U.S. patent application number 11/424271 was filed with the patent office on 2007-12-20 for set of iron clubs with constant ground roll.
Invention is credited to Michael Scott Burnett, Peter J. Gilbert, Charles E. Golden, David A. Shear.
Application Number | 20070293339 11/424271 |
Document ID | / |
Family ID | 38862265 |
Filed Date | 2007-12-20 |
United States Patent
Application |
20070293339 |
Kind Code |
A1 |
Burnett; Michael Scott ; et
al. |
December 20, 2007 |
Set of Iron Clubs with Constant Ground Roll
Abstract
A set of iron clubs where each club in the set has the same or
substantially the same ground roll. The set is produced by
adjusting at least two club design characteristics of the clubs
based upon measured or assumed player swing data. The design
characteristics of the clubs include club length, static clubhead
loft, location of the center of gravity, shaft flexibility, and
groove volume. Preferably, club length and static clubhead loft are
adjusted for coarse adjustments, while the other characteristics
are used to fine-tune the design.
Inventors: |
Burnett; Michael Scott;
(Carlsbad, CA) ; Gilbert; Peter J.; (Carlsbad,
CA) ; Golden; Charles E.; (Encinitas, CA) ;
Shear; David A.; (Raleigh, NC) |
Correspondence
Address: |
ACUSHNET COMPANY
333 BRIDGE STREET, P. O. BOX 965
FAIRHAVEN
MA
02719
US
|
Family ID: |
38862265 |
Appl. No.: |
11/424271 |
Filed: |
June 15, 2006 |
Current U.S.
Class: |
473/290 |
Current CPC
Class: |
A63B 53/005 20200801;
A63B 53/047 20130101; A63B 53/0408 20200801 |
Class at
Publication: |
473/290 |
International
Class: |
A63B 53/00 20060101
A63B053/00 |
Claims
1. A set of iron-type clubs comprising at least two clubs, wherein
a ground roll distance produced by each of the at least two clubs
is substantially the same.
2. The set of clubs of claim 1, wherein the iron-type clubs are
muscle-back clubs.
3. The set of clubs of claim 1, wherein the ground roll distance of
each of the at least two clubs is within one yard of a target
ground roll distance.
4. The set of clubs of claim 1, wherein one of the at least two
clubs has a first club length of between about 38 inches and about
42 inches and a static clubhead loft of between about 25 degrees
and 27 degrees, and wherein the other of the at least two clubs has
a second club length of between about 32 inches and about 35 inches
and a second static clubhead loft of between about 38 degrees and
about 42 degrees.
5. The set of clubs of claim 4 further comprising at least one
additional club having a third club length of between about 37
inches and about 39 inches and a third static clubhead loft of
between about 30 degrees and about 33 degrees.
6. (canceled)
7. (canceled)
8. (canceled)
9. (canceled)
10. (canceled)
11. (canceled)
12. (canceled)
13. (canceled)
14. (canceled)
15. (canceled)
16. (canceled)
17. (canceled)
18. A set of iron-type clubs comprising at least two clubs, wherein
a ground roll distance produced by each of the at least two clubs
is substantially the same, wherein a first club is a 3 iron having
a loft of about 25 degrees and a shaft length of about 41 inches
and a second club is a 9 iron having a loft of about 40 degrees and
a shaft length of about 34 inches and the remaining clubs within
the set have lofts and shaft lengths therebetween.
Description
BACKGROUND
[0001] The invention relates generally to a set of iron-type golf
clubs. In particular, the invention relates to a set of irons with
substantially constant ground roll.
