 Epicyclic gearing is used here to increase output speed. The planet gear carrier (green) is driven by an input torque. The sun gear (yellow) provides the output torque, while the ring gear (red) is fixed. Note the red marks both before and after the input drive is rotated 45° clockwise. Epicyclic gearing or planetary gearing is a gear system that consists of one or more outer gears, or planet gears, rotating about a central, or sun gear. Typically, the planet gears are mounted on a movable arm or carrier which itself may rotate relative to the sun gear. Epicyclic gearing systems may also incorporate the use of an outer ring gear or annulus, which meshes with the planet gears. Image File history File links Epicyclic_gear_ratios. ...
Image File history File links Epicyclic_gear_ratios. ...
Spur gears found on a piece of farm equipment A gear wheel is a wheel with teeth around its circumference, the purpose of the teeth being to mesh with similar teeth on another mechanical device -- possibly another gear wheel -- so that force can be transmitted between the two devices in...
Gear ratio
 The carrier (green) is held stationary while the sun gear (yellow) is used as input. The planet gears (blue) turn in a ratio determined by the number of teeth in each gear. Here, the ratio is -24/16, or -3/2; each planet gear turns at 3/2 the rate of the sun gear, in the opposite direction. The gear ratio in an epicyclic gearing system is somewhat non-intuitive, particularly because there are several ways in which an input rotation can be converted into an output rotation. The three basic components of the epicyclic gear are: Image File history File links Download high resolution version (677x615, 25 KB)Illustration of gear ratios in epicyclic gearing. ...
Image File history File links Download high resolution version (677x615, 25 KB)Illustration of gear ratios in epicyclic gearing. ...
Gears on a piece of farm equipment, gear ratio 1:1. ...
- Sun: The central gear
- Planet carrier: Holds one or more peripheral planet gears, of the same size, meshed with the sun gear
- Annulus: An outer ring with inward-facing teeth that mesh with the planet gear or gears
no In many epicyclic gearing systems, one of these three basic components is held stationary; one of the two remaining components is an input, providing power to the system, while the last component is an output, receiving power from the system. The ratio of input rotation to output rotation is dependent upon the number of teeth in each gear, and upon which component is held stationary.
One situation is when the planetary carrier is held stationary, and the sun gear is used as input. In this case, the planetary gears simply rotate about their own axes at a rate determined by the number of teeth in each gear. If the sun gear has S teeth, and each planet gear has P teeth, then the ratio is equal to -S/P. For instance, if the sun gear has 24 teeth, and each planet has 16 teeth, then the ratio is -24/16, or -3/2; this means that one clockwise turn of the sun gear produces 1.5 counterclockwise turns of the planet gears. A clockwise motion is one that proceeds like the clocks hands: from the top to the right, then down and then to the left, and back to the top. ...
This rotation of the planet gears can in turn drive the annulus, in a corresponding ratio. If the annulus has A teeth, then the annulus will rotate by P/A turns for each turn of the planet gears. For instance, if the annulus has 64 teeth, and the planets 16, one clockwise turn of a planet gear results in 16/64, or 1/4 clockwise turns of the annulus. Extending this case from the one above:
- One turn of the sun gear results in − S / P turns of the planets
- One turn of a planet gear results in P / A turns of the annulus
So, with the planetary carrier locked, one turn of the sun gear results in − S / A turns of the annulus.
The annulus may also be held fixed, with input provided to the planetary gear carrier; output rotation is then produced from the sun gear. This configuration will produce an increase in gear ratio, equal to 1+A/S.
These are all described by the equation:
(2 + n)ωa + nωs − 2(1 + n)ωc = 0
where n is the form factor of the planetary gear, defined by:  It has been suggested that this article or section be merged into Epicyclic gearing. ...
If the annulus is held stationary and the sun gear is used as the input, the planet carrier will be the output. The gear ratio in this case will be 1/(1+A/S). This is the lowest gear ratio attainable with an epicyclic gear train. This type of gearing is sometimes used in tractors and construction equipment to provide high torque to the drive wheels.
More planet and sun gear units can be placed in series in the same ring gear housing (where the output shaft of the first stage becomes the input shaft of the next stage) providing a larger (or smaller) gear ratio. This is the way some automatic transmissions work. An automatic transmission is an automobile gearbox that can change gear ratios automatically as the vehicle moves, thus freeing the driver from having to shift gears manually. ...
During World War II, a special variation of epicyclic gearing was developed for portable radar gear, where a very high reduction ratio in a small package was needed. This had two outer annular gears, each half the thickness of the other gears. One of these two annular gears was held fixed and had one fewer teeth than did the other. Therefore, several turns of the "sun" gear made the "planet" gears complete a single revolution, which in turn made the rotating annular gear rotate by a single tooth. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki TÅjÅ Casualties Military dead: 17,000,000 Civilian dead: 33,000...
This long range Radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to determine and map the location, direction, and/or speed...
 The mechanism of a pencil sharpener with stationary annulus and rotating planet carrier as input Image File history File linksMetadata Download high resolution version (1200x1600, 713 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Epicyclic gearing Metadata This file contains additional information, probably added from the digital camera or scanner...
Image File history File linksMetadata Download high resolution version (1200x1600, 713 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Epicyclic gearing Metadata This file contains additional information, probably added from the digital camera or scanner...
Image File history File linksMetadata Download high-resolution version (3812x1396, 407 KB) I TOOK THIS PIC. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
Image File history File linksMetadata Download high-resolution version (3812x1396, 407 KB) I TOOK THIS PIC. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
A simpler way to calculate the output RPM from the input RPM It is first drawn simplified as the sun, a single planet, the ring GEAR, and an arm holding the planet. Any gear can be the input or output, including the arm.
Now, simply plug in the known values and solve for wout:
where N is the number of teeth, w is rpm.
One caveat: if the arm is the input or output, say the ring is the output/input instead and reverse the direction (since if the arm moves a certain speed relative to the ring, the ring moves that same speed the other way relative to the arm, and obviously the arm does not have a tooth count to plug in)
To derive this, just imagine the arm is locked, and calculate the gear ratio wout : win = Nin : Nout, then unlock the arm. From the arms reference frame the ratio is always Nin/Nout, but from your frame all the speeds are increased by the angular velocity of the arm. So to write this relative relationship, you arrive at the equation from above.
Also, make sure Nsun+2Nplanet=Nring where N is the number of teeth. This simply says that the gears will fit, since N is directly proportional to diameter.
See also The Falkirk Wheel The Falkirk Wheel, named after the nearby town of Falkirk in central Scotland, is a rotating boat lift connecting the Forth and Clyde Canal with the Union Canal, which at this point differ by 24 metres, roughly equivalent to the height of an eight storey building. ...
Hub gears or internal-gear hubs are a type of gear system used on bicycles. ...
External links |
Feeds |
Contact