Sporting equipment

The swing of a golf club is changed by adding an additional weight, the center of gravity of the additional weight being at or below the center of gravity of the hand position on the gripping region of the club to provide a positive lever action for the club in the first cocked movement of the swing substantially the same moment of inertia in the first phase of the downswing wherein the golfer's hands are in the cocked position as conventional clubs and to provide a reduced moment of inertia for the club in the second uncocked movement of the swing between the uncocking of the golfer's hands and the striking of a golf ball.

BACKGROUND OF THE INVENTION 
The present invention relates to sporting equipment and more particularly 
to improvements in or relating to the design of golf clubs, hereinafter 
referred to as clubs. 
With known designs of clubs the weight, for any given weight of club, tends 
to be concentrated at the head of the club and whilst for the professional 
player this weight is controllable during striking of the ball for the 
amateur player the ball is often wrongly struck. 
The invention provides a golf club which is much easier to use than 
previous known golf clubs by reducing the moment of inertia about the 
wrist-cock axis relative to a prior art golf club to thereby enable better 
control to be achieved in the second critical part of the golfer's swing. 
It is an object of the present invention to provide a club with a weight 
distribution which enables the amateur player to strike the ball with 
greater accuracy and greater consistency. 
SUMMARY OF THE INVENTION 
The foregoing object is achieved by way of the present invention wherein a 
set of golf clubs wherein each of the golf clubs in the set are of a 
different length are provided with the weight specifically located in the 
shaft of each of the golf clubs of the set such that during a downward 
swing of any of the clubs of the set by a golfer the moment (M.sub.1) and 
a second moment of inertia (M.sub.2) about a wrist-cock axis are 
controlled so as to enable the amateur player to strike the ball with 
greater accuracy and greater consistency. In accordance with the present 
invention the shaft of each of the golf clubs is provided with a distinct 
grip disposed on the shaft which defines a normal gripping area for 
gripping the club by the golfer. The gripping area includes a normal 
central position located approximately four inches below the butt end of 
the shaft wherein the golfer's hands are normally located. In accordance 
with the present invention, an additional weight is provided on the shaft 
adjacent to the gripping area for altering the balance of the club so as 
to control the moment (M.sub.1) and second moment of inertia (M.sub.2) as 
aforesaid. The additional weight is positioned at a predetermined location 
adjacent the gripping area and the mass of the additional weight is 
calculated in accordance with the weight of the head of the club to 
achieve an inertia ratio of the club of greater than 2.0. Inertia ratio is 
defined by the following equation: 
EQU (I+MR.sup.2)/I 
wherein I is the moment of inertia, M is the total weight of the golf club, 
and R is the effective length of the golfer's arm. In accordance with the 
particular feature of the present invention the center of gravity of the 
additional weight is located about between 0 to 4 inches below the normal 
central position of the golfer's hand on the gripping area. By locating 
the additional weight as aforesaid the moment (M.sub.1) about the 
wrist-cock axis during movement of the golf club during the downswing of 
the golf club is less than 24.5.times.10.sup.3 GMCM and the moment of 
inertia (M.sub.2) about the wrist-cock axis during movement of the club 
during the downswing of the golf club between the uncocking of the 
golfer's wrists and striking of the ball is less than 1.9.times.10.sup.6 
GMCMS.sup.2. By controlling the moment (M.sub.a) and moment of inertia 
(M.sub.2) as aforesaid the amateur player is able to strike the ball with 
greater accuracy and greater consistency. 
Preferably in a further embodiment the second moment about the wrist-cock 
axis is less than 1.8.times.10.sup.6 gm cm.sup.2 and the first moment is 
less than 23.5.times.10.sup.3 gm cm. 
In a still further preferred embodiment, the moment about the wrist-cock 
axis is less than 1.7.times.10.sup.6 gm cm.sup.2 and the first moment is 
less than 23.0.times.10.sup.3 gm cm. 
In accordance with the present invention, a method is provided for 
designing a set of golf clubs having the inertia ratio, moment (M.sub.1) 
and moment of inertia (M.sub.2) as described above. In accordance with the 
method of the present invention the weights of the head, shaft and grip of 
each golf club in the set of golf clubs are determined in weight of the 
head of the golf club is reduced and the additional weight is applied to 
the shaft based on the weights of the head, shaft and grip of the golf 
club so as to locate the additional weight in order to obtain the desired 
characteristics of the golf club of the present invention as described 
hereinabove.

