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The mathematical exegesis of this article is extremely poor. After introducing the concepts of Sun (s), Planet (p) and Annulus (a), the reader is then presented with two equations involving a 4th factor c (which I assume in the gear ratio, but this is never explained) and two quantities, N and w (omega). From the following text, it emerges that N refer s to the number of teeth, but it's not at all clear what w refers to. This is unfortunately typical of math articles on Wikipedia, in which the equations are pasted into an article may indeed be correct and canonical, but are not explained for the casual reader and often do not seem to be fully understood by the article editors. 98.248.125.108 ( talk) 22:48, 17 July 2013 (UTC)
Why does a planetary geartrain have multiple planets? Is this about power transfer or stability or something?
Isn't the sun gear in the picture gray? -- snoyes 22:36, 19 Nov 2003 (UTC)
Isn't the maximum gear ration always less than one? If so, it would be nice to note it in the descriptions.
Gear ratios given in this article conflict.
In the section under discussion, it is written that N(s)*omega(s)+N(r)*omega(r)=(N(s)+N(r))*omega(c). This is consistent with equations found at http://www.roymech.co.uk/Useful_Tables/Drive/Epi_cyclic_gears.html and www.md.kth.se/~fredrikr/AM2D/gearReport.pdf. The latter references "Vedmar Lars, Maskinelement, Lunds Tekniska Högskola, 2002" for the equation.
On the other hand, the equation given in the gear ratio section, with some simplification (notably substituting N(r) for 2N(p)+N(s)), may be written as Omega(r)*N(r)+Omega(s)*N(s)=(N(p)+N(c))*2*omega(c).
The equations need to be made consistent; based on references, I believe that the one in this section is more accurate, but I would prefer some kind of consensus before changing the other.
The derivation for the equation given in the section under discussion states that omega(r)/omega(s)=N(s)/N(r), when it ought to be -N(s)/N(r). With that negative sign, I can derive the equation as given with the method described. I would like to write that derivation more clearly in the article, but seem to be unable to edit a flagged section. Tomvreomfodj ( talk) 18:56, 13 December 2010 (UTC)
It seems that many combinations of power flow are available from the gearset. If power input is to the outer ring gear, wouldn't the "planetary" carrier rotate in the ring gear direction and the central "sun" gear in the opposite direction? Useful for driving grinding wheels in opposite directions?
Further, what about its use as a "differential"? The whole article is written on the assumption that it is a way of achieving a few fixed ratios by holding one part stationary. In the Hybrid Synergy Drive, which is referenced, it's used as a 3-way power-split device, and all parts are usually in motion. -- KJBracey 08:37, 18 November 2005 (UTC)
Who makes a two speed planetary gearbox? —Preceding unsigned comment added by 67.201.136.122 ( talk) 20:31, 5 October 2008 (UTC)
OK, it's about time we got some examples of how the gear ratios work in this thing. Preferably a version that is easy to understand for the non-mathematician (namely, me). I found this site that attempts an explanation, but it leaves me somewhat baffled. Ideally, a thorough exposition of how the ratios are calculated would be nice, but a simple formula would suffice for now. Three cases:
In each case, what is the ratio between the remaining gearsets, in simple terms of how many teeth each gear has? For the second case, it's fairly easy, since the sun and annulus simply turn in opposite directions, in the ratio sun/annulus = -teethannulus/teethsun (this is our reverse gear, as mentioned above). For the others, there's some angular velocity of the carrier involved, which taxes my brain. Assistance would be welcome. -- Wapcaplet 00:41, 23 Jul 2004 (UTC)
Nevermind. I found a much better explanation, which I will try to work into the article.
Hello, I just added a stub article on the above & got a message that it seems to be the same as Epicyclic gearing, looking at the page it seems to be the case that it is either the same thing or epicyclic gearing is a more advanced form of the original sun and planet gear. I am not an engineer & have some problems understanding technical articles (only created the s&pg as I'm working on the article of the engineer who invented it - William Murdoch) so I'm not too sure about the differences & the terminology. Does anyone know if the terminology 'sun and planet gear' is outdated or whether epicyclic gearing is the common modern (or American) phrasing for this? If so it might be better if I add a link from s&pg to epicyclic gearing as the s&pg article (while a stub) deals with the original invention. Otherwise it might be better to merge the articles & put in a re-direct. Can you please let me know what you think. AllanHainey 12:35, 6 September 2005 (UTC)
Someone posted this question above: "Why does a planetary geartrain have multiple planets? Is this about power transfer or stability or something?"
