Ball Flight Laws

[canadianpro]

Here is another thought on the "laws"...your comments please

Originally Posted by canadianpro
I'm referring to the youtube videos posted by John Dunigan and TheGolf Evolution that state that clubface angle at impact determines what line the ball starts on and that the relativity of the face angle to the path detrmines the curve

CanadianPro,

Explosive Golf School Ball Flight Info:

The Initial ball direction falls between the club face angle and club path

Here is the KEY and what I was driving home about the error Homer Kelley made:

What constitutes the club face angle ?? The club face position at ball club separation?? Homer Kelly thought so, book literalists still think so but they are wrong.

The club face angle that influences the direction of the ball is very close to the maximum compression point of the impact interval. Whew!!!

Let me explain and shrink down the complexity:

The club face influence on the ball in 3D space take places at a point between impact point and ball club separation very close to the point of maximum distortion.

So like I said in the Ball Flight Guide 'Dynamic Loft' article, the club and ball are in contact for a brief moment in time and during that time they travel together while the ball distorts {compresses} on the club face. The ball and club travel together for approx. 3/4 of an inch on pretty much all speeds and swing sizes. During the time the ball and club are in contact, the compression of ball and club reaches a maximum point. Obviously, this maximum compression point is not the location of the initial contact and not the location of ball club separation. It is located with the 3/4 of an inch travel of ball / club impact. SO, that is the 'magic' point of club face influence. NOT SEPARATION -

Now let me continue,
The initial start direction is very close to 80-85 % influenced by the club face when hitting a driver and closer to 72-77% when hitting an iron.

The remaining smaller percentage of initial direction comes from the resultant path of the club head.

The further apart the club face and club path diverge from each other {basically - point in different directions} the more the ball's spin axis tilts and the more curvature exists on the shot.

By the way - THERE IS NO SUCH THING AS CONVENTIONAL THOUGHT OF SIDE SPIN

Hope that helps !! Great discussion by the way


--------------------------------------------------------------------------------

Michael Jacobs
PGA Professional

[iacas]

I agree. Except the part about 72-77% with the iron, as Trackman says it's not that low... that it's almost never below about 80%.

But yeah, maximum compression point, not point of separation. Agree with that part (that seems to be the only real point here aside from the percentages).

The clubface doesn't rotate or change its orientation much from initial contact to point of separation or maximum deformation, though, so who cares about 1/2 of a degree or so?

[Andrew Rice]

Something else that might be interesting to note is that TrackMan does not measure the clubface, but calculates it. It would be interesting to see what formula they use and at what point it is applied.

[iacas]

Something else that might be interesting to note is that TrackMan does not measure the clubface, but calculates it. It would be interesting to see what formula they use and at what point it is applied.

Yeah, that's the thing - Trackman will show a ball hit towards the toe as having a more open face than it does because it sees the ball starting right, says "87% of that is the clubface, so the clubface must have been open x degrees," and will report completely erroneous numbers.

[canadianpro]

I just emailed the forum comments to trackman...will advise if I get a reply

[Chas]

I just emailed the forum comments to trackman...will advise if I get a reply

Please post a link to your guide, or a reference that I can get to - very interesting. How much do the physical properties of the ball (e.g. compressibility, adhesiveness, coefficient of restitution etc etc) influence your numbers? Not enough to bother about or does it matter comparing a softer, high feel ball with a distance one?

[canadianpro]

OK!...Here is the official response from Trackman

Hi Peter,

It’s indeed a very interesting discussion about a topic that we been investigating as well. Measuring club face orientation at the very impact location is in fact very difficult and even the most sophisticated high speed camera systems are having difficulties. Measuring the relative change in face angle before and after impact is somewhat possible, but as the club moves during impact, this also needs to be taken into account. In addition to that calibration is in general difficult to do accurately with camera based systems, although I believe they are currently the best option to measure face angle. So just obtaining accurate measurement data for club face orientation analysis is very difficult and the measurements typically have some kind of a bias from setup to setup.

The club rotates during impact due to two reasons:

1) The club rotation as a result of the swing
2) The rotation in the club head happening because of the ball impact.

The first can be neglected (it gives a contribution of about 0.1-0.2 degrees for a drive), whereas the second one can be quite significant for off center impacts (several degrees).

The TrackMan unit unfortunately cannot measure the orientation of the clubface directly. We could possibly determine the impact location (heel-center-toe) to some extent, but that is not something we are currently considering doing (impact tape also does that very well). So the face angle and dynamic loft that we output, are derived from the measurement of the ball and club movement before and after impact. We have access to accurate measurement data of the club face, which have been used to make the advanced model that we use, but unfortunately the model is not something we can share so I can’t provide much detail about the actual calculations. However, the numbers that we output can be considered an effective face angle / dynamic loft, which contains both the contribution from the static face angle and the rotation in the club face. We believe that is a very good reference for most purposes.

We are very concerned about distinguishing between measured and estimated values, so face angle and dynamic loft values are always outputted in grey and italic, which is how we indicate an estimated value.

It’s a very interesting discussion, but unfortunately we cannot provide a direct measurement of the orientation of the club face during impact, only an estimated value.

Let me know if you have any questions about the impact location or the TrackMan system in general and I’ll be happy to assist you.

Best regards,
Nicolaj P. Hermansen,
Product Manager for TrackMan Net & Tour
M.Sc.E.E.
TrackMan A/S
Stubbeled 2, DK-2950 Vedbaek, Denmark
Phone: (+45) 45 57 08 50 / (+45) 45 74 47 47 (Direct)
Cell: (+45) 27 58 96 91
Fax: (+45) 45 74 00 39
Web: http://www.trackmangolf.com
Email: nh@trackman.dk

[sean_miller]

The clubface rotates closed a little bit due to the swing arc and a bit more due to impact with the ball. On this point I submit that feel is, in fact, real.

[iacas]

The clubface rotates closed a little bit due to the swing arc and a bit more due to impact with the ball. On this point I submit that feel is, in fact, real.

I'm not sure I get your point. First, center contact won't increase the rate of closure much (heel hits can, while toe hits can make the rate of closure go negative - the club will open - during impact). And second, the amount of closure during impact is small - 0.1 to 0.2 degrees according to the Trackman guy. I've heard it's as high as 0.75 degrees, but still, very small.

So what's your point, exactly?

[sean_miller]

I'm not sure I get your point. First, center contact won't increase the rate of closure much (heel hits can, while toe hits can make the rate of closure go negative - the club will open - during impact). And second, the amount of closure during impact is small - 0.1 to 0.2 degrees according to the Trackman guy. I've heard it's as high as 0.75 degrees, but still, very small.

My point was a small one. Any closing of the clubface during a solid swing is minimal, and on a solid strike it doesn't feel like the clubface went offline in any way. On even a slightly off-centre strike the clubface feels like it opens or closes a bit, because it does. The clubface feels like it opens up (or closes) more as the contact gets farther away from the COG and it does.

Maybe I'm alone, but the amount of increased push or pull seems to be consistent with this twisting feeling. Like I said, it was a small point - probably not worth posting.

[iacas]

s_m, I agree with everything you said, but I'm still not sure why you said it. Anyway... heh. Okay.