Matched Set Of Golf Clubs

Abstract

A matched set of golf clubs, of which each club comprises a shaft and a club head carried thereon, wherein the flexural rigidity of the shaft of any wood or iron of the set is not more than that of any longer wood or iron, respectively, of the set. Thus the club shafts became more flexible per unit length as they get shorter, this being opposite to conventional trends. This reversed trend has been found to be very advantageous particularly in that matched sets of clubs can be provided having matched moments of inertia and matched frequency of vibration. Thus, all the clubs of the set will have a very similar feel in use.

Description

This invention relates to matched sets of golf clubs.

It is the common experience of golfers that for a set of golf clubs to be really satisfactory not only must each individual club suit them as far as its length, weight and flexibility is concerned, but that the set as a whole should "feel right", that is the clubs of the set should have common characteristics which give the golfer the same feel when making strokes with the various clubs of the set. Reference in this Specification to "a set of clubs" refers to the woods and the irons, but does not include the putter.

At present the generally accepted method of matching golf clubs into a set is by what is known as the "swing weight" method in which the moment of weight of the clubs is measured with respect to points on the various types of clubs all at the same distance from the grip end of the club. Although this method is in common use, it is not really satisfactory in producing matched sets of clubs. A greatly improved method is one in which the matched clubs all have the same moment of inertia about points in their shafts which are the same distance from the grips of the clubs.

Such a method and apparatus is described in the assignee's co-pending U.S. Pat. No. 3,703,824 issued Nov. 28, 1972.

Whichever method of matching clubs is adopted, however, it has been common practice for the various types of clubs in the set to show a gradation of flexural rigidity throughout the set, the rigidity increasing with descreasing length of club. Thus, the rigidity of the shaft of a conventional No. 1 wood, whose length is usually 44 inches, is less than that of the shaft of the No. 3 wood whose length is usually 43 inches. Similarly, the rigidity of shaft of conventional irons increases from the No. 2 iron whose shaft is usually 39 inches long to the No. 9 iron whose shaft is usually only 351/2 inches long. Hitherto, this gradation of rigidity has been thought essential. However, I have now found that this is not so and that considerable advantages can be obtained if gradation of rigidity throughout the set is the converse of the common practice. Alternatively, the flexural rigidity can be the same for all the clubs or at least have a common value for all the irons and a common value (which can be different from the common value for the irons) for all the woods.

Accordingly, in one aspect the present invention provides a matched set of golf clubs in which the flexural rigidity of the shafts of the clubs is such that the flexural rigidity of the shaft of the shortest iron or wood is not more than that of the longest iron or wood respectively.

Where there is a gradation in rigidity it is preferably a progressive decrease throughout the woods from the longest to the shortest or a progressive decrease throughout the irons from the longest to the shortest, though two or more of the woods or irons can, if desired, have the same rigidity, especially if they are adjacent clubs in the set.

It has further been found that the clubs of this invention are of particular value where the clubs are made so that at least all the woods have a common frequency of vibration, and where the irons also have a common frequency of vibration which generally will be different from, but may be the same as, the common frequency of the woods.

The gradation of rigidity of this invention can be achieved in various ways. In one way, the stepped pattern of a conventional set of shafts is retained (i.e. the same lengths and external diameters of the various steps and sections are used), but different wall thicknesses of tube are used such that the shafts in the set get progressively lighter as they get shorter, instead of remaining constant in weight or getting progressively heavier, as is the usual case. In this way a progressive reduction in wall thickness can be specified such that the flexural rigidity is either maintained at a fixed value or is progressively reduced.

A second way of obtaining the necessary gradation in rigidity is to use tubes of the same wall thicknesses as for a conventional set of shafts, but to choose the length and position of the various steps such that the necessary regidity is obtained. In general, this means that the first section or lowermost step on the shaft gets longer and (preferably) the last section or uppermost step (which bears the golf grip) gets shorter as the shafts get progressively shorter in the set whilst the length of the intermediate steps remain constant. Because the lowermost section is of lesser diameter than that of the other sections, the result is to decrease the overall rigidity of the shaft. A third way of obtaining the necessary gradation in rigidity, which applies only to roll-tapered unstepped shafts, is to taper the shafts at a substantially constant rate but in such a way that the uppermost generally parallel section of each shaft (which bears the golf grip) gets shorter as the shafts progressively shorten through the set.. Again this means that as the shafts get shorter, a greater proportion of the shaft length has a lower effective diameter which leads to a reduction in rigidity.

In the set of clubs described below as exemplification of the present invention the gradation in rigidity is obtained by a preferred form of the second of the methods described above, in which the lowermost step (that is, the step nearest to the head end of the shaft) increases in length with decreasing length of club shaft, but the lengths of the other steps remains constant.

Sets of clubs of overall increased or decreased rigidity can be obtained either by using a lowermost step of decreased or increased length respectively or by using a tube of increased or decreased diameter respectively at the grip end.

The invention is illustrated by the following Examples with reference to the accompanying drawings. In the drawings:

FIG. I is a diagrammatic representation of the shaft of the woods of all three Examples; and

FIGS. II, III and IV are respectively diagrammatic representations of the shafts used respectively for the "medium" clubs of Example 1, the "whippy" clubs of Example 2 and the "stiff" clubs of Example 3.

FIG. V illustrates a conventional Golf Club having a stepped shaft with increasing thickness of the wall, FIG. 5A having the thinnest wall and FIG. 5C the thickess wall.