DETAILED DESCRIPTION 
The designs of golf clubs have changed significantly over recent years and 
many technological advances have been made. New materials have been used 
in place of the conventional iron and wood heads, new shapes of head with 
better aerodynamics and different weight distribution have been tried, and 
shafts of reinforced plastic are becoming common, particularly in the 
United States and Japan. However the fundamental make up of the club 
remains the same. Of the overall weight of 350 to 500 gms, typically 60% 
is in the head, 30% in the shaft and 10% in the grip. 
The dynamics of the swing of any piece of sporting equipment are complex. 
The equations of motion are however relatively straightforward and lead to 
general qualitative solutions. To specify the quantitative solutions for 
particular cases requires a knowledge of the forces that come into play, 
applied by the human frame, arms and wrists and these are not well 
defined. To proceed to a solution previous researchers have therefore used 
observations of professional swings. The constants in the equations can 
then be determined from these observations and the calculated patterns of 
the swing compare well with the actual swing. 
Two particular pieces of existing research are relevant to this invention. 
1. Williams, D. The Dynamics of the Golf Swing. Quarterly Journ. Mech & 
Applied Math Vol XX Pt 2 1967. 
2. Jorgensen T. On the dynamics of the swing of a golf club. American 
Journal of Physics. Vol 38 No 5 May 1970. 
Although their treatment of the equations is different they both show that 
there is an `optimum` way to swing the club to achieve the maximum 
clubhead velocity at the impact of club and ball, for a given energy 
input. This maximisation of velocity is very important in that not only 
does it cause the ball to travel longer distances with the driver and long 
irons but it causes the generation of much backspin on the ball for short 
irons, which is essential for good shots to the green. Any deviation from 
the optimum swing not only reduces the velocity at impact but also 
significantly changes the line of the swing. The clubhead/ball impact is 
not square and the ball often slices away on a curve to the right (for a 
right-handed player). Golfers often refer to this phenomenon as hitting 
from the top. The significance of this phrase is the essence of this 
invention. 
First consider the implications of the work of Williams and Jorgensen. The 
optimum swing can be described, beginning from the completion of the 
backswing, as follows: 
The body and arms of the golfer accelerate the club from rest at about 20 
m/s.sup.2. The wrists remain cocked in the position attained at the top of 
the swing. This phase continues with the wrists still locked in position 
for approximately 60 to 65 degrees of rotation of the body with the 
acceleration rising to 300 m/s.sup.2. At this stage, and no earlier, the 
wrists begin to uncock. The hands continue in an arc at roughly constant 
velocity and the club rotates with increasing angular velocity about them. 
The velocity of the clubhead therefore has two components, that due to the 
speed of the hands and that due to the rotation of the club about them. If 
the swing has been timed correctly the hands will reach the bottom of the 
swing at the exact moment that the clubhead reaches the bottom. This is 
the condition that Williams and Jorgensen refer to as optimum. 
The attainment of such a swing is governed by the muscular effort of the 
swinger and the weight of the components he is swinging. Many muscles are 
used in the effort and to achieve the optimum they must be combined in a 
particular way. It is particularly important for the first phase of the 
swing (where the wrists remain cocked) to encompass the full angle 
mentioned above. Only then will the uncocking process of the wrists bring 
the clubhead square on impact and at high speed. Now all tests and 
research has so far been conducted mainly on professional golfers or 
golfers with excellent swings. These individuals have generally been 
brought up to play the game from an early age, or have had the benefit of 
a natural talent for the game or a good teacher and much practise of the 
correct manner of swinging. Thus the muscles, and specifically the balance 
between the muscles, is developed to suit the requirements of a good 
swing. (An obvious example of this, in another sport, is the gross 
development of the arm of a professional tennis player). True there are 
individuals who have what appear to be poor swings even in the ranks of 
the professional but eventually they acquire the ability to bring the 
clubhead square at impact. The time and effort to do this is beyond the 
means of the general amateur player. Most amateurs, particularly men, come 
to the game when their balance of muscles is very inappropriate to a good 
golf swing. They have strong back and leg muscles, and moderate upper arm 
muscles. They are able to lock the wrists in the direction of the line of 
the arms as would be required for lifting heavy weights, but they lack the 
ability and strength to control the rotation of the wrists about the arms 
under a large load. In the swing this load comes from the very large 
centrifugal accelerations generated at the clubhead during the first phase 
of the swing. Consider now the swing of an amateur golfer: 
The body and arms accelerate the club from rest at the top of the 
backswing. Being strong in the back and leg this acceleration can be as 
high and sometimes higher than a professional golfer achieves. 