The reason for having multiple planets is that you can connect more than one shaft to the planetary gear. That's part of the ingenuity of planetary gears: you can input power from multiple shafts and output power in one, or more, shafts, as necessary.
Take, for instance, the planetary gear connected to two pistons on the right. Here a drive shaft inputs power into the sun gear, which in turn rotates the two planets, timed so the pistons move up and down one right after the other. (Note that the pistons are not actually pictured, but are connected to the "moving crankshafts.")
Of coarse stability is the first and main reason.
Animated gifs, showing each locking configuration would be very helpful - its very difficult to visualise this kind of thing.
THE ARTICLE NEEDS AN ANIMATION!!!
This one is not smooth enough. You don't need to animate very much time, but you do you need to see the individual gear teeth move. Helvitica Bold 21:36, 11 May 2011 (UTC)
What is method t calculate the maximum planet gears can involved in a Epicyclic gear system?
To me, this article feels incomplete. I would expect to see a discussion of the advantages/disadvantages of planetary gears versus other gearing arrangements (i.e. when would you want to use planetary gears? when would you not?) For example, advantages include high power density, large reduction in a small volume, multiple kinematic combinations, pure torsional reactions, coaxial shafting. Disadvantages include high bearing loads, inaccessibility, design complexity. I have studied planetary gears in graduate school and could add such a section if others think it would add value... This would be my first attempt at contributing to wikipedia so I wanted to test the waters before jumping in... Kiracofe8 02:51, 6 February 2007 (UTC)
I'd say this article is lacking the history of the epicyclic gear and the application of the gear. GraemeLeggett ( talk) 12:15, 26 August 2009 (UTC)
(First, I am harmless).
In the page on epicyclic gears, one section calls the annulus the ring gear. Either is correct but at least stick to one.
Malcolmcochran@hotmail.com —Preceding unsigned comment added by 86.137.178.200 ( talk) 11:58, 9 September 2009 (UTC)
Although not essential, the image seems a bit weird, ie the carrier design is not really standard, see the image at http://www.mvwautotechniek.nl/Motor/Transmissie/automatisch.htm M. van Wijk 14:01, 22 March 2016
I think that Regular Planetary Gearsets use basic pinions for switching gears, and not oil, see http://mysite.du.edu/~jcalvert/tech/planet.htm
Is this correct ? I also wonder whether other setups than the double reduction, single overdrive can be used for regular planetary gearsets (that way, ie 3 overdrives or 3 reductions can be put in place which would be more useful for specific tasks such as for wind turbines) 91.182.226.145 ( talk) 14:27, 13 December 2010 (UTC)
91.182.79.197 ( talk) 13:40, 14 December 2010 (UTC)
This article should be called planetary gearing because planetary gear-trains are just a specific instance of epicyclic gear-trains and there are many other configurations of epicyclic gear trains, for example a differential gear-train. — Preceding unsigned comment added by Cdhickam ( talk • contribs) 23:46, 29 March 2011 (UTC)
Is it possible to have the section on formulas protected, som that edits like this/vandalism will be prevented? Keanu ( talk) 08:43, 6 May 2011 (UTC)
The first two (seminal; general) gear ratio equations in the section https://en.wikipedia.org/?title=Epicyclic_gearing&action=edit§ion=3 do not appear to originate from the cited work [6]: L. Meirovitch: Elements of Vibration Analysis, McGraw-Hill, New York, 1986.(?) I would appreciate any assistance locating their origin(s) so it(they) may be correctly (and/or more specifically) cited - important not only for correctness here, but for readers wishing to trace the more complex / powerful methodologies / models by which they were obtained. 100kWhr ( talk) 15:57, 9 October 2017 (UTC)
I've deleted the formulas section, because a lot of these formulas are incorrect (at least 7b and 8b are, and probably more). This should be checked upon! I don't have time to do this right now but I think no formulas is better than wrong formulas so I deleted them all. Here they are for future notice: (I will see if I can get back on this, but I'm leaving on a vacation in a few hours)
Name | Number of teeth | Speed |
---|---|---|
Sketch | Output speed | Sketch | Output speed | Sketch | Output speed | Sketch | Output speed |
---|---|---|---|---|---|---|---|