[0002] In a set of irons, various design characteristics are varied
from one club to the next. For example, individual iron club heads
in a set typically increase progressively in face surface area and
weight as the clubs progress from the long irons to the short irons
and wedges. The shaft length shortens as the clubs progress from
the long irons to the wedges, and the loft angle typically
increases through the same progression. These design variables and
others can be modified so that a particular club, for example a
3-iron, produces certain flight characteristics. Specifically, the
clubs are designed to produce specific launch angles and to impart
a certain amount of backspin to the ball, when the ball is struck
correctly, i.e., with an anticipated speed and at the nominal
hitting point, typically a point on the hitting face about 18 mm or
less above the ground when the club is in the address position.
When struck in the appropriate manner, the combination of ball
speed, launch angle and backspin produces an anticipated flight
path, with the ball achieving a specific height at the maximum
point of the parabolic arc of the path and a specific carry
distance.
[0003] In traditional iron sets, flight path height (distance above
ground) and carry distance are generally the performance parameters
which a golf club is designed to achieve. However, another
parameter, ground roll of the ball, is relatively neglected in the
overall design of the club, with ground roll being dependent upon
the design characteristics selected to achieve a specific flight
path. As such, traditional iron sets result in longer shots having
the ball roll more on a green than do the shorter shots. This
creates difficulty in hitting long shots which will stop on a
green. Also, some short shots can roll backwards on the green. As a
result, precisely controlling the total distance achieved by a shot
may prove difficult if the player cannot accurately account for
ground roll distance. A shot hit with a club from an iron set would
be easier to control, i.e., the distance attained for a shot from
each iron would be more predictable, if each would roll a
prescribed distance.
[0004] Therefore, a need exists for a set of iron clubs having
predictable ground roll. Such a set of clubs may have the same
ground roll for each club in the set.
SUMMARY OF THE INVENTION
[0005] An aspect of the invention is directed toward a set of
iron-type clubs comprising at least two clubs, wherein a ground
roll distance produced by each of the at least two clubs is
substantially the same.
[0006] Another aspect of the invention is directed toward a method
for producing a set of golf clubs with constant ground roll
comprising the steps of (i) selecting a target ground roll, (ii)
selecting a club, (iii) obtaining a ground roll performance curve
for the club and at least one other performance curve using the
club, and (iv) adjusting at least two design characteristics of the
club to achieve the target ground roll while maintaining the at
least one other performance curve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0008] FIG. 1 is a schematic view of a standard iron club;
[0009] FIG. 2 is a graph showing the variation in clubhead speed
versus club length for a typical PGA Tour player;
[0010] FIG. 3 is a graph showing the variation in carry distance
versus club length and static club loft for 3-irons;
[0011] FIG. 4 is a graph showing the variation in ground roll
versus club length and static club loft for 3-irons;
[0012] FIG. 5 is a graph superimposing the graph of FIG. 4 onto the
graph of FIG. 3;
[0013] FIG. 6 is a graph showing the variation in ground roll and
carry distance versus club length and static club loft for
6-irons;
[0014] FIG. 7 is a graph showing the variation in ground roll and
carry distance versus club length and static club loft for
9-irons;
[0015] FIG. 8 is a graph showing the variation in clubhead static
loft versus iron number for three sets of iron-type golf clubs, one
conventional set and two constant roll sets;
[0016] FIG. 9 is a graph showing the variation in club length
versus iron number for three sets of iron-type golf clubs, one
conventional set and two constant roll sets; and
[0017] FIG. 10 is a graph showing the variations in flight
trajectories for conventional and constant roll 3-, 6-, and
9-irons.
DETAILED DESCRIPTION
[0018] As illustrated in the accompanying drawings and discussed in
detail below, the present invention is directed to a set of
iron-type golf clubs, wherein the clubs have substantially the same
ground roll distance throughout the set. Each club 1 in a set
includes a club head 10 attached to a tubular portion 18 of a shaft
17 in any manner known in the art, such as with an adhesive,
welding, or screwing threaded portions of club head 10 to a
correspondingly threaded portion of tubular portion 18. The length
of club 1 is determined by measuring from a grip or handle portion
19 of shaft 17 to a sole 22.