(Biomechanical Analysis of a golfer's back. T. M. Hosea; C. J. Gatt, K. M. 
Gacci, N. A. Langrank, J. P. Zawadsky. Proceedings of the First World 
Congress of Golf, St. Andrews 1990.) However the weakness of the wrists 
does not allow him to complete the first phase of the swing with the 
wrists firmly cocked. The clubhead, under high centrifugal accelerations, 
begins to rotate about the arms. Because of this the clubhead moves out of 
the desired plane of the swing and continues to do so for the rest of the 
swing. Impact is often made with the clubhead moving from the outside to 
inside of the correct plane. Clockwise spin (looking down on top of the 
ball) is created on the ball which results in a curved motion of the ball 
in flight commonly known as a slice. In addition the maximum clubhead 
velocity is not achieved at impact. The combination of these failings 
results in a poor shot. 
One solution to the problem is to reduce the speed of the club and the arms 
in the first phase. If this can be made to match the resistance of the 
wrists at the correct angle of completion of this phase then the 
subsequent impact will be square. The maximum velocity of the clubhead 
will now occur at impact but the magnitude of this velocity will be less 
than the professional, with stronger wrists, can achieve. In effect the 
result is that the ball will travel straight and true but will carry less 
distance than the professional's shot produces. This is infinitely 
preferable to a short slice, the most common shot in golf. Armed with the 
correct sequencing of the shot the golfer may now, if he wishes, develop 
the muscles of the lower arm (and only these muscles) to enable him to 
produce a quicker version of his basically sound new swing thereby 
achieving longer distances of shot. This definition of the swing also 
shows why golfers find it easier to swing the `short` irons since with 
these clubs the swing angle is much less and the accelerations much 
smaller. This ideally sequenced swing is often referred to as the grooved 
swing. 
The imbalance of muscular effort is also seen in the young player, 
particularly if they are also playing another sport more common to school 
activities than golf. The principles outlined here are equally applicable 
to this category of player. 
The golf professional, and many other knowledgeable teachers, are often 
heard to remark on the speed of the swing of the amateur. A slower swing 
is said to produce better `timing` of the shot. The explanation given 
above shows why this is the case. 
For most amateurs this change to a slower swing is nearly impossible to 
achieve and another solution to the problem must be sought. 
From a technical appreciation of the swing, a study of an analysis of the 
mathematics of it and a deep knowledge of the game from the points of view 
of the amateur and the professional, we have invented a club which aids 
the amateur to generate the correctly sequenced swing. It is of benefit to 
all amateurs who, no matter what their standard, will hit bad shots and to 
professionals in that it is more controllable. 
The technical explanation of the design is as follows. Jorgensen shows that 
the equations of motion of the swing result in: 
______________________________________ 
T.sub.s = 
.theta. [J + MR.sup.2 + RS cos ( - .theta.)] + [I + RS cos 
( - .theta.)] - [ .sup.2 - .theta..sup.2 ] RS sin ( - .theta.) 
T.sub.c = 
I + .theta. RS cos ( - .theta.) + .theta..sup.2 RS sin ( - 
.theta.) 
T.sub.s = 
torque applied to the system by the golfer 
T.sub.c = 
torque applied to the club 
J = moment of inertia of the arms taken about an axis 
through the spine about which the arms swing. 
M = total mass of the club. 
I = moment of inertia of the club about the golfers wrists 
S = first moment about the same axis 
R = effective length of the golfers arms 
= angle between the club and the horizontal 
.theta. = 
angle of rotation of the system from the horizontal 
______________________________________ 
The torque T.sub.c, applied to the club basically involves the first moment 
(S) and moment of inertia (I) the club about the golfers wrists. If these 
can be decreased then the torque reduces. In consequence the amateur 
golfer would find it much easier to control the natural uncocking of the 
wrists and delay this process until the correct period of the swing. In 
addition the professional golfer will find the club easier to manipulate 
for different types of shot. These moments involve the mass of the 
clubhead, the mass of the shaft and the length of the shaft. It is noted 
that the last quantity decreases for the short irons but the head weight 
is increased to keep the swing weight (which is in effect the first 
moment) constant. Assuming therefore that the shaft weight remains the 
same, the mass of the head would need to be reduced to reduce T.sub.c. 
