Hinge Action meets "The D-Plane"

[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.

[KevCarter]

I have spent some time studying D-Plane, I'm sure it's good stuff, but it just made my brain hurt. I'm not wired that way.

What's wrong with:

2-D-0 DIRECTIONAL FACTORS
The direction of the ball will always be practically at right angles to the Clubface and square to the leading edge of the Clubface at separation HOMER KELLEY

Thats good enough for me.

John Dunigan does a really good job of describing it the same way, very simply.

"Take my word for it."

I Love it!

Kevin

[Daryl]

What's wrong with:

2-D-0 DIRECTIONAL FACTORS
The direction of the ball will always be practically at right angles to the Clubface and square to the leading edge of the Clubface at separation HOMER KELLEY

Thats good enough for me. Kevin

Yes. I agree. Anyone who reads 2-D-0 should understand "practically at Right angles" in the context it was stated. "Practically at Right Angles" when the Player has used Hinge Action.

[KevCarter]

Daryl, your approach to TGM is rubbing off on me. The big difference is I need a lot more help in getting it. I appreciate your insight and assistance!

Kevin

[Daryl]

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:



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.

I imagine that Contact is lost because the Clubface moved around the ball. The Ball doesn't slide, the Driver Face Slides.

When the Ball and Clubface are wet, the force of Impact transfers the water from the ball to the face of the driver. The Driver face was almost dry by the time it struck the ball. As impact occurs, water is forced away from the impact point and compresses at the impact perimeter.

As the Driver Face moves through the Ball location it's provided with a steady spray of water (at 100 MPH). This interrupts the flow of water away from the impact point perimeter. Water at the Top of the Impact perimeter will escape upwards because of the Sloped Driver face(but not fast enough). But water at the bottom of the Impact perimeter will also escape upwards, into the Impact point. Keep in mind that you're creating as much compressive force on the water as you are on the ball but water flows easier than a solid. As the ball begins to separate from the clubface, the clubface hold on the ball is at its weakest and the water pressure is at its greatest. It's that moment, I imagine, that the slide occurs. So even though it may feel like a solid shot because you feel the heaviness of Impact, compression was lost when the clubface/ball contact was most vulnerable.

Dry the Ball before placing it on the tee and the bottom of the ball may stay dry enough. Grooves on the Clubface help relieve the water pressure but only to a point, until they're filled.

As the Driver face slides down the ball, farther from ball center, compression is relieved at the initial compression point and the ball will travel less distance. It will also have a higher launch angle. Reduced Backspin will cause the ball to wobble in flight.

One drop of water is more than enough to wet the entire contact surface between the ball and clubface. But to get that driver face to slide, we're talking about a lot of water. At least 5,6,7,8,9 drops.

-------------
The D Plane may be able to add additional material for TGM but not to the science regarding collision. Only what happens afterward.

[O.B.Left]

Yes. I agree. Anyone who reads 2-D-0 should understand "practically at Right angles" in the context it was stated. "Practically at Right Angles" when the Player has used Hinge Action.

I like this idea about the context in which 2-D-0 was presented. It should be noted, given the current state of affairs where people try to trash Homer in the light of new scientific evidence ( be it real or imagined) . If I may offer my personal perspective .....

2-D-0 DIRECTIONAL FACTORS
".....The direction of the ball will always be practically at right angles to the Clubface and square to the leading edge of the Clubface at separation....."

In Homer's time the PGA of America, perhaps with some help from John Jacobs (who might not have read Search for the Perfect Swing) thought the ball left the clubface in accordance with the clubheads line of flight and curved to where the face was pointing. A belief that was shared by most every golfer from the Sunday morning hacker to the PGA Tour pro....... until quite recently actually.

Homer didnt agree. Though he wasnt the first to propose that the opposite was actually true, his views on the subject were still considered to be "different". Even the tape recordings of his GSEM sessions contain some lengthy discussions on this subject.

So, its my opinion that in Homer's day 1-L 16 and 17 were somewhat controversial (ish) pronouncements. There's the context. Today, where we have an argument over whether Homer was correct vis a vis Trackman etc it should be remembered that the fight in his day had him on the compete opposite side of the geometry. A fight he won. So dont take "square to the leading edge too lightly" although its wasnt anything like the "Frankly Scarlet , I dont give a damn" of its day, golfwise it was "different". That more than Trajectory was where the controversy lay.

And now for the rest of the story..... The word "practically". You could take that to mean "almost" or you could take that to mean "for practical purposes". I believe Homer meant the latter. The book he once said was "written for the guy standing on the tee". So I believe he meant something like.. "for practical purposes", the player should align the clubface as if the ball will leave vertical to the face and square to the leading edge. Did Homer actually think that the ball responded that way literally, every time? No. Although again, I believe he thought the variance was far more pronounced in terms of Trajectory than in terms of Direction (left and right from a birds eye perspective).

