In contrast, while the swinger has some other advantages that the hitter does not have, the swinger wouldn't have the advantage of a "prestressed" clubshaft - because the nature of the physics is different- the "pulling" on the shaft in this context creates a "bowing up" of the shaft- not a "bowing forward" of the shaft that happens when one is pushing/hitting.
It is interesting that Homer said the Swinger's Clubshaft is also stressed, but during the change of direction at Start Down.
Even though the "bowing up" effect does bend the shaft, it is not regarded as a prestressed Clubshaft? So the term prestress refers to the stress placed on the shaft in only one dimension? There are lots of Swingers with a bent shaft at Impact, but this is obviously not what Homer was getting at.
It is interesting that Homer said the Swinger's Clubshaft is also stressed, but during the change of direction at Start Down.
Even though the "bowing up" effect does bend the shaft, it is not regarded as a prestressed Clubshaft? So the term prestress refers to the stress placed on the shaft in only one dimension? There are lots of Swingers with a bent shaft at Impact, but this is obviously not what Homer was getting at.
Just to throw it out there, here's what I have gleened from my reading about impact dynamics from a clubmaking perspective. It was interesting that the "prestressed" condition is considered bent away from the target, because it is pretty well documented that for 95% or more of golfers the shaft at the head end is actually bent forward (and down) at impact. There's video, stills and deflection graphs (True Temper Shaft Lab) that have shown this.
Regarding the deceleration issue, C&S tested a clubhead on a hinge at the end of a shaft and concluded that it made no difference to the ball flight. The still impact pictures are very interesting. Basically, they conclude (as have others including Jorgensen mentioned by Steph) that the head at the point of impact basically acts as if it is disconnected from the shaft. That's why in the impact formula (conservation of momentum), the weight of the shaft is not considered - only the head. C&S also figured that the player doesn't feel the impact until the ball is well on its way.
I don't think this at all negates the imperatives of TGM - these factors in my view aren't really necessary to support the model and I'm guessing HK did not have access to some the equipment that has been used to characterize impact and shaft bending.
One area where the physics guys do basically support Homer is in the ball flight laws in which TGM is somewhat at odds with the more popular ball flight laws put forth by John Jacobs and others but that's probably another discussion....
It is interesting that Homer said the Swinger's Clubshaft is also stressed, but during the change of direction at Start Down.
Even though the "bowing up" effect does bend the shaft, it is not regarded as a prestressed Clubshaft? So the term prestress refers to the stress placed on the shaft in only one dimension? There are lots of Swingers with a bent shaft at Impact, but this is obviously not what Homer was getting at.
Prestressed- means stressed before it's going to be stressed. So it's only in reference to that dimension that the ball will cause the shaft to be stressed.
When you say Homer said the Swinger's Clubshaft is also stressed- Which may be very accurate- where did he say that- where's the reference being used for that statement?
When you say Homer said the Swinger's Clubshaft is also stressed- Which may be very accurate- where did he say that- where's the reference being used for that statement?
Thanks,
Mike
Second paragraph of 6-C-2-A.
"The Clubshaft is stressed by the weight of the Clubhead resisting a change in its direction or velocity – which is Acceleration. Acceleration bends the Clubshaft during Radial Acceleration (10-19-A). Change of direction bends it during Longitudinal Acceleration (10-19-C) which may be, or just include, the Clubhead Lag Pressure Point in addition to its main function of Acceleration Control."
"The Clubshaft is stressed by the weight of the Clubhead resisting a change in its direction or velocity – which is Acceleration. Acceleration bends the Clubshaft during Radial Acceleration (10-19-A). Change of direction bends it during Longitudinal Acceleration (10-19-C) which may be, or just include, the Clubhead Lag Pressure Point in addition to its main function of Acceleration Control."
It is interesting that Homer said the Swinger's Clubshaft is also stressed, but during the change of direction at Start Down.
In a 1981 GSEM Class discussion, Homer Kelley referred to two types of Clubshaft Bend for Swingers. The first -- "Acceleration Bend" -- stresses the top of the Shaft during the Start Down. During the second -- "Release Bend" -- the stress is opposite the Acceleration Bend as the toe of the Club attempts to get in line with the #3 Pressure Point.
The Hitter's stress is at the back of the Shaft and does not vary.
In a 1981 GSEM Class discussion, Homer Kelley referred to two types of Clubshaft Bend for Swingers. The first -- "Acceleration Bend" -- stresses the top of the Shaft during the Start Down. During the second -- "Release Bend" -- the stress is opposite the Acceleration Bend as the toe of the Club attempts to get in line with the #3 Pressure Point.
The Hitter's stress is at the back of the Shaft and does not vary.
Love it when you post these little gems, but why the "toe" of the Club, and not the Sweet Spot?
Last edited by armourall : 05-11-2006 at 12:11 PM.
Love it when you post these little gems, but why the "toe" of the Club, and not the Sweet Spot?
I used the phrase "Toe of the Club" because that is exactly the phrase Homer Kelley used. I wondered the same thing as I wrote the post and here would be my answer (not his):
Remember, during Release, both the Clubshaft and the Toe of the Club are rotating around the Sweetspot. And the Toe of the Swinger's Club is rotating counter-clockwise trying desperately to get 'in line' with the Sweet Spot and #3 Pressure Point for Horizontal Hinging through Impact. Hence, Homer's reference to the Toe causing the Release Bend.
Interesting sidelight:
That's why those old-timey wooden golf clubs were made with such long Toes. They were virtually impossible to Angled Hinge!
If it is only the stress of the clubshaft (which stiffens the shaft) that helps to resist impact deceleration, why does it matter in which direction it is stressed?
Hybrid Mode
