Talk:Center of percussion

Redirect

I think 'centre of percussion' should redirect here but I do not know how to do it 130.88.168.247 (talk) 18:00, 14 January 2008 (UTC)

Warning

The derivation presented here and in reference 1 differ in their use of the moment of inertia. In this article, I is about the CoG, while in the reference I is about the pivot. Both derivations are correct as long as they are not mixed together. Turidoth (talk) 00:08, 4 August 2008 (UTC)

A or b ?

IMHO I think that the formula should have been soved for A, not for b as b is already given as the point of impact of F. Huibc --84.197.88.254 (talk) 14:42, 30 January 2009 (UTC)

The important distance to be found is the distance of the centre from the pivot. This distance is also the length in the pendulum formula. Dbfirs 08:47, 7 March 2009 (UTC)

impact under zero gravity

So would I be right in thinking that, if a racket (say) which is positioned vertically in outer space and under zero gravity were hit normally at the Center of Percussion, the resulting motion of the racket would be purely rotational (ie no translational motion) and the racket would rotate around an axis at the handle of the racket only? Thanks —Preceding unsigned comment added by 91.111.20.10 (talk) 13:27, 18 April 2009 (UTC)

Only partly right. It is not possible to produce purely rotational continuous motion by a single impact on a free object (regardless of whether it is in outer space or under gravity), but the racket would rotate about an axis through the handle initially, causing the centre of mass to start moving in the direction of the impact as the racket continued to rotate with constant angular speed. It is usual to regard this motion as linear motion of the centre of mass plus rotation about the centre of mass, but it amounts to the same thing.
To produce pure rotation, you would have to confine the racket with an axis through the handle. Initially, at the instant of the blow, there would be no force at all at the axis, but a force would appear as the racket rotated, preventing linear motion of the handle and constraining the motion to pure rotation.
The same applies to a racket suspended by its handle under gravity. If it is hit at its centre of percussion, there is no horizontal force at the axis initially, but one gradually builds up to keep the racket moving in a vertical circle. Dbfirs 09:53, 19 April 2009 (UTC)

Thank you - most helpful. —Preceding unsigned comment added by 91.111.20.10 (talk) 21:20, 19 April 2009 (UTC)

Constantinesco torque converter

There isn't a distinct article on the Constantinesco torque converter, which does operate through the way that impulses transfer through lever arms that have mass and moments of inertia, which is just precisely what makes centres of percussion work as they do. However, that link just redirects to Constantinesco (automobile), so I simply put in a "see also" straight to that. As it was just a "see also", it seemed wrong to put in clarifying text there. Does anybody have any constructive suggestions on how to bring out the connection better? PMLawrence (talk) 10:13, 14 June 2013 (UTC)

The car article doesn't mention centre of percussion, nor do the other articles about the transmission system that I've found elsewhere, but I can see why the concept would be important in the design. Do you have plans to create an article on the Constantinesco torque converter, with an explanation of how centre of percussion is relevant? If so, I would strongly support a link to this article. Dbfirs 14:58, 14 June 2013 (UTC)

I once tried to set up a section on that within the torque converter article proper, with Constantinesco torque converter redirecting to that, but other editors pushed that down to a mere mention of the Constantinesco (automobile). So the only viable thing at the moment is the car article itself; anything more detailed gets shot down. PMLawrence (talk) 01:20, 15 June 2013 (UTC)

(split replies)

Your contributions to the torque converter article are still there. Nothing has been "shot down". Dbfirs 06:51, 15 June 2013 (UTC)

That is incorrect. I once attempted to put a proper discussion in there. Others removed it and wouldn't hear any suggestions to the contrary. They were willing to allow me to put in a mere mention of the Constantinesco approach instead, but it is wrong to suppose that that means my "contributions to the torque converter article are still there". It just means that a gravestone over those is there. PMLawrence (talk) 09:30, 16 June 2013 (UTC)

Your discussion is still there, as is your contribution. What was removed? I see that you disagree with Andy Dingley on whether or not the Constantinesco design is an example of continuously variable transmission. (I'm inclined to agree with you that it is.) Dbfirs 14:52, 16 June 2013 (UTC)

