Tutelman's new article about Gear Effect and Roll Radii

[LyleG]

I would love to get into this, but I don't have the time right now to read the article. Soft tip negating spin? Sounds wacky.

I have seen a few tests from different people that confirm this. I have never seen a game like golf where opposites rule the day as often.

 

[David Hillman]

Both agree on the idea of bulge. Wishon believes that ROLL is useless, because it produces inconsistent launch angles versus a face with no roll. Tutelman disagrees.

Hmmm... one guy is designing and building prototypes __and testing them__ with humans and a robot. One guy is doing back-of the-napkin estimates that are barely more than SWAGs in some cases. For example, Tutelman's entire VGE premise rests on this casual estimation... "Some approximate calculations suggest that, for most driver heads, Iv will be some fraction of Ih, probably between .5 and .66 of Ih."

 

[Adam Pettman]

You have to stop using inches. Its just silly, catch up.

 

[MCDavis]

You have to stop using inches. Its just silly, catch up.

Metric sucks!

Funny story. 10 years ago or more the US Army Corps of Engineers (they handle construction at Ft. Bragg) decided they were going to bring the NC const. industry into the metric age by requiring their buildings to be bid, submitted, and built in metric. The only problem was, once they got in the field they realized that all the material came in inches/feet. NO ONE would provide metric materials, and NO ONE would use metric measuring devices.

On top of that, many subs simply stopped bidding their work.

They quickly dumped their metric program.

 

[TheWOAT]

Metric? Who cares, it wouldnt improve anything, and just cause some initial headaches. Besides, alot of things bought and sold here are labeled in metric and are required by law to do so... Its there but no one pays attention to it...

Anways, Tutelman's seems to be right based on my range sessions... Im sure he feels he is right on paper, but on paper alot of things look good(like Microsoft Zune)

 

[SilverUberXeno]

Hmmm... one guy is designing and building prototypes __and testing them__ with humans and a robot. One guy is doing back-of the-napkin estimates that are barely more than SWAGs in some cases. For example, Tutelman's entire VGE premise rests on this casual estimation... "Some approximate calculations suggest that, for most driver heads, Iv will be some fraction of Ih, probably between .5 and .66 of Ih."

Hm. I thought I argued with you about VGE before, and you were on the side of Tutelman's new theory. I was going to apologize and everything if you were right

I've been thinking about it all morning; the VGE. And frankly I can't imagine it's better than a no-roll face with a proper angle of attack. I'm thinking that hitting higher ont he face with a NORMAL AofA may net better numbers. But center-face contact is where you get the best ball speed and best power transfer. I still think a golfer would be better off getting a properly lofted driver to match his desired AofA, then learning to swing up into it and hitting center-face.

I will read Tutelman's article this weekend and make a more intelligent assessment of the science. But it doesn't seem very logical to me right now.

 

[RickinMA]

I'm curious to see more launch monitor data on this. I'm also looking forward to more engineers reviewing it all and commenting.
It would be interesting to see if Wishon begins experimenting with different GRT combos (I think it was currently 20" radius on the bottom and 15" on top) maybe 9-10" top radius while leaving the bottom alone is the way to go

 

[SilverUberXeno]

I have seen a few tests from different people that confirm this. I have never seen a game like golf where opposites rule the day as often.

Again, I haven't read thr article, but I can sort of see how this may be the case in my mind.

Gear effect, again, is the rotation of the head around either the vertical or horizontal axis (passing through the CoG). Horizontal gear effect takes place when the ball is struck off the heel or toe side of the CoG; the clubhead twists from the recoil, sending the ball on a non-straight path.

Bulge is the curve from toe to heel on a club, which takes advantage of gear effect int he following way:

When the ball strikes off the toe, for instance, the clubhead turns clockwise away from the ball. since the face is curved slightly, the ball and the clubhead act like gears; the clubhead, simply by bulge design, will put corrective sidespin on the ball. As the toe rotates clockwise, it puts counter-clockwise spin on the ball. The ball will start to the right as normal for a toe-mishit, but then draw back slightly toward the center. Bulge radius is built-in forgiveness.

Vertical gear effect is debateable, obviously. The following is/was my argument as to why VGE is more trouble than anything else.

This curve is from sole to crown, which naturally changes the loft across the clubface. Launch angle is very important. Bulge does not effect loft, because it is a horizontal curve. The vertical curve WILL screw with launch angles. High-face contact will send the ball UP, and a low-face shot will keep the ball very low. VGE, supposedly, creates a counter-directional spin, just like bulge.

In this instance, a low shot will spin more and get closer to the desired height. This sounds nice, but it begs the question; why not keep the entire face the same loft? Then you wouldn't get a low shot unless you hit it off the sole-- in which case, no amount of spin will help you.

A high-face shot will conversely be sent off with much reduced backspin, due to the roll of the clubface and VGE. The ideal is that this produces a high-launch, low spin shot. THAT is the ideal drive.

BUT VGE is most likely (at least, as I picture it in my mind) not NEARLY as prevelent as horizontal GE. This is because:

a.) The crown/sole distance is smaller than the heel/toe distance
b.) The shaft is in the head on a much more vertical axis, which will reduce the clubhead's ability to rotate vertically.

