Editing Connecting rod (section)

=== Master-and-slave rods ===
{{multiple image
| align             = right
| direction         = vertical
| width             = 220
| image1            = Radial_engine_timing-small.gif
| caption1          = Operating principle of a radial engine
| image2            = Renault 190HP conrods fig5.jpg
| caption2          = Master–slave rods in the 1916–1918 [[Renault 8G]] V8 aircraft engine
}}
[[Radial engine]]s typically use master-and-slave connecting rods, whereby one piston (the uppermost piston in the animation), has a master rod with a direct attachment to the crankshaft. The remaining pistons pin their connecting rods' attachments to rings around the edge of the master rod.

Multi-bank engines with many cylinders, such as [[V12 engine]]s, have little space available for many connecting rod journals on a limited length of crankshaft. The simplest solution, as used in most road car engines, is for each pair of cylinders to share a [[crank journal]], but this reduces the size of the rod bearings and means that matching (i.e. opposite) cylinders in the different banks are slightly offset along the crankshaft axis (which creates a [[Couple (mechanics)|rocking couple]]). Another solution is to use master-and-slave connecting rods, where the master rod also includes one or more ring pins which are connected to the big ends of slave rods on other cylinders. A drawback of master–slave rods is that the stroke lengths of all slave pistons not located 180° from the master piston will always be slightly longer than that of the master piston, which increases vibration in V engines.

One of the most complicated examples of master-and-slave connecting rods is the 24-cylinder [[Junkers Jumo 222]] experimental airplane engine developed for World War II. This engine consisted of six banks of cylinders, each with four cylinders per bank. Each "layer" of six cylinders used one master connecting rod, with the other five cylinders using slave rods.<ref>{{Cite web |url=http://www.flugzeug-lorenz.de/index.php?eID=tx_cms_showpic&file=uploads%2Fpics%2FYY_169-1_Jumo222_Stirnschnitt.jpg&width=10000m&height=10000m&bodyTag=%3Cbody%20style%3D%22margin%3A0%3B%20background%3A%23fff%3B%22%3E&wrap=%3Ca%20href%3D%22javascript%3Aclose%28%29%3B%22%3E%20%7C%20%3C%2Fa%3E&md5=3a4da1957d3bd583a511bb5044efc2d8 |title=Image |access-date=2014-07-11 |archive-date=2014-04-13 |archive-url=https://web.archive.org/web/20140413224411/http://www.flugzeug-lorenz.de/index.php?eID=tx_cms_showpic&file=uploads%2Fpics%2FYY_169-1_Jumo222_Stirnschnitt.jpg&width=10000m&height=10000m&bodyTag=%3Cbody%20style%3D%22margin%3A0%3B%20background%3A%23fff%3B%22%3E&wrap=%3Ca%20href%3D%22javascript%3Aclose%28%29%3B%22%3E%20%7C%20%3C%2Fa%3E&md5=3a4da1957d3bd583a511bb5044efc2d8 |url-status=dead }}</ref> Approximately 300 test engines were built, but the engine did not reach production.
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