Sun and planet gear
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![Animation of Sun & Planet gear using Meccano. Notice that the sun and flywheel rotate twice for every circuit of the planet when they have a 1:1 ratio of teeth.](/Images/godic/202502/14/Meccano_Sun_&_planet_animation1800.gif")
![Animation](/Images/godic/202502/14/Sun_and_planet_gears1800.gif")
The sun and planet gear (also called the planet and sun gear) is a method of converting reciprocating motion to rotary motion and was used in the first rotative beam engines.
It was invented by the Scottish engineer William Murdoch, an employee of Boulton and Watt, but was patented by James Watt in October 1781. It was invented to bypass the patent on the crank, already held by James Pickard. It played an important part in the development of devices for rotation in the Industrial Revolution.