Talk:Gear

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[edit] Is this relevant?

I think this paragraph in the article is completely irrelevant to the article and should be deleted. Comments? "There are several outcomes of gear shifting in motor vehicles. In the case of air pollution emissions, there are higher pollutant emissions generated in the lower gears, when the engine is working harder than when higher gears have been attained. In the case of vehicle noise emissions, there are higher sound levels emitted when the vehicle is engaged in lower gears. This fact has been utilized in analyzing vehicle generated sound since the late 1960s, and has been incorporated into the simulation of urban roadway noise and corresponding design of urban noise barriers along roadways.[2]" -- Dalebert 10/19/07 —Preceding unsigned comment added by 192.158.61.142 (talk) 12:39, 19 October 2007 (UTC)


[edit] Help me design a gear train

I need design procedure for winch means all the components of winch and how to design them

How about some nomenclature, such as pitch etc. Also maybe some of the physics involved (torque ratios etc) 7legs 010306

I think you need more help than Wiki is prepared to give you. Perhaps someone can refer you to a good textbook or handbook?
Atlant 15:16, 1 March 2006 (UTC)
I do not think one sets out design a gear train. In this case it is a winch, motorised or otherwise to launch a boat ? Start with the motor you have, then the load you want to move and then you can design a gear train that will get the job done in a certain amount of time..

Gregorydavid 07:52, 16 May 2006 (UTC)

[edit] Axis versus Axes

This can be tricky.. Each gear has its own axis of rotation. Two gears have their respective axes of rotation.. In a train of gears there is the axis of rotation of the input and the output which can have the same orientation in space, ie along the X axis.. But changing my changing 'axes' to 'axis' yesterday wa wrong.. Gregorydavid 08:11, 16 May 2006 (UTC)

[edit] Added Images of Helical Gears and a Worm and Pinion

I took some photographs of gears from a Meccano construction set to make these images. Arthur Clarke 17:48, 31 July 2006 (UTC)

[edit] Removed US Specific Annotation

I removed the US specific annotation "stick shift" against the reference to Manual transmission as there is already a redirection from "stick shift" and Manual transmission is the primary, and more explicit, title. Arthur Clarke 17:48, 31 July 2006 (UTC)

[edit] Page contains errors of varying degees of obscurity

I put this in the discussion because I've never edited a Wikipedia page before... so I'm shy, big deal. If anybody else wants to incorporate my suggestions, feel free. For reference authority, it's probably tough to beat Machinery's Handbook (practically any edition since the late Bronze age).

Double helical gears: A *train* of herringbone (double-helical) gears can usually (see below) be used instead of a train of spur gears without any need for different bearings because neither require bearing for axial thrust. However, it is *not* true that herringbone gears [of nonzero helix angle] "can be interchanged with spur gears" [of finite face width] because the teeth won't mesh (unless all gears in the train are 'interchanged', or in the trivial case of zero helix angle that doesn't warrant the 'herringbone' designation).

Note also that a pair of herringbone gears will mesh in only one axial position, aligning both helix angles of each gear. Spur or helical gears, on the other hand, can remain in mesh if one is axially displaced relative to the other. Which is advantageous (or disadvantageous) depends on the machine, of course.

It's probably worth noting the two obvious (but obviously incompatibale) standard ways to make a double-helical gear: The two opposing helices might meet in the middle of the gear with (a) addenda (teeth) from each helix coincident, or (b) addenda of one helix coincident with dedenda [spaces] of the other. The latter are "Wuest" herringbone gears.

Double helical gears: The teeth aren't "V-shaped", their shape of their flanks are involute (usually, though other forms also give correct action) just like those of spur and helical gears. I realize that profile isn't what the writer refers to, but IMO too few people appreciate that (non-rack) gear teeth are *not* v-shaped in transverse section. There must be a better way to say what is meant here, though nothing pops readily to my tiny mind.

Bevel gears: Should read "where two axes [not axles] cross at [a] point". Nothing really difficult about crossing axles at a point, except (a) difficult to arrange so both can rotate, and (b) it's generally not a feature of actual bevel gear sets (e.g. the floodgate example photo)

Bevel gears: While it's true that helical gears can be arranged to provide for "ninety degree rotation" of the *projected* axes of rotation, (a) the existing text is too limiting; helical gears can provide for any such angle, not just ninety degrees, and (b) the existing text omits an important detail; the two axes cannot be coplanar [except for the 'trivial' case of parallel axes]

It may be worth noting that internal and external spur gears are special limiting cases of bevel gears. Bevel gears mesh between coplanar axes; the term is generally reserved for intersecting axes. Ordinary (external) spur gears are one limiting case of parallel axes, i.e. zero pitch "cone" angle; internal spur gears are another limiting case of parallel axes, i.e. pitch "cone" angle of 180 degrees [though most spur gears use involute teeth and standard bevel gears use octoidal teeth, that's merely a standards-implementation detail]. Similarly, spur gears are a limiting case of helical gearing, i.e. zero helix angle. [It's not clear {to me, anyway, and I know no reference} whether helical gearing is a case of the various standard forms of spiral bevel gearing {e.g. Gleason's Coniflex, et al; I suspect not}].

