Gear effect and driver face curvature.

[billchao]

yes. As I understand it, measured against a flat standard, though I can't tell you the z axis, (I believe its 1 inch) which is pulled from either a 10 or 14 inch x and y width and height, thus effecting the radius. It doesnt matter to me as a consumer since I have few choices, I tend to get the larger radius as they are flatter. And dont act like I know that much about bulge and roll...its hearsay from the back of yet another proshop somewhere in Alabama. I would say that as far as my hybrids go, I really really want a iron face. I absolutey want the least correction on my trouble shots, which are left or right off the tee, and I have to bend the next shot to straighten up. OR if is a sidehill, where I am bending the shot to counter the natural effect the lie has on the shot to one side or the other. Those Adams seem fairly flat, though I am hitting TM resues now and they are bulgy. I tried some X2hot hybrids but took them back for some wedges. They werent better than what I have now.

Do you actually purchase your clubs based on whether they have face roll, or do you hit them, first? I know a lot of people get caught up on the looks of a club and I just don't get it. I'll play a rainbow colored driver head if it's what I hit best. A little OT, but I did this the last time I bought clubs. I just tried a bunch of different sets from different manufacturers and picked the one with the best results. I would have never picked that particular set if I went in to purchase with any kind of bias at all.

[trickyputt]

I figure if the face of a club is the major component of the direction of ball flight why would I want to hit a ball with a ball? Its really not that big a deal for me, I am more interested in a consistently hot face than anything, especially the lower lip. I try other players clubs. I hate simulators. Sometimes I just buy them to see. Whats different is I am fairly committed to the type of shafts I like, so I may try a different head, but most oem shafts have too much action for me and my clubs all have the same shaft. That really isolates the head designs I like.

[mvmac]

I would say that as far as my hybrids go, I really really want a iron face. I absolutey want the least correction on my trouble shots, which are left or right off the tee, and I have to bend the next shot to straighten up.

The correction or way the ball curves, when you hit a shot off center, is due to the gear effect, it's not the bulge and roll.

I figure if the face of a club is the major component of the direction of ball flight why would I want to hit a ball with a ball? Its really not that big a deal for me, I am more interested in a consistently hot face than anything, especially the lower lip.

If I toe a driver it only helps me that it starts a little further right because it's going to draw a little more. It's not going to start some crazy amount off line because the face is curved.

[trickyputt]

[QUOTE name="trickyputt" url="/t/77545/gear-effect-and-driver-face-curvature#post_1064255"] I would say that as far as my hybrids go, I really really want a iron face. I absolutey want the least correction on my trouble shots, which are left or right off the tee, and I have to bend the next shot to straighten up. [/QUOTE] The correction or way the ball curves, when you hit a shot off center, is due to the gear effect, it's not the bulge and roll.  [QUOTE name="trickyputt" url="/t/77545/gear-effect-and-driver-face-curvature/18#post_1064270"] I figure if the face of a club is the major component of the direction of ball flight why would I want to hit a ball with a ball? Its really not that big a deal for me, I am more interested in a consistently hot face than anything, especially the lower lip.[/QUOTE] If I toe a driver it only helps me that it starts a little further right because it's going to draw a little more. It's not going to start some crazy amount off line because the face is curved.

Yes. I want less variables right now. But I am fickle and may change my mind next year. Right now when I end up long left in the trees on a particular par 5 that bends right, I have to draw out to hit it straight because the ball is below my feet promoting fade. I have a lot going on for the second shot. Its usually my 17 hybrid. I just dont want another variable in that example. I believe bulge and roll is designed into the clubs to promote the gear effect. I play 14 inch radius bulge because they have less correction. The 10 inch makes me hit all over the place.

[mvmac]

I believe bulge and roll is designed into the clubs to promote the gear effect.

Again, the bulge and roll has nothing to do with the gear effect. It has to do with where the ball contacts the club in relation to the club's center of gravity. Irons have gear effect.

