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Kinematic pairs are the connection between 2 links that can have relative motion between them.

But In six bar chain as shown below:

chain with 6 links

There are five pairs for them to be a kinematic chain. But if I consider links between ((1,4),(3,4),(3,2),(2,1),(2,6),(6,5),(5,1)).I get 7 kinematic pairs. I have the resources suggesting that this chain has only 5 kinematic pairs. How?

EDIT: IT BELONGS TO:http://site.iugaza.edu.ps/mhaiba/files/2013/09/CH-5-Simple-Mechanisms.pdf.In

Sankara Narayan
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  • Does it fit the equation? See https://engineering.stackexchange.com/q/42561/10902 – Solar Mike Apr 27 '21 at 19:49
  • It fits the equation when it it has 5 pairs but actually when counting the pair, It has 7 pairs. – Sankara Narayan Apr 28 '21 at 03:25
  • Yes.But they also form kinematic pair B forms with link (2,1) . And G forms kinematic pair with link (2,6). – Sankara Narayan Apr 28 '21 at 03:51
  • What is the exact wording in your assignment. Because it seems to me that your paraphrazing of the question is tge error at hand. – joojaa Apr 28 '21 at 04:10
  • http://site.iugaza.edu.ps/mhaiba/files/2013/09/CH-5-Simple-Mechanisms.pdf.In page 20. It doesn't say anything but they have substituted kinematic pairs as 20 in the equation.If the file is not available see the edit in my question. – Sankara Narayan Apr 28 '21 at 04:12
  • They have not done anything at all like what you say – joojaa Apr 28 '21 at 04:19
  • In the equation L= 2p-4 .They have substituted P as 5. But P should be 7. – Sankara Narayan Apr 28 '21 at 04:20
  • Sorry in the 5th comment I have said they have substituted kinematic pairs as 20 but actually, it is 7. typing error. – Sankara Narayan Apr 28 '21 at 04:29
  • Yeah, the wording is a bit unfortunate they are using the word pair, and are not refering to kinematic pair directly as such. So its easy to conflate the two. – joojaa Apr 28 '21 at 05:14
  • It is probably better if you concentrate on the kuzbach mobility criterion as its more useful. Especially ifyou modify it so that you calculate joints as per how many degrees of freedom they have instead then only the first part of the equation is needed. Andits easierto deal with the 3D case. – joojaa Apr 28 '21 at 05:31
  • so you tell that there are 7 kinematic pairs and so if I substitute that in the equation ,it wont be equal. IT would be like (6 < 2 x 7 - 4) – Sankara Narayan Apr 28 '21 at 05:31
  • Well, $p \neq$ kinematic pair your getting confused because you think p is equal to kinematic pairs. Your assumption is wrong. – joojaa Apr 28 '21 at 05:37
  • but that equation is only valid when pairs are kinematic and If its not kinematic pairs too..there are 7 pairs .(not kinematic) – Sankara Narayan Apr 28 '21 at 05:40
  • Yes but they are not really counting kinematic pairs they are counting dyads. Its just that your source material has succeded in confusing you because of unfortunate language choice. – joojaa Apr 28 '21 at 05:55
  • Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/123535/discussion-between-joojaa-and-sankara-narayan). – joojaa Apr 28 '21 at 06:03

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