7b and 8b probably refer to the image the formula belongs to. move your mouse over it and you see the name an the bottom of your screen. Deleting wrong information would be better than showing it is my opinion. Better not no post anything which is not veryfied at all. I found mistakes in other formulas too. Formula for Gear 13 contains a blue Z. However the arm is blue and has no teeth at all. Formula 12a and 12b are wrong, If all gears have the same number of teeth it would still rotate, but the formula results in devide by 0 Formula 9 If the planets are equal and the rings are equal both rings will rotate at the same speed. Since one is locked, the other will not rotate. the formula does however not result in 0. — Preceding unsigned comment added by 62.194.118.254 ( talk) 13:16, 5 February 2012 (UTC)
I've fixed formula 8a, 8b, 9, 10a, 10b, 13 although the graphics for 10a and 10b need to be properly tweaked (the blue gears should be removed). 7b, as the original deleter posited, is not wrong. If there are other wrong formulas, I haven't found them, and as far as I can tell, the whole section is now correct. 10a and 13, and 9 and 10b are the same gear formations, and are redundant, although both are correct. 97.124.82.32 ( talk) 17:57, 24 September 2012 (UTC)
Name | Number of teeth | Speed |
---|---|---|
Sketch | Output speed | Sketch | Output speed | Sketch | Output speed | Sketch | Output speed |
---|---|---|---|---|---|---|---|
Here's my updated table, I haven't arranged it, but I have deleted 4 redundant formulas and graphics. ADAzriel ( talk) 02:04, 8 October 2012 (UTC)
References
It would be nice if it gave an intuitive explanation for the basic operation of increased rotation. With the sun gear held stationary, and carrier rotated, the annulus will spin faster. My intuitive explanation is that at any moment each planetary gear is like a tiny lever, with the fulcrum resting on a sun gear tooth, the effort at the center of the planetary gear, and the load at an annulus tooth. Clearly, this configuration increases motion of the load.
Also, the gear ratio section has an example with the carrier held stationary. It shows the ratio of the sun gear to a planetary gear, but this seems irrelevant; just the number of teeth on the sun and annulus matter. The planetary gears essentially "move" the sun gear closer to the annulus so it's as if its teeth were touching the annulus directly (except moving in the opposite direction). For every tooth of the sun gear that moves past a line from the center outward, one tooth of the planetary gear moves past the same point where this line intersects the annulus. I see that it eventually shows this with math. I'd like more "intuitive" explanations like this. 72.48.75.131 ( talk) 19:55, 19 December 2011 (UTC)
The comments above on formulas 9, 12a, 12b is at best incomplete. Under the conditions stated the equations degenerate and kinematic relations are no more determined, i.e. one component becomes loose. The formula in 13, however is indeed misprinted, the blue z is to be red. Snoloven ( talk) 20:32, 28 March 2012 (UTC)
Hold on, the wikipedia article on the Antikythera mechanism says that the device was definitively found not to contain any planetary gear mechanisms, and this was realized over a decade ago. Why does this page contradict the other wikipedia page? I think we ought to take down the reference to the Antikythera mechanism on this page. — Preceding unsigned comment added by 50.131.61.86 ( talk) 11:46, 19 September 2013 (UTC)
At the end of par. Gear Ratio, I've added an argument that I think is simple, intuitive and precise, establishing the general formula that relates the angular velocities of sun, carrier and annulus (plus two standard applications). This might cause other explanations superfluous, but I made no further changes. KeesDoe ( talk) 21:57, 27 March 2015 (UTC)
I've made some animated gifs and some schematics that might help in this article.
There is a full list on my profile page => DaveRcWiki ( talk) 21:38, 5 February 2024 (UTC)
For some of us who have been studying planetary gear trains for over 5/8 of a century, this article has several problems. The first is that in the United States, the correct title should be Planetary Gear (Train). The USPTO classification is: Class 475 PLANETARY GEAR TRANSMISSION SYSTEMS OR COMPONENTS. "Epicyclic" seems to be the term that is preferred in England. However, unless there is a circular fixed sun gear, with circular planets in the same plane, (none of which are required), there are no points that trace out an epicycle.
The rest of the definition is not general. It only describes one of the most simple types. The main definition should say that "a planetary gear train has some gears whose axes are not fixed, but move in relation to the movements of the gears in the train".
