moves relative to the cam.
- For knife edge followers, the pitch curve and cam profile are the same.
- For roller followers, the pitch curve is offset from the cam profile by the radius of the roller.
Governor vs. Flywheel
- Governor: Regulates the mean speed of an engine, adjusting the fuel supply in response to changes in load.
- Flywheel: Stores rotational energy, smoothing out fluctuations in engine speed caused by variations in load.
Slip and Creep in Belt Drive
- Slip: Occurs when the belt slides on the pulley surface, leading to a loss of power transmission.
- Creep: A slow, continuous movement of the belt relative to the pulley, even when there is no slip. Creep results from the elastic deformation of the belt material under load.
Differential Gearbox
- Construction: Consists of two bevel gears (pinion) meshed with a larger gear called the crown gear.
- Working: The pinion gears rotate freely on the input shaft. The crown gear rotates with the output shaft. The differential mechanism allows for the independent rotation of the two wheels on a vehicle, making turns possible.
Initial Tension in Belt Drive
- Initial tension: The amount of tension applied to the belt when the system is at rest, before power transmission begins.
- Importance: Initial tension ensures proper belt engagement with the pulleys, reduces slippage, and provides a starting point for power transmission.
Factors Affecting Power Transmission in Belt Drive
- Belt Material: The elasticity and friction coefficient of the belt material influence power transmission.
- Belt Tension: Optimum tension is critical for efficient power transmission and prevents slippage.
- Pulley Diameter: Larger pulley diameters reduce belt speed and increase the power transmission capability.
- Pulley Alignment: Misalignment can cause premature belt wear and power loss.
- Operating Temperature: High temperatures can reduce the strength and elasticity of the belt.
Functions of Governor and Flywheel
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Governor:
- Regulates Engine Speed: Ensures consistent engine speed even when the load changes.
- Improves Fuel Efficiency: By optimizing engine speed, governors minimize fuel consumption.
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Flywheel:
- Smooths Engine Operation: Reduces speed fluctuations and ensures a more uniform energy delivery.
- Increases Power Output: Allows the engine to store energy during the power stroke and release it during the other strokes, improving overall power output.
- Reduces Shock Loads: Absorbs shock loads from the engine and transmission, protecting components from damage.
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Description
This quiz covers the classification of cam followers and various types of brakes, including internal expanding shoe brakes. It explores the mechanics of motion and energy transformation in braking systems, providing insights into their functioning. Ideal for students studying mechanical engineering concepts.