[0019] Club head 10 includes, generally, a body 12 and hosel 14.
Body 12 includes a striking or hitting face 16 and a rear face 20.
Body 12 is attached to hosel 14 at an angle, such that a loft angle
30 is defined between a hosel center line 18 and hitting face 16.
Further, the relative configuration of body 12 and hosel 14 results
in an offset 34 between the leading edge of the base of sole 22 at
the base of hitting face 16 and the forward-most point 15 of hosel
14.
[0020] In typical sets of golf clubs, the area of hitting face 16,
the heel-to-toe length of body 12, loft angle 30, and offset 34
vary from club to club within the set. For example, long irons,
such as a 2- or 3-iron using conventional numbering, typically
include relatively long shafts 17, relatively small areas for
hitting face 16, and relatively low loft angles 30. Similarly,
short irons, such as an 8- or 9-iron using conventional numbering,
typically include relatively short shafts 17, relatively large
areas for hitting face 16, and relatively high loft angles 30. In
one embodiment of the present invention, these parameters are
particularly chosen to maximize the performance of each club 1 for
its intended use in terms of carry distance.
[0021] The total distance achieved by a ball struck by a club is
the carry distance plus the distance the ball rolls upon landing,
also referred to as "ground roll". Ground roll is generally
influenced by initial conditions of the ball upon impact, such as
launch speed, launch angle and back spin. Many factors influence
the ground roll distance, including club design characteristics and
player swing characteristics. In a set of clubs according to the
present invention, the design parameters of the clubs in the set
and/or the player swing characteristics are matched and selected
not only to maximize the performance of each club for its intended
use, for example as a wedge, but also to achieve a predictable
level of ground roll of a ball struck by any club in the set, such
as constant or substantially constant ground roll.
[0022] In accordance with an aspect of the present invention, the
inventive iron golf clubs are designed to have substantially the
same carry distance as conventional iron golf clubs. Each inventive
iron golf club is designed to hit golf balls a prescribed distance
in the air, and to stop on the green or fairway in a predictable
manner. Expected ground roll distances for conventional irons
ranges from about 6 yards for a 3-iron, 2 yards for a 6-iron and 0
yards (or less) for a 9-iron. Hence, it is difficult for a player
to make the ball stop on the green with a 3-iron. The present
invention includes a method for creating a set of iron clubs that
has substantially the same ground roll for each club, while
maintaining the same carry distance as the conventional clubs.
Preferably, each club should have the same ground roll distance
.+-.1 yard.
[0023] Using actual golf ball launch data, the carry distance and
ground roll are calculated using a mathematical model. First, a
targeted ground roll is selected, i.e., 2 yards.+-.1 yard. Next,
adjustments are made to adjust the ground roll to reach the target
roll. For example, if the data suggest that the landing roll for a
particular club is longer than the target ground roll, then
adjustments are made to reduce the roll. Adjustments include, but
are not limited to, the following factors: [0024] i.
increasing/decreasing shaft length to adjust clubhead speed and
initial ball speed; [0025] ii. increasing/decreasing static loft
angle to adjust trajectory and backspin; [0026] iii. flexing
characteristics of the shaft to adjust clubhead speed and initial
ball speed; [0027] iv. location of the center of gravity (c.g.) of
the clubhead, including lowering the c.g. and/or moving the c.g.
aft of the hitting face, to adjust trajectory of the ball; and
[0028] v. varying groove geometry to adjust the amount of ball
spin
[0029] A high launch/high spin combination makes the ball fly
higher and reduces carry and roll distances. In one example, higher
trajectory is coupled with longer shaft length (or shaft flex) to
increase ball speed to make up for the loss of carry distance, but
to keep the ground roll unchanged. Hence, in this example, after
the adjustments the club maintains its expected carry distance
while the ground roll distance has been adjusted to meet the
targeted roll distance. This method is repeated for each club in
the set to achieve the same targeted roll distance for all the
clubs.