The very first line says "is a gear reduction assembly". A planetary gear train can be used for increase as well as reduction. One of the most widely used planetary gears in the world, with millions of units in daily use, is the bicycle 3-speed hub. It can decrease the speed to 75%, or increase it to 133 1/3 %, or leave it unchanged, the three being selected by various ratchet pawls. agb 173.233.167.50 ( talk) 18:38, 29 April 2024 (UTC)
This
level-5 vital article is rated B-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||||||
|
The mathematical exegesis of this article is extremely poor. After introducing the concepts of Sun (s), Planet (p) and Annulus (a), the reader is then presented with two equations involving a 4th factor c (which I assume in the gear ratio, but this is never explained) and two quantities, N and w (omega). From the following text, it emerges that N refer s to the number of teeth, but it's not at all clear what w refers to. This is unfortunately typical of math articles on Wikipedia, in which the equations are pasted into an article may indeed be correct and canonical, but are not explained for the casual reader and often do not seem to be fully understood by the article editors. 98.248.125.108 ( talk) 22:48, 17 July 2013 (UTC)
Why does a planetary geartrain have multiple planets? Is this about power transfer or stability or something?
Isn't the sun gear in the picture gray? -- snoyes 22:36, 19 Nov 2003 (UTC)
Isn't the maximum gear ration always less than one? If so, it would be nice to note it in the descriptions.
Gear ratios given in this article conflict.
In the section under discussion, it is written that N(s)*omega(s)+N(r)*omega(r)=(N(s)+N(r))*omega(c). This is consistent with equations found at http://www.roymech.co.uk/Useful_Tables/Drive/Epi_cyclic_gears.html and www.md.kth.se/~fredrikr/AM2D/gearReport.pdf. The latter references "Vedmar Lars, Maskinelement, Lunds Tekniska Högskola, 2002" for the equation.
On the other hand, the equation given in the gear ratio section, with some simplification (notably substituting N(r) for 2N(p)+N(s)), may be written as Omega(r)*N(r)+Omega(s)*N(s)=(N(p)+N(c))*2*omega(c).
The equations need to be made consistent; based on references, I believe that the one in this section is more accurate, but I would prefer some kind of consensus before changing the other.
The derivation for the equation given in the section under discussion states that omega(r)/omega(s)=N(s)/N(r), when it ought to be -N(s)/N(r). With that negative sign, I can derive the equation as given with the method described. I would like to write that derivation more clearly in the article, but seem to be unable to edit a flagged section. Tomvreomfodj ( talk) 18:56, 13 December 2010 (UTC)
It seems that many combinations of power flow are available from the gearset. If power input is to the outer ring gear, wouldn't the "planetary" carrier rotate in the ring gear direction and the central "sun" gear in the opposite direction? Useful for driving grinding wheels in opposite directions?
Further, what about its use as a "differential"? The whole article is written on the assumption that it is a way of achieving a few fixed ratios by holding one part stationary. In the Hybrid Synergy Drive, which is referenced, it's used as a 3-way power-split device, and all parts are usually in motion. -- KJBracey 08:37, 18 November 2005 (UTC)
Who makes a two speed planetary gearbox? —Preceding unsigned comment added by 67.201.136.122 ( talk) 20:31, 5 October 2008 (UTC)
OK, it's about time we got some examples of how the gear ratios work in this thing. Preferably a version that is easy to understand for the non-mathematician (namely, me). I found this site that attempts an explanation, but it leaves me somewhat baffled. Ideally, a thorough exposition of how the ratios are calculated would be nice, but a simple formula would suffice for now. Three cases:
In each case, what is the ratio between the remaining gearsets, in simple terms of how many teeth each gear has? For the second case, it's fairly easy, since the sun and annulus simply turn in opposite directions, in the ratio sun/annulus = -teethannulus/teethsun (this is our reverse gear, as mentioned above). For the others, there's some angular velocity of the carrier involved, which taxes my brain. Assistance would be welcome. -- Wapcaplet 00:41, 23 Jul 2004 (UTC)
Nevermind. I found a much better explanation, which I will try to work into the article.
Hello, I just added a stub article on the above & got a message that it seems to be the same as Epicyclic gearing, looking at the page it seems to be the case that it is either the same thing or epicyclic gearing is a more advanced form of the original sun and planet gear. I am not an engineer & have some problems understanding technical articles (only created the s&pg as I'm working on the article of the engineer who invented it - William Murdoch) so I'm not too sure about the differences & the terminology. Does anyone know if the terminology 'sun and planet gear' is outdated or whether epicyclic gearing is the common modern (or American) phrasing for this? If so it might be better if I add a link from s&pg to epicyclic gearing as the s&pg article (while a stub) deals with the original invention. Otherwise it might be better to merge the articles & put in a re-direct. Can you please let me know what you think. AllanHainey 12:35, 6 September 2005 (UTC)
Someone posted this question above: "Why does a planetary geartrain have multiple planets? Is this about power transfer or stability or something?"
