Talk:Cam (mechanism)

Short

The article about cams is much too short. -Unsigned/Undated

this article is sad

it's much too short. i agree with the last person who started this discussion. and i need to base a whole research paper on this too! No picture either :( Davidbod 00:51, 28 May 2006 (UTC)

• Added in a nice animation from the camshaft article, makes it a bit better. 209.47.162.98 14:48, 22 August 2006 (UTC)

It should use simple diagrams to show how it works.

Why does the "prime circle" reference point to a rock band? Was a dis-ambiguity link removed?

"The reason the cam acts as a lever is because the hole is not directly in the centre, therefore moving the cam rather than just spinning." It's a vague statement - I have observed many cams rotating in machines with a hole in centre. Altaf —Preceding unsigned comment added by 203.81.231.159 (talk) 06:31, 20 March 2009 (UTC)

Redux

This article was written so poorly I can't tell the difference between vandalism and poor writing/a poor attempt to explain what the purpose of cam lobes are...this article IS sad —Preceding unsigned comment added by 67.246.13.226 (talk) 02:05, 1 June 2009 (UTC)

Actually, one just needed to look at the history to see what the vandalism edit shortly before yours had overwritten (ie, most of the lede). The article wasn't quite as sad as you thought. I reverted to the pre-vandal version. Cheers, — ¾-10 05:18, 1 June 2009 (UTC)

Definition

Brushed up definition; it was way too hard to understand properly eg by people without engineering skills. Now it states:

A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice versa. It is often a part of a rotating wheel (eg. an eccentric wheel) or shaft (eg a cylinder with an irregular shape) that strikes a lever at one or more points on its circular path. —Preceding unsigned comment added by 91.176.221.125 (talk) 09:41, 13 September 2009 (UTC)

References

Image

File:Rotary to linear motion conversion cam.JPG

Added this [first] image. Needs CGI'ing dough.

I've removed this image, because it does not depict a cam, but rather an eccentric. I watched the source you listed on the image and I heard them refer to the eccentric as a cam, which is just incorrect. Wizard191 (talk) 19:50, 13 September 2009 (UTC)

I agree. The first image appears to be a complicated slider crank, not a cam nor an eccentric. - AndrewDressel (talk) 19:31, 20 September 2009 (UTC)

Changed my original picture and uploaded it at eccentric page. Added this [second] image instead. - 91.176.222.111 (talk) 16:29, 20 September 2009 (UTC)

The second image, Rotary to linear motion conversion cam 1.jpg (replaced with a dupe on commons so name is changed --MGA73 (talk) 08:11, 4 October 2009 (UTC)), looks like a crank, as in crankshaft, to me. -AndrewDressel (talk) 18:49, 20 September 2009 (UTC)

Andrew, you are quite right, that is not a cam, but rather a crank. Wizard191 (talk) 18:16, 21 September 2009 (UTC)

Thanks for the correction, changed the images

KVDP (talk) 11:26, 23 September 2009 (UTC)

new reference

When i get some time, I'd like to add a displacement diagram to the article. This handbook should be referenced in this article: C. H. Moon, Cam design, a manual for engineers designers and draftsmen, AMCAM, 1961 ---BAxelrod (talk) 01:58, 9 July 2010 (UTC)

cam pulley

Can we talk about this concept? It's what the nautilus cam used I think. DB (talk) 01:13, 28 April 2011 (UTC)

Crossbow trigger mechanism

A crossbow trigger mechanism does not rotate around its own axis. Thus it is not a cam. You should not let your China first syndrome get the better of your judgment. Gun Powder Ma (talk) 09:30, 14 April 2020 (UTC)

Sounds like you don't know how the Chinese crossbow trigger mechanism works. The book I quoted shows pictures, if the trigger mechanism doesn't rotate around its axis then the trigger wouldn't even work, but it does work because there's enough replicas of it working. As for your accusation of China first syndrome, you do realize I changed it back so that Western discoveries came first, right? [here]. And I've added some non-Chinese inventions too such as [here] or [here]. Looking at your past history, when's the last time you changed something back so that a non-Western achievement comes first? So don't even start. ArchimedesTheInventor (talk) 18:38, 14 April 2020 (UTC)

