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Post by imperfectgolfer on Sept 15, 2019 23:41:33 GMT -5
DG,
You should address the question to Sasho as I generally do not believe in the validity of his theoretical constructs. However, I can easily believe that the total torque (red curve) drops dramatically after P6.
Jeff.
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Post by dubiousgolfer on Sept 17, 2019 5:26:22 GMT -5
The increase in clubhead speed from the time that purple arrow 'MOF' takes over to impact is only 4 mph from 55mph to 59 mp but there is still some positive 'Couple' torque from P5.5 to P6.5 .
If Dr Sasho MacKenzie's inverse dynamic modelling is correct what could be causing that positive couple? I find it hard to believe that the couple could be caused by independent wrist torque so could it be a secondary effect via the right hand due to the passive release of PA5# (ie. the combination of 'right arm adduction/right shoulder downplane') but also in combination with 'right lateral side bend/right pitch elbow' + 'the paddling movement of the right arm'?
I will send Dr MacKenzie an email and ask him whether he has any theories about what causes this 'In Plane Couple'.
DG
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Post by imperfectgolfer on Sept 18, 2019 7:50:08 GMT -5
DG, You wrote-: " That force is directed more vertically from P6.5 onwards and its 'tail end' is in front of the clubshaft's COM which (due to physics) can cause a positive torque (and I assume will assist in increasing clubhead speed into impact).
I am assuming that the purple vector force is caused by a pull by the lead arm and is a secondary effect due to an active pivot that rotates the lead shoulder socket 'up and back' from P6.5 - P7.
Is this 'positive' torque just something unique to Justin Thomas (and some other Tour golfers) who seem to be 'jumping up' from P6.5 -P7 and are utilising 'Parametric Acceleration'?"
I would generally agree with Sasho that the total torque (red graph) diminishes very rapidly after P6 and that any remaining torque present at impact is directed centrally (centripetally) as shown by the purple force vector arrow. I believe that the centripetally-directed torque is present in any TGM swinger and it counteracts the centrifugal (outward) pull of the club thereby resisting any tendency for the hub path to be pulled outwards near-and-at impact. I don't believe that the centripetally-directed torque can increase clubhead speed. If a golfer pulls the club handle upwards (by jumping-up and lifting the left shoulder socket even further skywards) to a degree that is more than the amount needed to maintain a standard hub path radius near impact, then he can very slightly increase clubhead speed via the phenomenon of parametric acceleration.
Jeff.
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Post by dubiousgolfer on Sept 19, 2019 17:02:40 GMT -5
Many thanks Dr Mann
I've just realised that the Justin Thomas swing graph is for a 'half-swing 7 iron' (almost a punch type of shot- see video 2:46 -3:04) . I was originally confused as to why that graph was showing positive 'couple' so late up to P6.5 and was expecting the club to have already been released earlier (using a CF-evoked swingers release - D'Alembert).
Isn't JT using an active pivot to create that positive couple (via the hands) so late in the downswing? If one looks at his left pectoral, its almost pushing his upper left arm around until it separates from his chest just before P6.5.
DG
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