Hinge Action meets "The D-Plane"

[O.B.Left]

Doesn't anybody read "Search For The Perfect Swing"? It showed that with good friction during collision, the ball will start in a direction which is 65% of the difference between the clubface angle and the clubhead path, favoring the clubface angle. Reduced friction moves the starting direction closer to the clubface angle. The book debuted in '68, way before "The Physics of Golf", and one year before Homer's. The research findings are all being confirmed present day by TrackMan. I don't think Homer was too pleased that a golf "science" book came out one year before his life's work. I don't beleive that many TGM devotees have studied "Search", but if you want a plethora of good science regarding the impact collision and much else, including biomechanics of the golf swing, then read "Search". It can only aid your understanding of TGM.

Thats interesting, Max I'll have to try to get a copy, thanks. Did it talk about an impact interval then as opposed to it being instantaneous?

When you say "65% of the difference between the clubface angle and the path"........are you suggesting that was similar to TGM's at right angles to the leading edge? Leading edge to me implies left to right not up and down. And how would that compare to modern thinking in terms of left to right ? Isnt Trackmans 85% an up and down variance? Not sure, but Id be interested in knowing.

[John Graham]

Thats interesting, Max I'll have to try to get a copy, thanks. Did it talk about an impact interval then as opposed to it being instantaneous?

When you say "65% of the difference between the clubface angle and the path"........are you suggesting that was similar to TGM's at right angles to the leading edge? Leading edge to me implies left to right not up and down. And how would that compare to modern thinking in terms of left to right ? Isnt Trackmans 85% an up and down variance? Not sure, but Id be interested in knowing.

Yes, it does talk about an interval and how the club moves about 3/4 inch during that interval. Haven't finished yet but so far is very good.

As far as starting direction, it is 3 dimensional. You can't separate left and right from up and down. It is going to do both. IIRC the 85% number is a 2d representation of a 3d image.

[O.B.Left]

Yes, it does talk about an interval and how the club moves about 3/4 inch during that interval. Haven't finished yet but so far is very good.

As far as starting direction, it is 3 dimensional. You can't separate left and right from up and down. It is going to do both. IIRC the 85% number is a 2d representation of a 3d image.

K, thought Id read somewhere that the 85% was more the launch angle than the "left and right" in my sad terminology. What is "IIRC"?

[John Graham]

IIRC - "If I Remember Correctly"

[Max Impact]

Thats interesting, Max I'll have to try to get a copy, thanks. Did it talk about an impact interval then as opposed to it being instantaneous?

When you say "65% of the difference between the clubface angle and the path"........are you suggesting that was similar to TGM's at right angles to the leading edge? Leading edge to me implies left to right not up and down. And how would that compare to modern thinking in terms of left to right ? Isnt Trackmans 85% an up and down variance? Not sure, but Id be interested in knowing.

If there is friction between the clubface and ball (and unless you put WD40 on your clubface, there will be), then the ball will start off in a horizontal direction between the horizontal vectors of the "normal" to the clubface and the direction that the clubhead is moving during collision (If they are the same, obviously there is no difference). This frictional element is also the reason that your 56* sand wedge will only launch in the neighborhood of 30*, vertically, which is a percentage of the vertical vector of the "normal" to the clubface and the vertical vector of the direction that the clubhead is moving (Angle of Attack). So the ball launches both vertically and horizontally to a % of the difference between the 2 vectors for each. 85%, favoring the clubface, is an average. The actual % varies with friction and has been identified by TrackMan to be 65-95%, again, always favoring the clubface.

It's all in "Search". I'm still trying to figure out exactly what is in TGM. But I do know that this stuff is not.

[golfguru]

I have not read In Search of in years. It is basic reading for anyone doing the GCA clubmakers course. A good read, lots of good stuff but plenty of missing bits too.

Launch angles never took into account how far forward hands vs clubface were, which explains a heap of the difference between a clubs vertical measurement and actual launch.

InSearch never even considered right arm thrust, so was purely swinging in theory.

Having started with InSof, and then being taught TGM, there were paradigms to overcome in my mind. TGM just blew it away, adding to and exchanging some bits.

Most studies just miss the 'glance or crush' impact-separation area. Time is relative but far from irrelevant.

In Gummers book, was it not TJ who Homer had his book ticked off by?

Good to see Clubface is now seen as of a much higher order than Path by most out there now.

