Calling Mandrin

[Guitar Hero]

Interesting experiment, but the COR calculations show that the final velocity immediately after impact would be in the 80mph range for a 121 mph clubhead velocity. However, the 3-D machine measurements show that there is an immediate slowdown in club rotational velocity right after impact followed by a recovery 25-30 milliseconds later. Why the recovery? I'm guessing the golfer is still adding force(torque) to the club after impact and thus it recovers to some value which is what I guess would be measured by a radar system after impact. Some golfers may be more able to achieve a higher recovery velocity due to the nature of how they add torque to the club at the bottom of the swing. Still, per previous discussion, a recovery some 25-30 milliseconds later would do nothing to an impact lasting in the 5 millisecond range. Did you measure his ball speed? Probably around 180mph which is predicted by the "disconnected clubhead theory". Interested to hear mandrin explain it better.

I think you might be correct about the recovery phase. I know the club head weight is 230 grams which is heavier. This might have something to do with it as well.

 

[jmessner]

I think you might be correct about the recovery phase. I know the club head weight is 230 grams which is heavier. This might have something to do with it as well.

Yes, the heavier clubhead will bring both the ball speed up some and also the resulting head speed which would rise maybe 5% to 84mph. Pretty gifted to swing that heavy a head over 120mph. I wonder what the swingweight (or MOI) is on that club.

 

[Guitar Hero]

Yes, the heavier clubhead will bring both the ball speed up some and also the resulting head speed which would rise maybe 5% to 84mph. Pretty gifted to swing that heavy a head over 120mph. I wonder what the swingweight (or MOI) is on that club.

The overall weight is 375 grams. It is a proto type driver I have been testing to see how much distance can be gained with more head weight. As for club head speed he was 8 mph slower with the heavy head driver than with his driver. I did get his angle of attack up from +3 degrees to + 6.

 

[mandrin]

Mandrin a little help please.

I know you have talked about this in earlier threads but what I witnessed today I was hoping you could explain why. I believe it has to do with many contracted muscles at impact but I would like to hear the science behind this.

A good friend who is an instructor and long ball hitter stopped by today and he was talking about how his club head at impact was only slowing down 7-10 mph with his swing and 10 to 15 mph with good players he is teaching. I set up a radar gun to measure the club head speed just after impact. Here are the readings. Club head speed at impact 121- 123. Just after impact 112 to 115.

I know science says we cannot add to impact but can we provide some kind of a solid structure or brace that has the club head slowing down less? How much should the club head slow down at impact for most golfers? Is this a trick he was pulling on me. Please explain.

​

Guitar Hero,

The physics of impact dictates a club head slowing down considerably, much more than your friend and you have been measuring.

I think that the answer to your questions lies more likely in the measuring equipment. A radar beam pattern is relatively broad in contrast to for instance a very narrow focused laser beam. It reflects hence simultaneously off the club head, shaft, ball etc. I don’t quite know how the signal processing is done, there is likely some information somewhere but it is more fun to simply do some educated guessing.

There is a mix of various Doppler frequencies in the reflected signal and it is all a matter how one processes the incoming signal to select the appropriate Doppler shift. There is basically a mix of two different and varying Doppler frequencies, one due to the ball velocity and one due to the club head velocity. They really are not specific frequencies but are spread out and occupy both a certain bandwidth.

If the unit is geared towards measuring the maximum frequency shift in the reflected signal it should shift more towards the ball velocity. But the amplitude also must play a role in the processing and is likely much larger form the relatively large metal head than the ball. Since these units likely don’t have a very sophisticated signal processing, there is probably some complicated unpredictable mix as result.

Perhaps a more appropriate and accurate type of measurement is by distinctly measuring only the club head velocity. For instance having the head interrupt two sets of adjacent narrow light beams, such as produced by laser emitting diodes and measure the two time intervals, one just prior and one just beyond impact.

Another accurate, elegant, and much simpler approach is to incorporate a micro accelerometer onto/into the club head and integrate the measured acceleration change to produce the velocity change of the club head during the impact phase.

All this is just quick educated guessing, so do take it simply as work in progress produced by intuition craving for some sleep. LOL

 

[Guitar Hero]

​

Guitar Hero,

The physics of impact dictates a club head slowing down considerably, much more than your friend and you have been measuring.

I think that the answer to your questions lies more likely in the measuring equipment. A radar beam pattern is relatively broad in contrast to for instance a very narrow focused laser beam. It reflects hence simultaneously off the club head, shaft, ball etc. I don’t quite know how the signal processing is done, there is likely some information somewhere but it is more fun to simply do some educated guessing.

There is a mix of various Doppler frequencies in the reflected signal and it is all a matter how one processes the incoming signal to select the appropriate Doppler shift. There is basically a mix of two different and varying Doppler frequencies, one due to the ball velocity and one due to the club head velocity. They really are not specific frequencies but are spread out and occupy both a certain bandwidth.

If the unit is geared towards measuring the maximum frequency shift in the reflected signal it should shift more towards the ball velocity. But the amplitude also must play a role in the processing and is likely much larger form the relatively large metal head than the ball. Since these units likely don’t have a very sophisticated signal processing, there is probably some complicated unpredictable mix as result.

Perhaps a more appropriate and accurate type of measurement is by distinctly measuring only the club head velocity. For instance having the head interrupt two sets of adjacent narrow light beams, such as produced by laser emitting diodes and measure the two time intervals, one just prior and one just beyond impact.

Another accurate, elegant, and much simpler approach is to incorporate a micro accelerometer onto/into the club head and integrate the measured acceleration change to produce the velocity change of the club head during the impact phase.

All this is just quick educated guessing, so do take it simply as work in progress produced by intuition craving for some sleep. LOL

The ball velocity was 178 to 186 so I know the numbers for the club head speed after impact were not correct with the radar gun. I will try what you suggested by measuring only the club head velocity just prior to impact and just beyond impact.

Thanks

 

[h71y6]

libro,

You will find here linked some information I put together on the role of the wrist torque in the down swing. It conforms the advice often given to novice golfers to be passive with the hands/wrists in the down swing. Early release and poor contact are likely to occur when using a positive torque. For many amateurs it is probably better to strive actually for a bit of negative wrist torque - giving a crisper, superior impact and even a bit higher clubhead impact speed. Golf is truly a game of paradoxes. A positive wrist torque leads to increased clubhead impact speed only when applied close to impact. Hence it has to be timed correctly and be very vigorous to have a noticeable effect.

WOW! That truly is golden info.