TGM perfect?

In a thread on LBG - TGM perfect? - there is a discussion about TGM being the alpha and omega of golf. A well known TGM instructor – Michael Jacobs, GSED - has made some comments about the TGM being old-fashioned in some areas. This elicited the following response from Yoda, (Lynn Blake, site administrator).

[i]The Enemy Within

Not one sentence in the book indicates Homer was anything but open minded and non-dogmatic. “Complexity is far more acceptable and workable than mystery is.” What a great sentence.

Homer Kelley was a very cool guy. His understanding of Golf Stroke Mechanics had no progenitor. Nor, to date, even a parallel.

Meanwhile, we have today a captained handful of TGM ‘nouveau-sect’ focused on their own negative bias: Namely, their molehill perception of miniscule error against the mountain of irrefutable fact that is absolutely correct .

Few, if any, of those comprising this sect (which joys in confrontation) ever met the man himself. I find it very curious: These misfits – they welcome the characterization, at least with regards to TGM – readily acknowledge their debt to Mr. Kelley. Yet, they then turn their entire attention to damning his work.

All while flying the TGM colors.

An odd world, isn’t it ? [/i]

Yoda, by asserting so strongly HK’s work to be a “mountain of irrefutable fact that is absolutely correct “, also, paradoxically, sets the bar of excellence so high that if only one core idea is shown to be totally wrong will than put a serious doubt into it all. :slight_smile:

Let’s look, for instance, at impact, a very important element in TGM, and see what HK has to say about it. No need for esoteric complexity or sophisticated mathematical equations to show a basic flaw in HK’s understanding of basic impact physics.

The moving clubhead at impact has acquired a certain amount of momentum in the down swing which is conserved during impact. Whatever the ball acquires as momentum, during impact, has to come from the clubhead and, as the total amount of momentum remains constant, by definition, reduces the momentum of the clubhead by an equal amount.

Giving up momentum, the clubhead slows down, thus decelerates. However, HK’s perception of ideal impact – consisting of zero clubhead deceleration – actually makes it totally impossible for any transfer of momentum to occur from the clubhead to the ball. :unamused:

Hence KH’s point of view that, “Zero deceleration is what would give maximum ball speed for any and all approach speeds”, is not a “molehill perception of miniscule error“ but rather a serious fundamental error. :blush: (TGM, Impact Physics, 2-E).

Only if the clubhead is assumed infinitely heavy will the deceleration be approaching zero but for the real world case of collision of clubhead and ball there is actually a very large deceleration of the clubhead taking place during the transfer of momentum from clubhead to ball. :exclamation: :exclamation:


i have not read homer kelley–nor have i any knowledge of tgm beyond what i’ve learned on this forum–and i don’t wish to either defend him or refute him. i know even less about lynn blake. however, i don’t think your analysis is correct.

from what i understand of the law of conservation of momentum, it implies a closed system of objects with no external forces. i understand that to mean that when using the law of conservation of momentum to analyze collisions, it is assumed that the objects under collision are not accelerating, for otherwise there would necessarily be an external force. therefore, if the club head is indeed accelerating into impact with the golf ball, it seems to me that you cannot use the law of conservation of momentum to draw your conclusions about velocity after impact.

if i am wrong, please accept my apology and let me know where my reasoning is flawed so that i can better understand.


My #1 argument against TGM is that there is no component “cataloging” for the right arm RESISTING extension through impact.

TGM only offers passive extension, or active right arm thrusting for full golf swings.

The right arm striving to stay bent, pulling against the outward forces of CF is more than a viable move. Not only does it require the pivot to fully activate, it also does wonders to stabilize lowpoint, AND does wonders for keeping the shaft on plane through impact AND does wonders for minimizing post impact clubface rotation… which as Trevino so eloquently described as “keeping the clubface looking at the target just a little bit longer”

To top things off, this overlooked protocol was used by the arguably the greatest ball striker of all time.

But instead of embracing this, Homer spent time cataloging "The Paw, The Bat and other less than desirable novelties or stroke patterns.

I just don’t believe you can really get it … or understand it until you approach mastery of the action… because the sensations and intentions are SO different than what you could ever extrapolate from stills, videos, or studying swing sequences… and this is why I am so much more interested in studying what great ball strikers say they feel, than putting the swing on a two dimensional swing analysis grid.

