Mechanical Components: Cams, Gears, Brakes, and Belts
Types of Cams and Followers
Cams are rotating or sliding pieces in a mechanical linkage that drive follower components with a specific motion. The main types of cams include:
- Radial or Disc Cams: These have a contour on the surface of a rotating disc to guide the follower.
- Cylindrical Cams: These feature a cam profile on the surface of a cylinder.
- Translating Cams: These cams move in a straight line rather than rotating.
Followers are components that are driven by the cam to perform specific motions. They can be classified as:
- Knife-edge Follower: The contact point is a sharp edge.
- Roller Follower: A roller is mounted on the follower to reduce friction.
- Flat-face Follower: Features a flat surface that contacts the cam.
- Spherical Follower: Includes a rounded surface to contact the cam.
Cam Terminology
Understanding cam terminology is essential for design and application:
- Base Circle: The smallest circle from the cam center that the cam profile encloses.
- Prime Circle: The circle from which the cam profile starts to deviate.
- Pitch Curve: The curve that defines the follower’s motion.
- Pressure Angle: The angle between the direction of the follower force and the normal to the profile.
- Trace Point: Point on the follower that is used to generate the cam profile.
Comparison of Rigid and Flexible Drives
Rigid Drives, such as gears and chains, are best for precise, unyielding transmission of power. They are suitable for high-load, high-speed applications where minimal slippage is critical.
Flexible Drives, such as belts, are used where flexibility is more important than precision. They can absorb shock and vibration, handle misalignments, and operate quietly, but they may slip under heavy loads or when improperly tensioned.
Types of Belts
Belts are commonly used in mechanical systems to transmit power between shafts. Major types include:
- Flat Belts: Used for high-speed, light loads; offer quiet operation.
- V-belts: Have a trapezoidal cross-section, suitable for higher power transmission.
- Timing Belts: Have teeth to prevent slippage, ideal for synchronous applications.
Chordal Action of Polygonal Chains
Chordal action refers to the minor variations in speed and tension that occur in chain drives as the sprockets rotate. This is due to the polygonal shape of the sprocket, where the chain engages and disengages the sprocket teeth. The effect is more pronounced in chains with fewer teeth or larger pitches.
Classification of Brakes
Brakes can be classified based on several criteria:
- Mechanism: Drum brakes, disc brakes.
- Actuation: Hydraulic, pneumatic, mechanical, electric.
- Application: Industrial, automotive, aerospace.
Classification of Gears
Gears can be classified by the orientation of their shafts and the shape of their teeth:
- Spur Gears: Parallel shafts, straight teeth.
- Helical Gears: Parallel or non-parallel shafts, angled teeth.
- Bevel Gears: Intersecting shafts, cone-shaped gears.
- Worm Gears: Non-parallel, non-intersecting shafts.
Methods to Avoid Interference in Gearing
Interference in gears occurs when non-conjugate portions of the gear teeth contact. Methods to avoid this include:
- Proper Gear Design: Using involute profiles.
- Correct Center Distance and Alignment.
- Using Undercutting Where Necessary.
- Ensuring Adequate Profile Shifting.
These solutions help maintain smooth and efficient gear operation without premature wear or noise.