Sun and planet gear

The sun and planet gear converted the vertical motion of a beam, driven by a steam engine, into circular motion using a 'planet', a cogwheel fixed at the end of the pumping rod (connected to the beam) of the engine. With the motion of the beam, this revolved around, and turned, the 'sun', a larger rotating cog which turned the drive shaft, thus generating rotary motion. An interesting feature of this arrangement, when compared to that of a simple crank, is that when both sun and planet have the same number of teeth, the drive shaft completes two revolutions for each stroke of the beam instead of one. Note the planet-gear is fixed to the pumping rod and thus does not rotate around its own axis.The axis of the planet gear is connected to the axle of the sun gear, and therefore the flywheel, by a linkage that freely rotates around the axis of the sun gear and keeps the planet-gear engaged with the sun-gear.