MOTION TRANSMISSIONMOTION TRANSFORMATIONComplex Mechanical Functions

Vocabulary• System: A set of components in a technical object that share the same function. Ex – in a bike, the pedal, chain and sprocket and wheels all share the function to move the bike forward.• Complex Mechanical Function: The role played by a set of components in transferring motion inside a technical object.• Motion Transmission System: A system that relays motion from one part to another without changing the direction of the motion.• Driver: The root of the systems power. This is the component that receives force from the user.• Driven: The component(s) of a system that receive the motion created by the driver.

…• Speed Change: Occurs in a motion transmission system when the driver does not turn at the same speed as the driven.• Motion Transformation System: A system that relays motion from one part to another while modifying the nature of the motion.

Motion Transmission System• A system that relays motion from one part to another without changing the direction of the motion.• The types of motion are:• Translation or Linear• Rotation or circular• Helical or Spiral

• Motion is transmitted from one component to another in a system in one of five ways.• Chain and sprocket• Belt and pulley• Gears• Friction wheels• Worm and Worm Gear

Gears• A system of at least two toothed wheels that fit inside one another. • They turn in the opposite direction from one another.• Type of motion: Rotation

Friction Wheels• Friction wheels resemble a gear system, except without teeth.• Because these wheels are touching one another, one wheel moves the other through friction, turning in opposite directions of one another.• Type of motion: rotation

Chain and sprocket• The chain and sprocket transmits motion between two components that are relatively far from one another. They are connected by a chain.• Ex – bicycle. When you bicycle, you apply force on the pedals. The chain and sprocket transmit this force to the wheels of the bike.• The chain and sprocket turn in the same direction as one another.• Type of motion: Rotation

Belt and pulley• A belt works in the same way as a chain, except instead of being wrapped around a toothed wheel, the belt is wrapped around a pulley and connected by a belt.• When a pulley is turned, the belt follows the same direction, turning another pulley in the same direction.• Type of motion: rotation.

A Worm and Worm Gear• Transmits a rotational motion to non-parallel parts. These are both toothed components that fit inside one another.• The teeth of the worm gear fit inside the teeth of the worm.• Type of motion: rotation.

Summary – Motion Transmission

Motion Transmission System

Component Wheels

Touching or Connected

Type of Motion

Same Direction or Opposite Directions

Gears Toothed Touching Rotation Opposite

Friction Wheels

Smooth Touching Rotation Opposite

Worm and Worm Gear

Toothed Touching Rotation Opposite

Chain and Sprocket

Toothed Connected by a chain

Rotation Same

Belt and Pulley

Smooth Connected by a belt

Rotation Same

Speed Change• Motion transmission relays motion from the driver component of a system to the driven component(s). • The speed of the motion, however, can vary. This is called speed change.

Speed Change in Friction Gears and Pulley and Belt Systems• Friction Gears and Pulley and Belt Systems:• Rotational speed depends on the diameter of the wheels or pulleys.• Rotational speed increases when motion transmits to a

wheel or pulley of a SMALLER size.• Speed decreases when motion transmits to a wheel or

pulley of a GREATER size.• Speed is UNCHANGED when the wheels or pulleys are the

same size.

AB

CBC

A

Speed Change in a Gear Train and Chain and Sprocket System• Friction Gears and Pulley and Belt Systems• In a gear train and in chain and sprocket systems, the wheels all contain teeth. The teeth prevent slipping, so long as they are of the same size.• Speed change in these systems depends on the number of teeth. So, those which are larger in diameter will have more teeth.• Speed increases when motion is transmitted from one

component to another with FEWER teeth, (or is smaller).• Speed decreases when motion is transmitted from one

component to another with MORE teeth, (or is larger).• Speed is UNCHANGED if they have the same number of

teeth.

Summary – Speed Change• Speed increases when:• The driven component is smaller than the driver

component.• The driven component contains less teeth.

• Speed decreases when:• The driven component is larger than the driver component.• The driven component contains more teeth.

• Speed is unchanged when:• The driven component and driver component are the same

size.• The driven component and the driver component contain

the same number of teeth,

MOTION TRANSFORMATION

Vocabulary• Transformation of motion: When the motion is transmitted through an object and is modified or changed.• The driver and the driven do not make the same motion.

• The four mechanisms for transforming motion are:• Rod and crank• Cam and follower• Rack and pinion• Screw and nut

Rod and Crank• The rod and crank transform a circular motion into a bidirectional linear motion.• Ex – Train, engines• https://www.youtube.com/watch?v=T831-i3ShX8• http://www.technologystudent.com/cams/crkslid1.htm

The Cam and Follower• Circular bidirectional linear.• A cam is an egg-shaped disk that turns. The follower is a bar that moves up and down as the cam turns.

Rack and Pinion• Changes a circular motion into a linear motion.• It is composed of a toothed wheel, (pinion), that turns and moves along a toothed bar, (rack).• This is often seen in steering mechanisms.

Screw and Nut• Transforms a circular motion into a linear motion.• Once the nut turns, the nut moves along the length of the screw in one direction or another.

Summary – Motion Transformation

Motion Transformation System

Components Touching or Connected

Type of Motion

Slider and Crank

Smooth Connected by a rod

Rotation – Linear

Cam and Follower

Smooth Touching Rotation – Linear

Rack and Pinion

Toothed Touching Rotation – Linear

Screw and Nut Toothed Touching Rotation - Linear