I know how the mechanism works. The trigger does not make a full turn, much less does it make repeated turns. Nor can you equate the firing of the crossbow, where the bolt leaves the entire device to never return back, to linear motion. A cam is an integrated machine element that works with full turns and continuous motion. You are now outright pushing crank theories. Gun Powder Ma (talk) 23:24, 16 April 2020 (UTC)

You're using your personal definition of cam and personal understanding of the Chinese crossbow trigger. This article itself even gave a "Sash window lock" as an example of a cam, in which case it don't make a full turn either. "Cam locks" are pretty common nowadays, they don't do full turns. And they do "repeated turns" in the way that crossbow trigger mechanisms do "repeated turns": Manually. Also, the definition in the article says that cams is "used especially in transforming rotary motion into linear motion", it did not say that cams are "only used in transforming rotary motion into linear motion", it can transform other types of motion that doesn't have to be linear. "Especially" is not the same as "Only". Anyway, I have a verifiable source regarding the Chinese crossbow trigger as an example of a cam mechanism. Until you find a better quality source which says otherwise about the Chinese crossbow trigger, then it stays. I'm not holding your personal opinion regarding the cam above verifiable sourcing that's specifically about Ancient Chinese Mechanisms with Illustrations. ArchimedesTheInventor (talk) 22:00, 16 April 2020 (UTC)

The trigger mechanism does not even make a quarter turn. And where is the linear motion? And how do both reciprocate? Gun Powder Ma (talk) 08:53, 18 April 2020 (UTC)

ArchimedesTheInventor, please quote the passage from your source which states that the trigger mechanism uses a cam.· · · Peter Southwood ^(talk): 13:27, 18 April 2020 (UTC)

Gun Powder Ma, Please present your evidence that the mechanism is not a cam. Bear in mind that the definition given in the article is not necessarily complete. · · · Peter Southwood ^(talk): 14:10, 18 April 2020 (UTC)

On pg 70 in Mechanisms in Ancient Chinese Books with Illustrations:

Cam mechanisms had been used fairly early in ancient China. About 600 BC, the trigger mechanism of the crossbow was an intricate cam-shaped swing arm. Hence, the invention of the cam may be traced back to the Spring-Autumn and Warring Periods (770-222 BC). Figure 4.6a shows a bronze trigger mechanism found in the excavation site of Changan City of the Qin Dynasty (221-206 BC), now Xian City in Shanxi Province. Figures 4.6b-d show the corresponding original illustration, structural sketch, and chain of the trigger mechanism respectively.

On pg 38 of the same book:

A cam (Ka) is an irregularly shaped link that serves as a driving member and it imparts a prescribed motion to a driven link called a follower (Kaf). The trigger of an ancient Chinese crossbow is a typical cam mechanism, and it can be dated back to the 6th century BC (Zhang et al. 2004).

Hope that helps. ArchimedesTheInventor (talk) 10:30, 18 April 2020 (UTC)

@Peter Southwood: Negative evidence is by its very nature harder to provide but this monograph from Antiquity (journal) discusses Chinese crossbow trigger mechanisms in depth without a single time referring to them as "cams". Gun Powder Ma (talk) 22:27, 18 April 2020 (UTC)

The Chu repeating crossbow of 400 BC also seemed to have used a cam (different design than the stereotypical Zhuge Nu repeating crossbow). From page 750 and 754 of Advances in Reconfigurable Mechanisms and Robots I, by Jian S Dai, Xianwen Kong, Matteo Zoppi, Published June 13, 2012, Springer London:

(pg 750) Based on archaeological finds, the repeating crossbow consists of six members and first appeared around 400 BC in the tomb in Hubei Province as shown in Fig. 67.1b. The magazine fixes on the top of the stock and contains twenty bolts, and the device is worked by moving the input link forward and backward. Two bolts can be shot at once in the reciprocating motion of the input link. Since the tomb belonged to Chu State during the War States Period (475-221 BC), the device was named Chu State repeating crossbow.....

