Machine Assembly Round 1

The size of a gear is usually specified by the pitch circle diameter. This is the diameter of the imaginary circle that intersects with the gear teeth and represents the average size of the gear. It is an important parameter in gear design and is used to calculate various other dimensions and properties of the gear, such as the number of teeth and the gear ratio. The pitch circle diameter provides a standardized and consistent way to describe the size of gears, making it easier to design and manufacture gears that are compatible with each other.

Rankine's formula is used in designing a connecting rod. The formula is named after the Scottish civil engineer William John Macquorn Rankine. It calculates the maximum stress induced in a rod due to the combined effect of axial and bending loads. This formula takes into account the material properties, dimensions, and applied loads to determine the maximum stress that the connecting rod can withstand without failure. By using Rankine's formula, engineers can ensure that the connecting rod is designed to handle the expected loads and prevent any potential failures or damage.

Rolling contact bearings are commonly referred to as antifriction bearings because they are designed to reduce friction between two moving parts. These bearings use rolling elements such as balls or rollers to carry the load, allowing for smooth and efficient movement. The use of lubrication in these bearings helps to further reduce friction and wear, enhancing their antifriction properties. Therefore, antifriction bearings is the correct term to describe rolling contact bearings.

In static loading, the yield point refers to the maximum stress a material can withstand before it starts to deform permanently. In fatigue loading, the material is subjected to repeated stress cycles, which can lead to damage and failure over time. Since fatigue loading involves repetitive stress, the yield point is typically lower compared to static loading. Therefore, the correct answer is higher.

Antifriction bearings refer to ball and roller bearings. These types of bearings are designed to reduce friction between moving parts, allowing for smooth and efficient operation. Unlike thick lubricated bearings or plastic bearings, ball and roller bearings rely on the rolling motion of balls or rollers to minimize friction. This design enables them to handle high loads and operate at high speeds, making them suitable for a wide range of applications in various industries.

The pitch point of a cam refers to a specific point on the pitch curve where the pressure angle is at its maximum. The pressure angle is the angle between the direction of motion of the follower and the normal to the pitch curve at that point. By identifying the pitch point with the maximum pressure angle, it helps to determine the maximum force or pressure exerted on the follower by the cam.

The correct answer is 20 to 30%. This means that the bearings of heavy series have a capacity that is 20 to 30% greater than the medium series bearings. This suggests that the heavy series bearings are designed to handle heavier loads and have a higher load-carrying capacity compared to the medium series bearings.

The backlash for spur gears depends on both the module and the pitch line velocity. The module refers to the size of the gear teeth, while the pitch line velocity is the speed at which the gears rotate. Both of these factors contribute to the amount of backlash present in the gears. The tooth profile, although important for the overall performance of the gears, does not directly affect the backlash.

When the shaft rotates in the anticlockwise direction at a slow speed in a bearing, it will move towards the left of the bearing, resulting in metal to metal contact.

Malleability refers to the ability of a material to be easily rolled or hammered into thin sheets without breaking or cracking. This property is a special case of ductility and is different from plasticity and elasticity. Plasticity refers to the ability of a material to permanently deform under stress, while elasticity refers to the ability of a material to return to its original shape after being deformed. Therefore, malleability is the correct answer in this case.

Tempering is the process usually adopted to remove internal stresses produced by hardening the steel. During the hardening process, the steel undergoes rapid cooling, which can result in internal stresses and brittleness. Tempering involves reheating the hardened steel to a specific temperature and then allowing it to cool slowly. This process helps to relieve the internal stresses and improve the steel's toughness and ductility, making it less brittle. Therefore, tempering is the correct answer in this case.

Wrought iron is commonly used for crane hooks due to its high strength and durability. It is a tough and malleable material that can withstand heavy loads and harsh conditions. Wrought iron also has excellent resistance to corrosion, making it suitable for outdoor applications. Additionally, its ductility allows for easy shaping and customization of the hooks according to specific requirements. Overall, wrought iron is a reliable choice for crane hooks, ensuring safe and efficient lifting operations.