[Mike O]

Thats interesting, Max I'll have to try to get a copy, thanks. Did it talk about an impact interval then as opposed to it being instantaneous?

When you say "65% of the difference between the clubface angle and the path"........are you suggesting that was similar to TGM's at right angles to the leading edge? Leading edge to me implies left to right not up and down. And how would that compare to modern thinking in terms of left to right ? Isnt Trackmans 85% an up and down variance? Not sure, but Id be interested in knowing.

OB,
Here's something that may help. It's important that you understand that the clubface can point at the target at separation or maximum compression or where ever you think the greatest moment of impact would be - and the ball can leave the clubface at right angles - AND the ball won't fly at the target!! Because it's riding on the clubhead.

Think of another example - The train is moving down the tracks at 100MPH (clubhead) and you throw a ball off the train (clubface) at a right angle to the path of the train at 100MPH - you threw it at right angles to the track- did it fly at right angles to the track? NO, it flew at a 45 degree angle to the track even though it separated from the train at right angles to the track.

There's more there - if you're interested but this creates a condition where on the small picture Homer Kelley's statement that the ball leaves the clubface at practically right angles to the clubface - The ball in relation to the clubface at right angles is dead on! While the ball movement in relation to the target would be flying in a straight line right of the target. The affect of the 65% or 70% or 85% clubface orientation of the ball flight in relation to the target - would be determined by the Vector quantity of the clubhead i.e. the train, based on clubhead speed, efficieny of compression, etc. - Let's say you are going to run over Bucket with your car and you have a slanted snow plow on the front - the more force you can create with the car, and the more he sticks to the blade and rides along with the blade before bouncing off - the more effect the car vector will have on his flight into the ditch.

Does it leave the face at right angles - YES. Does the clubface influence the flight say 70% versus 30% for the clubhead - YES It's not either or. You just need to identify the context in which you are discussing the subject matter at hand.

[O.B.Left]

OB,
Here's something that may help. It's important that you understand that the clubface can point at the target at separation or maximum compression or where ever you think the greatest moment of impact would be - and the ball can leave the clubface at right angles - AND the ball won't fly at the target!! Because it's riding on the clubhead.

Think of another example - The train is moving down the tracks at 100MPH (clubhead) and you throw a ball off the train (clubface) at a right angle to the path of the train at 100MPH - you threw it at right angles to the track- did it fly at right angles to the track? NO, it flew at a 45 degree angle to the track even though it separated from the train at right angles to the track.

There's more there - if you're interested but this creates a condition where on the small picture Homer Kelley's statement that the ball leaves the clubface at practically right angles to the clubface - The ball in relation to the clubface at right angles is dead on! While the ball movement in relation to the target would be flying in a straight line right of the target. The affect of the 65% or 70% or 85% clubface orientation of the ball flight in relation to the target - would be determined by the Vector quantity of the clubhead i.e. the train, based on clubhead speed, efficieny of compression, etc. - Let's say you are going to run over Bucket with your car and you have a slanted snow plow on the front - the more force you can create with the car, and the more he sticks to the blade and rides along with the blade before bouncing off - the more effect the car vector will have on his flight into the ditch.

Does it leave the face at right angles - YES. Does the clubface influence the flight say 70% versus 30% for the clubhead - YES It's not either or. You just need to identify the context in which you are discussing the subject matter at hand.

Im fascinated by this stuff, thanks.

[Daryl]

Wow. I wrote this, then realized, it's a long and vapid post. Sorry for the inconvenience. All of the following Jorgensen quotes are from chapter 9 of his book.

I think that people who explain Jorgensens "D Plane" stretch it a bit too much.

The D Plane as a Practical Tool
The D plane for a golf swing contains the path along which the club-head is moving at impact, the normal to the clubface, and the initial path of the ball after impact. The D plane also contains the aerodynamic lift force, since the lift force is perpendicular to the axis of spin and this axis is perpendicular to the D plane

Normal to the Face. Now, I don't know about anyone else, but "Normal to the Face" is not exactly normal to the face. When the clubhead is halfway down to the ball; is the clubface square to the path of the clubhead? I don't think so. How about when the Clubhead is traveling up and in after low-point. Is the Clubface square to the path of the Clubhead? I don't think so.

So somewhere along the line, the clubface becomes square to the path of the clubhead. Does Jorgensen say where along the path the Clubface becomes square? No, but we can assume somewhere around Impact. Does he tell us "How" the Clubface became Square to the Path? No, but who's asking anyway.