[0030] In accordance with one aspect of the present invention, at
least two of the above five club factors are used to reach the
targeted ground roll. It is noted that other factors may be used
for this purpose.
[0031] The properties of the golf balls may also affect the
targeted ground roll. For instance, the ball's compression, total
hardness, cover material, and dimple pattern, among other factors,
can affect both the carry distance and roll distance. The ball
launch data includes multiple types of golf balls. Hence, the
mathematical model is applicable to all golf balls, and the
inventors expect that when the inventive iron golf clubs are used
with a particular ball, the targeted ground roll distance remains
the same throughout the set. However, the targeted ground roll may
be different for different balls. For example, a higher performance
golf ball such as the Titleist Pro-V1.RTM. or Pro-V1x.TM. would
produce one targeted ground roll distance for the inventive set,
while another ball would produce another targeted ground roll
distance for the inventive set.
[0032] Discussed further below is an understanding of the players'
swing characteristics, such as clubhead speed, angle of attack,
loft at impact and nominal impact position. One of these player
swing characteristics that impacts ground roll is the angle of
attack, i.e., the angle between the path on which the clubhead
strikes the ball and the horizontal ground plane. A typical forward
swing for a golfer follows an arc, starting with a downswing,
traveling through a fairly level portion at the bottom of the
downswing before heading into the upswing part of the swing.
Typically, the angle of attack for irons in generally downward,
i.e., the ball is struck in the downswing portion of the swing arc.
As the angle of attack becomes more level, the launch angle
increases and the backspin decreases. The nominal impact location
also affects the flight path. An ideal nominal impact location, the
striking point on the hitting face of a club, is about 18 mm or
less measured from ground when the club is in the address position.
In the absence of ground contact, "thin" hits, hits lower than the
nominal striking point, decrease the launch angle of a ball, and
"fat" hits, hits higher than the nominal striking point, increase
the launch angle of a ball.
[0033] In one embodiment of the present invention, club design
characteristics are manipulated based upon assumed or measured
player swing characteristics to achieve constant ground roll
through the set. In other words, clubs of the set are designed so
that a ball struck by any club in the set rolls the same distance,
regardless of which club in the set is used to strike the ball. To
achieve this effect, in one embodiment a set is designed so that
each club, for example, a 3-iron, has the same or nearly the same
flight trajectory as its conventional counterpart while ground roll
remains constant. In a first embodiment, the club design parameters
are chosen based upon a typical PGA Tour player's swing, where the
model for the characteristics of the swing is derived from
empirical data collected from a number of actual PGA Tour players.
In another embodiment, a custom set may be developed by collecting
data from an individual player and adjusting the club design
parameters to match the swing characteristics of that specific
player in order to achieve constant roll through the set. An
individual's custom launch measurements can be obtained easily
during a standard fitting session using a launch monitor system,
such as the Titleist performance monitor (TPM).
[0034] As discussed above, one club design characteristic that may
be manipulated to influence ground roll is the clubhead speed. A
player will swing a club with a certain amount of strength and
skill to achieve a player-dependent swing speed. While swing speeds
may vary widely among the general population, swing speed for PGA
Tour players tends to be consistent and will fall within a
relatively narrow range for a given club. For instance, it is
uncommon for a PGA Tour player to swing a 3-iron outside of the 95
mph to 105 mph range, whereas a non-professional could easily fall
well below the 100 mph mark. It is known in the art that clubhead
speed also varies with club length given a certain swing speed, so
the clubhead speed may be manipulated to control ground roll by
altering the club length. FIG. 2 shows graphically how the clubhead
speed of a club swung by an average PGA Tour player varies with
club length for a conventional set of irons. The average clubhead
speed variation with club length, as determined from the data shown
in the graph of FIG. 2, is about a 2.35 mph increase in clubhead
speed per 1 inch increase in club length. The corresponding
increases in ball speed per 1 inch increase in club length for 3-,
6-, and 9-irons are shown below in Table 1.