2-B TRAJECTORY CONTROL:

Clubface loft (2-C-1) and Hinge Action (2-D) determine altitude and backspin and are the basic elements of Ball Control.

Also per 2-D-0 again, "deviations" in Horizontal Hinge Action during Impact can influence initial direction but only by virtue of the fact the clubface is pointed in another direction.

2-D-0

"....... Deviations in Horizontal Hinge Action during Impact can produce considerable variation in the direction but little change in trajectory. Deviations in Vertical Hinge Action during Impact can produce great variations in trajectory but little change in direction. Angled Hinge Action on the flatter Planes (10-6 , 10-7) approaches the Horizontal Hinge characteristics and as the Plane steepens it moves toward Vertical Hinge characteristics. Study 2-G"

Does this mean Homer is at odds with Trackman etc? I dont know. I dont care really. Its an argument about how correct Homer was given the theoretical fight he was in during his day. I'd be interested in seeing how Trackmans 15% is divided amongst what Homer termed Direction and Trajectory. Which one has more associated variance? I bet its Trajectory. Is that where most of the 15% lies? Anyone know?

[innercityteacher]

I like this idea about the context in which 2-D-0 was presented. It should be noted, given the current state of affairs where people try to trash Homer in the light of new scientific evidence ( be it real or imagined) . If I may offer my personal perspective .....



In Homer's time the PGA of America, perhaps with some help from John Jacobs (who might not have read Search for the Perfect Swing) thought the ball left the clubface in accordance with the clubheads line of flight and curved to where the face was pointing. A belief that was shared by most every golfer from the Sunday morning hacker to the PGA Tour pro....... until quite recently actually.

Homer didnt agree. Though he wasnt the first to propose that the opposite was actually true, his views on the subject were still considered to be "different". Even the tape recordings of his GSEM sessions contain some lengthy discussions on this subject.

So, its my opinion that in Homer's day 1-L 16 and 17 were somewhat controversial (ish) pronouncements. There's the context. Today, where we have an argument over whether Homer was correct vis a vis Trackman etc it should be remembered that the fight in his day had him on the compete opposite side of the geometry. A fight he won. So dont take "square to the leading edge too lightly" although its wasnt anything like the "Frankly Scarlet , I dont give a damn" of its day, golfwise it was "different". That more than Trajectory was where the controversy lay.

And now for the rest of the story..... The word "practically". You could take that to mean "almost" or you could take that to mean "for practical purposes". I believe Homer meant the latter. The book he once said was "written for the guy standing on the tee". So I believe he meant something like.. "for practical purposes", the player should align the clubface as if the ball will leave vertical to the face and square to the leading edge. Did Homer actually think that the ball responded that way literally, every time? No. Although again, I believe he thought the variance was far more pronounced in terms of Trajectory than in terms of Direction (left and right from a birds eye perspective).

2-B TRAJECTORY CONTROL:



Also per 2-D-0 again, "deviations" in Horizontal Hinge Action during Impact can influence initial direction but only by virtue of the fact the clubface is pointed in another direction.

2-D-0




Does this mean Homer is at odds with Trackman etc? I dont know. I dont care really. Its an argument about how correct Homer was given the theoretical fight he was in during his day. I'd be interested in seeing how Trackmans 15% is divided amongst what Homer termed Direction and Trajectory. Which one has more associated variance? I bet its Trajectory. Is that where most of the 15% lies? Anyone know?

I am not an engineer but the beauty of a detail is not lost on me, either, esp. since my Financial Planning days when I learned that the "Law of 72" means that when interest is paid on an investment or bank account, money "almost doubles" when time and interest multiplies to produce 72 (9 years @ 8%). That's interesting, right? Useful, too! But there are a lot of if's in there, like the D-Plane.

I saw John's video and John seems pretty level-headed. I see the value of knowing where the ball will go and how it'll get there. I really do. My caveat is that the situation is similar to me beating balls on a range, even a dirt range. Supposing certain things happen at impact is supposing a lot.

My home course is really flat whereas my local courses are very hilly. Whatever distances I get at the range are simply conversation starters for my local courses. The D-Plane is just that for me, a conversation starter.

Thank God for engineers of all sorts. When a detail taunts them, they smile and say "just wait!" When a 4th-grader taunts me, I smile too, much like Godzilla dreaming of downtown Tokyo! Our challenges inspire us and define us!

Can't wait until April!

ICT

[BerntR]

I think the D-plane was a conversation starter for Homer as well. But I guess no one was interested in that conversation when the book was written so he didn't develop it any further than he did.

Chapter 2 certainly has all the fundamentals in place for deducting the d-plane from theory. It all starts with the line of compression not being identical to the face angle of the club...

[Amen Corner]

I think that all here has heard of that Gary Wiren, as the Director of Education, Learning and Research for PGA in the past, sent the book to MIT and to the University of Nebraska for a test.

The feedback was that the science was basically sound.

The interesting thing is that one of the scientists that examined the book was..........

Theodore Jorgensen


who btw was involved in the manhattan project in his early days.