Facts re Impact

[Guitar Hero]

The trampoline effect is a real phenomenon and has increased the average driving distance on the PGA Tour by 10 yards or more in just three years. Nothing has had so great an effect in such a short period of time.

However for the average golfer the difference seems to be rather minor.

Is that due to the lower club head speeds of the week end golfer?

 

[mandrin]

The trampoline effect is a real phenomenon and has increased the average driving distance on the PGA Tour by 10 yards or more in just three years. Nothing has had so great an effect in such a short period of time.

However for the average golfer the difference seems to be rather minor.

Is that due to the lower club head speeds of the week end golfer?

Guitar Hero,

Yes, I think this to be the reason. At higher club head velocities there is more energy loss due to deformation. The trampoline effect therefore, at the much higher impact velocities for pros, can be more effective reducing this energy loss then at the lower impact velocities obtained by the average amateur. Also the average amateur does not hit very often hit the ball with the sweet spot and is hence further disadvantaged re. the pro for being able to exploit the trampoline effect.

 

[Guitar Hero]

Guitar Hero,

Yes, I think this to be the reason. At higher club head velocities there is more energy loss due to deformation. The trampoline effect therefore, at the much higher impact velocities for pros, can be more effective reducing this energy loss then at the lower impact velocities obtained by the average amateur. Also the average amateur does not hit very often hit the ball with the sweet spot and is hence further disadvantaged re. the pro for being able to exploit the trampoline effect.

Mandrin,

I was going to mention the sweet spot contact but I was looking at the club head speed only as if it was tested by Iron Byron and the sweet spot contact was not an issue. Is there is any data out there or can you help with the differences between a 95 mph and 120 mph swing.

Also I am sure you have an answer for this question. How much further would the golf ball go if the driver head was 305 grams instead of 205 for the driver? The same applies as if Iron Byron was making a 95 mph swing with the two different weighted heads.

Thanks,
Guitar Hero

 

[ej20]

I am not using reaction time in my opening post about impact dwell time and peak force. However I made further on in the thread a simple common sense observation -


ej20, I just can’t imagine anyone not agreeing with above, hence very curious indeed to hear any arguments you might possibly have to substantiate your critique.

You did not use reaction time in your mathematics concerning dwell time and peak force but you do use the term to explain why we are not equipped to feel the precise moment of impact.

I don't disagree with this if you read my last post again.I was just pointing out that reaction time has nothing to do with why the ball is long gone by the time we feel impact.Its got more to do with the speed at which neurons can travel from hand to brain.

The ball is even further away by the time we can react(reaction time of 0.3 sec) to the feel of impact so yes,it's impossible to control the clubhead during impact using the feel of impact as the signal to react.

Not disagreeing....just being a bit more precise in the explanation

 

[jmessner]

During impact a substantial percentage of the kinetic energy of the club head is transferred to the golf ball and consequently the club head slows down substantially during this impact interval.

​

Figs 1, 2, and 3, using the mathematical model derived for the analysis of the trampoline effect (1*), show respectively the deceleration, the velocity and the displacement of the club head during impact. The displacement of the club head during impact obtained can be shown to be 1.66 cm (0.65 inch).

With a rather different approach using the law of conservation of momentum, such as in my post on Impact Physics (2*), one can obtain the value for the displacement for the clubhead as being 1.68 cm (0.66 inch).

impact velocity = 44.7 m/s (100 mile/hr)
mass head = .2 kg
mass ball = .0457 kg
COR = 0.78 (3*)


1*) http://www.brianmanzella.com/forum/golfing-discussions/7763-trampoline-effect.html

2*) http://www.brianmanzella.com/forum/golfing-discussions/7554-golf-impact-physics.html

3*) Science and Golf IV - Lemons - Experiments in Golf Ball - Barrier Impacts.

Thanks, mandrin, somehow I had missed your two articles referenced above.

