Well the results are in and they are
definitive...
Controlling one's hand path is the key to attaining more clubhead speed with less effort. I feel vindicated having argued this very point with another ad infinitum on a lesser forum over the past couple of years.
In the posts below we discussed the research efforts of Professor Steve Nesbit (of Lafayette University) and professor Moria's earlier findings. Using today's most sophisticated modelling softwae and methods, Nesbit has developed, using accurate 3D measurements, a validated model of the golf swing... the first of its kind.
By putting measured kinematic (path and velocity) data into his model he can accurately determine the forces, torques consequently total work and power. In his latest effort employing said model, Professor Nesbit and his student researcher (Mr McGinnis) set out to determine the role hand path plays in golf swing efficacy. The results (although not unexpected by some of us) are astonishing and highly significant. Breifely summaraized:
1) Double pendulum math models of the golf swing are garbage ... nobody swings a golf club that way and they overlook the key factor...(hand path). The hand path (ie hub) radius is constantly changing as is the center of curvature.
2) Hand Path plays a key role in determining maximum club-head speed given an individual golfer's constraints: maximum torque, maximum force generated. Tiny women golfs can achieve great results because they use their hands better.
3) All golfers have similar maximum hand speeds (slightly more than 11 m/s in this study) and only one of the subjects tested hands slowed down prior to impact (his by 11% and he's a high handicapper). Kinetic chain snapping is garbage.
4) All golfers likely have big room for improvements...
side note* There is NO centrifugal force in the model because (aside from gravity) the only forces involved are those attributable to the hands. See free body diagram:
http://www.jssm.org/vol8/n2/11/F1.htm
I'll focus the rest of this post on item 4. Nesbit and McGinnis discovered (at least this it the first time I've ever read about it described as such) 3 distict phases of the golf swing. All test subjects exhibited them.
http://www.jssm.org/vol8/n2/11/F5.htm Transitions between phases are defined by local minima in the hand path radius which also correspond with changes in the direction of the center of curvature (of hand path).
They singled out their scratch golfer subject for optimization. They took is individual constraints (max and min hand path radii, max force(s) (i.e. normal and tangential) max torque (hitter effort in TGM terms) etc. and let the computer go to work optimizing his hand path. After 80 million iterations the computer arrived at a hand path for the scratch golf that would (again given his personal constraints) allow him to achieve 4% more club head speed with considerably less (-16%) effort (less power in the true mechanical senses of the words)
http://www.jssm.org/vol8/n2/11/T7.htm. Phases 2 and 3 of the optimized path resemble a logarithmic spiral. See for yourself:
http://www.jssm.org/vol8/n2/11/F7.htm
Here is a link to the paper:
http://www.jssm.org/vol8/n2/11/v8n2-11text.php#7
********* from the paper ************
KEY POINTS
-The golf swing hub path was found to have a complex geometry with significantly changing radii, and a constantly moving center-of-curvature during the downswing.
-The hub path differed considerably among subjects, however a three phase radius-based pattern was revealed that aligned with distinct stages of the downswing.
-The shape and purpose of the hub path geometry appears to result from a complex combination of achieving equilibrium between the golfer and the club, and a purposeful configuring of the path to control the outward movement of the club while minimizing the kinetic loading on the golfer yet transferring the maximum kinetic quantities to the club.
Threaded Mode