The golf swing to work properly is a 3D motion, and needs to be treated that way when learning the correct biomechanical actions that will oddly enough create nice visual 2D renderings.

The problem with trying to learn your swing plane using flashlight drills is that those drills are completely and totally void of the forces, opposing forces, and the actual pressures that are going to HAVE to be in place to properly swing the golf club ON PLANE THROUGH IMPACT.

If I were to show a TGM instructor my intentions with a flashlight, they’d do better looking up and all over the wall, and even the ceiling, more than the base line on the floor… I want nothing to do with that as far as intentions. However, moving through impact at high speed, I will have a brief flash of brilliance right at impact because I am NOT trying to do that… in fact trying everything I can NOT to be on plane at any point in the golf swing.

All you have to do is watch Moe or Hogan when they demonstrated things… They were never showing any kind of on plane intentions… and they were correct.

The golf swing is more like twisting a towel at opposite ends… if you do this in an opposing direction, you create a towel that is no longer limp, but has firmness and structure. This is what creates dynamic swing plane… and this is how you swing a golf club.

I’ve never read TGM (I might one day)…I don’t know Lynn Blake, never visited his website or any of his forums.

I did however listen to a lengthy interview on the website a week or two ago. Whilst he came across as a pleasent enough chap, he also recited TGM like a preacher recites their Bible. Had I been a student of TGM, that would have made me feel a little uneasy.


Mandrin, I think you have misquoted Lynn somewhat. Lynn asserts that “Namely, their molehill perception of miniscule error against the mountain of irrefutable fact that is absolutely correct .”

In other words he is saying that while there is room for critique within the work of Homer, there is also a lot of merit in his work.

He then goes on to say that, "Homer Kelley would be the first to encourage additions to his Body of Knowledge. In fact, he did exactly that:

“Because of questions of all kinds, reams of additional detail must be made available – but separately. And probably endlessly.” (1-H)

He would, however, be a formidable competitor to those who would prove his basic premises wrong. That argument would start first with a correct understanding of the premise in question. Unfortunately, that understanding is almost always the first stumbling block of “those who would be king”. "

Perhaps a link to the discussion would be fair…

For those who don’t know Lynn or never met him, he’s truly one of the nicest people in the golf instruction industry you will meet.

I think it’s obvious to see the errors in TGM. But we have to remember:

  1. HK didn’t have nearly the resources that we have today to figure it out and he made 7 editions of the book, meaning he understood that much of his work needed to be tweaked for accuracy.
  2. He died in 1983, so he really didn’t have the chance to expand upon his work.

I think the golfers who go onto the internet for more detailed and precise instruction (like myself) often forget the barren wasteland of quality golf instruction and quality golf swing research and study before the 21st Century.

I was introduced to TGM back in 1996, which was less than 15 years ago. Finding a TGM instructor back then was almost as rare as finding a child stricken with polio. Mac O’Grady’s MORAD instruction was secretive and for the most part, was in its infancy stages as far as passing that knowledge to other pros. Other than that, your typical instruction was at best based around whatever Leadbetter said or whatever was in Hogan’s ‘5 Lessons’ or some rehashed Jimmy Ballard stuff.

I couldn’t imagine the dearth in good golf instruction back in 1983.

And since MORAD came from TGM and Stack and Tilt came from MORAD, I think it’s safe to say that TGM really brought forth a major leap in how we think about the swing.

Even with the errors, a lot of the time I find that it’s still very strong conceptually. The ‘down, out and forward’ will get the golfer’s path going out to the right, but I can see why HK thought that is what you do if you want to hit it straight and usually in golf, golfers go ‘down and in’ too much. Endless Belt (2-K) is flawed, but I can see where he was going with the belt concept.

I think the issue that Lynn has, as well as myself from time to time, is that there are many guys who freely admit that they are a TGM AI, yet they go out of their way to antagonize the book in almost a brutal fashion. Brian Manzella once eloquently stated that he views TGM much like when he found out as a child that his father wasn’t perfect. I think the issue that Lynn and I have with some of the anti-TGM crowd is that if they ‘found out that their father wasn’t perfect’, they would try to light their father on fire instead of accepting it and still loving it for what it is.