Jorgensen is only stating 2-D-0:

2-D-0 DIRECTIONAL FACTORS Another need for a “perfect circle” motion is for directional control. If the Clubface is maintaining a constant relationship to the radius of its rotation – whether the face is open, closed or square – then the direction imparted at any one point of the arc will always be the same for “centered” (Sweet Spot) Impact (2-F).

Something Jorgensen said is very interesting:

Consider a collision for which the clubhead at impact is moving directly toward the chosen target and the normal to the clubface is directed to a point exactly above the target. The D plane for such a collision contains the target, and the plane is vertical. After the collision, the ball will be moving in this plane toward the target with the line of flight a little below the normal to the clubface.

He further explains:

. If the reader takes the usual stance with a five iron and swings the club directly in the direction of an assumed target with the clubface square to the target, neither toed in or toed out, then the D plane for the swing will be a vertical plane containing the velocity of the clubhead, the velocity vectors of the ball and the normal to the clubface, and the target. To illustrate this swing, the card representing the D plane should be held so that the line representing the clubhead motion points horizontally toward the target and the line representing the normal to the clubface points directly toward but above the target. For such a swing, in the absence of a crosswind, the ball will fly directly toward but above the target without a hook or a slice.

I don't know what you guys think, but after reading TGM, I would say that that Ball is going to curve.

It's not that the "D Plane" is anti-TGM, it's that Jorgensen did not consider Hinge Action. Jorgensens "D Plane" is based on "Glancing Blow" Theory. Glancing Blow theory is great for Ping Pong and Tennis Balls but the Golf Ball has a "Solid-ish" core. "Compression" theory is applicable to explain the spin cause by the collision between a Golf Ball and Club.

The Two Theories are very different. The following example can highlight their difference.

Jorgensen said:

When the ball is hit out of deep rough and a layer of grass lubricates the contact between the clubface and the ball, there may not be enough friction to give the ball the usual amount of spin. Under this condition the ball may leave the clubface along a line closer to the normal than usual.

If we view this situation using "Compression" theory, we might say that the amount of grass between the Clubface and Ball caused the Clubface to lose contact with the Impact Point before separation, which caused a loss of spin producing compression. We would also claim that the ball flight will be a little right of target for the same reason.

Consider test results when Clubface surfaces are altered. A clubface without grooves can produce nearly the same amount of spin from one with Grooves when hit from a dry and tight lie. A study I recently read, compared 3 surfaces, Smooth, roughed and grooved and under 3 different conditions, dry, oiled and oiled wiped-off. The results were not supportive of the Glancing Blow theory. In fact, there's hardly any mentionable difference in spin rates.

I think the "D Plane" is an acceptable way to explain Ball Flight for anyone that swings the Club and can hold the clubface square to the clubhead path during Impact.

I also think that "Trackman" can improve by using Low-Point of the Sweet-spot Orbit to calculate the Horizontal Swing Plane rather than the Ball Location. But their interest is explaining "How" the ball tracked, not "Why". "How" and "Why" is like "night" and "day".

[BerntR]

Well thought Daryl. The two frameworks seem somewhat differnt to me, but not mutually exclusive. I think the biggest difference is that TGM is more clear about what happens during the impact interval (hinge action) while Joergensen's D-plane is a more explicit and systematic and perhaps more accurate description of what TGM says about D-plane-ish character of the ball flight.

Not quite sure about this though:

If we view this situation using "Compression" theory, we might say that the amount of grass between the Clubface and Ball caused the Clubface to lose contact with the Impact Point before separation, which caused a loss of spin producing compression. We would also claim that the ball flight will be a little right of target for the same reason.

How do you see it loose contact with the impact point? By rolling up the club face?

I have a driver that is cryo treated or something. Very hard surface that I can still use as a mirror after 5+ years of use. It's by far the best driver I've ever used. But I can't use it in rainy weather. If both the ball and the club face isn't dry I get very little back spin, only 50-60% of normal carry and a sometimes a weird ball flight.

This must be due to hydro planing or some other mechanical condition that reduces the friction significantly. I'm thinking the former. But this shouldn't affect the quality of compression as far as I can see. And it doesn't feel like it does so either. I am guessing a glancing impact with good ball compression here. But that's only a guess.