This can be easily done by redesigning the head accordingly. However, the 
same terms appear in the first equation for the torque T.sub.s, applied by 
the body and legs. In essence therefore the balance has not been changed 
between the two components of torque and what will be achieved is merely a 
faster version of the incorrectly sequenced swing. This in part, explains 
why lightweight clubs have never been successful. If significant weight is 
now added to the club below but in the vicinity of the golfers hands two 
effects occur. First the overall weight of the club increases. This 
increases the torque T.sub.s (by virtue of the term MR.sup.2) and reduces 
the speed with which the club is swung from the top. The torque T.sub.c, 
of the second phase remains virtually unaltered since the weight is placed 
high on the shaft. We have therefore achieved a change to the balance of 
the club, and therefore the balance of muscular effort required to swing 
it, which can be made to match the requirements of the amateur golfer. 
This club design increases the moment of inertia to maintain a slow swing 
from the top in the first phase which, because of the much reduced moment 
of inertia about the wrist-cock axis, can now be completed without the 
wrists uncocking, thereby producing the correct sequencing of the swing. 
FIG. 1 for instance shows the percentage decrease in the ratio T.sub.s 
/T.sub.c for a 6 iron and a driver, for different added weights and 
different positions of these weights. It is concluded from this that the 
position of the weight is much less important than the magnitude of the 
weight. Larger changes to the ratio come with larger added mass. A 
comparison is also shown for a lightened head. A balance has to be struck 
between achieving a significant change to the ratio between the torques 
required in each phase and the difficulty of swinging a heavy club. In 
essence it would be preferable therefore to keep the moment of inertia 
over the first phase of the swing high whilst having a low moment of 
inertia in the second phase. This can be done by combining the two changes 
described in FIG. 1, using a light head mass and a separate added mass in 
or near the gripping area. 
FIG. 2 plots the calculated results of doing this for a range of values of 
head mass and added weight. The lower vertical lines show the range of 
inertia ratios. 
EQU (I+MR.sup.2)/I 
for current clubs. Within each range are ladies clubs, heavy headed gents 
clubs, using composite and steel shafts in a range of lengths. By 
decreasing head weights from the current range by between 13% and 30% and 
adding suitable weights in various locations at or below the gripping 
area, the inertia ratios are greatly increased. The upper vertical lines 
show the range achieved again using ladies clubheads, gents clubheads and 
composite or steel shafts of various lengths. The criteria used in FIG. 2 
for these calculations is that the inertia for the first phase should be 
within .+-.5% of the value for the standard club and the inertia for the 
second phase should be reduced by at least 20%. In fact values up to 30% 
are contained in the range. 
It should be noted that the range of ratio values is very much larger than 
in current clubs, enabling the designer to select clubs for the wide range 
of abilities of golfers. 
Another benefit of the design is also shown in FIG. 2. Whereas the inertia 
ratio for a current driver is much less than for a current seven iron, 
reflecting the greater difficulty in using the driver, it is possible with 
the proposed invention to design clubs which have roughly constant ratios 
across the range of loft and length values. 
The weight added to the shaft of the club below the centre of gravity of 
the hands is preferably greater than 50 gms and may be between 80 and 160 
gms. The centre of gravity of the additional weight is preferably within a 
distance of 300 mm from the butt end of the shaft, but below the centre of 
gravity of the hands. 
The head of the club is preferably lightened in accordance with the 
additional weight but by a lesser amount. In the above examples 30 gms and 
between 40 to 50 gms is preferably removed from the head respectively. 
Tests on clubs designed with this principle show that 75 to 150 gms added 
below the grolfer's hands is able to produce good conditions for all of 
the golfers tested. In addition, tests on a professional swing show that 
the clubhead is easier to control. The golfer can rotate the head and 
bring it to square on impact much more easily than with the standard head. 