[trickyputt]

I disagree. I had to go look it up. I even found some patents on my R1. 9 inch bulge 6 inch roll. Go figure. Its to enlarge the sweetspot. Turns out the gear effect can be too little, too much or just right for you based on bulge. They even have diagrams of that.

[saevel25]

Again, the bulge and roll has nothing to do with the gear effect. It has to do with where the ball contacts the club in relation to the club's center of gravity. Irons have gear effect.

If anything, wouldn't bulge ans roll negate some gear effect. If a toe shot helps produce a spin axis more towards a draw. Doesn't the roll create a more open face angle at the toe, hence less draw curve?

[trickyputt]

Here was one page that had a decent chart. My problem is I want less action on my shots. They give me too much help in the head design and I overdraw/slice because its a hair trigger sensitivity. http://www.golfclub-technology.com/gear-effect.html Without bulge I guess they say the ball would stay out right on a toe shot instead of drawing back.

[mvmac]

I disagree. I had to go look it up. I even found some patents on my R1. 9 inch bulge 6 inch roll. Go figure. Its to enlarge the sweetspot. Turns out the gear effect can be too little, too much or just right for you based on bulge. They even have diagrams of that.

Ok, you can disagree all you want but that's just the way things are. It's physics. Bulge and roll has nothing to do with gear effect.

Here was one page that had a decent chart. My problem is I want less action on my shots. They give me too much help in the head design and I overdraw/slice because its a hair trigger sensitivity.

http://www.golfclub-technology.com/gear-effect.html

Article is wrong when it says this, "There is a certain amount of curvature to the face of a club which causes gear-effect."

[trickyputt]

Good video. He said the same thing as the article. The only difference is the article doesnt seperate the gear/bulge term because they are two mechanical functions that are occuring at the same time, whereas the other (newer?) school does separate the terms for discussion purposes. When I hit the ball however, both functions occur simultaneously so its good to know. In the chart from the article, the flight effects described in the video are presented so I think they say the same thing with different terminology. When you say one has "nothing" to do with the other, it is technically correct and contextually wrong at the same time relative to my point. This thread does make me want to count how many times my ball flight crosses the target line with a club. Good stuff.

[mvmac]

Good video. He said the same thing as the article. The only difference is the article doesnt seperate the gear/bulge term because they are two mechanical functions that are occuring at the same time, whereas the other (newer?) school does separate the terms for discussion purposes. When I hit the ball however, both functions occur simultaneously so its good to know. In the chart from the article, the flight effects described in the video are presented so I think they say the same thing with different terminology. When you say one has "nothing" to do with the other, it is technically correct and contextually wrong at the same time relative to my point.

This thread does make me want to count how many times my ball flight crosses the target line with a club. Good stuff.

The article isn't quite clear, it does talk about CoG but it also says stuff like, "There is a certain amount of curvature to the face of a club which causes gear-effect" and "Bulge, which is responsible for horizontal gear-effect". It also just mentions woods so people would be left to believe that gear effect only occurs with woods.

The point is, the bulge and roll of the club head doesn't tilt the spin axis, it just starts the ball a little more left or right to compensate for the increased tilt to the spin axis.

Just to point out real quick, hitting it off the toe doesn't guarantee a draw, same with hitting it off the heel, there are obviously other factors that determine how the ball is going to curve.

[trickyputt]

You bring up a particularly interesting point about tilting a ball and it was mentioned in the video also. I am all ears about that, but unfortunately its off the topic of this thread.

[mvmac]

You bring up a particularly interesting point about tilting a ball and it was mentioned in the video also. I am all ears about that, but unfortunately its off the topic of this thread.

The ball spins in one direction, on one axis, an axis called the spin axis. So there is no such thing as "side spin".