The reason for having multiple planets is that you can connect more than one shaft to the planetary gear. That's part of the ingenuity of planetary gears: you can input power from multiple shafts and output power in one, or more, shafts, as necessary.
Take, for instance, the planetary gear connected to two pistons on the right. Here a drive shaft inputs power into the sun gear, which in turn rotates the two planets, timed so the pistons move up and down one right after the other. (Note that the pistons are not actually pictured, but are connected to the "moving crankshafts.")
Of coarse stability is the first and main reason.
Animated gifs, showing each locking configuration would be very helpful - its very difficult to visualise this kind of thing.
THE ARTICLE NEEDS AN ANIMATION!!!
This one is not smooth enough. You don't need to animate very much time, but you do you need to see the individual gear teeth move. Helvitica Bold 21:36, 11 May 2011 (UTC)
What is method t calculate the maximum planet gears can involved in a Epicyclic gear system?
To me, this article feels incomplete. I would expect to see a discussion of the advantages/disadvantages of planetary gears versus other gearing arrangements (i.e. when would you want to use planetary gears? when would you not?) For example, advantages include high power density, large reduction in a small volume, multiple kinematic combinations, pure torsional reactions, coaxial shafting. Disadvantages include high bearing loads, inaccessibility, design complexity. I have studied planetary gears in graduate school and could add such a section if others think it would add value... This would be my first attempt at contributing to wikipedia so I wanted to test the waters before jumping in... Kiracofe8 02:51, 6 February 2007 (UTC)
I'd say this article is lacking the history of the epicyclic gear and the application of the gear. GraemeLeggett ( talk) 12:15, 26 August 2009 (UTC)
(First, I am harmless).
In the page on epicyclic gears, one section calls the annulus the ring gear. Either is correct but at least stick to one.
Malcolmcochran@hotmail.com —Preceding unsigned comment added by 86.137.178.200 ( talk) 11:58, 9 September 2009 (UTC)
Although not essential, the image seems a bit weird, ie the carrier design is not really standard, see the image at http://www.mvwautotechniek.nl/Motor/Transmissie/automatisch.htm M. van Wijk 14:01, 22 March 2016
I think that Regular Planetary Gearsets use basic pinions for switching gears, and not oil, see http://mysite.du.edu/~jcalvert/tech/planet.htm
Is this correct ? I also wonder whether other setups than the double reduction, single overdrive can be used for regular planetary gearsets (that way, ie 3 overdrives or 3 reductions can be put in place which would be more useful for specific tasks such as for wind turbines) 91.182.226.145 ( talk) 14:27, 13 December 2010 (UTC)
91.182.79.197 ( talk) 13:40, 14 December 2010 (UTC)
This article should be called planetary gearing because planetary gear-trains are just a specific instance of epicyclic gear-trains and there are many other configurations of epicyclic gear trains, for example a differential gear-train. — Preceding unsigned comment added by Cdhickam ( talk • contribs) 23:46, 29 March 2011 (UTC)
Is it possible to have the section on formulas protected, som that edits like this/vandalism will be prevented? Keanu ( talk) 08:43, 6 May 2011 (UTC)
The first two (seminal; general) gear ratio equations in the section https://en.wikipedia.org/?title=Epicyclic_gearing&action=edit§ion=3 do not appear to originate from the cited work [6]: L. Meirovitch: Elements of Vibration Analysis, McGraw-Hill, New York, 1986.(?) I would appreciate any assistance locating their origin(s) so it(they) may be correctly (and/or more specifically) cited - important not only for correctness here, but for readers wishing to trace the more complex / powerful methodologies / models by which they were obtained. 100kWhr ( talk) 15:57, 9 October 2017 (UTC)
I've deleted the formulas section, because a lot of these formulas are incorrect (at least 7b and 8b are, and probably more). This should be checked upon! I don't have time to do this right now but I think no formulas is better than wrong formulas so I deleted them all. Here they are for future notice: (I will see if I can get back on this, but I'm leaving on a vacation in a few hours)
Name | Number of teeth | Speed |
---|---|---|
Sketch | Output speed | Sketch | Output speed | Sketch | Output speed | Sketch | Output speed |
---|---|---|---|---|---|---|---|
