Talk:Differential (mechanical device)

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Pinion Gear Rotation[edit]

Neither of the pics makes sense to me. If the pinion gear is indeed interfacing between each side gear, then for one to turn, the other must be turning in the opposite direction. The pic seems to indicate that if the ring gear receives torque in the illustrated direction, the left driveshaft will necessarily spin in that direction. If the pinon gear interfaces with the left side gear, then the pinion gear will necessarily spin counterclockwise (looking from above, as in the pic). If the pinion gear interfaces with the right side gear, this will necessarily drive the right side gear in the opposite direction from the left side gear. What am I missing? JunkCookie 21:58, Aug 20, 2004 (UTC)

  • Yeah, the pics could stand to be clearer. The top image is meant to show that the entire assembly rotates forward; picture it without the ring gear for a moment, and imagine the green pinion gear rotating around the other two gears. The pinion gear is pushing against both side gears, so the pinion gear itself can't rotate unless one of the side gears meets some kind of resistance. When there is resistance on one side (as in the second picture), the pinion gear starts rotating, turning the other side with additional speed. The link to the HowStuffWorks version is much better at explaining this than what we currently have here, unfortunately. -- Wapcaplet 23:51, 20 Aug 2004 (UTC)
I figured out what I was missing. I didn't realize that the cage to which the pinion gear is mounted actually rotates with the ring gear. Somehow I had it in my head that the ring gear was fixed to the left side gear, and that the pinion is used to transfer the rotation to the right side gear. The animated pics at HowStuffWorks gave me the 'Aha!'. JunkCookie 20:59, Aug 23, 2004 (UTC)
And the fact that you needed another site to figure it out underscores that our figure is unclear. The figure does for instance not make clear that the cage is separate from the left side gear. Anybody up for making an animation? - Mglg 23:24, 4 June 2006 (UTC)
The problem with making an animation is that the politically correct thought police will only allow certain file formats to be loaded. I suspect that given the time that it would take to build the model, and then go through all the hoops required to turn it into an acceptable file format that very few people know of (ogg video) will put them off. Leastways it does me.Greg Locock (talk) 22:14, 26 January 2008 (UTC)
The animation is good enough. The real problem is the constant reference to Sun and planet gear arrangements when the picture is clearly of a bevel gear design. Also, since the drawing shows a spur-type ring gear as is commonly used in front wheel drive, transverse engine transaxles, it is misleading and incorrect to use language that equates "open" bevel gear differentials to rear wheel drive. --Speed Daemon (talk) 23:19, 29 May 2014 (UTC)

Antikythera mechanism[edit]

Wright, M T. (2005). "The Antikythera Mechanism and the early history of the Moon Phase Display". Antiquarian Horology 29 (3 (March 2006)): 319–329.

This reference is used to support the statement, "the assumption of the existence of a differential gearing arrangement was incorrect". I scanned the referenced article [1] and it does not mention differential gearing. Please improve the reference to point to the exact phrase which supports this statement. --beefyt (talk) 21:46, 10 December 2010 (UTC)

