Warlock

I wonder if GEARS has the capability to check the below: 1. How the tour pros PA2 angle is released in the downswing. Basically, a graph showing rate of change of the angle between shaft and lead forearm. For example, when looking at these kinematic sequence graphs, Rory's lead arm seems to have a greater angular velocity than the club (ie. the blue graph moves temporarily above the brown line). Same happens for Ricky Fowler, Ernie Els, Grant Waite and JB Holmes. Does this mean that the angle between the lead arm and club shaft is actually decreasing in the early downswing for the golfers I've just mentioned? 2. For tour pros, does an extension of their club shaft trace a 'swing plane line' as demonstrated by Martin Hall's old you-tube video? For example, Dr Kwon mentions that tour pros shafts swing on a functional swing plane (FSP) between MD (mid-downswing) and ZC (zero wrist-cock) in the image below which also traces the FSP plane base line. He shows how the shaft deviates off that FSP in the downswing but there isn't any indication whether an extension of the shaft still continues to trace that FSP plane base line. TGM proponents would define that tracing of the swing plane line throughout the downswing as swinging 'On Plane'.

Many thanks again

Apologies again - old age I'm afraid and I've corrected my post.

Hi iacas You actually mentioned the below so were you correct about closure rate in rpm being measured relative to the target line? "Why are the RPM and the "closure rate" marked the same? Hmmm, maybe it's the Cheetham/Sasho measurement for clubhead closure rate: 431 rev/min * 360°/rev * 1 min/60 sec = 2,586°/sec. That's pretty close. Actually that might be my only question. Maybe in GEARS the "°/sec" is showing relative to the path or instantaneous plane, and the rpm is showing relative to the target line."

Oops sorry iacus (typo error). Below is what you said in a previous post and wondering whether you were able to confirm if 'T_Closure Rate' measured in rpm was actually the shaft rotational rate? Also, when you say, 'shaft rotational rate', do you mean the actual rotation of the shaft about the longitudinal axis of the shaft? "The fact that 512° and 514° are similar, but 27.4 rpm and 431 rpm are wildly different, but both are listed as "closure rate" makes me wonder about a lot of things here. 😛 The thought just occurred to me that maybe the "rpm" one is the shaft rotational rate and the "°/s" is the clubface's rotational rate"

Iacus, Did you ever find out what GEARS metric 'Closure Rate' in rpm was measuring? Is it different to 'Closure Rate' in degrees/sec?

Now I understand what Phil means. His functional plane is tilted/pointed to the right and not on the target line, that's why it looks like there are 2 different slopes from a DTL view.

Hi Phil I'm a little confused when you say the blue lines represent where the FSP is likely to be . Here is Figure1 from Dr Kwon & others research article (link below). https://ojs.ub.uni-konstanz.de/cpa/article/viewFile/5641/5134 Am I wrong in assuming that the image is portraying a functional swing plane (like a sheet of glass) cutting through the mid-trunk of the golfer? Therefore, when one looks at a pure DTL view of a golfers swing the FSP should look like a single inclined line? Your blue lines look to have different slopes when viewed in 2D DTL from P6-P7, so I am assuming you are inferring that the slope angles are actually the same relative to the ground (in 3D) if you are using a frame of reference attached to the rotating golfer . But I don't think Dr Kwon is using a moving frame of reference when he describes the FSP.

Are you saying the same things? Here is a diagram from Dr Kwon's website. The mid-hand-point generally staying on the FSP between MD-ZC . The clubhead is on the FSP between MD-ZC The shaft is on the FSP between MD-ZC The midhand point and the hand centers are all defined along the shaft. If the shaft aligns along the FSP, all these points should be on the plane between MD and ZC." Phil said : "The clubhead and hands will move on different planes"

Many thanks. I did ask Dr Kwon on his you-tube channel and he's replied below. I'm more inclined to believe that @phillyk is correct that the hands and clubhead move on different planes so maybe its just a very close approximation that the whole shaft is moving on the same functional plane. "Between MD and ZC, if the midhand point is on the FSP, the individual hand centers should be on the plane, too. The midhand point and the hand centers are all defined along the shaft. If the shaft aligns along the FSP, all these points should be on the plane between MD and ZC." In the video he says from mid downswing to zero cocking the hand centre stays pretty much on the swing plane.