(pg 754) The structural characteristics of the device are:

1. It is a cam mechanism with five-member or six-member

2. The frame (Kf) is a ternary link and adjacent to a pair of binary links

3. The bow (Kbc) is a binary link and adjacent to the frame (Kf) with a bamboo joint (Jbb).

4. The bowstring (Kt) is a binary link and adjacent to the bow (Kcb) and a percussion link (Kpl) or a connecting link (Kl) with thread joints (Jt)

5. The input link (Kt) is adjacent to the frame (Kf) with a prismatic joint (Jpx)

6. The percussion link (Kpl) is adjacent to the frame (Kf) with a cam joint (Ja)

ArchimedesTheInventor (talk) 19:34, 18 April 2020 (UTC)

This monograph happens to reconstruct a Chinese crossbow mechanism from the said Chou dynasty, but does not call it once a cam: E. Morton Grosser: The Reconstruction of a Chou Dynasty Weapon, Artibus Asiae, Vol. 23, No. 2. (1960), pp. 83-94. Nor does he in his follow-up article: E. Morton Grosser: A Further Note on the Chou Dynasty Pistol-Crossbow, Artibus Asiae, Vol. 23, No. 3/4. (1960), pp. 209-212.

And this author, who has been compiling over a hundred specimen of Chinese crossbow mechanism, does not refer to the mechanism either as a cam (K.P. Mayer: On Variations in the Shapes of the Components of the Chinese 'Nu-Chi' (Crossbow Latch), T'oung pao, vol. 52 (1965/1966)), pp. 1-7 (7):

The Chinese nu-chi (crossbow latch) has three moving parts:

• (a) the ear-shaped piece
• (b) the claw-like sears or teeth, also called klou hsüan with a vertical upward projection which is called the regulator kuei, also called wang shan and
• (c) the hsüan-tao, also called pan chi trigger.

These three moving parts in most specimens work in a kuo (metal housing) and in all cases are held in position and also pivot on cotterpins.

That makes it four monographs from reputable journals that discuss the trigger mechanism but never use the term. Gun Powder Ma (talk) 06:26, 19 April 2020 (UTC)

A cam (Ka) is an irregularly shaped link that serves as a driving member and it imparts a prescribed motion to a driven link called a follower (Kaf). The trigger of an ancient Chinese crossbow is a typical cam mechanism, and it can be dated back to the 6th century BC (Zhang et al. 2004).Thank you ArchimedesTheInventor. That is sufficient for my needs. The definition given is very broad, but within the scope of my experience as a mechanical engineer, and supported by other apparently reliable sources. It may even exclude some mechanisms which would also be considered cams. Until an authoritative source can be found that rebuts that definition, I consider the point to be made. The mechanism shown in the linked video above fits that description. It may not be a "typical" cam as claimed, but it has the functional characteristics of a cam according to the quoted definition, which is sufficient. The more detailed descriptions appear to be referring to an illustration, and without inspecting the illustration I cannot say much about it.

Gun Powder Ma, One acceptably reliable source making a claim is sufficient in the absence of any reliable sources refuting the claim. There are many valid ways to describe cam mechanisms without ever using the word "cam". The choice of words often depends on the background of the author and the expected audience. An archaeologist my use a different term to an engineer, and both may be right, and a translator may use a different term again, to remain closer to the original. I hope this explanation is sufficient to settle this point. As a further illustration of this phenomenon, your example below uses the term "crossbow latch" which could also legitimately be termed a "lock", a "trigger mechanism", or a "release mechanism". Cheers, · · · Peter Southwood ^(talk): 08:46, 19 April 2020 (UTC)

Thank you Pbsouthwood, I agree that "there are many valid ways to describe cam mechanisms without ever using the word "cam". The choice of words often depends on the background of the author and the expected audience." Gun Powder Ma wanted a qualified opinion [here] and [here]. Because you are a mechanical engineer I'd say your opinion is more than qualified and even the video he shared [here] as you've stated fits the definition. Since you determined that my sourcing is sufficient, I think it is in good taste now to add back the citations that's been deleted from the article. ArchimedesTheInventor (talk) 09:03, 19 April 2020 (UTC)

