Talk:Universal joint

Something is wrong with the velocity-formula. The average velocity of one rotation should be equal to the driven velocity which is clearly not the fucking case.


 * I inserted the missing 'squared' (as in the reference I added under ==References==). --Heron 19:22, 23 August 2005 (UTC)

The angular acceleration equation is not correct...the entire denominator must be squared to be correct. lstike 2/13/06
 * Right! Corrected. MH 20:44, 29 August 2006 (UTC)

Merge Gear coupling to Universal Joint?
I would disagree with this proposed merger. While the two devices may serve similar roles and their articles certainly should be inter-linked, they are mechanically very different and I believe the current separate write-ups are entirely justified.

Atlant 5 July 2005 11:43 (UTC)


 * Likewise. There are another dozen types of flexible couplings as well. They won't all fit here once they are done. Meggar 05:34, 30 October 2005 (UTC)

CV joints
There is already a write-up on Constant-velocity joints. Wouldn't be better to remove the section in here and link to the other write-up? Soupisgoodfood 11:11, 3 November 2005 (UTC)
 * Done Kallog (talk) 17:09, 6 June 2008 (UTC)

NPOV name
It seems arbitrary to call this device "the Spicer joint" when it is well known that Girolamo Cardano invented the universal joint centuries earlier. In fact, there are even accounts of the use of such a device in the ballistae of ancient times. I checked the history of this article and it seems that it originally listed various names for the device, before a vandal clumsily chopped off part of the text: compare with the previous revision. The last few edits failed to notice that the article had been vandalized, patching up the mutilated sentence for grammar correctness alone. The article has now been fixed. 23:04, 15 May 2006 (UTC) —The preceding unsigned comment was added by 82.55.247.187 (talk • contribs).

Equally, it now seems odd that there is no mention or explanation of the spicer name and its origin. I feel this ort to be included, if only to the tune of 'The joint is also called the hardy-spicer joint because...'

175.41.133.18 (talk) 02:55, 14 June 2013 (UTC)


 * Thanks!


 * Atlant 15:38, 16 May 2006 (UTC)

Speed ratio?
What is the speed ratio of the input shaft to the output shaft? —The preceding unsigned comment was added by 156.63.207.123 (talk • contribs).


 * On average, 1:1. But if the two shafts are not co-linear (aligned with each other), then the speed ratio varies throughout a half-revolution of the shafts. The article has the formula.


 * Atlant 16:31, 25 May 2006 (UTC)

Note that I wrote "Over large time intervals". When driving shaft turns a hundred times, driven shaft will turn a hundred times. When driving shaft makes 100 rotations in one minute, driven shaft too will make 100 rotations in that minute. Of course, when driving shaft rotates for 90 degrees, driven shaft will rotate for less, or more. Speeds of the shafts are the same, in the same sense as speed of a car which passes 100Km going 100Km/h is the same as speed of car which goes 200Km/h but stopps for an hour in the middle of the trip are the same.

As apparently 156.63 found it confusing, and I too was thinking for a moment "wait, if speeds are not the same then where did angular momentum go?", I believe that what I wrote should be in the article in some way. Perhaps it could be said that average speed is the same.

If you wish to nitpick note that, in the same sense of the word, speeds of gears with 1:1 ratio are not the same because the driven gear jerks a bit too, though it's far less visible than with universal joint ;) Nikola 23:19, 24 January 2007 (UTC)

Thompson Coupling - a new constant velocity universal joint
No discussion on universal joints is complete without mentioning the Thompson Coupling, a true constant velocity universal joint which can withstand an axial force such as the force applied by a rotating helicopter prop. Reference: cvcoupling.com - Simon Purser

It would be cool if someone could create a visual simulation of the Thompson Coupling, similar to the one that was created for the Universal Joint.

Double cardan diagram
It would be very helpful to have a diagram of the double cardan joint as well as the standard universal joint. —Preceding unsigned comment added by 82.141.225.26 (talk) 17:24, 20 March 2008 (UTC)

missed sign?
Sorry I alter the minus sign in the angular acceleration formula.

The angular velocity is

w2=w1 cosB/(1-sin²B*sin²F)

B stands for beta and F is phi in the text. It is F=F(t) and d/dt F = w1, also w1 is function of time, i.e. w1=w1(t). Deriving with respect to time follows:

d/dt w2= d/dt (w1 cosB/(1-sin²B*sin²F))= cosB/(1-sin²B*sin²F) d/dt w1 + w1 cosB d/dt 1/(1-sin²B*sin²F)= A1 cosB/(1-sin²B*sin²F)+ w1 cosB d/d(1-sin²B*sin²F) 1/(1-sin²B*sin²F) d(1-sin²B*sin²F)/dt=A1 cosB/(1-sin²B*sin²F)+w1 cosB (-1/(1-sin²B*sin²F)²) (-sin²B) d/dt sin²F= = A1 cosB/(1-sin²B*sin²F)+w1 cosB sin²B/(1-sin²B*sin²F)² 2 sinF cosF d/dt F

Finally A2= A1 cosB/(1-sin²B*sin²F)+ (w1)² cosB sin(2F) sin²B/(1-sin²B*sin²F)²

(recall: sin(2F)=2 sinF cosF; d/dt cosF = -sinF d/dt F; d/dt sinF = cosF d/dt F).