TABLE-US-00001 TABLE 1 Increase in Ball Speed Given a 1-inch
Increase in Club Length Club Number Increase in Ball Speed (mph) 3
3.17 6 3.03 9 2.80
As clubhead speed increases, the initial velocity of the ball upon
impact is also increased. As such, the ball will tend to have a
greater carry distance and greater ground roll with increased
clubhead speed, as is shown and discussed in greater detail below
in the Example.
[0035] As the clubhead speed increases, so does the backspin
imparted to the ball. Backspin, the backward rotation of the golf
ball in flight along its horizontal axis, is imparted to the ball
by the grooves formed in the hitting face of a club and friction
between the ball and the striking face. When struck, the ball
compresses into and slides along the hitting face, encountering the
grooves. A tangential force is imparted to the ball which causes
the backward rotation of the ball. As is well known in the art,
backspin produces aerodynamic lift for greater carry distances.
Also, backspin influences ground roll by slowing, stopping or even
reversing the direction in which the ball is traveling when the
ball hits the ground. In other words, ground roll is shorter or
even backwards with greater backspin. Backspin generally increases
with clubhead speed. Table 2 shows the increase in backspin for a 1
mph increase in clubhead speed for selected clubs from a set of
muscle-back clubs, assuming a PGA Tour player swing hitting a
Titleist.RTM. ProV1x.TM. ball.
TABLE-US-00002 TABLE 2 Increase in Backspin of a 1 mph Increase in
Clubhead Speed Club Increase in Backspin (revolutions per minute)
3-iron +40 rpm 6-iron +58 rpm 9-iron +88 rpm
[0036] Backspin also generally increases with static clubhead loft,
i.e., the loft angle (element 30 in FIG. 1) of the club as measured
when the club is in the address position. As loft angle increases,
backspin increases. Static loft also impacts initial ballspeed,
which decreases, with increasing static clubhead loft. Therefore,
as the static loft increases, the ground roll decreases through a
combination of lower ballspeed and increased backspin, as discussed
above. Launch angle also affects ground roll, as ground roll
generally decreases with increased launch angle. Table 3 shows the
changes in ballspeed, backspin and launch angle for a 1 degree
increase in static loft for selected clubs from a set of
muscle-back clubs, assuming a PGA Tour player swing hitting a
Titleist.RTM. ProV1x.TM. ball.
TABLE-US-00003 TABLE 3 Per Degree Change in Ballspeed, Backspin and
Launch Angle Increase in Static Loft Change in Backspin Change in
Ballspeed (revolutions Change in Launch Club (miles per hour) per
minute) Angle (degrees) 3-iron -0.83 mph +251 rpm +0.71.degree.
6-iron -1.15 mph +242.8 rpm +0.67.degree. 9-iron -1.16 mph +191.8
rpm +0.63.degree.
[0037] Additional design characteristics which impact carry
distance and ground roll include those design characteristics which
impact launch angle. For example, the position of the center of
gravity of the club influences launch angle, where a center of
gravity closer to the sole of the clubhead increases the initial
launch angle. Additionally, increased flexibility of the shaft also
increases the initial launch angle. Further, the geometry of the
grooves impacts backspin, with larger-volume and sharper radius
grooves imparting greater backspin.
[0038] For the purposes of designing a set of constant ground roll
clubs according to the present invention, the design of a
conventional set of clubs with the desired flight path
characteristics may be provided as a basic starting point.
Alternatively, a set of clubs may be independently designed to
obtain a set of clubs with the desired flight path characteristics.