Of course, I think a lot of the brutal backlash against TGM imperfections is due to the loyal following. But even those people who are vicious in their TGM attacks because of those blind loyalists need to remember what it was like when you found out more concrete information about the golf swing and it translated to you playing better and being much less confused. It’s truly a fun and liberating feeling. And that’s why they have their loyalists…at the end of the day it works for golfers more often than not. Most golf instruction cannot say that.

Lastly, the critics that really go after TGM usually show me that they really do not understand the book. After reading about Homer Kelley’s life and his occupation at Boeing, it became apparent to me that the book was a manual on a system to use to develop a good golf swing by using the basic, acquired, and total motion curriculum along with learning feel from mechanics. The scientific stuff that Homer wrote about (and got wrong) took up a lot of the pages, but the true heart of the book is about the development of the golfer’s swing. The feel from mechanics in my mind is the big one and the one that separates the book from popular golf instruction methods that haven’t improved golfers in the past 80 years.


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When an object is dropped from a certain height, the earth on impact will move a bit. However it requires an incredible large number of decimal places to cope with it. Hence normally and safely we assume the earth not to move. :wink:

We have to approach the impact between golf ball and clubhead in the same practical manner. Yes there are forces exerted on the head via the shaft but are negligible relative to the very large impact forces existing between ball and clubhead during impact.

From an engineering point of view the impact between ball and clubhead can truly be considered to be an almost ideal closed system and the conservation laws of angular/linear momentum therefore definitely apply with great precision.


Lynn Blake misquoted somewhat ? Yet, his entire post, as such, is included in my post !

I have seen the argument that Homer Kelley would welcome criticism ad nauseam, yet any poster on LBG hardly dares to question anything. :unamused:

You seemingly completely missed the gist of my post. It is not on nitpicking small [size=125]details[/size].

I am clearly showing that Homer Kelley was fundamentally wrong on a very [size=125]basic premise[/size] regarding impact physics.


Your arguments in this post feel very much like contrasting forward and reverse dynamics.

The traditional way to instruction is comparable to inverse dynamics -

One uses known motion to derive the associated forces in the system.

Your approach is more like forward dynamics -

One starts from known forces to predict movements of the system.


i’d like to discuss this further, and i think doing so here in the forum can be worthwhile, for i think properly understanding momentum and acceleration will shed light on why it matters to be accelerating into and through impact. if this discussion is hijacking your thread, we can create a new one.

my problem with an engineering point of view is that it sometimes over simplifies for the sake of ease of understanding and expediency. for this reason, please bear with me in this analysis. let’s first look at the non-accelerating, constant momentum (and hence constant velocity) case. to make this clearer, let’s also substitute a car for the club head and a pylon for the ball. also, let’s for now ignore frictional forces.

if the car is traveling at a constant velocity (zero acceleration) and hits the stationary pylon, then yes the car will slow down and hence decelerate, and the pylon will start moving and hence accelerate. now let’s look at the case where the car is accelerating at a constant rate.

let’s say the car is accelerating at 5 mph per second. in other words, as each second goes by, the car is traveling 5 mph faster. so if the car is going at 30 mph right now, then it will be going at 35 mph a second from now, and 40 mph two seconds from now, and so forth. if in this constant acceleration scenario, the car hits the pylon, the car need not slow down (decelerate). the car may only lessen its rate of acceleration, say from 5 mph per second to 4 mph per second. thus, far from decelerating, it may indeed still be accelerating! i say ‘may’ and not ‘will’ because there are several sub-cases to look at.

before getting into the sub-cases, let’s ask this question: in the first case–the constant velocity (zero acceleration) case–what makes the pylon accelerate and the car decelerate? there must be a force present. this force is usually called the impact force. but where does this force come from? from what i understand, it’s actually all the atomic electrical forces of repulsion and attraction of the electrons and protons of the atoms that make up the two objects when the objects are squeezed together. since all these forces are very complicated to calculate, it’s easier to combine them all and think about them as one singular force–the impact force.

now this impact force acts on both the car and the pylon in an equal but opposite way. so, if the car is moving from left to right, the impact force acts to the right on the pylon and acts to the left on the car, and it does so in an equal amount. the reason the pylon will accelerate more than the car will decelerate is that the mass of the car is much greater than the mass of the pylon. F = ma. here the F is the same, so if the m is greater, the a has to be smaller, and vice-versa.