Think of it like wings on an airplane. The spin axis will tilt whenever the face and path head in different directions. So let's say your face is 2 degrees right of the target, path is 5 right of the target, face is closed to the path, spin axis will be tilted to the left, that's what makes the ball draw.

Let's say your face is 0, path is zero but you toe it, the gear effect will tilt the spin axis left. Ball will start at the target and curve left somewhat.

[boogielicious]

Is there math behind the gear effect.  I'm asking you @jamo our most recent Mechanical Engineering graduate!  Old inquiring engineers want to know!

[saevel25]

Is there math behind the gear effect.  I'm asking you @jamo our most recent Mechanical Engineering graduate!  Old inquiring engineers want to know!

Above my pay grade

[MS256]

Good video. He said the same thing as the article. The only difference is the article doesnt seperate the gear/bulge term because they are two mechanical functions that are occuring at the same time, whereas the other (newer?) school does separate the terms for discussion purposes. When I hit the ball however, both functions occur simultaneously so its good to know. In the chart from the article, the flight effects described in the video are presented so I think they say the same thing with different terminology. When you say one has "nothing" to do with the other, it is technically correct and contextually wrong at the same time relative to my point.

This thread does make me want to count how many times my ball flight crosses the target line with a club. Good stuff.

I like the chart. What it says to me is that possible* gear effect is the same and that the bulge helps correct initial path. Too much bulge = over-correction. Too little bulge = no correction.

What common sense would indicate all along.

* The reason I used possible is because I hit plenty of balls toward the toe or the heel where the flight doesn't show any visible gear effect or even does the opposite of what a gear effect would indicate.

IMO. Present gear effect in those cases (like off of the heel for me) probably simply turns a hook into less of a hook or a draw into a straighter ball because of a bad path to face angle on that swing.

[jamo]

I like the chart. What it says to me is that possible* gear effect is the same and that the bulge helps correct initial path. Too much bulge = over-correction. Too little bulge = no correction. What common sense would indicate all along. * The reason I used possible is because I hit plenty of balls toward the toe or the heel where the flight doesn't show any visible gear effect or even does the opposite of what a gear effect would indicate. IMO. Present gear effect in those cases (like off of the heel for me) probably simply turns a hook into less of a hook or a draw into a straighter ball because of a bad path to face angle on that swing.

Yes. Gear effect doesn't just disappear occasionally, but if you hit one off the toe with a huge slice swing, it might still slice. [quote name="boogielicious" url="/t/77545/gear-effect-and-driver-face-curvature/30_30#post_1064300"]Is there math behind the gear effect.  I'm asking you @jamo our most recent Mechanical Engineering graduate!  Old inquiring engineers want to know! [/quote] I would, but @mvmac has it nailed. Gear effect (which is mostly a product of CoG and MOI) and bulge/roll are two different things.

[RandallT]

Is there math behind the gear effect.  I'm asking you @jamo our most recent Mechanical Engineering graduate!  Old inquiring engineers want to know!

http://mytrackman.com/media/9f72695f-2dd7-41a9-9556-2056c3291078/Content/5_%20Editorial/Newsletter%2001-2013/2_pdf Page 4 of 16 here too: http://mytrackman.com/media/9f72695f-2dd7-41a9-9556-2056c3291078/Content/5_%20Editorial/Newsletter%2001-2013/2_pdf I remember a year or two ago researching gear effect for myself and stumbling across these Trackman resources. I thought they were informative, and they align with what has been said. Just a bit more "mathy " and some quantifying numbers of the impact. A driver hit off center by one dimple results in spin that can result in 10yds left or right. 6-iron off by one dimple, just a couple yards. Edit: This quote also found in 2nd PDF: "Luckily the club manufactures have added a curvature to the club face (the bulge) on woods and drivers. This means that when you impact the ball on the heel your face angle at the impact point will most likely be closed, hereby starting the ball more left and tilting the D-plane towards a draw spin. The net effect will be a much straighter shot compared to the zero face angle situation."