For the purposes of simplicity in the discussion, the set used as
the basic starting point is referred to as "the conventional set"
even if the set is specifically designed. Any two or more of the
above-discussed parameters may be manipulated or slightly varied in
order to substantially maintain the flight path characteristics of
the conventional set, in particular the carry distances and/or the
difference in carry distance from one club to the next in the set,
while obtaining the desired constant or substantially constant
ground roll. Preferably, club length and loft angle are the
parameters which are varied from the conventional set, although any
combination of parameters may be adjusted. Club length and loft
angle are preferred in part because relatively minor changes in
these parameters have a greater impact on carry distance and ground
roll than do the other parameters discussed herein. In other words,
club length and loft angle can be used for coarse corrections to
carry distance and ground roll, while parameters such as shaft
flexibility, groove volume, and center of gravity locations can be
used to fine-tune carry distance and ground roll.
[0039] In one example, a set of constant ground roll clubs
according to the present invention were predicated off of the
design of a conventional set of iron clubs, the Titleist.RTM. 670.
In other words, the flight path characteristics of the conventional
set were chosen as desirable flight path characteristics. In order
to achieve the same or similar characteristics, the conventional
set's general overall design was maintained, while each club's
length and loft angle were manipulated to produce the desired
ground roll. In this example, it is desired to have all clubs roll
to within one yard of the ground roll achieved by the conventional
set 6-iron, although one of skill in the art will recognize that
any ground roll may be selected as the target ground roll. In other
words, if the 6-iron of the conventional set has a ground roll of 2
yards, the inventive set iron should have a ground roll between
about 1 yard to about 3 yards. The conventional set is a
muscle-back type iron made from forged steel. The conventional set
3-iron, 6-iron and 9-irons all have similar centers of gravity,
both as measured from the ground when the club head is in the
address position and as measured from a point on the hitting face
about 15 mm above the ground when the club is in an address
position.
[0040] As discussed above, it is preferred that the clubs of the
conventional set are adjusted by slightly varying club length and
static clubhead loft in order to obtain the inventive constant roll
set. FIG. 3 shows how carry distance is affected by static clubhead
loft and club length. Point A on FIG. 3 indicates the distance
traveled by a 3-iron of the conventional set, which has a static
clubhead loft of 22.degree. and a club length of 39 inches. Isobars
B show carry distance performance curves in 10-yard increments,
with carry distance increasing generally as club length increases.
As shown, increasing only the club length of the 3-iron of the
conventional set by one inch (to 40 inches) increases the carry
distance by about 5 yards, and decreasing only the club length of
the 3-iron of the conventional set by one inch (to 38 inches)
decreases the carry distance by about 5 yards. Similarly,
increasing only the static clubhead loft by one degree (to 23
degrees) decreases the carry distance by about 4 yards, and
decreasing only the static clubhead loft by one degree (to 21
degrees) increases the carry distance by about 3 yards. Therefore,
manipulating both parameters results in relatively large changes in
carry distance. For example, by increasing the club length of the
3-iron of the conventional set by one inch (to 40 inches) and
decreasing the static clubhead loft by one degree (to 21 degrees),
a carry distance increase of about 10 yards can be achieved.
Similarly, by decreasing the club length of the 3-iron of the
conventional set by one inch (to 38 inches) and increasing the
static clubhead loft by one degree (to 23 degrees), a carry
distance decrease of about 9 yards can be achieved.
[0041] FIG. 4 shows how ground roll is affected by static clubhead
loft and club length. Point C on FIG. 4 indicates the ground roll
of a 3-iron of the conventional set. Isobars D show ground roll
performance curves in 2-yard increments, with ground roll
increasing generally as static clubhead loft decreases. As shown,
increasing only the club length of the 3-iron of the conventional
set by one inch (to 40 inches) decreases the ground roll by about
1/2 yard, while decreasing only the club length of the 3-iron of
the conventional set by one inch (to 38 inches) increases the
ground roll by about 1/2 yard. Further, increasing only the static
club loft by one degree (to 23 degrees) increases the ground roll
by about one yard, while decreasing the static club loft by one
degree (to 21 degrees) decreases the ground roll by about one yard.