let’s now go back to the constant acceleration case. whatever the force due to impact is, lets call it F. this F, if the car is moving from left to right, acts on the car to the left. since the car is accelerating at a constant rate, there must be a force acting on the car to the right. let’s call this force L. so, F and L are acting in opposite directions. now we can look at the sub-cases: L > F, L = F, and L < F.

if L > F, then i maintain that the car does not decelerate, and in fact it only lessens its acceleration. if L = F, again, the car does not decelerate, it will just stop accelerating. finally if L < F, the car will decelerate.

getting back to the club head and the golf ball, where L is the force due to the master golfer maintaining acceleration of the club head into and through impact, and F is the impact force upon the club head’s collision with the golf ball, it seems to me that your position is that not only is L < F, but that L is miniscule compared to F. in all honesty, i don’t know, but i am certainly not convinced that this is the case. if i had to guess, i would say quite the opposite, that while it’s difficult to achieve L > F, it is not impossible. only thorough testing with proper equipment and using a master golfer who can maintain shaft flex (acceleration) into impact can we know definitively.

at any rate, i hope this long post makes clear these subtle yet important points. please let me know if you or anyone else finds any misconceptions in my understanding.



Impacts usually occur in a very short time span - in effect so short a time interval that they escape our sensory system. Therefore intuitive reasoning is not a good guide to discuss these matters. Why not have first a look at some material I put together quite a while ago for another forum. The crux of the matter is that for 0.0004 sec, during impact, the clubhead and ball have a very private meeting and the golfer is simply not invited to the party. :mrgreen:

Very well said…

This reminds me of Knudson’s description of the ball feeling incidental.

Mandrin, i assume the material you produced is one way of explaining deceleration during impact.

As you said, this short time span of 0.0004 sec where in your example slows the clubhead down from 100 to 68 mph, couldnt we instead take a basketball instead of a golf ball and hit it? This would show an even more drastic deceleration over a longer time span and make it more visual for our sensory system, wouldnt it?

Or would an object with more mass than a golf ball throw your whole thought process out of context?

Clearly, John - you are a ‘Nouveau-sect’ misfit molehill perceptionist standard-waving heretic! :wink:

Captain Chaos


I’ve enjoyed your posts on this and other forums. I’m curious if you feel the shaft and grip of the golf club are invited to the “private party”. For instance…although you’ve shown the clubhead must lose velocity at impact, does that mean that the shaft and grip must also? Can we treat the clubhead/ball as a “black hole”?


i hear what you are saying about the ball feeling incidental and is what i am after. but, if the club head is decelerating, or at any rate as much as mandrin says, wouldn’t the ball not feel incidental? it seems to me that, relatively speaking, it would rather feel like a speeding car hitting a deer instead of hitting a small bird. if you’re driving a car and suddenly (within .4 milliseconds) went from 100 mph to 68 mph, as mandrin’s analysis says is happening to the club head, would you consider this incidental? this is why i’m questioning what mandrin is saying. i’m not saying he’s wrong, i’m just questioning.


thanks for the link. i have read through it and am very familiar with such equations. however, i don’t agree with how you arrived at v(t2) = 68 mph for the external force case. let me be clear. i understand how you calculated it from your equation 15. it’s that your equation 15 assumes no external force. then you use this result to arrive at all of your subsequent results. in other words, you are assuming a zero acceleration case to determine the exit velocity and then use this value to reason about cases when the object is accelerating into impact (i.e. there exists an external force). this to me is a fallacy.

i am saying that when there is an external force, the object (car or club head) may or may not decelerate upon impact, depending on how much external force is present and how it compares with the impact force. you have to measure the external force, you can’t calculate it by first assuming a zero external force condition.

as far as time in contact, while 0.4 milliseconds seems small, it in fact does not matter how small the interval is. all that matters is the net force during impact, however small in duration the impact is, which is the difference between the external force and the impact force, or L-F in my notation.

it seems to me that you are saying that this net force will be negative and only very slightly smaller in magnitude than F. that is, that F is much, much larger than L, and hence L is negligible. but if this is so, then what would be the advantage to having an accelerating swing over a non-accelerating swing? if there is none, wouldn’t you be in direct disagreement with lag?