Worm gear: The part that looks like a screw is a *worm*; the wheel with which it mates is the *worm gear* (well, usually; a worm will mate with spur and helical gears of corresponding tooth form and normal pitch, but only in point contact that is suitable only for light loads rather than the broader "line contact" it would achieve with a proper worm gear). The teeth of a worm gear extend across its concave face to contact the worm teeth through a greater angle of the worm's rotation. That is a worm and worm gear are *not* a special case of helical gearing (a worm might be a special case of a helical gear, though standard worm thread forms differ from standard helical gear teeth).

Worm gear: (same guy, later date): It is incorrect to claim that the worm is *always* the driver. It is *often*, but not always, true that the worm and gear are "self locking (the gear cannot drive the worm). If the helix angle of the worm is sufficiently high for the coefficient of friction between the worm and the gear, the gear can drive the worm.

Sector gear: Is merely a segment of a gear, which is not necessarily a spur gear. In the mentioned example of automotive steering gear, the sector gear is a typically a segment of a worm gear, not a spur gear.

Rack and pinion: Not limited to spur gears. There's nothing un-gearlike about helical pinions mating with skewed -- or even straight -- racks as long as the systems can deal with -- or profitably employ [e.g. backlash takeup] -- the resulting thrust or displacement. [no, I don't have any handy example]. The rack is a special case of spur (or helical) gear, with infinite pitch diameter and tooth count; all real racks are therefore special cases of sector gears. We are one of biggest gear drive & speed reducers manufacturer like: Planet carrier, ring gears, helical gears and worm reducers and helical geard motors cyclo drive, Planetary Gearboxes manufacturers in China. For more details please visit our website: http://www.china-reducers.com

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Crown gear: Does *not* mesh correctly with a spur gear pinion [of finite face width]. A crown and spur gear could be made to turn each other through point contact at the ends of the teeth nearest the crown gear axis, but that would still not transmit uniform angular motion because the radius to the point of contact would vary as teeth engage and disengage. A crown gear is a special case of bevel gear (90-degree pitch cone angle); a bevel gear is required for correct mesh because the size of the crown gear's teeth (and spaces) vary with distance from its axis. The angle of the axes between a crown gear and fully-engaged bevel pinion must therefore be greater than 90 degrees, since the pinion must have some pitch cone angle greater than zero and less than 90 degrees (well, two crown gears can mesh, but that hardly deserves the name "gearing"; it's a clutch.

Hypoid gearing is different from all the above, industrially important, and may be worth mentioning; it's generally what's used in motor vehicle differentials IIRC. I don't have an authoritative reference defining the type.

Oops... originally didn't know how to "sign". 129.230.241.5 22:55, 4 October 2006 (UTC)

[edit] History of Gears

It would be nice to see a section on the history of gear wheels. This New York Times articlementions that

  • a geared computing device existed in the 2nd century B.C.
  • According to Dr. François Charette of the University of Munich museum, "It seems clear [that] much of the mind-boggling technological sophistication available in some parts of the Hellenistic and Greco-Roman world was simply not transmitted further... The gear-wheel, in this case, had to be reinvented."

I came to Wikipedia to determine when, prior to such discoveries as this, the gear had been considered to have been invented. But no info in this article. Wareh 21:44, 29 November 2006 (UTC)

Well, if anyone wants to work on this, see the response at Wikipedia:Reference desk/Archives/Science/2006 November 29#History_of_Gears, and possibly consider such objects as Antikythera mechanism (the one in the Times article I linked), South Pointing Chariot, watermills and Salisbury cathedral clock. Wareh 01:20, 1 December 2006 (UTC)

[edit] The rare driven worm

The article currently contains the following statement:

The worm is always the driving gear.

While this is true probably 99-44/100% of the time, this isn't always true. I once saw a mechanism that drove a very-high-pitch worm in order to achieve a very large speed step-up ratio in a single gear pair. I can't remember exactly what was being driven; it might have been a flyball governor.

Unless somebody has a citation, we probably shouldn't edit the article, but I thought I'd note this for the record here ion the talk page.