So, this analysis is for the displacement of the clubhead from a position it would have been in without accounting for impact? Also, what would the displacement graph look like if it was extended out beyond the impact duration? I assume it would be some damped sinusoidal type response that would show an even greater negative displacement than what is show right at separation. Also, from your previous analysis, a higher COR value would produce a larger clubhead displacement during impact I presume.

Jay

 

[mandrin]

Mandrin,

I was going to mention the sweet spot contact but I was looking at the club head speed only as if it was tested by Iron Byron and the sweet spot contact was not an issue. Is there is any data out there or can you help with the differences between a 95 mph and 120 mph swing.

Also I am sure you have an answer for this question. How much further would the golf ball go if the driver head was 305 grams instead of 205 for the driver? The same applies as if Iron Byron was making a 95 mph swing with the two different weighted heads.

Thanks,
Guitar Hero

​

Guitar Hero,

I can’t answer the question which regard to distance, that is a rather complicated subject involving many variables such as ball departure speed, horizontal and vertical launch speed, spin rate and its orientation, ball aerodynamics and environmental properties.

However Fig1 will give you an idea of the increase in ball departure speed as a function of clubhead mass for two clubhead impact speeds, 95 and 120 mile/hr.

 

[mandrin]

So, this analysis is for the displacement of the clubhead from a position it would have been in without accounting for impact? Jay

Jay, I am not sure what you really mean, so somewhat guessing. The analysis is not about a relative displacement of the club head, comparing two cases of having or not having a golf ball present at impact. It is the actual magnitude of the displacement versus time as it occurs during the impact interval.

Also, from your previous analysis, a higher COR value would produce a larger clubhead displacement during impact I presume. Jay

Quite the contrary. A higher COR value results in a smaller displacement for the club head during the impact interval. Just think of an almost perfect elastic collision between two identical steel balls suspended from strings so that they touch when in their equilibrium position. We pull one of the balls back and let it go. It collides elastically with the other ball. The moving ball comes to complete stop, no displacement during impact, and the other takes all the energy and momentum. We all have seen most likely these demonstration apparatus, usually equipped with 5 steel balls.

 

[jmessner]

mandrin,

Ok, that'll teach me to read while I'm doing about three things at once. I totally misinterpreted the displacement parameter. I had this thought you were addressing the topic of the head going from a leading position at impact to lagging after impact and the displacement was some measure of that effect. Upon closer inspection, that is obviously not the case and it is the absolute displacement (or movement) during impact. That confusion makes the following statements I made pretty much meaningless except that in my case the larger displacement I presumed with a higher COR actually translates to a smaller displacement per your actual meaning so I got that right - sort of.

Jay

 

[ggsjpc]

just to clarify

Bronco Billy tries constantly in various ways to attract attention - his last post being particularly noteworthy for being stark naked way out in left field. Trying to educate Bronco Billy is like trying to lift oneself against gravity pulling on one's socks. However his post made be think of posting some interesting experimental data.

From the paper “Is the Impact of a Golf Ball Hertzian ? ”, published by Prof I. R. Jones in 'Science and Golf IV ', I have taken the experimental data regarding both the amplitude and duration of the force pulses which are generated when a golf ball impacts against a plane solid surface at the full range of velocities normally encountered in the game of golf for one particular make of golf ball. The data concern impact speeds from putting and tiny shots around the green to full range normal golf shots.

​

Notice from Figs 1 and 2 that with increasing impact velocity the dwell time DECREASES whilst simultaneously the impact force INCREASES. Notice also that from a tiny putting stroke to a high speed driver swing the impact dwell time barely changes by a factor of 2 whilst there being nevertheless a difference in magnitude in associated impact force of about 50 times. Those still strongly holding on to their beliefs of heavy hit, sustaining line of compression, etc., etc., will have likely some interesting food for thought.

For my own clarification:

Basically, this information states that the ball stays in contact with the clubface for a longer period of time at a slower clubhead velocity vs. a faster clubhead velocity?