As such, manipulating both parameters results in relatively large
changes in ground roll. For example, by increasing the club length
of the 3-iron of the conventional set by one inch (to 40 inches)
and increasing the static clubhead loft by one degree (to 23
degrees), a ground roll decrease of about 1.5 yards can be
achieved. Similarly, by decreasing the club length of the 3-iron of
the conventional set by one inch (to 38 inches) and decreasing the
static clubhead loft by one degree (to 21 degrees), a ground roll
increase of about 1.5 yards can be achieved.
[0042] FIG. 5 shows how simultaneous changes in static clubhead
loft and club length affect both ground roll and carry distance,
assuming an average PGA Tour player swing, by overlaying a portion
of the graph of FIG. 3 onto the graph of FIG. 4. Isobars D show
ground roll differentials of 2 yards, with Isobar D' showing the
target ground roll. Isobar G shows the carry distance of the 3-iron
of the conventional set. Point E on FIG. 5 indicates the carry
distance and ground roll of the 3-iron of the conventional set. By
following Isobar G to the desired ground roll point on Isobar D',
as indicated by Point F, the club length and static clubhead loft
that will produce the target ground roll can be determined while
holding all other design parameters constant and maintaining the
desired carry distance. As such, to decrease the ground roll of the
3-iron of the conventional set to the target ground roll, the
static clubhead loft is increased to nearly 26 degrees and the club
length is increased to about 41 inches.
[0043] FIG. 6 is similar to FIG. 5 in that it shows how
simultaneous changes in static clubhead loft and club length
simultaneously affect ground roll and carry distance, assuming an
average PGA Tour player swing. However, FIG. 6 shows these changes
for a 6-iron of the conventional set. Isobars I show ground roll
differentials of 1/2 yard, with Isobar D' showing the target ground
roll point. Isobars H show carry distance differentials of 15
yards. Isobar J reflects the carry distance of the 6-iron of the
conventional set. Point L on FIG. 6 indicates the carry distance
and ground roll of the 6-iron of the conventional set, a 37.5 inch
club with a static clubhead loft of 32 degrees. By following Isobar
G to the desired ground roll point on Isobar D', as indicated by
Point K, the club length and static clubhead loft that will produce
the target ground roll can be determined while holding all other
design parameters constant and maintaining the desired carry
distance. As such, to increase the ground roll of the 6-iron of the
conventional set to the target ground roll, the static clubhead
loft is decreased to about 31.7 degrees and the club length is
decreased to about 37.3 inches. Notably, the adjustments to the
club length and static clubhead loft for the 6-iron are relatively
minor as compared with the changes made to the 3-iron in order to
obtain the same ground roll for both clubs, as the desired ground
roll is closer to the ground roll of the conventional 6-iron than
the conventional 3-iron. As such, it would be appropriate to use
the conventional 6-iron as the 6-iron of the inventive set, to
avoid re-tooling or redesigning the club while still having
approximately the same amount of ground roll as the rest of the
set.
[0044] FIG. 7 is similar to FIGS. 5 and 6 in that it shows how
changes in static clubhead loft and club length simultaneously
affect ground roll and carry distance, but for a 9-iron, assuming
an average PGA Tour player swing. Isobars M show ground roll
differentials of 1/2 yard, increasing in distance with decreasing
club length, with Isobar D' indicating the desired ground roll for
the inventive set. Isobars N show carry distance differentials of
20 yards, generally increasing with increasing club length. Isobar
O reflects the carry distance of the 9-iron of the conventional
set. Point P on FIG. 7 indicates the carry distance and ground roll
of the 9-iron of the conventional set, a 36-inch club with a static
clubhead loft of 25 degrees. By following Isobar O to the desired
ground roll point, as indicated by Point Q on Isobar D', the club
length and static clubhead loft that will produce the target ground
roll can be determined while holding all other design
characteristics constant and maintaining the desired carry
distance. As such, to increase the ground roll of the 9-iron of the
conventional set to the desired level reflected by Isobar M', the
static clubhead loft is decreased to about 38 degrees and the club
length is decreased to about 32 inches. As this point remains on
Isobar O, the carry distance remains the same for the inventive
9-iron as the conventional 9-iron. As will be recognized by those
in the art, the club length for the 9-iron may be shorter than is
comfortably played for many players. Therefore, it is within the
scope of the invention to lengthen the 9-iron, such as to a more
comfortable 34.125 inches. As the target ground roll need only be
within one yard of the ground roll identified by Isobar M', a
static loft of about 42 degrees may be selected to achieve a ground
roll within tolerances.
