Friction and Governors

Introduction

Friction and governors are important concepts in the field of Theory of Machines & Machine Design. Understanding the fundamentals of friction and governors is crucial for designing efficient and reliable machines.

Friction

Friction is the force that opposes the relative motion between two surfaces in contact. It plays a significant role in various mechanical systems and has different types.

Types of Friction

There are three main types of friction:

1. Dry Friction: Dry friction occurs between solid surfaces in contact without any lubrication. It can be further classified into static friction and kinetic friction.

   a. Laws of Dry Friction: The laws of dry friction describe the relationship between the frictional force and the normal force.

2. Rolling Friction: Rolling friction occurs when an object rolls over a surface. It is generally lower than dry friction.

3. Friction of Pivots and Collars: Friction of pivots and collars is encountered in rotating machinery where the shafts are supported by bearings or collars.

Applications and Examples of Friction

Friction has various applications in machine design, including:

1. Clutches: Clutches are used to transmit power from one shaft to another. There are different types of clutches, such as single disc clutches, multiple disc clutches, and cone clutches.

2. Anti-Friction Bearings: Anti-friction bearings, such as ball bearings and roller bearings, are used to reduce friction and provide smooth rotation.

Governors

Governors are devices used to regulate the speed of engines or machines by controlling the fuel or steam supply. There are different types of governors with their own constructional details and analysis.

Types of Governors

The main types of governors are:

1. Watt Governor: The Watt governor is a centrifugal governor widely used in steam engines. It consists of two rotating balls and a central spindle.

   a. Constructional Details: The construction of the Watt governor includes the balls, spindle, and linkage mechanism.

   b. Analysis of Watt Governor: The analysis of the Watt governor involves determining the equilibrium speed and the controlling force curves.

2. Porter Governor: The Porter governor is a modification of the Watt governor and is used in engines where a wide range of speed control is required.

   a. Constructional Details: The construction of the Porter governor includes the balls, spindle, and linkage mechanism.

   b. Analysis of Porter Governor: The analysis of the Porter governor involves determining the equilibrium speed and the controlling force curves.

3. Proell Governor: The Proell governor is a type of inertia governor used in high-speed engines. It consists of two rotating masses and a central spindle.

   a. Constructional Details: The construction of the Proell governor includes the rotating masses, spindle, and linkage mechanism.

   b. Analysis of Proell Governor: The analysis of the Proell governor involves determining the equilibrium speed and the controlling force curves.

Key Concepts and Principles of Governors

Governors operate based on certain key concepts and principles:

1. Effect of Friction on Governors: Friction plays a significant role in the operation of governors. It affects the controlling force curves and the stability of the governor.

2. Controlling Force Curves: The controlling force curves represent the relationship between the controlling force and the speed of the governor. They determine the stability and sensitivity of the governor.

3. Sensitiveness: Sensitiveness refers to the ability of a governor to respond quickly and accurately to changes in speed.

4. Stability: Stability is the ability of a governor to maintain a constant speed despite external disturbances.

5. Hunting: Hunting is an undesirable oscillation of the governor caused by changes in the controlling force.

6. Iso-Chronism: Iso-chronism refers to the ability of a governor to maintain a constant speed regardless of the load variations.

7. Power and Effort of a Governor: The power and effort of a governor determine its ability to control the speed of an engine or machine.

Step-by-Step Walkthrough of Typical Problems and Solutions related to Governors

To better understand the concepts and principles of governors, let's walk through a typical problem and its solution:

Problem: A steam engine is equipped with a Watt governor. The engine is running at a speed of 200 RPM, and the controlling force curve is given. Determine the equilibrium speed of the governor.

Solution: To determine the equilibrium speed, we need to find the intersection point of the controlling force curve and the speed line corresponding to 200 RPM. By calculating the controlling force at that point, we can determine the equilibrium speed.

Balancing of Rotating Masses

Balancing of rotating masses is an important aspect of machine design to minimize vibrations and ensure smooth operation.

Static Balancing

Static balancing involves arranging the masses in such a way that the center of gravity of the system lies on the axis of rotation.

Dynamic Balancing

Dynamic balancing involves balancing the rotating masses in both the static and dynamic conditions. It requires the consideration of both the mass distribution and the angular position of the masses.

Balancing of Rotating Masses in One Plane

Balancing of rotating masses in one plane is achieved by adding balancing masses at specific locations to counterbalance the unbalanced masses.

Balancing of Rotating Masses in Different Planes

Balancing of rotating masses in different planes is more complex and requires the consideration of both the mass distribution and the angular position of the masses in multiple planes.

Real-World Applications and Examples of Friction and Governors in Machine Design

Friction and governors have numerous real-world applications in machine design, including:

• Automotive industry: Friction is utilized in clutches, brakes, and tires, while governors are used in engine speed control.
• Industrial machinery: Friction is important in belt and chain drives, while governors are used in turbines and generators.
• Aerospace industry: Friction is crucial in landing gear systems, while governors are used in aircraft engine control.

Advantages and Disadvantages of Friction and Governors in Machine Design

Friction and governors have their own advantages and disadvantages in machine design.

Advantages of Friction:

• Provides necessary traction for motion
• Allows for controlled deceleration
• Enables power transmission in clutches and brakes

Disadvantages of Friction:

• Causes wear and tear on surfaces
• Generates heat and energy loss
• Can lead to reduced efficiency and increased maintenance

Advantages of Governors:

• Regulate and maintain desired speed
• Provide stability and control
• Protect machines from overspeeding

Disadvantages of Governors:

• Additional complexity and cost
• Requires maintenance and adjustment
• May introduce vibrations and noise

Conclusion

Friction and governors are fundamental concepts in the field of Theory of Machines & Machine Design. Understanding the different types of friction, the construction and analysis of governors, and the principles associated with them is essential for designing efficient and reliable machines. By considering the advantages and disadvantages of friction and governors, engineers can make informed decisions in machine design to achieve optimal performance and longevity.

Summary

Friction and governors are important concepts in the field of Theory of Machines & Machine Design. Friction is the force that opposes the relative motion between two surfaces in contact and has different types such as dry friction, rolling friction, and friction of pivots and collars. It has various applications in machine design, including clutches and anti-friction bearings. Governors are devices used to regulate the speed of engines or machines and have different types such as the Watt governor, Porter governor, and Proell governor. They operate based on key concepts and principles such as the effect of friction, controlling force curves, sensitiveness, stability, hunting, iso-chronism, power, and effort. Balancing of rotating masses is important to minimize vibrations and ensure smooth operation. Friction and governors have real-world applications in machine design in various industries such as automotive, industrial machinery, and aerospace. They have their own advantages and disadvantages in machine design, and understanding them is crucial for designing efficient and reliable machines.

Analogy

Friction can be compared to the resistance experienced while walking on a sandy beach. The sand particles create friction with the soles of your feet, making it harder to move forward. Similarly, in machines, friction opposes the motion between two surfaces, making it necessary to overcome this resistance for smooth operation. Governors can be compared to the cruise control system in a car. Just like the cruise control maintains a constant speed, governors regulate the speed of engines or machines by controlling the fuel or steam supply.