With reference now to FIG. 22 in order to illustrate the substantial 
differences between the moments of inertia in the second phases of the 
golfer's swing compared to prior art clubs, these have been plotted as 
first moment about the wrist-cock axis and moment of inertia about the 
same axis for conventional clubs presently on the market and also for a 
number of clubs which have been modified for specific reasons and which 
have been patented in the USA, and clubs designed according to the present 
invention. 
Referring now to FIG. 22, the first moment about the wrist-cock axis is 
plotted on the "Y" axis and the moment of inertia about the same axis on 
the "X" axis. This is often called the second moment. The first moment is 
in gm cm.times.10.sup.2 .times.10.sup.6. The graph is similar to the plot 
of FIG. 3 of U.S. Pat. No. 4,415,156, the values being calculated in the 
same manner. 
For the purposes of the present invention, the first moment (M1) and moment 
of inertias are defined as follows: 
EQU M1=M.sub.h .multidot.L.sub.h +M.sub.s .multidot.L.sub.s +M.sub.w 
.multidot.L.sub.w 
EQU M2=M.sub.h .multidot.L.sub.h.sup.2 +M.sub.s .multidot.L.sub.s.sup.2 
+M.sub.w .multidot.L.sub.w 2 
where M.sub.l, M.sub.s and M.sub.w are the masses of the head, the shaft 
and the additional weight if added (M.sub.w is zero for the prior art 
cases), and L.sub.h, L.sub.s and L.sub.w are distances between the centres 
of gravity of the head, the shaft and the added weight and the position of 
the centre of the golfer'hands. There is an additional term from the mass 
of the grip but its centre of gravity is very close to the position of the 
centre of the golfer's hands and therefore the contribution to both the 
moment from the grip are negligible. 
Turning now to specific plots on the graph and again with cross reference 
to U.S. Pat. No. 4,415,156 the clubs designed by Jorgensen are shown by 
the black rectangle. These have a first moment M1 between 
25.7.times.10.sup.3 to 25.9.times.10.3.sup.3 gr cm and a second moment 
between 1.97.times.10.sup.6 to 1.98.times.10..sup.6 gm cm.sup.2. 
In Jorgensen U.S. Pat. No. 4,415,156 the conventional clubs are also shown 
in FIG. 2 and these are also shown as CON 9 (9 iron), CON 4 (4 iron), CON 
1 (1 iron), and CON DR (Driver). Club CON 9 has a first moment M1 of 
26.0.times.10.sup.3 gm cm and a second moment M2 of 1.93.times.10.sup.6 gm 
cm.sup.2. The driver CON DR. has a first moment of 24.9.times.10.sup.3 gm 
cm and a second moment of 2.1.times.10.sup.6 gm cm.sup.2. 
It can therefore be seen that Jorgensen produces a set of clubs which are 
matched in inertias of both the first and second moment as compared with 
those of a conventional club. However these inertia values are high being 
higher than 25.8.times.10.sup.3 gm cm (M1) and 1.97.times.10.sup.6 gm 
cm.sup.2 (M2). 
U.S. Pat. No. 4,058,312 (Stuff et al) relates to an invention wherein the 
centre of gravity of each club in a set is for all clubs in a set. The 
values for the first and second moments for the clubs in Chart II (U.S. 
Pat. No. 4,058,312) Stuff et al are shown in FIG. 22 for the 9 iron, 
(Stuff 9), 4 iron (Stuff 4), 2 iron (Stuff 2), 3 wood (Stuff 3W) and 
Driver (Stuff DR). 
It may be seen that the values of the first moment for the clubs in Stuff 
et al are high being approximately between 25 and 26.times.10.sup.3 gm cm. 
The spread of the second moments are substantial being between 1.86 to 
2.19.times.10.sup.6 gm cm.sup.2. Thus in the second phase of movement for 
the Driver and second moment of inertia is approximately as high as that 
for a convention driver. Hence the set of clubs designed by Stuff et al 
are more difficult to use than conventional clubs because they have a very 
wide spread for the second moment of inertia. 
U.S. Pat. No. 4,128,242 (Elkins) also discloses a modified set of golf 
clubs to provide a corrected set, in much the same manner as U.S. Pat. No. 
4,415,156 Jorgensen with the addition of constant total weight and this is 
illustrated by the hatched circle labelled "Elkins-all clubs" which shown 
that both the first and second moments of these clubs are indeed carefully 
matched. 
