THE GEAR EFFECT
This
is most easily understood if we imagine a clubhead to be stationary and a ball
projected at it. If it strikes the clubface opposite the CENTER OF GRAVITY
it just knocks the clubhead straight back. If it strikes the clubface near the
toe it not only knocks the clubhead back, but in addition sets it turning
around its CENTER OF GRAVITY.
This
effectively opens the clubface a little, which in the absence of any other
effect would then take on the slicing spin normally caused by an open face.
However, if the CENTER OF GRAVITY lies back from the clubface, as it does in a
wooden driver, the rotation set up by the off-center blow causes the point of
contact between the clubface and the ball to move sideways as well as back.
This pushes the clubface across the back of the ball, and so imparts, in the
case of a toed shot, hooking spin, which, with a perfectly flat driver face is
more than enough to counteract the slight opening of the clubface.
The
same holds true for heeled shots, which will tend to take on a slicing spin. The effect has been called THE GEAR EFFECT since ball and clubface behave like two enmeshed gear wheels, with the
clubface rotating in one direction and the ball in another.
Getting the right amount of BULGE;
When
the ball is hit near the toe two opposing effects come into play. First, the
force of the blow opens the clubface sending the ball off a little to the right
of the intended line and secondly the GEAR EFFECT imparts hooking spin.
With perfectly flat faced drivers the GEAR EFFECT predominates and a
toed shot sets off to the right but hooks violently back across the intended
line to the other side of the fairway or rough.
A
convex bulge on the face of a driver can help restore a balance simply because
it makes the toe of the club a little open, (and the heel a little shut).The
correct amount of BULGE usually a 10” radius on wooden woods and a 12” radius
on metal woods leaves the GEAR EFECT in the ascendant, and imparts just enough
hooking spin to a toed shot to bring it back to the middle of the fairway
To much BULGE gives the GEAR EFECT no chance to counteract the extreme openness of the toe of the clubface
Heeled shots are affected in a similar way by BULGING the clubface.