Just seen this Dr Kwon video below about functional swing plane but cannot reconcile his opinion that the club shaft remains on that plane between MD (P6) and ZC (Zero lead wrist cocking - approx P7.3) vs Chris Ryan's video further below. Please see 15:00 - 17:22 where he says the mid-hand-point and the clubhead (and therefore whole club shaft) are swinging on that functional swing plane. Chris Ryan says that the hands move in as the clubhead moves out and when I took a snapshot blur image (see further below) , the club shaft doesn't seem to be swinging on some constant functional swing plane. I cannot understand how the lead hand grip section can still remain on some unchanging functional plane if there is an angle between the lead arm and club shaft approaching impact while the forearm supinates to try and square the clubface. Am I making a mistake somewhere in my interpretation of these videos?

There is another thread about this where the discussion got a bit more detailed. I sent an email to Michael Neff about the AMG videos where they showed 2 Pro golfers where 'Grip Roll' rate was increasing but 'Closure Rate' decreasing approaching impact (which didn't make sense to me at the time). He offered a telephone call to discuss but I'm going deaf so wasn't able to accept his offer. I thought that maybe a change in the golfers club path was offsetting against the increased rotation of the clubface about the shaft axis (due to increasing Grip Roll approaching impact). I'm wondering whether Iacus figured out what 'Closure Rate' in rpm means (see below). I was also wondering what was meant by 'shaft rotational rate' as I thought that was the rotation of the shaft about its longitudinal axis (like Grip Roll).

So which is more meaningful or is ROC meaningless ( see my drawing below)? 1. Rate Of Closure relative to path 2. Rate Of Closure relative to target 3. Rate of Closure measured in degrees/sec 4. Rate of Closure measured in degrees/distance

I sent an email to Dr Sasho MacKenzie about the 'Closure Rates' at impact for those 2 Pro golfers on the AMG video. His reply: "Those numbers seem low even if they are measuring the rate at which the face closes to the path. My numbers line-up with Phil's data, Rob Neal’s data, and Ping data. "

For those AMG golfers in the 1st video I posted the 'Closure Rate' is slowing down between P6.5-P7 and not just at impact , so it is possible that the clubhead path is less in-out from P6.5-P7 than it was from P6-P6.5. You mentioned a possible reason why Dr Sasho Mackenzie/Phil Cheetham ROC measurements at impact could be so different to Gears 'Closure Rate' measurement, that they could be using different frames of reference . Dr Phil Cheetham used AMM3D for his research and a 'Global Frame Of Reference' (ie. the origin or zero point) positioned behind the golfer. Wouldn't the room which holds the Gears cameras be the 'Frame Of Reference' ?

I am aware that the club path changes but the confusion I have is regarding the AMG GEARS video I first posted . This is a tour pro golfer whose GRIP ROLL is increasing ~944 deg/sec at P6 (shaft horizontal) to 1734 deg/sec at P7 (impact). Yet the 'Closure Rate ' increases from -525.44 deg/sec (P6) to -613.10 deg/sec (P6.5) but then suddenly decreases to -359.62 deg/sec (P7). As per the GEARS method of measuring 'Closure Rate' , if the 'Grip Roll' is increasing (ie. increasing the rate of closing clubface rotation), then the club path must be moving from outside the target line at P6.5 then back into impact by P7. That's the only way I can perceive how the 'Closure Rate' can decrease from P6.5-P7 while the 'Grip Roll' is increasing.