An universal coupling is used to connect two shafts whose axes intersect at a small angle. This type of coupling allows for flexibility and compensates for any misalignment between the two shafts. It can accommodate angular misalignment, making it suitable for applications where the shafts are not perfectly aligned. By allowing the axes to intersect at a small angle, the universal coupling can transmit torque smoothly and efficiently between the shafts, even when they are not in exact alignment.

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When a machine part is subjected to an axial compressive force, it is called a strut. This means that the force is acting along the axis of the part, pushing it inward and causing it to compress. A strut is designed to withstand this type of force and provide support or stability to the structure it is a part of.

Bearing stress refers to the localized compressive stress that occurs at the area of contact between two members. This type of stress is commonly seen in structures where one component is bearing the weight or load of another component. It is important to consider bearing stress when designing structures to ensure that the materials can withstand the compressive forces and prevent failure at the contact points.

White metal is a type of alloy that is commonly used for bearings subjected to heavy loads. It is known for its high strength, low friction, and excellent load-bearing capacity. White metal alloys typically consist of tin, lead, and antimony, which provide the necessary properties for withstanding heavy loads. This makes white metal a suitable choice for bearings in applications where heavy loads and durability are required.

A sunk key is a type of key that is used to connect a hub and a shaft. It is designed in such a way that half of it fits into the keyway of the hub and the other half fits into the keyway of the shaft. This design ensures a secure and tight connection between the hub and the shaft, preventing any relative movement between them. Therefore, a taper key that fits half in the keyway of the hub and half in the keyway of the shaft is known as a sunk key.

Tapered roller bearings are designed to handle both radial and axial loads. The ratio of these loads being greater than unity means that the axial load is greater than the radial load. This indicates that the bearing can withstand higher axial loads compared to radial loads.

Toughness is the property that is desirable in parts subjected to shock and impact loads. Toughness refers to the ability of a material to absorb energy and deform without fracturing. In situations where there are sudden and intense forces, such as shock and impact loads, a material with high toughness will be able to withstand and absorb the energy, reducing the risk of fracture or failure. Therefore, toughness is an important property for parts that are exposed to such loads.

A knuckle joint is used to connect the valve rod to an eccentric rod in a steam engine. This type of joint allows for a flexible connection between the two rods, allowing them to move in different directions. The knuckle joint consists of two forks or yokes connected by a pin, which allows for rotation and movement. This joint is commonly used in applications where there is a need for flexibility and movement in different directions, making it suitable for connecting the valve rod to the eccentric rod in a steam engine.

The major diameter of a screw refers to the largest diameter of its threaded portion. It is an important specification because it determines the size of the hole that needs to be drilled to accommodate the screw. The major diameter ensures a proper fit and prevents the screw from being too loose or too tight in the hole.

A parallel fillet welded joint is designed for shear strength. In this type of joint, two pieces of metal are joined together by a fillet weld that runs parallel to the direction of the applied force. This design allows the joint to resist shear forces effectively, as the weld material provides strength and stability to prevent the pieces from sliding or separating under shear stress. Therefore, a parallel fillet welded joint is specifically designed to withstand shear loads.

The rivet head used for boiler plate riveting is usually a snap head. A snap head rivet has a rounded, domed shape which provides a smooth surface and prevents it from catching on any objects. This type of rivet head is commonly used in applications where a flush or low-profile finish is desired, making it suitable for boiler plate riveting. The snap head also provides a strong and secure connection between the plates being riveted, ensuring structural integrity.

When bevel gears with equal teeth and equal pitch angles are used to connect two shafts whose axes intersect at a right angle, they are referred to as mitre gears. Mitre gears are specifically designed to transmit motion and power between intersecting shafts at a 90-degree angle. They are commonly used in applications where space is limited and a right angle transmission is required.