...However, I have a hard time understanding how the hosel rotates around the sweetspot-to-grip axis - especially with respect to the Robot-Fit golf club testing machine.
Firstly, if the toe of the club is traveling counter-clockwise (closing Clubface) and the Sweet Spot is the COG of the club, it would follow that the hosel would be traveling counter-clockwise around the same axis.
An analogy that I use is painting a line with a wide paintbrush. Start painting a thin line with the wide brush. As you continue the line, start twisting the brush so that the line becomes wider. Finish the line with the line becoming thinner. The center of the brush (the Sweet Spot) traveled on the same line. The top and bottom of the brush (the toe and heel) rotated around the center, and they travel from on-to-off-to-on the line.
Secondly, as far as the robot goes, it's been so long since I've given a robot a lesson that I can't remember what it does. All kidding aside, I made a phone call to a friend that works for a company that has one. I'll ask him about it as soon as he calls me back.
I can understand what you state about the hosel rotating counterclockwise around the sweetspot axis when the clubface closes - from a conceptual perspective. However, it doesn't "feel" like the hosel is rotating around counterclockwise when I swing through impact - even though I can understand the concept.
I can easily understand the painting brush analogy because the handle is in the center of the brush, and the brush ends are rotating around the sweetspot which is inline with the handle - because in that situation the handle stays centralised while the brush twists. I find it harder to mentally picture the situation if the handle is at one end of the brush and there is a straight line relationship between the grip end of the handle and the one endpoint where the handle attaches to the extreme end of the brush - because the handle will have to twist with that end of the brush.
I can understand what you state about the hosel rotating counterclockwise around the sweetspot axis when the clubface closes - from a conceptual perspective. However, it doesn't "feel" like the hosel is rotating around counterclockwise when I swing through impact - even though I can understand the concept.
I can easily understand the painting brush analogy because the handle is in the center of the brush, and the brush ends are rotating around the sweetspot which is inline with the handle - because in that situation the handle stays centralised while the brush twists. I find it harder to mentally picture the situation if the handle is at one end of the brush and there is a straight line relationship between the grip end of the handle and the one endpoint where the handle attaches to the extreme end of the brush - because the handle will have to twist with that end of the brush.
Jeff.
Then, use a paint roller. Slide the roller, twist it until it rolls, then keep twisting until it slides. It's the same analogy, with an imaginary COG.
Have you seen a lathe in action, and do you get that analogy?
The CG of the club (any club) is not on the sweet spot ... its at a point in space. But the club face sweet spot is connected to the hands via the hossel and shaft not some imaginary line connecting it. If it were not constrained by hands gripping the shaft connected to the hossel, the face would want to open (not close) on the downswing as the inertia caused it to want to line up with hossel on the plane.
I have to disagree. I would say it almost exactly opposite. The Clubshaft should never remain on-plane when it is swinging through Impact. If the Clubshaft stayed on Plane, it would result in a shank. The club has a CG or CM, which is an imaginary line that extends from Sweet Spot through the #3 pressure point.
“2-F…
Regardless of where the Clubshaft and Clubhead are joined together, it always feels as if they are joined at the Sweet Spot – the longitudinal center of gravity, the line of the pull of Centrifugal Force. So there is a “Clubshaft” Plane and a “Sweet Spot,” or “Swing”, Plane. But herein, unless otherwise noted, “Plane Angle” and “Plane Line” always refer to the Center of Gravity application. Study 2-N. Except during Impact, the Clubshaft can travel on, or to- and – from, either Plane because the Clubshaft rotation must be around the Sweet Spot – not vice versa. So Clubhead “Feel” is Clubhead Lag Pressure (6-C) and is a Golfing Imperative. (2-0). If Lag Pressure is lost the Hands tend to start the hosel (instead of the Sweet Spot) toward Impact – that mysterious “Shank.” When in doubt, “Turn” the Clubface so both the Clubshaft and Sweet Spot will be on the same plane at Start Down. Both Planes always pass through the Lag Pressure Point. Study 6-C-2-A.”
guyz, what does the last part mean? about the when in doubt, turn the clubface so both the shaft and sweet spot on same plane at start down? how dos that stop a shank? how do you feel it happening? is it a fanning of the face? what is turn the clubface?
thanks
(ok i admit, i shanked a few last outing...need help!!!