It is found however that both moment are well above those for normal clubs, 
the first moment being approximately 27.2.times.10.sup.3 gm cm and the 
second moment 2.25.times.10.sup.6 gm cm.sup.2. These clubs are therefore 
very difficult to swing. 
In comparison, the clubs designed according to the present invention 
wherein weight is removed from the head and wherein an additional weight 
is placed beneath but close to the hands, are much easier to swing, in the 
second phase of movement. 
Reference is now made particularly to the Driver, this being traditionally 
regarded as the most difficult club to swing. For the conventional driver, 
the Stuff Driver and the Elkins driver the second moments are all greater 
than 2.15.times.10..sup.6 gm cm.sup.2 whereas for the driver of the 
present invention the second moment is a maximum of 1.9.times.10.sup.6 gm 
cm.sup.2 for a head weight reduction of 30 gms shown in FIG. 22, a 
decrease of over 10%. The Jorgensen driver is at approximately 
1.970.times.10.sup.6 gm cm.sup.2 and thus the decrease is not as marked. 
Comparing now the first moments for the drivers, it is noted that the 
conventional, Stuff and Jorgensen and Elkins drivers are all above 
24.9.times.10.sup.3 gm cm whereas the driver according to the present 
invention is 22.4.times.10.sup.3 gm cm again showing a 10% reduction over 
the prior art range of clubs. 
With reference now to FIG. 23 which shows the effect of reducing head 
weight by 40 gms and introducing the additional weight just below the 
hands, as described above, the effects are even more marked. The first 
moment is reduced to below 21.5.times.10.sup.3 gm cm and the second to 
1.805.times.10.sup.6 gm cm.sup.2 giving a 10% reduction compared with 
Jorgensen (1.98.times.10.sup.6 gm cm.sup.2 to 1.805.times.10.sup.6 gm 
cm.sup.2) and an approximate 18% reduction in second moment compared with 
conventional clubs. 
With reference to FIG. 24 which shows the effect of reducing head weight by 
50 gms and introducing additional weight just below the hands, within 0-4 
inches as described above the effects are further marked. 
Again, concentrating on the driver, the first moment is 20.4.times.10.sup.3 
gm cm as against 24.9.times.10.sup.3 gm cm for Stuff and 
25.7.times.10.sup.3 gm cm for Jorgensen and the second moment is 
1.705.times.10.sup.6 gm cm.sup.2 as against 2.15.times.10.sup.6 gm 
cm.sup.2 for Stuff and 1.98.times.10.sup.6 gm cm.sup.2 for Jorgensen. 
Thus the second moment is reduced by approximately 22% and with respect of 
conventional clubs and by approximately 14% with respect of the special 
design of clubs in the Jorgensen patent. 
Thus the clubs designed in accordance with the present invention are 
substantially easier to swing, particularly in the second phase of 
movement of the golfer's swing. 
From the graphs of FIGS. 22 to 24 it may be seen that the other woods and 
irons (3W [3 wood] to 9 [09 iron]) are similarly much easier to swing in 
the second phase of movement, the nine iron in FIG. 24 having an inertia 
of only 1.61 as compared with a conventional 9 iron at 1.93. 
The reduction in inertia during the second part of the swing reduces the 
torsional effects on the golfer and in addition to making the club easier 
to swing reduced the strain imposed on the golfer. The club head, being 
more easily controlled will be more likely to strike the golf ball 
correctly thereby giving a better chance of a straight perfectly timed 
shot. 
FIGS. 25 and 26 illustrate the calculated additional weight positions for 
the clubs illustrated in FIGS. 22 and 23. 
In these examples the core position (centre of gravity) have been set at 
constant distances from the butt end of the shaft, 6 inches for the wood 
clubs and 8 inches for the irons. 
The figures also illustrate the variation of calculated core weight 
throughout the set and between sets. 
The trimming details show for a particular example of club the way in which 
each end of a standard core weight insert is trimmed to achieve the desire 
result. 
Finally, the forces causing bending of the shaft are lower. The 
accelerations throughout any swing are large, particularly during the 
important second phase. These act through the centre of gravity of the 
system, which for most golf clubs is offset from the line of the shaft. 
