Friction drive

A friction drive or friction engine is a type of <a href="/facts/Transmission_(mechanics)/eoNqAufN">transmission</a> that utilises the <a href="/facts/Static_friction/d0108Rpu">static friction</a> of two smooth surfaces (instead of contact <a href="/facts/Pressure/eyc37GRG">pressure</a> of meshing teeth) to transfer <a href="/facts/Torque/KcrcvNtV">torque</a> between two rotating parts.
This type of mechanism is also called a traction drive, although this term often refers specifically to drives where a layer of traction fluid (that becomes momentarily solid under pressure) is used to increase the <a href="/facts/Friction/d0108Rpu">friction coefficient</a> between the two parts, to 0.1 or more.
In general, least one of the two parts is rigid, and it may be any <a href="/facts/Solid_of_revolution/lDNv2P7p">solid of revolution</a>, such as a disk, cylinder, or cone. While the bulk of the rigid part(s) may be constructed of any hard material, such as metal or plastic, at least one of the surfaces where they come into contact usually is coated with some high-friction material, such as <a href="/facts/Hard_rubber/d7lb6zJa">hard rubber</a> (or, in early systems, paper or <a href="/facts/Leather/kvQtwHPH">leather</a>).
The most common example of friction drive is a <a href="/facts/Pulley/Mrq15sdg">pulley</a> and (smooth) <a href="/facts/Belt_(mechanical)/k2zQ5tGv">belt</a> pair. However, the name "friction drive" is more often used when both parts are rigid.

Friction drive open-in-new

Friction drive