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Sun and Planet Wheels, first devised by James Watt to avoid the use of a crank, which was patented. In his device the epicyclic train arm was replaced by the stationary groove, shown as green, which kept the two wheels in gear. The yellow circle represents the engine shaft, to which the red gear was fastened, purple connecting rod attached to walking beam (here it is attached to the piston). The blue gear was rigidly attached to the end of the connecting rod. While with such an arrangement it is not strictly true that the blue gear does not turn. Since connecting rod rigidly attached to blue gear, the blue gear oscillates while it is hard to see this oscillation. At the same time, the red gear does not rotate smoothly. It's rotation also oscillates around a smooth rotation.

The yellow engine shaft and red gear will make two turns every time the blue gear passes around it.

04 Sep 2013

Nice one , Thanks a lot

12 Dec 2013

Thanks, I am working in EMAL, Dubai. I have seene this type of combination of gear box in some machine.
More knowldge .......abt this..

12 Dec 2013

The sun and planet gear (also called the planet and sun gear) was 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.

12 Dec 2013

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 connecting rod (connected to the beam) of the engine. With the motion of the beam, this revolved around, and turned, the 'sun', a second rotating cog fixed to 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 double stroke of the beam instead of one. The planet gear is fixed to the connecting rod and thus does not rotate around its own axis.

Note that the axle of the planet gear is tied to the axle of the sun gear by a link that freely rotates around the axis of the sun gear and keeps the planet gear engaged with the sun gear but does not contribute to the drive torque. This link appears, at first sight, to be similar to a crank but the drive is not transmitted through it. Thus, it did not contravene the crank patent.

Arun kumar
09 Jan 2014

Today i have a seminar, so i'll search this topic vry intrstn to known abt sunplanet gear... Thank u guys..

Batuhan Özdemir
20 Apr 2014

Hi, we have a term project about sun and planet wheels and our professor want us to analyze all of things. If you have , can you post me those? my e-mail:
Thank you!!

17 Feb 2015

This stinks!

Manoj kumar
11 Apr 2016

Thank this is very helpful for me for doing seminar

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