Yes , that makes sense , but if the 'Grip Roll' or 'Handle Twist Velocity' is increasing as the club approaches impact but the 'Closure Rate' decreasing , then I must assume that it's due to a change in clubhead path.

Still trying to get this clear in my head: Gears 'Closure Rate' is the rate of change of the angle between these 2 vector directions in deg/sec 1. An instantaneous vector direction perpendicular the leading edge of the club or the bottom groove. 2. A vector showing the instantaneous clubhead path direction (which I assume is the path of the sweet spot or the 'Geometric Centre' of the golf clubhead). The AMG video I first posted shows 'Grip Roll' increasing its rate deg/sec all the way into impact . Which I suppose means an increasing rate of closing clubface rotation of 'point 1 vector' above. But if Gears 'Closure Rate' is decreasing from say P6.5-P7 doesn't this infer that 'point 2 vector' above is changing in such a way that it is counteracting the closing rate of 'point 1 vector' above? That there is a change in clubhead path from P6.5-P7 that is more 'out -in' approaching impact ? Does that make sense?

Many thanks for this reply.

Looks like I've found a video that explains 'Closure Rate' and its not measured the same way as Dr Sasho MacKenzie or Dr Phil Cheetham. It does seem to be related to the rate of change of D-Plane .

So I'm still confused about how they measure 'Closure Rate '. Do they take some instantaneous vector normal to the clubface and compare how quickly it changes with respect to the instantaneous vector clubhead path direction? That sounds more like a rate of change of D-Plane angle.

Please see Dr Phil Cheetham dissertation link below slide 22 and check out the graph of Handle Twist Velocity (I'm assuming this is the same as Grip Roll) vs Clubhead Closing Velocity where they are highly correlated (they are both measured in degrees/sec as in GEARS). If the Grip Roll is increasing so should the Clubhead Closing Velocity but that isn't happening in that AMG video. Dissertation (philcheetham.com) You will also note that the minimum Clubhead Closing Velocity is about 1000 deg/sec while Dr Sasho MacKenzie says in his article the following: "RoC peaks near impact and a typical range for any group of golfers, regardless of level, would be between 1800 °/second and 3600 °/s. " The AMG video is showing Closure Rate for those 2 golfers at impact as being -258.87 deg/sec and -359.62 deg/sec. See GEARS link below and look for Closure Rate Gears Golf: Club and Ball Metrics - Gears Sports Closure Rate is a measure of the rotation of the club face as it approaches the impact point. This measurement is calculated relative to the club’s path. Also, Michael Neff in his video below defined Grip Roll as "how much the grip is turning in plane' . That sounds like an angular measurement , not a rate as shown in the AMG video (degrees/sec) and in the video below. Yet the Gears metric weblink I posted above defined Grip Roll as : Grip rotation is an angular measurement that measures the rotation of the shaft between the top of the backswing and impact. So the above definition seems to clarify what Michael Neff said in his video but why is it showing as a rate in GEARS? I'm assuming there is some error in the definition of Grip Roll as I am guessing it is the same as Dr Phil Cheetham's definition of 'Handle Twist Velocity' (which is a metric term also used in GEARS but defined differently).

How does GEARS measure 'Closure Rate'? I've looked at their website but it doesn't seem to go into detail on the method they used. For example , when I looked at this AMG video (who use GEARS) , I couldn't understand how the 'clubface closure rate' could be decreasing for the 2 Golf Pros as the club approached impact . Also the magnitudes seem very small compared to the article I read from Dr Sasho MacKenzie (unless I've misinterpreted something). What is 'rate of closure' and can it help your golf swing? Rate of Closure is an emerging term you might have heard in golf instruction. We asked Dr. Sasho Mackenzie to explain what it is.

I remember something about 'phantom cameras' being used to check their computer generated images.

Oops ! Should have said "What are the factors for increasing clubhead speed " not " What are the factors for increasing hand speed earlier?" Apologies for that error.