However, with a SOFT TIPPED SHAFT, the ability of the clubhead to rotate vertically would certainly increase.

Still though... A proper loft with a stiff tip shaft will produce more consistent results. On the bottom of the clubface, roll is worse than inconsequental, because it produces low shots. No roll on the bottom of the face would result in shots that left he clubface much closer to the ideal launch angle.

High on the face, no roll would reduce the likelyhood of skyballs and ballooners. Keep in mind, you're not SUPPOSED to be hitting it up here! But roll IS more justified on the top, because if you do send it off high, you will want less spin in order to get the most distance possible out of the mishit. This is assuming a measurable amount of VGE, which is what is currently under debate. If VGE is minimal or inconsequential (see a.), b.) ) then there is no reason for roll at the top of the face.

Wishon went to a slight-roll design because producing a perfectly flat face was very difficult in the real world. The faced occasionally became concave in production. Allowing for MINOR roll produced more viable heads.

In closing, I'll say that roll on the bottom of the face should be near zero. When I say "NO roll" I don't actually mean FLAT on account of production difficulty. But it should be as close to zero as is possible on a practical level.

The roll on the top of the face should still be marginal, though it would be reasonable to have more there than on the bottom. If using a soft-tipped shaft, which will enhance VGE, roll on the top of the face may assist in forgiveness. However, if VGE is inconsequentially small by design, a no-roll face is the optimum here as well.

 

[David Hillman]

Hm. I thought I argued with you about VGE before, and you were on the side of Tutelman's new theory. I was going to apologize and everything if you were right

We had a slightly different dispute, IIRC. I'm a skeptic as regards all claims of gear effect influencing ball flight, in any plane. I don't think there's significant benefit to roll, or bulge.

 

[LyleG]

SUX,

My theory on why a lot of players get better spin numbers with softer shafts, especially softer tipped shafts is not based on science, but on what I see in my fitting. Now from a scientific stand point this may seem ludicrous, but I really do believe every word of it. Maybe I am a nut (wouldnt be the first time that theory has been discussed LOL), but I do know for sure I am not a scientist. Here is my theory.

Much of what happens during the golf swing is subconscious. Our brains instruct or bodies to do a wide variety of things we have no idea we are doing. When a player is swinging a shaft that is too stiff we cant feel the shaft doing what it is suppose to do. We may not realize it, but as a result we make compensations. The biggest and most detrimental compensation being we get the hands involved, especially the wrists, which tend to get "flicked" at impact. This loses speed, increases loft, and increases spin. It also causes players to swing harder in a effort to regain feel, again whether they realize it or not. With a softer shaft we feel the shaft bend, we feel the shaft work. Now we compensate by increasing our lag, maintaining the wrist angle through impact, and following through well past. All resulting in shots that have more speed, fly slightly lower and have less spin.

Now I could be way off, but this is what I believe is happening. And please remember I am not a true scientist LOL.

 

[ezra76]

So why is it that I drove the ball like crap yesterday and the face of my driver looks like this?

 

[twofast2s]

I would love to get into this, but I don't have the time right now to read the article. Soft tip negating spin? Sounds wacky.

A soft tipped X flex? Kind of anti-redundant, don't you think?

you can correlate tip flex and shaft flex together. but over all you're right. people w/ higher swing speed tend to favor and perform better w/ stiffer tip section.

i can kinda see where this argument is coming from, but i think to notice the difference, your swing has to be very consistant, like anything else. for me, having a softer tipped or softer flex shaft causes me to flip my hand more so that boardier shafts. so for me, i would have to play one of the other for long time to see the difference. just not feasible for me.

 

[Augster]

SUX,

In your gearhead mind, I think you will see absolutely that Tutelman is more than likely right after reading the entire article.

Dana Upshaw's monitor, and results, show this. Lyle has alluded to it also. Then there is Tutelman's breakdown of the entire theory. Tutelman was a skeptic also, along with the TM claims, and has seen the light. I just don't know how Wishon's tests have looked over this.

The dropoff, going vertically on the face, of COR/CT is negligible at best. Here is Wishon's testing 2 years ago....

http://www.wishongolf.com/etechreport/2007/may/index_std.html

If you look at the 919THI, the center is .828 and 1/2" ABOVE center is .822. A loss in COR of .006. What is that? A yard of carry?

But when you don't hit the center, you introduce VGE. On-center, you don't.

I love the slow-mo pics in the article that shows the clubhead still folding BACKWARD a good 2 or 3 feet after the hit.

Read the article when you have a few hours to kill. Since this is brand new stuff (not really, well the article is), hopefully Wishon will start looking into the claims with a bit more vigor and fire up his Trackman to prove/disprove the VGE claims.

I can see maybe fooling a Vector launch monitor. You can't really fool the math though. Math is math.

 

[Wi-Golfer]

This entire thread makes my head hurt.:bang:

 

[TheWOAT]

A year or so ago, wasnt there a few threads on the old Maltby CT250 driver, where in order to get the best distance you had to tee it up higher and hit the higher on the face?