perhaps another way to look at it is to consider the impact distance rather than the impact duration. that is, how far in distance does the club head or ball travel while still in contact with each other. from the image on your webpage, it seems to be more than the radius of the top of the rubber tee. if there is an external force, i.e. if the club head is accelerating into impact, then work due to this external force is being done to the ball over that distance. if the club head is not accelerating and thus there is zero external force, then no work due to an external force is being done to the ball. in fact the distance may not even be the same for the two cases.

a test using a high speed camera could be used to measure this distance using an accelerating swing and a non-accelerating swing, assuming impact velocity is the same for both, and see if there is a larger impact distance for the former. if there is, this could explain why accelerating swings produce more accurate ball flights than non-accelerating swings.



A scientific explanation is not one of choice but following from basic premises and laws. Having bigger or smaller masses does not change the analysis and the law of conservation of momentum.

The dwell time of impacts in many sports is quite small. For tennis it is about .0045 sec, hence about 10 times larger than in golf, yet still too short to be readily sensed.

To be very clear about it, the sensory system plays no role during the head/ball impact interval whatsoever. It has also no role in the analysis.

It is mentioned specifically for those who consider impact as if something we have some control over. Before, yes. After, yes. During, no.

Homer Kelley however in TGM (2-0) mentions that -

[size=125]“The Mechanics of Golf is the production and manipulation of the “Line of Compression”. The Secret of Golf is sustaining the “Line of Compression.”[/size]

This suggests clearly that an useful action can be taken during impact interval itself. From my comments it is clear that I don’t agree. A basic case of erroneous science in TGM.

Homer Kelley should have never warped his ideas in rather pompous scientific jargon. He should have simply stuck to golf only.

Certainly there must be a difference in impact science between a clubhead that is moving at a constant rate of speed or velocity, or one that is instead accelerating into impact with a pre stressed clubshaft?

With the analogy of a car hitting an object… there would be a difference between coasting into a collision compared to flooring the gas pedal?

If we say two impacts are going to be at 40 mph… one coasting, the other moving from 35 to 45 with impact happening at precisely 40?

There must be a difference here scientifically…

The other big factor would be the weight of the object… is it a bowling ball or an air filled beach ball? The weight of the object must be having a significant effect upon the data released from the collision for analysis?

IMO, Homer was pretty to the point with regards to impact. The quote doesn’t seem as stupit when it is read in the context of the whole paragraph:

This means that even with precise geometrical alignments the ball will not separate from the club at more than 80% of their approach speed. That producess, roughly, this condition - the Clubhead approaching Impact at 100 MPH has slowed to 80 MPH at separation. The ball leaves the club at about 70 MPH (70% of 100 MPH approach speed). To do this the ball must be travelling 150 MPH of the Clubhead “approach” speed (so there must be resistance to deceleration). Zero Deceleration is what would give maximum ball speed for any and all approach speeds. Speed (Centrifugal Pull) and Prestress (Acceleration) stiffen the Clubshaft for consistent (minimum to maximum) resistance to Impact Deceleration. Treat that “heavy” feel of “Clubhead recovery” after Impact as though it were all Impact, even though the ball is actually long gone.


One aspect which is very important to consider is the extremely short time span of impact. Just to try to make a bit more plausible what I am trying to convey let’s do a simple experiment.

In a bath tub or swimming pool do the following experiment. Gentle move one hand vertical downwards to and through the water surface. Progressively do it faster and finally do it as quickly as you can muster. The water surface behaves quite different for slow and quick movements of the slapping hand. Eventually for extremely quick movements the water surface behaves virtually like a solid surface.

It has to do with the sound velocity in water. When the water surface is hit suddenly with force, the water particles simply don’t have the time to move out of the way and hence make the surface appear to be rather solid.

The time scale also plays a similar crucial role when considering the behavior of the shaft of a golf club. Statically and quasi statically the shaft behaves like a spring. However for the very, very small impact dwell times the shaft, for traverse and longitudinal impacts, behaves in a completely different manner.

The propagation time of a disturbance in a shaft, due to impact, is such that the ball is already gone before the disturbance can travel up and down the shaft. Therefore the shaft, and even more so the grip, plays no role during impact. The hosel and some adjoining shaft are in a grey zone, in between.

Conclusion - the ball and clubhead are having their moment of fun all by themselves. :mrgreen: