That is what I thought you meant, which is why I don't understand. If by cg you mean centre of mass, which is my understanding of the term, then how can it be in front of the face if all of the club, and hence its mass, is behind it. Am I missing something?
Whats the science behind a tour pitch
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That is what I thought you meant, which is why I don't understand. If by cg you mean centre of mass, which is my understanding of the term, then how can it be in front of the face if all of the club, and hence its mass, is behind it. Am I missing something?
Virtuoso
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Yes Leon, you are missing something. Where is the center of gravity of a boomerang?
Remember how long and heavy the hosel is on a forged lob wedge.
Jim Kobylinski
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I know brian well enough that it would be a diet coke and no cigarettes but i'm sure everything else fits lol
birly-shirly
New
Thanks for the explanation, Virtuoso - although I'm still trying to get my head round what it means.
If I've followed you correctly, then:
Backspin is the product of friction, but not dependent on where the ball contacts the face. So, is normal "sweet" contact optimal, or does it still help to have a low contact to take off some of the initial ballspeed?
Friction is only maximised for a certain clubhead speed at a certain delivered loft. Does friction relate to the "glancingness" of impact? In other words, is the open clubface and leftwards path also helping maximise friction and backspin? Is the relationship between spin loft and spin not such a simple one?
Maximal friction drags the launch angle down from the clubface normal towards the angle of attack, in the same way does friction also drag the ball's lateral launch somewhat more towards the leftwards clubpath, negating somewhat the directional influence of the open clubface?
Putting that altogether, the clubface would be more open and more lofted at impact than you would guess from the ballflight.
Do you think the ability to generate clubhead speed is a limiting factor for "decent amateurs" (say driver speed in region of 100mph)?
Hope I haven't wildly misunderstood what you were saying!
Cheers
BS
ok, thanks for the clarification. Of course if you include the hosel mass it will pull the cg forward & up. Still suprised it would be in front of the face, but happy to take your word for it.
Virtuoso
New
Hi Birly,
Well, spin (overall spin) is dependent on where it hits the face because the head will twist if the ball impacts a place other than the balance point/sweetspot, but, on this shot, it is not dependant in the sense that there is shear force created by gear effect. More like, if the ball hits the toe, it will spin to the right because the face opens (yes, this applies to the vertical plane as well).
BUT, these effects are substantially overwelmed in the vertical plane by the "glancingness" or "obliqueness" of the impact (as you've correctly pointed out). If you have a dynamic loft of 58 and your attack is 5 degrees down then your vertical face/path differential is huge. Does the friction caused by the obliqueness drag the launch angle down? Yes, but the face angle still dominates by a long shot.
BUT, is it just the obliqueness of the impact that creates the "perfect storm" of friction, and thus launch/spin? No, there is much more. Ball cover material, internal construction, groove properties (ie, things like what angle the edge radius of the grooves "see" the ball, and how many grooves), lie condition, moisture, type of grass, wind direction, angle and condition of the green that the player is hitting to, and probably more things I can't remember.
Do you have to swing left with an open face to hit this shot? Well, if you have a 60 degree lob wedge and you want to deliver about 58 degrees at impact, and you are going to have about 6 degrees foward lean of the shaft at impact, then don't you have to open the face some? If you take a 63 degree wedge and swing straight with a square face can you produce the shot? Why not?
Brian Manzella
Administrator
Nope.
The CG is NOT located in front of the face.
We called our expert, Paul Wood and he said this:
"...no, the cg is not in front of the face on an L-Wedge. I suppose that it would technically be possible to do something like that with tons of offset, a hugely heavy hosel and a few other weird design features but certainly not in any of our wedges and we're fairly sure not in any of our competitors either..."
The CG is NOT located in front of the face.
We called our expert, Paul Wood and he said this:
"...no, the cg is not in front of the face on an L-Wedge. I suppose that it would technically be possible to do something like that with tons of offset, a hugely heavy hosel and a few other weird design features but certainly not in any of our wedges and we're fairly sure not in any of our competitors either..."
Virtuoso
New
Brian, I stand corrected. And my apologies to Leon for leading him astray. Did Paul Wood tell you where it actually is located?
No worries, to be honest it made me curious more than anything.
You could get an idea of cg location by chopping the clubhead up into a few lumps of simple(ish) geometry (figuratively, no need to get out the angle grinder!) Say you have 3 lumps - the face, the sole and the hosel. These should be simple enough shapes to do a bit of maths. In each of 3 orthogonal directions multiply the mass of each lump by the distance of its centre of mass from some point of interest (eg the face centre). Add all of these multiples together, then divide by the total mass. This will give you the distance from the face centre to the cg. Simple right?
When I get access to my clubs, a calculator and a ruler I'll have a go at a rough calculation.
Virtuoso
New
No worries, to be honest it made me curious more than anything.
You could get an idea of cg location by chopping the clubhead up into a few lumps of simple(ish) geometry (figuratively, no need to get out the angle grinder!) Say you have 3 lumps - the face, the sole and the hosel. These should be simple enough shapes to do a bit of maths. In each of 3 orthogonal directions multiply the mass of each lump by the distance of its centre of mass from some point of interest (eg the face centre). Add all of these multiples together, then divide by the total mass. This will give you the distance from the face centre to the cg. Simple right?
When I get access to my clubs, a calculator and a ruler I'll have a go at a rough calculation.
Hi leon, this is the reference material I was using to make that assertion, but i made some mistaken assumptions and could have checked other resources closer to me to confirm/deny.
(Brian, don't know if posting this pic is a copyright infringment on Ralph Maltby so take down if need be)
Certainly shows cg in front of face. I wonder how accurately it is drawn though. Plus, as Brian mentioned, there looks to be a TON of offset in those irons.
birly-shirly
New
Thanks again for the lengthy explanation. Think I've got it now. Not necessarily in the sense of being able to hit it, but there you go.
Cheers
Virtuoso
New
Leon, I have a lot of respect for Maltby and I think he made those measurements correctly. How well the pic actually represents positioning I don't know even though the scale is 1 to 1. I'm sure that is an accurate measurement for whatever club that was, but I made a big mistake by assuming similar characteristics to modern forged L-wedges. Brain fart on my part.
BUT, my main point was that the cg is not far enough back from the face plane to create gear effect, as is the case with "most" irons. In this fact, I have complete confidence.
Doesn't the cg being 'behind' the face guarantee gear effect. It may be so small that it isn't significant, but I would think its still there.
Virtuoso
New
Hey Leon, the term gear effect relates to the ball spinning the opposite direction that the club is twisting. This only happens when the cg is far enough behind the face plane to make the clubhead rotate like a merry-go-round during a cg offset (ie mishit). The face is then sliding sideways across the ball.
With the cg close to the face, the club turns more like a see-saw....it falls away from the ball. This creates spin the same direction as the twist, and thus cannot be defined as gear-effect.
So, most irons: strike it on the toe, the face opens, the ball starts right and spins right.
Aside: on some cavity back, super wide-soled irons, the cg is actually back far enough to create slight gear effect.
yeah, I understand gear effect. That was kind of my point. If the cg is behind the face then for an off 'centre' hit which causes face rotation all points ON the face will, at least intially, have some component of lateral motion relative to the cg. It might be small, but its there.
Of course if the face rotates enough so the impact point 'passes' the cg, then relative lateral motion goes back the other way.
Somewhat counterintuitively, the component of lateral motion is greatest near the centre of the face for a given angle of rotation, but of course the nearer to the centre you hit it, the less rotation.
I haven't seen any numbers for degrees of rotation against impact location. I'd be interested if anyone knows.
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Virtuoso
New
yeah, i figured, with your background, you had a good handle on this stuff and you are absoloutely correct. If the cg is back of the face plane at all there will be some lateral movement of the face plane--ie, it won't just completely fall away like it would if the pivot point was right on the plane.
But, I think my point is that the equations are such that, on an iron, how much the face "falls away" overwelms how much it "moves sideways" and thereby can't generate sidespin the opposite direction. At some cg depth this is no longer true and gear effect happens.
But, I think my point is that the equations are such that, on an iron, how much the face "falls away" overwelms how much it "moves sideways" and thereby can't generate sidespin the opposite direction. At some cg depth this is no longer true and gear effect happens.
Virtuoso
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yes, I guess this is a bit of a cancelling out feature.
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