Mechanical Power Transmission Elements

Brakes

Disc Brakes

A disc is connected to an axle. Brake pads apply pressure to the disc via friction.

Band Brakes

A drum is connected to an axle. A flexible band applies pressure to the outside of the drum.

Drum Brakes

A drum is connected to the axle. A pair of brake shoes apply pressure to the inside of the drum via friction.

Energy Absorption and Dissipation

Springs

Springs are devices that, thanks to the elasticity of their materials and their shape, can absorb energy when force is applied. This energy can then be dissipated in a controlled way. Depending on the type of external force applied, springs work in different ways:

• Compression: Pushing on the spring makes it shorter (e.g., a sofa).
• Traction: Pulling on the spring makes it longer (e.g., a metal frame).
• Torsion: Bending the spring makes it curve (e.g., a clothes peg).

Suspension Systems

Shock absorbers are usually made with spiral steel springs. Leaf springs are made with high-elasticity pieces of steel of different lengths placed on top of each other and joined in the middle. Both systems absorb and dissipate motion on uneven road surfaces, making driving more comfortable.

Couplings and Clutches

Coupling mechanisms transmit rotation from one axis to another. Different types exist depending on the axes' positions, which may be separated by a distance, at an angle, or misaligned.

• Rigid couplings: Used to permanently engage axes.
• Clutches: Engaging a clutch transfers power from the engine to the transmission; disengaging it stops the transfer.

Friction Clutch

The ends of two shafts come into contact. When one shaft turns, friction turns the second shaft.

Jaw Clutch

Two shafts are connected by interlocking teeth. A jaw clutch is very reliable and doesn't slip easily.

Flexible Couplings

Used when the axes are not aligned.

Oldham Coupling

Connects parallel shafts that are not continuously aligned.

Cardan Joint

Connects two shafts at an angle to each other.

Bearings

Bearings support and hold rotating shafts in place, reducing friction and allowing smoother rotation.

• Plain bearings: Allow the shaft to slide through them.
• Antifriction bearings: Have rolling parts (e.g., metal balls or rollers) to reduce surface contact.

Free Wheel

Consists of two sawtoothed, spring-loaded discs that press against each other. When pedaling forwards, motion is transmitted by the chain to the back wheel; when pedaling backwards, the wheel turns freely.