Talk:Involute gear

Title
Please explain what the title of the article has to do with the article itself. RickK 02:21, 28 Oct 2003 (UTC)


 * As a gear maker myself I agree the title need changing "Involute Gear" and the article could do with fleshing out a bit e.g. a french mathematician invented the curve in the 14-1700 ? but its application to gearing was not understood until the 18xx also there are other gear forms. Therefore keep and rename Archivist 23:54, Oct 30, 2003 (UTC)


 * The title seems to be refering to a particular gear in an anamorphic movie camera lens but the article is about the involute gear type. Archivist 00:07, Oct 31, 2003 (UTC)

From VFD: "* Anamorphic gear is sort of gandu, and not real written. Plus, the contents are describing 'involute profiles'; what does that have to do with 'Anamorphic gears'? -- Khym Chanur 07:52, Oct 28, 2003 (UTC)
 * Keep. It is missing a connection between the two, but I'd wait and see if someone can finish the article to a useful point - Marshman
 * Keep and rename. As a gear maker myself I agree the title is wrong for the text it needs changing to 'Involute Gear' and the article could do with fleshing out a bit e.g. a french mathematician invented the curve in the 14-1700 ? but its application to gearing was not understood until the 18xx also there are other gear forms etc. The title seems to be refering to a particular gear in an anamorphic movie camera lens but the article is not. Archivist 00:18, Oct 31, 2003 (UTC)
 * This article is fine for an encyclopedia. And with all the complaints of 'geek priorities', I'm sure there's someone here who knows enough about them to complete this article. Wiwaxia 02:04, 3 Nov 2003 (UTC)"

Misleading figure
The figure is misleading in that the base radius does not necessarily correspond with the minor diameter of the teeth. With large number of teeth it is less, and with small number of teeth it could become more, and that is why a "correction" is needed. 203.51.92.229 (talk) 02:05, 17 December 2009 (UTC)

Sliding contact
The use of the word "sliding" to describe the contact between the teeth is incorrect. In a properly meshed pair of involute gears, the contact is actually a rolling action with no sliding involved. This is one of the reasons why the involute form for the gear teeth is so successful: there is little friction between the teeth and thus very little wear. I will attempt to change the text to reflect this. EPA3 (talk) 21:18, 30 July 2010 (UTC)

Involute gears have sliding contact except the point of contact on the line between the gear centers. The advantage to the involute is the 'gear ratio' remains constant through the entire contact without regard to center distance, unlike cycloidal gears which have less sliding, but are sensitive to center distance. Physical evidence for this has been in the form of gears with tooth faces damaged everywhere except for the above mentioned contact point, and the remainder of the material sheared away from that contact point. —Preceding unsigned comment added by 199.73.74.5 (talk) 13:09, 6 October 2010 (UTC)

Above unsigned poster is correct. Involute teeth do NOT achieve rolling contact throughout their mesh. This is demonstrable with a trivial vector analysis of the velocities at the contact point (see discussions of non-circular gears for related math). The fact that there is sliding involved is even apparent just from looking at the animation in the article. —Preceding unsigned comment added by Drewm1980 (talk • contribs) 21:17, 15 November 2010 (UTC)

Both involute and worm gearing slide (as others have pointed out, no sliding at the pitch point for invlute gearing though). But there vaugely is something to his comment: worm gearing generally slides MUCH more and is MUCH less efficient, though I think you could design cross-helical involute gearing to emulate the configuration worm gear designs tend to have, in which case the efficiency/sliding would be very similar. Regardless, SPUR involute gearing doesn't slide nearly as much as typicaly designed worm gearing. Eboomer (talk) 20:37, 24 April 2013 (UTC)

What about circular-to-linear motion?
I am intrigued by Leonhard Euler's design of circle-involute gear teeth that maintain an exact constant ratio of angular velocity between two such meshed gears.

But what if one of them is not a circle, but a straight line (with the same circle-involute gear teeth)? I know these are called rack-and-pinion gears, but I don't know whether they maintain an exact constant ratio of angular speed to linear speed. (And whether the circular gear rolling on the straight one remains along an exact straight line.)

Can someone knowledgeable on this matter please add answers to these questions to the article? It would be a natural thing to find in this article. Thanks.Daqu (talk) 15:25, 10 July 2014 (UTC)

Cycloidal gear form and clocks
Thanks for fixing my mistake, but... are you sure it was a mistake? I'm checking more carefully, and I'm not sure.

I changed "cycloidal gearing" to "cycloidal gearing". The revert says ''rv cycloidal. Cycloidal gears are a specific form, not that used here. First of all, obviously they're not involute'' gears. That's the whole point of the sentence it appears in: "The involute gear profile is the most commonly used system for gearing today, with cycloidal gearing still used for some specialties such as clocks." And indeed cycloidal gear says "The cycloidal gear profile is a form of toothed gear used in mechanical clocks, rather than the involute gear form used for most other gears."

Sure seems like the same thing. The latter article goes on to say "The gear tooth profile is based on the epicycloid and hypocycloid curves, which are the curves generated by a circle rolling around the outside and inside of another circle, respectively." And, indeed, those two forms are not actually cycloids. (They're all members of a family distinguished by the curvature of the fixed circle. A true cycloid has a curvature of 0, meaning the "circle" is has infinite radius, a straight line.)

So I agree that it's a different thing, but I think my edit corrects an error. Cycloid doesn't mention gears, and every reference I can find to clock gearing or cycloidal gearing describes the cycloidal gear form.

So why should the link remain to cycloid? AFAICT, there is no gear whose teeth actually contain cycloid curves in the strict sense. 71.41.210.146 (talk) 10:14, 13 March 2017 (UTC)
 * Sorry, this is my mistake and the redirect confused me.
 * A link to cycloid gear would be correct. This is the form of gear tooth, used for otherwise conventional gears, that has been used in clocks. WP doesn't have a great article here, but it does have something.
 * A link to cycloidal drive would be wrong. A link to the redirect cycloidal gear (as you added) confused me, as I'd assumed that it was pointing to cycloidal drive (which makes more sense for the redirect generally, but is wrong for clocks) when it actually points to cycloid gear, which is the right place.
 * This article ought to link directly to cycloid gear. Andy Dingley (talk) 10:55, 13 March 2017 (UTC)


 * Ah, okay, thanks! I'm just glad to understand what happened. 71.41.210.146 (talk) 02:50, 14 March 2017 (UTC)