Editing Transmission (mechanical device) (section)

== Applications ==
=== Early uses ===
Early transmissions included the right-angle drives and other gearing in [[windmill]]s, [[horse]]-powered devices, and [[steam engine|steam]]-powered devices. Applications of these devices included [[pump]]s, [[mill (grinding)|mills]] and [[Hoist (device)|hoists]].{{cn|date=January 2023}}

===Bicycles===
{{main|Bicycle gearing}}
[[Bicycle]]s traditionally have used [[hub gear]] or [[Derailleur gear]] transmissions, but there are other more recent design innovations.

=== Automobiles ===
[[Image:Powerband.gif|thumb|right|Power and torque curves for two example car engines]]
Since the [[torque]] and [[Horsepower|power]] output of an [[internal combustion engine]] (ICE) varies with its [[Revolutions per minute|rpm]], [[car|automobiles]] powered by ICEs require multiple gear ratios to keep the engine within its [[power band]] to produce optimal power, [[fuel efficiency]], and smooth operation. Multiple gear ratios are also needed to provide sufficient acceleration and velocity for safe and reliable operation at modern highway speeds. ICEs typically operate over a range of approximately 600–7000 rpm, while the vehicle's speeds requires the wheels to [[rotational speed|rotate]] in the range of 0–1800 rpm.<ref>{{cite book |last1=Naunheimer |first1=Harald |last2=Bertsche |first2=Bernd |last3=Ryborz |first3=Joachim |last4=Novak |first4=Wolfgang |title=Automotive Transmissions: Fundamentals, Selection, Design and Application |date=2011 |publisher=Springer |isbn=978-3-642-16214-5 |pages=100–114 |url=https://link.springer.com/chapter/10.1007/978-3-642-16214-5_4 |access-date=21 January 2023 |language=en |chapter=Power Conversion: Selecting the Ratios|doi=10.1007/978-3-642-16214-5_4 }}</ref>

In the early mass-produced automobiles, the standard transmission design was [[manual transmission|manual]]: the combination of gears was selected by the driver through a lever (the [[gear stick]]) that displaced gears and gear groups along their axes.  Starting in 1939, cars using various types of [[automatic transmission]] became available in the US market.  These vehicles used the engine's own power to change the effective gear ratio depending on the load so as to keep the engine running close to its optimal rotation speed. Automatic transmissions now are used in more than two thirds of cars globally, and on almost all new cars in the US.

Most currently-produced passenger cars with gasoline or diesel engines use transmissions with 4–10 forward gear ratios (also called speeds) and one reverse gear ratio. [[Electric vehicle]]s typically use a fixed-gear or two-speed transmission with no reverse gear ratio.
{{clear right}}

[[Image:Helicopter Bristol 171 Sycamore main gear box and rotor head.jpg|thumb|Transmission for a [[Bristol Sycamore]] helicopter]]

=== Motorcycles ===
{{main|Motorcycle transmission}}