This offset force produces significant bending in the shaft which will be 
reduced if the proposed design is adopted, and there is less weight in the 
head. With less bending the face of the club is less angled on impact. The 
shaft is therefore redesigned if necessary to compensate for this. 
Design of Golf Club 
Typical designs are shown in FIGS. 3 and 4. In FIG. 3 the additional weight 
W, of at least 50 gms, is placed in or around the gripping area of the 
club with its centre of gravity within 300 mm of the butt end of the 
shaft. This may be distributed as a solid (FIGS. 4a, 4e) or hollow section 
(FIGS. 4c, 4d) typically over 10 cms, or as a concentrated load (FIG. 4b) 
such as a spherical ball B placed firmly into the tube up to 300 mm from 
the butt end supporting lead shot L held in place by a cork C. The ball 
fixing has the advantage that contact is made with the tapered shaft over 
a small area thus creating the least change to the handling 
characteristics of the shaft. With any of the distributed weight systems 
the shaft may be slightly stiffened over the area of contact producing 
less deflection and a different flex point in the shaft. Calculations show 
that the stiffening effect is very small on most shafts but the same 
calculations can be used to redesign the shaft to have the original 
desirable characteristics. 
In FIG. 4d, the shaft is shown made of stepped steel in the conventional 
way with a thicker section. In shafts of reinforced plastic the weight, in 
any of the forms mentioned above, can be cast in during the manufacture of 
the shaft. 
The clubhead must be lighter than standard. For the wooden headed club 
removal of the central section of the head around the centre of gravity 
and the lead weight normally placed there would produce a weight reduction 
of 15 to 25 gms. It is essential to remove more than this, but since this 
is impracticable for strength reasons, a redesign of the clubhead will be 
required. More ideal is the metal headed wood which is cast. This clubhead 
can either be made from lighter material of sufficient strength or by 
removing metal from least sensitive stress areas. The irons can be treated 
similarly, using lighter materials or conventional materials of different 
design, perhaps with hollow sections. 
With reference now to FIGS. 5 to 7 the principal of operation of the golf 
club according to the present invention will now be explained in further 
detail and will be contrasted with a known prior golf club described in 
U.S. Pat. No. 4,058,312 (Stuff) the principal of operation of which is 
shown in FIGS. 8 to 10. 
With reference to FIG. 5, the golf club comprises a shaft 100, a head 200 
and a grip 300. The golf club is gripped by a players hands in the area of 
grip 300 and the club when swung by the golfer has a pivot point P 
(illustrated as conventionally shown for pivots) which is generally 
between the two hands of the golfer and which is thereby within the length 
of the grip 300. The grip of a typical golf club is in known manner 
comprised of a rubber sleeve which is slid over the butt end of the shaft 
100 and is typically 10 to 12 inches in length. The grip is tapered and is 
a force fit on the shaft. The hands of a golfer obviously vary in the size 
but they are on average approximately 4 inches across the palm and thus in 
known manner both hands fit on the grip 300. It is universally accepted 
that the centre of the golfer's hands is 4 inches below the butt end of 
the club. 
With reference to FIGS. 6 and 7 the additional weight +W is added (see 
hereinbefore with reference to FIG. 1) such that its centre of gravity is 
below the pivot point P (see hereinafter FIGS. 14-21). 
This provides a positive lever for the golfer which is contrasted with the 
known prior art club shown in FIGS. 8, 9 and 10 wherein the added weight 
+W is provided above the pivot point P, this arrangement providing a 
counter lever. 
By contrast, therefore, and with reference particularly to FIGS. 6 and 9 
when the golfer G, (depicted by a triangle representing the shoulder width 
SW, arm lengths AL1 and AL2 the golfer's head being represented by a black 
circle) swings the golf club above his head, the weight +W in FIG. 6 
provides a positive lever weight whereas in FIG. 9 it provides a counter 
weight. In the known arrangement of FIGS. 7 to 10 the club when raised 
above the golfers head feels extremely light, the golfer having no feeling 
of inertia about the hands when the club is in this position. This is 
because the club is counterbalanced. Thus the golfer has great difficulty 
in controlling the club over the first part of the swing. In the second 
part of the swing the club is turned as the wrists are uncocked and the 
counterbalance weight in FIG. 10 then performs the function described in 
U.S. Pat. No. 4,058,312 but it is in the first or upper part of the swing 
that the problem arises. 