Pbsouthwood. Thanks Peter. Upon your suggestion that this is "not a typical cam" I added a source that supports this view. Gun Powder Ma (talk) 23:17, 20 April 2020 (UTC)

PS: I also replaced the bit on the Greek cams that I added many years ago with the ultimate source, Lewis 1997. Gun Powder Ma (talk) 23:24, 20 April 2020 (UTC)

I said it may not be a typical cam as I have no reference defining a typical cam, and have no strong personal opinion that such a thing exists other than in the eye of the beholder, based on their personal experience. I would expect the lay person to generally consider a typical cam to be a continuously rotating mechanism because the automotive camshaft is familiar to a lot of people alive today, but I have no idea of what the actual numbers of different types of cam over the ages have been. A typical cam would have varied through history and by cultural background, depending on what was locally in use at the time. Typical is a word to be careful with in an encyclopedia.

The video shows a plastic replica of what I have assumed to be an ancient Chinese mechanism, as that is how it was described. I have not seen the original sources for the replica. Assuming that is is conceptually accurate, each of the moving parts of the trigger mechanism has an axis upon which it rotates, including the one which functions as a cam, though none of them can rotate continuously. However, continuous rotation is not a defining characteristic of a cam. I would also be careful about describing anything as an ultimate source, as it is unclear what that is intended to mean. · · · Peter Southwood ^(talk): 06:13, 21 April 2020 (UTC)

cam mechanisms appeared in water-driven pestles by the latter half of the Western Han Dynasty Please check on this mechanism as it seems likely that it uses a continuously rotating camshaft driven by a waterwheel. If it does not, I would be really interested to know how it was done. · · · Peter Southwood ^(talk): 06:50, 21 April 2020 (UTC)

It uses continuous rotating motion driven by a waterwheel here on page 2, and here on page 71. As for GPM's new edits, Needham mentioned nothing about how the Chinese trigger "did not rotate around its axis", I checked the source and it mentioned nothing about it. It's just something that GPM claimed when he first joined this talk page, and something I had already explained to him was factually incorrect. Needham did not support him in such a claim. That was the last straw and why I opened an administrator incident. Which means Gun Powder Ma needs to give the relevant quote from Lewis in "Millstone and Hammer", to prove that he mentioned a Hellenstic 3rd century automaton with "cams that rotated continuously and functioned as integral machine elements".ArchimedesTheInventor (talk) 18:55, 21 April 2020 (UTC)

For me it is simply that a cam has to be a curved actuator, inducing a cyclic motion in the NEXT item up the chain in the mechanism. The ones we are most familiar with are revolving cams, but they can just be a curved surface which cycles such as those found in printing machines for example.

I would not say that anything I have seen in these examples is a cam, they are simply actuating by sliding notch and peg/spigot. Chaosdruid (talk) 19:05, 20 February 2021 (UTC)

TT

Ty 72.175.182.129 (talk) 06:15, 24 November 2021 (UTC)

Requested move 2 January 2024

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this discussion.

The result of the move request was: Moved (closed by non-admin page mover) BegbertBiggs (talk) 22:02, 9 January 2024 (UTC)

---

• Cam → Cam (mechanism)
• Cam (disambiguation) → Cam

– (open to other dab modifiers) Too many other meanings for this one to be primary. Doesn't clear the pageviews field, and while common in Google Books and Scholar results, so are clippings of camera and various proper nouns. Hameltion (talk | contribs) 17:53, 2 January 2024 (UTC)

• Support per nom. In ictu oculi (talk) 17:32, 4 January 2024 (UTC)
• Support per nom. Crouch, Swale (talk) 18:47, 4 January 2024 (UTC)
• Strong support. This is a highly ambiguous term. BD2412 T 20:57, 5 January 2024 (UTC)
• Support per nom. No primary topic. -- Necrothesp (talk) 15:49, 8 January 2024 (UTC)
• I just wanted to mention that the pageviews field as linked above excludes people named Cam, yet if you add some of the more popular ones, like this, the graph goes completely out of whack because one of them is wildly more viewed than anything else. --Joy (talk) 16:42, 9 January 2024 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.