If I'm wrong in any detail, please let me know it.

193.145.150.39 (talk) 18:45, 30 June 2008 (UTC) juan

Knuckle Joint
At a certain point as a young teenager, I shifted from middle class and paper-based to rural and reality-based; I say rural but much of my experience as a teenager was on boats of all kinds. Nowhere then did the word universal exist; the term was "knuckle joint." When I used the word universal, which I had learned from reading and in school, I got dirty looks. I imagine now that the term universal joint is as common in rural communities as was knuckle joint, and knuckle joint may have since been deprecated, but I can check the next time I pass a truck stop or a marine engine shop.--John Bessa (talk) 00:09, 25 January 2009 (UTC)

Strictly speaking a knuckle joint has only one degree of freedom, a Hookes joint has two. I hope you enjoy explaining that to the truckies and boaties. Greglocock (talk) 11:25, 27 January 2009 (UTC)

Henry Ford
User:Van helsing created the history section and credited Henry Ford with coining the term universal joint on 28 Aug 2006, with no sources. An anonymous contributor corrected this, providing a counterexample to show that Ford did not coin the term on 19 Apr 2008. I cannot find any source that predates 2006 and gives Ford credit. All the sources I've found are likely to have been influenced by this error in Wikipedia. If someone can find an older source for this misattribution, please cite it in the History section. Otherwise, there is no reason to even mention Henry Ford here. Douglas W. Jones (talk) 20:28, 15 June 2010 (UTC)
 * Sorry Douglas, but it wasn’t me who wrote the history section, if you look closely at the dif, you can see I merely moved it up; Heron actually wrote the section back in 2004 . Like you, I can’t quickly find a source for that particular claim; at least not one that is not likely to have used this Wikipedia article itself as a source. Though it’s a long time ago, I’ll inform Heron, maybe he remembers were it came from. --Van helsing (talk) 14:57, 16 June 2010 (UTC)
 * I'm sorry, but I don't remember where I got that information from. I too have searched and failed to find any independent source, so I'm in favour of deleting the offending statement. The OED quotes Hooke himself as the first known user (if not the originator) of the term. --Heron (talk) 19:30, 16 June 2010 (UTC)

Joint phasing
The last photo in the article, showing a power transmission shaft using 2 U-joints, does not show the joints 90 degrees out of phase, whereas joint phasing is mentioned in the article as necessary for proper functioning. Simple U-joints are not a difficult topic, nor is posting info on the web a difficult activity. When things are this simple, it shouldn't be a complicated task on a "reference" site to get things right. — Preceding unsigned comment added by 76.11.81.207 (talk) 00:34, 3 October 2011 (UTC)

phasing of double cardans
in answer to a rather odd note in the article, the joints IN a double cardan joint are at 90 degrees to each other.Greglocock (talk) 08:47, 20 March 2015 (UTC)
 * Not always - infamously the steeply angled Range Rover front propshaft. http://www.landyzone.co.uk/lz/attachments/f10/21535d1297115843-front-prop-shaft-untitled1.jpg  This really doesn't like being assembled in phase and will give vibration problems if it is. I think there was also trouble with a similar shaft on the Class 55 Deltic locos. Andy Dingley (talk) 10:11, 20 March 2015 (UTC)
 * That's not a double cardan joint. That is a pair of Hooke's joints Greglocock (talk) 10:48, 20 March 2015 (UTC)
 * What's a Cardan if not a pair of Hooke's? Andy Dingley (talk) 11:34, 20 March 2015 (UTC)


 * A double cardan joint is a type of constant velocity joint, essentially two hookes with no shaft between them. Greglocock (talk) 01:09, 21 March 2015 (UTC)

However, in a double cardan shaft the phasing of the joints can be any value. If the axis of the input and output shaft are parallel or if the angle between the input shaft and the lay shaft is equal to the angle between the layshaft and the output shaft, and the axes are all coplanar the phasing is set to 90 degrees, that is the yokes on the layshaft lie in the same plane.Greglocock (talk) 01:44, 21 March 2015 (UTC)


 * Your last two comments contradict each other. Is a Cardan joint (which is obviously a pair of Hooke's joints) always phased to correct the angular velocity variation? (And if so, did Cardan know this?) Or is it any such combination, no matter what their phase? Andy Dingley (talk) 02:09, 23 March 2015 (UTC)

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