[0045] While only 3-, 6-, and 9-irons are discussed above, similar
analysis and design can be done for each club in a set to achieve
constant or nearly constant ground roll for each club in the set.
FIGS. 8 and 9 show the selected static lofts (FIG. 8) and club
lengths (FIG. 9) for the conventional, ideal constant roll and
nearly constant roll sets. In FIG. 8, curve 120 indicates the
static lofts of the conventional set. Curve 122 indicates the
static lofts of an inventive set that perfectly follows the graphs
discussed above, while curve 124 indicates the static lofts of a
preferred set which accounts for both nearly constant ground roll
within the desired tolerances and other aesthetic considerations,
such as a longer 9-iron than would be found in a set that strictly
follows the determinations of the performance curves, as discussed
above. In FIG. 9, curve 126 shows the club lengths for the clubs of
the conventional set, while curve 128 shows the club lengths for
the constant roll set. Curve 130 shows the preferred club lengths
for the nearly constant roll set. As shown in FIG. 9, the club
lengths of the nearly constant roll set more closely resemble those
of the conventional set than do the clubs of the constant roll
set.
[0046] As such, the desired carry distances for the inventive 3-,
6-, and 9-irons remain the same as those of the conventional 3-,
6-, and 9-irons, respectively, while each club in the inventive set
produces the same or nearly the same ground roll. This added level
of predictability is reflected in FIG. 8, which shows the
trajectories achieved by the inventive and conventional sets. The
trajectory of the conventional 3-iron is indicated by line 100,
with the inventive (constant roll) 3-iron trajectory indicated by
trajectory 102. Both 3-irons, as struck by an average PGA Tour
player, achieve the same downrange distance, with the conventional
3-iron having a higher maximum height above ground. Trajectory 104
indicates the trajectory of the conventional 6-iron, and trajectory
106 indicates the trajectory of the inventive 6-iron. As with the
3-irons, the same downrange distance is achieved with both 6-irons,
with the conventional 6-iron having a slightly higher maximum
height above ground than the inventive 6-iron. However, as
discussed above, the conventional 6-iron produces a ground roll
very similar to the target ground roll, so the conventional 6-iron
may be used in the inventive set, in which case trajectories 104
and 106 would be exactly the same. Finally, trajectory 108
indicates the trajectory of the conventional 9-iron, and trajectory
110 indicates the trajectory of the inventive 9-iron. As with the
irons discussed above, the same downrange distance is achieved with
both 9-irons, with the conventional 9-iron having a slightly higher
maximum height above ground than the inventive 9-iron.
[0047] While it is apparent that the illustrative embodiments of
the invention disclosed herein fulfill the objectives of the
present invention, it is appreciated that numerous modifications
and other embodiments may be devised by those skilled in the art.
Additionally, feature(s) and/or element(s) from any embodiment may
be used singly or in combination with feature(s) and/or element(s)
from other embodiments. Therefore, it will be understood that the
appended claims are intended to cover all such modifications and
embodiments, which would come within the spirit and scope of the
present invention. All publications discussed herein, including but
not limited to patents, patent applications, articles, and books,
are incorporated by reference in their entireties.
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