Although I agree with Andy Dingley that the Constantinesco torque converter does vary its torque continuously, I disagree with him that this makes it a continuously variable transmission in the ordinary sense of the term. That is because the Constantinesco torque converter varies its torque in an endogenous way rather than in an exogenous way according to an outside control parameter, the way that a continuously variable transmission does it. (Of course, in a practical car a continuously variable transmission may be embedded within a larger subsystem that provides that control, and then that larger subsystem does behave as a torque converter - but the smaller subsystem does have distinct behaviour.) PMLawrence (talk) 02:57, 17 June 2013 (UTC)

OK, I suppose it depends on exact definitions. Dbfirs 06:53, 18 June 2013 (UTC)

Andy Dingley just moved the mention to the end of the lead. You are still at liberty to create the main article. Dbfirs 06:51, 15 June 2013 (UTC)

That, too, is incorrect, unless the editors who got in the way have moved on. Notice, that article does exist, in a manner of speaking - as a rump, providing a redirect. Attempts to provide more were made but thwarted. PMLawrence (talk) 09:30, 16 June 2013 (UTC)

I can't see any thwarted attempts, but please let me know if I've missed something that was deleted. Dbfirs 14:52, 16 June 2013 (UTC)

That's weird. I can't see any trace of my own attempts to describe Constantinesco's work earlier than about two years ago. From memory, I once tried to provide a Constantinesco torque converter article (or an article that covered it, I forget precisely), and it got removed. This was a time when google couldn't find Constantinesco but some older search engines could; as I recall, the wikipedia edits were thwarted on the grounds that Constantinesco wasn't out there. Later, I tried putting stuff in the ordinary torque converter article (this seems to be where the currently recorded story starts, as tracked back about two years from current articles), once I saw that there was Constantinesco material around by then, with a view to putting in a basic reference/stub and working it up into more detail. That approach immediately got nobbled at the starting point, since Andy Dingley believed that the Constantinesco torque converter didn't qualify as something to be covered within that article itself rather than elsewhere, so I remarked on it in the talk, removed an inaccuracy that had been inserted, and gave up further attempts rather than sink any effort into a further round of editing stress to match the first one (have a look at what happened to the major editor on the gyroscopic monorail article! with that sort of shooting down around, I no longer put any effort in anywhere that I have been bitten more than once). If you can currently get something underway without getting shot down I would gladly start contributing - but I will not invite flak by being the first to stick my head out. PMLawrence (talk) 02:57, 17 June 2013 (UTC)

An admin might be able to find the deleted content for you. It seems a pity that it has been lost. I can understand your reluctance to start again after a bad experience here. I don't know enough about the technicalities to feel confident in writing the article, especially if there are snipers watching it! Perhaps we could just flag a requested article and see what happens? Dbfirs 06:53, 18 June 2013 (UTC)

I also got nobbled that way when trying to contribute to quarter square multiplication, when a sniper refused to accept that what I had provided was backed rather than original research - and stuck to that view even after I had got material emailed to me from an actuaries' association to substantiate that what I had outlined really had been done in real life! So now, I just leave the ball in others' courts. I do sometimes wonder what people's positions would be if I offered material I had written thirty years ago for an article, on the grounds that it only derived ultimately from me but had been through the vetting of another organisation's editing. (I thought of that because I did write something relating to hydrofoils for the Amateur Yacht Research Society, that did make use of centres of percussion.) PMLawrence (talk) 13:00, 21 June 2013 (UTC)

I'm sure I'm not the only reader who would find it interesting. See Wikipedia:Articles for creation, or just create the article (there's no need to have it approved first), though you might like to prepare it in user space (e.g. User:PMLawrence/Constantinesco torque converter) so that we can make sure it has good references before moving it to main space. If you don't feel able to create a full article just yet, perhaps you could expand the mention at Continuously variable transmission to a full paragraph? Dbfirs 06:51, 15 June 2013 (UTC)

Pivot point at COG

If pivot point seat at COG of rigid object, can we still find a center of percussion on it.

No, if the pivot is at the centre of gravity, then any impact will cause a reactive force at the pivot. Dbfirs 12:26, 13 October 2014 (UTC)

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