By contrast in the club according to the present invention the added weight 
+W being below the hands provides a positive lever when the club is lifted 
above the head in the upper or first position (FIG. 6) and thus the club 
has a heavier feel to it somewhat similar to a conventional club and thus 
the club does not have a light feel in the backswing therefore producing a 
much more controlled swing. Since, in the club according to the present 
invention, weight -W is taken out of the head the inertia in the first 
part of the swing shown in FIG. 6 is substantially the same as for 
conventional designed golf clubs but with reference to FIG. 7 the inertia 
in the second part of the golf swing is reduced because the head weight is 
reduced and the head, in the second and lower part of the swing is further 
from the shoulders as can be clearly seen by reference to FIGS. 6 and 7. 
With reference now to FIG. 11 there is shown a known conventional golf club 
shaft 100. Such shafts are in the common use and, therefore, the shaft 
will not be described in detail. The shaft is made of tapered steel and is 
tapered in steps 102 to provide the desired strength and bending 
characteristics. The shaft is generally circular in cross section. 
Alternatively, the shaft could be parallel throughout its length or 
tapered throughout its length. 
The centre of gravity of the added weight +W is required to be below the 
hands and it must not move during the life of the club. Also preferably it 
must not rattle or come loose as this will considerably detract from the 
attractiveness of the club. 
One preferred method for adding the weight is shown in FIGS. 12 and 13. The 
additional weight +W comprises an elongate rubber insert 104 which is 
shaped in a step tapered manner and is contoured to fit into the inside of 
shaft 100. The selected rubber preferably has specific gravity between 3.0 
and 4.0. Preferably the maximum length of the insert is in a preferred 
embodiment 20 cm (8 inches). 
The rubber insert 104 is preferably held in position by a bung 106 which is 
preferably of polyurethane material. 
The length of the rubber insert 104 is preferably adjusted as shown in FIG. 
13 by shortening the end portion 108, the step tapered portions 110, 112, 
114 remaining intact and thereby retaining the contoured feature. Thus the 
rubber insert may be trimmed at portion 108 to adjust the weight to be 
added and also to adjust to the length of the weight to the length of club 
which may vary from driver to said iron. FIGS. 14-21 show a preferred 
embodiment where the shaft has been designed to have a long parallel 
section at the butt end. 
With reference to FIGS. 14 to 21 the shafts for all golf clubs in a 
particular set are usually identically manufactured but cut to different 
lengths by shortening the butt end 116 or the tip end 117 (see FIG. 11). 
This is illustrated in FIGS. 16 to 21 by the step in the shafts being 
vertically aligned and wherein it may be seen that the butt end portion 
116 on the wedge (FIG. 21) is shorter than on the 1 iron (FIG. 16). 
The rubber insert 104 is also preferably cut to length (or designed to a 
specific length) which varies as shown being longer for the 1 iron and 
shorter for the 3, 5, 7, 9 and wedge. It will be seen that it is obvious 
that for the other clubs (the 2, 4, 6, 8 irons and sand wedge) not shown, 
the lengths of shaft and insert will be respectively intermediate to those 
shown. 
The centre of gravity (CG) of both the hands and the insert (added weight) 
is shown for each club. It may be seen that the CG of the insert is always 
well below the CG of the hands. The two centres are furthest apart for the 
longer irons (e.g. the 1 iron) and closer together for the shorter irons 
(e.g. the wedge) but the CG of the added weight is always below the CG of 
the hands. By suitably designing and trimming the shaft it is possible to 
make the distance between the two CGs constant throughout the set. 
The term CG of the hands is used here since this is easier to define by 
virtue of the position of the hands on the grip, than the pivot point P. 
The pivot point P will be substantially the same as the CG of the hands 
but will for most practical applications be in substantially the same 
position. The CG of the hands is essentially the centre point between the 
two hands on the grip. With reference to FIGS. 16-21 it may be seen that 
the whole of the added weight +W will be below the CG of the hands with 
the CG of the weight at a substantial distance below the CG of the hands. 
In contrast in FIGS. 14-15 with the wood clubs shown the CG of the hands 
is much closer to the CG of the weight. Hence the bottom hand may in this 
example overlap the top end of the added weight but the CG of the added 
weight will still be below the CG of the hands as shown.