Hold a golf club between the tips of your fingers at the end of the grip so the club dangles vertically. Now twist it in your fingers, note how the shaft moves around the COG of the club, not the head moving around the hosel.
A robot with fully flexible wrist joints won't know where the shaft is...it will know where it (the robot) mounts to (grips) the club, and where the COG is. As the club is swung then the plane through the COG will be what the robot can "sense" as centrifugal force will not be pulling down the shaft, but rather through the COG.
The CG of the club (any club) is not on the sweet spot ... its at a point in space. But the club face sweet spot is connected to the hands via the hossel and shaft not some imaginary line connecting it. If it were not constrained by hands gripping the shaft connected to the hossel, the face would want to open (not close) on the downswing as the inertia caused it to want to line up with hossel on the plane.
Since I'm the only alcohol virgin on this website, I may be the only one that remembers this trick. They don't call me the lifetime designated driver for nothing. I remember things that happen in bars.
The COG of the fork and spoon is not inside the fork or spoon. But, we can identify that the Z axis of the COG runs through the edge of the glass, where the toothpick rests. I'm sure that this is the point that you're making. But, it's a nice trick to leave the waitress. It's a real head scratcher.
There can be a rotational center that runs through the COG, and this is what we're seeking. We're looking on the Z axis, as a center of rotation could be found on other axes. The Clubshaft cannot be a center of rotation, since there is nothing on the underside of the hosel to counterbalance the Clubhead.
There is nothing so sad as a beautiful theory destroyed by one awkward fact.....
Unless a golfer's grip slips (not recommended) the clubface maintains the relationship it had at the time the grip was taken to the back of the left hand. Because it is anatomically impossible to get the left hand "back and up" there (top of the backswing) with out some rotation, the face fans open on the way up and closes again on the way back down. (And it is unfortunate that the process is likely not anywhere near as precise as with a set of high quality gears... ala iron byron). This has nothing to to with angular momentum vectors axis of rotation or lathe imbalance forces either.
Because it is anatomically impossible to get the left hand "back and up" there (top of the backswing) with out some rotation, the face fans open on the way up and closes again on the way back down. (And it is unfortunate that the process is likely not anywhere near as precise as with a set of high quality gears... ala iron byron). This has nothing to to with angular momentum vectors axis of rotation or lathe imbalance forces either.
So, regarding your "beautiful theory", are you suggesting that the rate of closing is always constant in the Downstroke?
Instead of having "nothing" to do with Angular Momentum, would a delay in the closing have something to do with Angular Momentum and/or an axis of rotation?
So, regarding your "beautiful theory", are you suggesting that the rate of closing is always constant in the Downstroke?
Instead of having "nothing" to do with Angular Momentum, would a delay in the closing have something to do with Angular Momentum and/or an axis of rotation?
I'm not suggesting anything is constant in a real golfer... but yes.. the gears make the rate proportional to the arm rotation angular velocity and.. its not my theory gone bad .... its yours Yodasluke.
As I was thinking about issue this I asked myself: why would they would they design clubface rotation into the swing machine since it complicates the machine (one more DOF to contend with). I made a call and the answer was because that was the way Byron Nelson (the model) did it and also because they found they needed gearing there to help manage the deceleration. (It took Battelle 3 years to develop the iron byron and initially they were breaking a lot of shafts). Then I asked myself why does iron Byron Nelson and everyone else fan the face open on the backswing? The answer to that is... TRY IT. You can't not.
As far as leaving the face open at impact goes (delay in closing?) bottom-line is golfer's left hand is not getting back where it was at takeaway.
Many golfers look a lot different at impact than they do at setup... hands may be way forward... shoulders too open or too closed etc. They can compensate for different impact positions by intentionally (closing usually) the club face at set up. (You would be amazed at how "toe-in" my dad sets up with his driver but it works for him... he's ALWAY down the middle) That way when they get back to impact the face is aligned where they need it to be.
Get the back of your left hand back to facing the target at impact (like it was at se-up) and your club face will be fine......
All kidding aside, I made a phone call to a friend that works for a company that has one. I'll ask him about it as soon as he calls me back.
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