Calling all Gear Effect experts

[Frans@France]

...I do not believe that bulge makes up for gear effect, although it does give you a fighting chance. One reason it could not be a perfect fit is that ball speed plays a role in how much the ball ultimately curves. I would venture a guess that there is one specific ball speed....

Instead of venture a guess you could also read the patent involved. "believe" might not be a wise advisor There is no need to adjust bulge to ball speed.

 

[Dan44GT]

Frans, everybody knows you cant adjust the bulge of a given club. But bulge will not make up for gear effect accurately every shot.

I say "venture a guess" because I have no proof, except for years of experience. That said, it is pretty much common sense that the ball will not come back perfectly to the, sweet spot/path related target line if you hit it with different speeds. Again, too much speed will curve the ball past the intended line, too little wont get it back to the line.

Example...

Sweet spot = 0.0
Club Path = 0.0
Impact = 1/2 inch off toe
True Face = 2* open
Ball Speed = 155
Result = Mega Hook past target Line

Now...

Change Ball speed to 100, the result will not be a major hook, maybe not even enough to get you back to the target line.

Therefore what I'm saying is that there is no perfect bulge setup for every shot.

BTW, this is what I "Believe", nothing more than that.

 

[savydan]

Dan,

1. Do the results stay the same if you swap clubhead speed for ball speed?

2. What do you think of Tuxen's rule that curvature is a result of axis tilt with no mention of clubhead speed (or ball speed)?

 

[Frans@France]

I say "venture a guess" because I have no proof

Therefor reading the patent would have provide the proof that your "believe" is wrong as it includes tests with a swingrobot set to hit shorter shots also.

Sweet spot = 0.0
Club Path = 0.0
Impact = 1/2 inch off toe
True Face = 2* open
Ball Speed = 155
Result = Mega Hook past target Line

Your assumption of the result "mega hook past target line" where does that come from?

 

[Dan44GT]

Kevin or Brian Confirm??

Your assumption of the result "mega hook past target line" where does that come from?

Observing 100's of shots on Trackman with a Face Open to Path and a negative spin axis due to obvious toe hits that curve hard left.

Certainly, one thing that has become very important to me with the use of trackman is the centeredness of contact with Driver specifically.


As for the patent statement, I'm not following. Post something tangible and maybe I will understand. I am just thinking about obvious real world examples and it would take a lot of convincing to make me believe that there is a bulge that equalizes gear effect perfectly for every shot, its just is not reasonable in my opinion. But I've been proven wrong before, that's for sure.

Savy,

I dont have an answer for question 1.

As for question 2, using strictly Trackman experience, my literal answer is that speed does not directly influence curvature, but it does indirectly. The two numerical direct influences on curvature are spin axis and backspin (spin rate). Now, I believe that spin rate increases with more ball speed, and ball speed increases with higher clubhead speed and smash of course.

I am certainly not the foremost expert in this topic, although I feel qualified, could Brian or Kevin share their opinions/experiences???

 

[Frans@France]

...Post something tangible and maybe I will understand....

Maybe this page All about Gear Effect - 1 will provide some more background information. If you still have questions after reading it I will be more then happy trying to answer them.

 

[Dan44GT]

Thanks for the link Frans. It completely proved my point.

I have visited that site often, just dont always make it down to the bottom of the pages. The graph at the bottom shows that bulge does not completely make up for gear effect. I will say though that I probably exagerated my example with the 1/2 inch off toe, probably more like 1 1/2 inches!

What I know is I see players with fast swing speeds hit big time hooks with a face open to path on trackman due to toe hits. I also see golfers with slower speeds hit obvious toe shots with Driver that never come back.

 

[Frans@France]

Thanks for the link Frans. It completely proved my point.

Then you might not have read it correctly

Let's retry the calculation for those two situations that you thought would provide prove that bulge should be depended on swing speed. You mentioned ballspeed 155 and ball speed 100

AoA 0, path 0, Face angle 0, 11Degree Loft, 12'' bulge
.5'' impact error, therefor horz. launch angle 2.1

155 mph :
Slice spin due to buldge : 698
Hook spin due to gear effect : 1150

Hook spin netto : 452, shot deviation 7,2 yards

100 mph :
Slice spin due to buldge : 450
Hook spin due to gear effect : 742

Hook spin netto : 292, shot deviation 1,4 yards.

So with some assumptions in the calculation we see a 6 yards difference in a shot that is almost 150 yards longer.

I don't think that these calculations prove your points you made earlier?

too much speed will curve the ball past the intended line, too little wont get it back to the line.

Ball Speed = 155..Result = Mega Hook past target Line...Change Ball speed to 100, the result will not be a major hook, maybe not even enough to get you back to the target line.

 

[Dan44GT]

Frans, trying to not be argumentative but we certainly dont communicate in the same manner. I dont have time to explain anymore, but I think most people get the point. Remember my statements are generalizations for simplicitys sake that is not inaccurate.

MY WHOLE POINT IS THAT THE BULGE WILL NOT COMPLETELY MAKE UP FOR GEAR EFFECT, IT JUST HELPS.

 

[Frans@France]

Frans, trying to not be argumentative but we certainly dont communicate in the same manner. I dont have time to explain anymore, but I think most people get the point. Remember my statements are generalizations for simplicitys sake that is not inaccurate.

MY WHOLE POINT IS THAT THE BULGE WILL NOT COMPLETELY MAKE UP FOR GEAR EFFECT, IT JUST HELPS.

Dan, no need to shout. I enjoy discussions like this but I enjoy them a bit more when I get challenged. What you miss in the calculation besides the fact that those are based on some estimates is the following quote from the site also

The errors due to bulge do a fine job of canceling out the errors due to gear effect. And they could be even better. A few calculations at a 10½" bulge radius shows very small errors, in the vicinity of a yard

In other words, in the calculation the bulge of 12'' used for this head was not the correct bulge in relation with it's center of gravity.

 

[Dan44GT]

Sorry Frans, I was not shouting, if you knew me, you'd know that I can count on one hand the times I've shouted in my life. I just wanted to type it in bold so that I knew you could read it.

I really dont like these discussions, I haven't learned from it, except to never answer another post again.

From now on, I am leaving it up to Brian and his staff as I should have in the first place.

I apoligize for ruining a good topic.

 

[mjstrong]

Dan, I think most of us were reading a good debate between two guys on a topic they were interested in. Don't pledge to stop posting; you made good points. Brian and his staff can't chime in on every single topic; that's why guys like you, Frans, and I are here - to discuss and debate. Let's keep it going.

 

[dominicscaife]

I probably exagerated my example with the 1/2 inch off toe, probably more like 1 1/2 inches!

Dan did mention he had probably exaggerated a little, Frans.

If you use 1.5'' offcentre instead of 0.5'' and ball speed of 100 vs 160 (hacker vs scratch)

Do you get similiar result?