7b and 8b probably refer to the image the formula belongs to. move your mouse over it and you see the name an the bottom of your screen. Deleting wrong information would be better than showing it is my opinion. Better not no post anything which is not veryfied at all. I found mistakes in other formulas too. Formula for Gear 13 contains a blue Z. However the arm is blue and has no teeth at all. Formula 12a and 12b are wrong, If all gears have the same number of teeth it would still rotate, but the formula results in devide by 0 Formula 9 If the planets are equal and the rings are equal both rings will rotate at the same speed. Since one is locked, the other will not rotate. the formula does however not result in 0. — Preceding unsigned comment added by 62.194.118.254 ( talk) 13:16, 5 February 2012 (UTC)
I've fixed formula 8a, 8b, 9, 10a, 10b, 13 although the graphics for 10a and 10b need to be properly tweaked (the blue gears should be removed). 7b, as the original deleter posited, is not wrong. If there are other wrong formulas, I haven't found them, and as far as I can tell, the whole section is now correct. 10a and 13, and 9 and 10b are the same gear formations, and are redundant, although both are correct. 97.124.82.32 ( talk) 17:57, 24 September 2012 (UTC)
Name | Number of teeth | Speed |
---|---|---|
Sketch | Output speed | Sketch | Output speed | Sketch | Output speed | Sketch | Output speed |
---|---|---|---|---|---|---|---|
Here's my updated table, I haven't arranged it, but I have deleted 4 redundant formulas and graphics. ADAzriel ( talk) 02:04, 8 October 2012 (UTC)
References
It would be nice if it gave an intuitive explanation for the basic operation of increased rotation. With the sun gear held stationary, and carrier rotated, the annulus will spin faster. My intuitive explanation is that at any moment each planetary gear is like a tiny lever, with the fulcrum resting on a sun gear tooth, the effort at the center of the planetary gear, and the load at an annulus tooth. Clearly, this configuration increases motion of the load.
Also, the gear ratio section has an example with the carrier held stationary. It shows the ratio of the sun gear to a planetary gear, but this seems irrelevant; just the number of teeth on the sun and annulus matter. The planetary gears essentially "move" the sun gear closer to the annulus so it's as if its teeth were touching the annulus directly (except moving in the opposite direction). For every tooth of the sun gear that moves past a line from the center outward, one tooth of the planetary gear moves past the same point where this line intersects the annulus. I see that it eventually shows this with math. I'd like more "intuitive" explanations like this. 72.48.75.131 ( talk) 19:55, 19 December 2011 (UTC)
The comments above on formulas 9, 12a, 12b is at best incomplete. Under the conditions stated the equations degenerate and kinematic relations are no more determined, i.e. one component becomes loose. The formula in 13, however is indeed misprinted, the blue z is to be red. Snoloven ( talk) 20:32, 28 March 2012 (UTC)
Hold on, the wikipedia article on the Antikythera mechanism says that the device was definitively found not to contain any planetary gear mechanisms, and this was realized over a decade ago. Why does this page contradict the other wikipedia page? I think we ought to take down the reference to the Antikythera mechanism on this page. — Preceding unsigned comment added by 50.131.61.86 ( talk) 11:46, 19 September 2013 (UTC)
At the end of par. Gear Ratio, I've added an argument that I think is simple, intuitive and precise, establishing the general formula that relates the angular velocities of sun, carrier and annulus (plus two standard applications). This might cause other explanations superfluous, but I made no further changes. KeesDoe ( talk) 21:57, 27 March 2015 (UTC)
I've made some animated gifs and some schematics that might help in this article.
There is a full list on my profile page => DaveRcWiki ( talk) 21:38, 5 February 2024 (UTC)
For some of us who have been studying planetary gear trains for over 5/8 of a century, this article has several problems. The first is that in the United States, the correct title should be Planetary Gear (Train). The USPTO classification is: Class 475 PLANETARY GEAR TRANSMISSION SYSTEMS OR COMPONENTS. "Epicyclic" seems to be the term that is preferred in England. However, unless there is a circular fixed sun gear, with circular planets in the same plane, (none of which are required), there are no points that trace out an epicycle.
The rest of the definition is not general. It only describes one of the most simple types. The main definition should say that "a planetary gear train has some gears whose axes are not fixed, but move in relation to the movements of the gears in the train".
The very first line says "is a gear reduction assembly". A planetary gear train can be used for increase as well as reduction. One of the most widely used planetary gears in the world, with millions of units in daily use, is the bicycle 3-speed hub. It can decrease the speed to 75%, or increase it to 133 1/3 %, or leave it unchanged, the three being selected by various ratchet pawls. agb 173.233.167.50 ( talk) 18:38, 29 April 2024 (UTC)