Atlant 17:03, 5 December 2006 (UTC)

You’re right, I remember that as well here (second music box) you see one (the little white metal speed regulator fan). --Van helsing 13:31, 8 December 2006 (UTC)
YES! That's it! If I get a chance, I'll take a photo and add it to the article (as a citation of sorts). Thanks!
Atlant 13:41, 2 February 2007 (UTC)

[edit] Whats a cog?

I was wondering if someone could put up a definition of a cog. I always knew it was gear related, but not eactly what it is. Fresheneesz 02:01, 11 January 2007 (UTC)

Cogs are the potruding pieces on gears that interlock with the potruding pieces on the other gears. They are also called "teeth". A gear could be called a "toothed wheel" or a "cogged wheel".
Baded upon the above, this gives rise to the saying that someone is just a "cog in the machine" - that means they are a very small part of a much bigger organization - just as one tooth is to the entire wheel or gear assembly.
Somewhat confusingly, the whole wheel (that is the whole gear) can also be called a cog.
Note that a cog can also mean other things. For instance, in carpentry, a cog is a tongue on a piece of wood which is intended to join into a corresponding grove on another piece of wood. (Note that this type of cog is performing sort of a similar function - that of interlocking into another piece) [1] Johntex\talk 04:47, 11 January 2007 (UTC)
Hmm, thanks. Do you think cog deserves its own disambiguation? Fresheneesz 05:48, 11 January 2007 (UTC)
It already has one. Please see Cog. Johntex\talk 06:42, 11 January 2007 (UTC)

[edit] An edit that had some good data

This edit:

contained some good data, albeit badly formatted. As time permits, we should take that data and incorporate it into the article. Or perhaps our anonymous editor will try again for us?

Atlant 13:39, 2 February 2007 (UTC)

'gears' are round mechanical objects often called toothed wheels, cogged wheels or cogs. a gear has teeth round its edge. these are what link with other cogs to form a rotational motion. the teeth can be called cogs too.


[edit] 1 rpm = 1/30π rad/s?

Stated in the article is 1 rpm = 120π rad/s. I think this is in error?

Actually, 1 rpm = π/30 rad/s. 120π = 3600 rpm.

[edit] Suggested merge of "Sprocket" into "Gear" article

Definitely not. They should obviously be in something like a "Power Transmission" category but apart from being round sprockets and gears are totally distinct: different tooth form, different direction of driven wheel, different ways of accomodating increased loading etc. MarkMLl 16:30, 14 September 2007 (UTC)

[edit] Suggesting a paragraph for the manufacturing methods of gears

There should be a paragraph which briefly describes the manufacturing of gears, and the machines used for this process.

[edit] Tooth contact nomenclature

Tooth contact nomenclature is currently split between this article and a host of other articles listed at List of gear nomenclature. I think these need to be merged. Biscuittin (talk) 13:20, 3 January 2008 (UTC)

I noticed that too, but I'm not very keen on the idea of merging more content into Gear because Gear is already such a very long article. I was wondering whether some content in Gear could be partly or wholly split off into other articles. The section on nomenclature is very long and rather breaks up the flow of the article; it could be split off and merged into List of gear nomenclature, or else transwikied to wikibooks per WP:NOT#GUIDE. - Neparis (talk) 04:35, 5 January 2008 (UTC)

[edit] Add a useful term: "backdrivable"

A suggestion for an additional term: backdrivable.

A transmission is backdrivable if a force or torque on its output can move its input. An example of a backdrivable transmission is an automotive steering mechanism: when rock climbing in a 4WD vehicle, you should keep your thumbs on the outside of the steering wheel, because lateral torques on the front wheels can violently spin the steering wheel. An example of a non-backdrivable transmission is a machine head on a stringed musical instrument; although the worm can be turned to drive the worm wheel and tighten the strings, the enormous force on the worm wheel is unable to cause the worm to spin.

I'm not sure where to work this in, though, without adding a whole new section, and the article is pretty piecemeal as-is. Perhaps the article could use some reorganization, collecting terms together into an "Other terms" section? --Dan Griscom (talk) 12:22, 24 February 2008 (UTC)

[edit] Definition of Module

Would it be possible for a definition of normal and circular module? Normal module is referred to in the profile shift and rack shift, but not actually defined. Also, looking at the equation for Diametral Pitch (transverse), it appears that module (m) is used (i.e. PD = 25.4/m), but again, not defined. As the module can be used for calculating the pitch diameter (i.e. D=number of teeth x module), I would have thought the inclusion of the module was fundemental to an article on gears. I'm currently scouring the text books on my desk for a definition (no luck so far), but if anyone else has a definition, could they please post it? Thanks! StephenBuxton (talk) 09:31, 20 May 2008 (UTC)

Found one from the Machinery's Handbook 26th Edition. I've also added a section about the module. Feel free to expand! StephenBuxton (talk) 16:15, 20 May 2008 (UTC)