Brakes and Dynamometers free study note for Diploma / BTech.

1. Introduction

Brakes and dynamometers are mechanical devices related to control and measurement of motion and power.

• Brakes → Used to reduce speed or stop motion
• Dynamometers → Used to measure power/torque of engines or machines

Key idea:
Brakes absorb energy, while dynamometers measure power (often by absorbing it).

2. Brakes

2.1 What is a Brake?

A brake is a mechanical device used to slow down or stop a moving body by converting kinetic energy into heat energy through friction.

2.2 Principle of Braking

• When brake shoes/pads press against a rotating surface (drum/disc), friction force is generated
• This friction opposes motion
• Kinetic energy is converted into heat

2.3 Types of Brakes

(a) Drum Brake

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• Brake shoes press inside a rotating drum
• Common in older vehicles

(b) Disc Brake

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• Pads press against a rotating disc (rotor)
• Better heat dissipation
• Widely used in modern vehicles

(c) Band Brake

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• A flexible band wraps around a drum
• Tightening the band produces braking

(d) Block Brake

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• A block presses directly on a rotating wheel

2.4 Components of Brakes

• Brake drum/disc
• Brake shoes/pads
• Actuating mechanism (mechanical/hydraulic)
• Springs and linkages

2.5 Advantages of Brakes

• Provide safety and control
• Simple operation
• Reliable and effective

2.6 Disadvantages

• Heat generation
• Wear and tear
• Maintenance required

2.7 Applications

• Automobiles
• Elevators
• Cranes and hoists
• Industrial machines

3. Dynamometers

3.1 What is a Dynamometer?

A dynamometer is a device used to measure torque and power produced by an engine or motor.

3.2 Principle of Working

• Measures force acting on a rotating shaft
• Calculates torque (T)
• Power is calculated using:

$$P = \frac{2\pi N T}{60}$$P=602πNT​

Where:

• $P$P = Power
• $N$N = Speed (rpm)
• $T$T = Torque

3.3 Types of Dynamometers

(A) Absorption Dynamometer

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• Absorbs entire power of engine
• Converts it into heat

Types:

• Prony Brake Dynamometer
• Rope Brake Dynamometer
• Hydraulic Dynamometer
• Eddy Current Dynamometer

(B) Transmission Dynamometer

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• Does not absorb power
• Measures torque while transmitting power

Types:

• Belt transmission dynamometer
• Torsion dynamometer

3.4 Advantages of Dynamometers

• Accurate power measurement
• Useful in engine testing
• Helps in performance analysis

3.5 Disadvantages

• Costly equipment
• Requires calibration
• Heat dissipation issues (absorption type)

3.6 Applications

• Engine testing laboratories
• Automobile industries
• Power plants
• Research and development

4. Difference Between Brakes and Dynamometers

Feature	Brakes	Dynamometers
Function	Stop or slow motion	Measure power
Energy	Dissipated as heat	Measured/absorbed
Application	Vehicles, machines	Testing equipment
Output	Retarding force	Power/torque

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