Is gear effect real?

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golfbulldog

golfbulldog

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Nobody ever talks about it anymore - is that because it never happened or the design of clubs went from curved face woods to flatter, bigger COR clubs...???

Presumably high COR clubs rotate less on off-centre impacts so gear effect is less??? Even less because high COR clubs have flatter faces than olde worlde woods???

Came across this stuff - not sure if he is right or wrong - any commments?

http://www.physics.usyd.edu.au/~cross/GOLF/GOLF.htm

Movie 4 seems to show it the way I had it in my mind...practical result being ball starts right of target and draws back to target line...right??

Does trackman data agree with this??

D plane is jsut for sweetspot impacts- right?

Thanks for any thoughts or corrections!
 
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mgranato

mgranato

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From a layman's POV - I've got two hybrids in the same loft. One with a flat face and one with some bulge and roll. When hit off the toe, the ball ends up in quite different locations :)
 
golfbulldog

golfbulldog

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Thanks for your replies.

So clubface rotation during the fraction of a second that is the impact interval causes sufficient spin to be imparted on the ball to influence it's flight a significant amount??

If so - how does that differ from the supposed clubface rotation during impact interval that was "hinge action"??

Is it just magnitude of clubface rotation during impact interval?? ie. gear effect has more clubface rotation than hinge action was supposed to??

Just asking a valid question rather than looking to go put in my application for "book literalist" - so stay calm ....;)
 
J

Jim Kobylinski

Super Moderator
golfbulldog said:
Thanks for your replies.

So clubface rotation during the fraction of a second that is the impact interval causes sufficient spin to be imparted on the ball to influence it's flight a significant amount??
Click to expand...

No, i don't have time to explain but do a search for how/what gear effect is. It has to do with the curve on the face and where the ball is struck.

so - how does that differ from the supposed clubface rotation during impact interval that was "hinge action"??
Click to expand...

See above, hinge action is a concept and gear effect is real and has nothing to do with clubface rotation

Is it just magnitude of clubface rotation during impact interval?? ie. gear effect has more clubface rotation than hinge action was supposed to??
Click to expand...
Again relates to my first answer.
 
B

blehnhard

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Gear Effect - simple explanation (or at least I hope so).

A ball struck not in line with the clubhead COG (center of gravity) will "spin / roll" toward the COG.

Bulge (horizontal curvature) and Roll (vertical curvature) are built into the face of a "wood" to lessen the amount of "roll / spin" toward the COG.

Wooden clubs due to their nature had COG's that were located significantly more "rearward" (away from the face) than Metal Woods (where they can keep the COG closer to the face). As a result, "wooden" clubs had noticebly more bulge and roll to help negate the stronger influence of the more rearward COG. If wood clubs had no bulge - toe hits would hook violently and heel hits would slice violently. Metal woods need much less bulge to negate the effect as the COG is closer to the face and on some metal clubs it would take a trained eye to detect the amount of bulge.

A well engineered club (either wood or metal) should have the appropriate amount of bulge and roll as determined by the distance of the COG back from the face. It was much more difficult to engineer wooden clubheads due to differences in density etc.

It is illegal to have bulge and roll on irons, but the effect of toe / heel hits is minimal due to the COG being for all intents and purposes on the face of the club (just fractions of an inch behind).

Roll (or the vertical curvature) was not as important as it did not effect direction - only spin and launch angle. Balls hit below the COG would tend to have slightly more backspin but lower launch and converse for ball hit above the COG - this is why some recommend striking metal drivers slightly above the COG - some reduction in spin + a slightly higher launch angle.

As Jim K has indicated, gear effect and the notion that you can influence ball flight by having the clubface rotate during the impact interval are 2 completely different issues. Gear effect is real and measurable. The jury is still in the jury room on the other issue.
 
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S

softconsult

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I don't think Center of Gravity has a thing to do with Gear Effect. Why the name Gear Effect?

Think of two wheels with teeth on them meshed together. When you rotate wheel 1 clockwise, the other wheel rotates counter-clockwise. Now think of Bulge as a gear, and the ball as a gear. Friction replaces the teeth. Hit a ball on the toe and the Gear Effect puts some draw spin on the ball. Heel is the opposite.
 
golfbulldog

golfbulldog

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blehnhard said:
Gear Effect - simple explanation (or at least I hope so).

A ball struck not in line with the clubhead COG (center of gravity) will "spin / roll" toward the COG.
Click to expand...

Does the ball roll to the COG of clubface or clubface roll to ball...or do they both give a little?
 
golfbulldog

golfbulldog

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softconsult said:
I don't think Center of Gravity has a thing to do with Gear Effect. Why the name Gear Effect?

Think of two wheels with teeth on them meshed together. When you rotate wheel 1 clockwise, the other wheel rotates counter-clockwise. Now think of Bulge as a gear, and the ball as a gear. Friction replaces the teeth. Hit a ball on the toe and the Gear Effect puts some draw spin on the ball. Heel is the opposite.
Click to expand...

I agree with you about the general desciption of gear effect but differ in that I , like Blehnhard, think COG has a role to play.
 
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softconsult

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Burner, that is a great link. The last time I thought about Gear Effect was probably around 1980 while reading Ralph Maltby's golf Bible!

I read the entire linked article, and as sometimes happens, I learned something. Maybe I should work on not hitting the Driver on the Toe and maybe I should tee it a smidge higher.

Tks
 
golfbulldog

golfbulldog

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Burner said:
There you go
Click to expand...

Thanks Burner,

It would appear that Dave Tutelman does describe clubhead rotation occuring because of off-centre impact and confirms that location of COG is important.

He reports that gear effect does not occur with irons but i suspect that it would be more precise to say that it does occur with irons, only that its magnitude is far less than with a driver - where COG location away from the clubface.

Clubhead rotation is almost independent of shaft torque.

Clubhead rotation during impact interval is the cause of the gear effect spin on the golf ball.

If those statements are true, can conscious clubface rotation during an on-COG strike manipulate ball flight in additon to the established D-plane effects??

Does the ball now why the clubhead/face is rotating during impact?

Is the gear effect really due to a gear-type analogy? Is it just that the clubface alters its alignment and hence D-plane alignment and the ball responds accordingly? ie. there is no "rolling of the ball on the clubface like gears meshing" during impact interval?? ;):rolleyes:

Any thoughts?
 
J

jmessner

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golfbulldog said:
Thanks Burner,


If those statements are true, can conscious clubface rotation during an on-COG strike manipulate ball flight in additon to the established D-plane effects??

Does the ball now why the clubhead/face is rotating during impact?

Is the gear effect really due to a gear-type analogy? Is it just that the clubface alters its alignment and hence D-plane alignment and the ball responds accordingly? ie. there is no "rolling of the ball on the clubface like gears meshing" during impact interval?? ;):rolleyes:

Any thoughts?
Click to expand...

No, I don't think the ball actually rolls, what happens is the face produces a shear force on the ball which imparts the sideways spin component once it separates from the face. Similar to how backspin is created - ball rolls first, then compresses then is sheared (shear force). The theory is that the type of material and construction dictates how it reacts to the shearing force and thus how it spins.

Re: intentionally rotating the clubface. I think we've addressed that before here that it doesn't play a role since you probably can't rotate it fast enough. However, a twist generated by on off-center hit probably produces a fairly high rotation rate during the impact interval.

Jay
 
ZAP

ZAP

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That is really interesting video. I guess I already suspected what happened but seeing it really drives it home.
 
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