Mechanism and Engine Types: Transmission & Function

Posted on Mar 13, 2025 in Technology

Mechanism and Engine Types

Transmission Mechanisms

The transmission ratio is the ratio of the velocities of two moving elements, represented by “r”.

A mechanism train is the union of several simple mechanisms. There are three main types:

  • Reducing Transmission System: Used to attach a pulley system to a system of gears. It reduces the speed of a motor and can be achieved with multiple pulleys.
  • Gear Train: Used to increase the speed of a mechanism. Employs multiple gears or pulleys.
  • Pulley Train: Used to reduce the speed of a motor.

Processing Mechanisms

Processing mechanisms change the type of movement, for example, from linear to circular motion or vice-versa, and from alternative to circular or vice-versa. The most important are:

  • Rack and Pinion and Spindle-Nut: For circular motion to linear motion transformations (and vice versa).
  • Connecting Rod-Crank, Eccentric, Crankshaft, and Cam: For alternative to circular motion transformations.

Heat Engines

Heat engines transform thermal energy into mechanical energy. They can be of two types:

  • External Combustion: The fuel is burned outside the engine, as in a steam engine.
  • Internal Combustion: The fuel is burned inside the machine, like in a car engine.

Four-Stroke Engine

The four-stroke engine is the most widely used and has four distinct phases:

  1. Intake
  2. Compression
  3. Combustion (Explosion)
  4. Exhaust

Two-Stroke Engine

The two-stroke engine performs the same functions as the four-stroke engine but with only two phases in a cylinder:

  1. Compression-Explosion
  2. Exhaust-Compression

Engine Displacement

Displacement is the sum of the total volume of all cylinders in a reciprocating engine. It is usually measured in cubic centimeters (cc) and is calculated as follows:

Where:

  • r = radius of the cylinder
  • h = stroke

Engines for Flight

  • Rocket Engine: Carries fuel in one tank and an oxidant (a substance that reacts with the fuel) in another.
  • Aircraft Engines: Include turbojet, turbofan, turboprop, ramjet, and pulse-jet engine.