Semi-automatic transmission

A semi-automatic transmission is a multiple-speed <a href="/facts/Transmission_(mechanics)/eoNqAufN">transmission</a> where part of its operation is <a href="/facts/Automation/3YlF2K5q">automated</a> (typically the actuation of the <a href="/facts/Clutch/yQLCtuGA">clutch</a>), but the driver's input is still required to launch the vehicle from a standstill and to manually change gears. Semi-automatic transmissions were almost exclusively used in motorcycles and are based on conventional <a href="/facts/Manual_transmission/jEehs2AT">manual transmissions</a> or <a href="/facts/Sequential_manual_transmission/ENyfohEM">sequential manual transmissions</a>, but use an automatic clutch system. But some semi-automatic transmissions have also been based on standard hydraulic <a href="/facts/Automatic_transmissions/bKBFLbyh">automatic transmissions</a> with <a href="/facts/Torque_converter/EWq1vwVv">torque converters</a> and <a href="/facts/Epicyclic_gearing/FMz8Fjg8">planetary gearsets</a>.
Names for specific types of semi-automatic transmissions include clutchless manual, auto-manual, auto-clutch manual, and paddle-shift transmissions. Colloquially, these types of transmissions are often called "flappy-paddle gearbox", a phrase coined by <a href="/facts/Top_Gear_(2002_TV_series)/5dntwH3q">Top Gear</a> host <a href="/facts/Jeremy_Clarkson/lp6HRzb7">Jeremy Clarkson</a>. These systems facilitate gear shifts for the driver by operating the clutch system automatically, usually via <a href="/facts/Switch/vqbNDgYm">switches</a> that trigger an <a href="/facts/Actuator/mF9qVJJR">actuator</a> or <a href="/facts/Servomechanism/lS3l6sY2">servo</a>, while still requiring the driver to manually shift gears. This contrasts with a <a href="/facts/Preselector_gearbox/Dno6c51Q">preselector gearbox</a>, in which the driver selects the next gear ratio and operates the pedal, but the gear change within the transmission is performed automatically.
The first usage of semi-automatic transmissions was in automobiles, increasing in popularity in the mid-1930s when they were offered by several American car manufacturers. Less common than traditional hydraulic automatic transmissions, semi-automatic transmissions have nonetheless been made available on various car and motorcycle models and have remained in production throughout the 21st century. Semi-automatic transmissions with paddle shift operation have been used in various <a href="/facts/Auto_racing/0ErdCCV3">racing cars</a>, and were first introduced to control the electro-hydraulic gear shift mechanism of the <a href="/facts/Ferrari_640/7y7o2mHm">Ferrari 640</a> <a href="/facts/Formula_One_car/RqutQ4Do">Formula One car</a> in 1989. These systems are currently used on a variety of top-tier racing car classes; including <a href="/facts/Formula_One/BwdePyWY">Formula One</a>, <a href="/facts/IndyCar/RHY5RVHs">IndyCar</a>, and <a href="/facts/Touring_car_racing/KaXlh2MX">touring car racing</a>. Other applications include motorcycles, trucks, buses, and <a href="/facts/Rail_transport/9nJQbsDV">railway vehicles</a>.

Semi-automatic transmission open-in-new

Semi-automatic transmission