There are plenty of refs out there that categiorize the reconstructed Antikythera as a differential. I think the old Sci Am article (a significantly early mention) did this. The claim that modern analyses shows it to not be a differential certainly needs better sourcing. Andy Dingley (talk) 22:25, 10 December 2010 (UTC)
This is weird and almost certainly wrong. There is little doubt that the mechanism does contain differential gearing, and there is a diagram here. Someone in the past edit history of the article seems to have a bee in the bonnet and overstated or misrepresented the sourcing on this issue.--♦IanMacM♦ (talk to me) 21:09, 25 December 2013 (UTC)
I found this article on the history of the Antikythera mechanism to be convincing PHASES IN THE UNRAVELING OF THE SECRETS OF THE GEAR SYSTEM OF THE ANTIKYTHERA MECHANISM. Prof McCarthy (talk) 22:28, 25 December 2013 (UTC)
This would be best presented by giving both sides of the argument, and pointing out that the conclusions of Derek J. de Solla Price have been questioned by more modern research. Previous edits to the article have either been uncited, poorly cited, or stated that the modern research was correct or better, without explaining why.--♦IanMacM♦ (talk to me) 22:52, 25 December 2013 (UTC)
Solla-Price in his 1972 "Gears of the Greeks" did indeed overstate the use of differential gearing in the device, based on skimpy x-ray material and perhaps some inborn prejudices. Numerous researches, while discounting Solla-Price's hunch, did in fact find a true differential gear in the piece of the mechanism which operated on the two inputs of the moon and sun locations to compute the angle between and display it as the phase of the moon. There is no simple way to otherwise have done that other than "dead reckoning" from some known date. That gearing is accepted by Wright, Jones and Freeth, the "biggees" in the field. Copious journal reports are available on the AM page. SkoreKeep (talk) 07:35, 17 June 2014 (UTC)
The only 3 mentions of differential in the Wright paper all say it was a mistaken deduction. Relevant quotes are firstly a summary of price's description on P28 followed by "Price was mistaken in identifying the epicyclic arrangement in the train to the lower back dial as a differential gear; in reality it appears to have had only one input, not two," and "That to the lower back dial includes an epicyclic assembly (Fig. 2b), which Price identified, incorrectly,as a differential gear". So where, specifically does Wright claim a differential? Greglocock (talk) 11:07, 17 June 2014 (UTC)
For the purposes of this article, what does it matter? We should state that the Antikythera has been identified as a differential, that it contains mechanisms of comparable complexity and that these specific intepretations are also challenged. All of these are easy to state and source to the level we need here. Content within the Antikythera article is rather harder, but that's outside this problem. Andy Dingley (talk) 11:49, 17 June 2014 (UTC)
Wright didn't see it; it was discovered by the Freeth team. See the article cited above by McCarthy. Isn't the history of a device or mechanical improvement important? That device is by far the earliest known use of differential gearing known in the world (with the possible exception of the Chinese), as well as and epicyclic and gearing practices in general. SkoreKeep (talk) 14:35, 17 June 2014 (UTC)
I went to the reference supplied (Wright). I searched for differential and got 3 hits, none of which confirmed that the mechanism was a differential. That's it. I have no skin in this game, I just resent being sent on wild goose chases.Greglocock (talk) 23:55, 17 June 2014 (UTC)
Ah,come on, Greg. Wild goose chases are the name of the game.  :) Nonetheless, I thought the McCarthy paper cited above would say something about the lunar phase indicator, but upon review, it doesn't, so I'll submit to you another paper by Wright: It's about the lunar phase display pretty exclusively, and he mentions the nature of the differential device used several times, with drawings based on studies of the x-rays and a reconstruction of the pieces. I hope that works for you. SkoreKeep (talk) 02:54, 18 June 2014 (UTC)

Edited First Paragraph in Overview section[edit]

I edited the first paragraph in the Overview so that the description of what a differential does (and why it is needed) are stated first. I also split off the sentences describing the basic automotive differential into a separate paragraph, since they cover a separate topic. Finally, I added references to the gear nomenclature pages for Pinion and Crown, and corrected a few misspellings. OldTimeNESter (talk) 20:33, 10 October 2014 (UTC)

Yes, it was pretty bad before! Andy Dingley (talk) 21:40, 10 October 2014 (UTC)

net vs. nett[edit]

Of all the silly things to have an edit war about, we're having one on the spelling of "net" with one "t" or two. Seriously? Editors are reaching the point of violating WP:3RR and getting banned over this? Well, okay, let's discuss, shall we?

I'll start with stating that "nett" seems a little old-fashioned, though less out-of-date in British English than American. WP:COMMONALITY under WP:ENGVAR actually says we should choose something common to both if possible; that seems like "net" to me. --A D Monroe III (talk) 20:16, 21 November 2014 (UTC)

We have a policy that we don't make nationalist spelling changes, we leave things be. Follow it. Andy Dingley (talk) 20:47, 21 November 2014 (UTC)
WP:ENGVAR is certainly policy; so is WP:COMMONALITY. Both "nett" and "net" are British English; per ENGVAR, we can use either one. To me, COMMONALITY says we should compromise on "net". --A D Monroe III (talk) 22:35, 21 November 2014 (UTC)

Nett / net[edit]

There's disagreement as to whether the spelling "nett" is acceptable in place of "net" in contexts such as "a net force". I have three dictionaries here. The Concise Oxford says "nett" is acceptable if the word means a trap to catch animals, etc., but not in the context we are discussing. Funk and Wagnall's does not include "nett" at all. Webster's says that "nett" can be used only as a verb. I suppose there may be dictionaries that include it in our sense, but it is certainly not universally accepted. In the past, I have seen several people editing this article to change "nett" to "net"., and the edits have been reverted. In the interests of clarity and harmony, I think we should just leave it as "net". DOwenWilliams (talk) 20:31, 21 November 2014 (UTC)

Discussion is above. --A D Monroe III (talk) 22:31, 21 November 2014 (UTC)

Too many technical terms in introduction[edit]

The introduction (the text at the very start of the article) needs to provide a simple description, understandable by the majority of readers. Jargon and technical terms should be avoided as much as possible in this section. Details can be provided later in the article. The current introduction can only be understood by someone who is already intimately familiar with gears (who probably doesn't need to read this article). — Preceding unsigned comment added by 2602:306:CEAE:E60:B09D:E317:D264:1402 (talk) 09:43, 17 May 2016 (UTC)

You are absolutely right, it is a shocker of a lede, and is obtuse, and jargon filled, and I suspect, wrong. Greglocock (talk) 10:29, 17 May 2016 (UTC)