FIG. VI illustrates the shafts for a wood set in its completed form;

FIG. VII illustrates representative examples of the shafts for a set of irons in their completed form.

EXAMPLE 1

This Example describes a matched set of golf clubs consisting of four woods and 10 irons, in which all the clubs have the same moment of inertia the woods have a common frequency of vibration and the irons have common frequency of vibration though different from that of the woods.

Table 1 below shows the moment of inertia, head weight, flexural rigidity and frequency of vibration of the clubs of this Example compared with the values for a conventional set of clubs. The lengths of the various types of clubs are the same in the two sets.

TABLE 1 __________________________________________________________________________ Moment of Inertia Head Weight Flexural Rigidity Frequency of (gcm.sup.2 .times. 10.sup.7) (g.) (gcm.sup.2 .times. 10.sup.7) Vibration (cpm) Nominal len- Conven- Inven- Conven- Inven- Conven- Inven- Conven- Inven- gth of shaft tional tion tional tion tional tion tional tion (inches) __________________________________________________________________________ WOODS 1 44 29.5 27.6 200 190 4.8 4.9 274 286 2 431/2 29.3 27.6 207 195 4.8 4.85 279 286 3 43 29.1 27.6 214 201 4.9 4.8 282 286 4 421/2 28.9 27.6 221 207 4.9 4.75 287 286 IRONS 2 39 28.0 27.6 254 248 4.8 5.8 305 333 3 381/2 27.8 27.6 261 256 4.9 5.7 313 333 4 38 27.6 27.6 268 264 5.0 5.6 318 333 5 371/2 27.8 27.6 275 272 5.0 5.5 323 333 6 37 27.4 27.6 282 280 5.1 5.4 326 333 7 361/2 27.5 27.6 289 289 5.1 5.3 335 333 8 36 27.4 27.6 296 298 5.2 5.2 339 333 9 351/2 27.3 27.6 303 308 5.4 5.1 349 333 10 351/2 28.5 27.6 320 308 5.4 5.1 347 333 SAND 351/2 30.0 27.6 345 308 5.5 5.1 343 333 __________________________________________________________________________

In obtaining the data given in Table 1 above the flexural rigidity of the shafts was measured as follows. The top 7.7 inches of the club shaft without its club head was firmly clamped in a vice and the distance L of the free length of shaft from the vice to the other end of the shaft was measured. A known weight W was suspended from the free end of the shaft and the resulting static downward deflection d of the free end was measured. The flexural rigidity of the shaft was then obtained from the following equation:-

Flexural rigidity (g.cm.sup.2 .times. 10.sup.7) = W. L.sup.3 /3d

where W is the suspended weight (grams)

L is the free length of shaft (centimetres)

d is the deflection of free end of shaft (centimetres)

Arbitrary lengths of the golf shaft other than 7.7 inches can be clamped to determine flexural rigidity and this will give slightly different values from those quoted. However, the desired gradation in rigidity will still be maintained.

The clubs of this Example had shafts, which each weighed between 41/8 and 45/8 ounces, were of hardened steel tube which has been formed into a "stepped" shape. The dimensions of the various steps are given in the Tables below.

The values for the frequency of vibration were obtained from the standard equation for the oscillation of a rod clamped at one end thereof and having a mass fixed at the other: ##SPC1##

where

f = frequency of vibration (cycles/minutes)

Yak.sup.2 = flexural rigidity of the club shaft (g.cm.sup.2)

L = free length of shaft (cm.)

M = mass of club head (grams)

m = mass of free length of shaft (grams)

G = gravitational constant

The frequency of vibration of the clubs can be obtained by direct measurement as follows. The top end of the shaft of the complete club is gripped firmly in a vice and the head end is "plucked" so that the free portion of the club vibrates. The number of vibrations per minute can then be counted, for example by an electric counting device. It is found that the values for frequency of vibration obtained experimentally agree with the calculated values within a margin of .-+. 5%, usually 3-5%.

The set of clubs of this Example were tested in play by 12 experienced golfers all of whom found them to be well matched as to feel and noticeably superior to the set of conventional clubs.

EXAMPLE 2

This Example relates to a set of clubs having a more whippy feel than those of Example 1.

A set of matched golf clubs was made in which the various types of clubs had the moment of inertia and head weights equal to those of the various types of clubs of the set of this invention of Example 1 but with different dimensions for the various steps of the shafts. The dimensions are given in the Tables below. The flexural rigidity of the shaft of each club was 0.25 g.cm.sup.2 .times. 10.sup.7 less than the values for the clubs of Example 1.

From playing tests with the clubs of this Example it was found that all the clubs were more whippy than the corresponding clubs of Example 1 and that the set as a whole was better matched than the conventional set.

EXAMPLE 3

This Example relates to a set of clubs having a stiffer feel than those of Example 1.

A set of matched golf clubs was made in which the various types of clubs had the moment of inertia and head weights equal to those of the various types of clubs of the set of this invention of Example 1, but with different dimensions for the various steps of the shafts. The dimensions are given in the Tables below. The flexural rigidity of the shaft of each club was 0.25 g.cm.sup.2 .times. 10.sup.7 more than the values for the clubs of Example 1.

From playing tests with the clubs of this Example it was found that all the clubs were stiffer than the corresponding clubs of Example 1 and that the set as a whole was better matched than the conventional set.

The external diameter and length of the various steps of the clubs of Examples 1, 2 and 3 are given below in Tables 2-5, of which Tables 2 and 3 relate to the woods whose shaft is shown in FIG. I and Tables 4 and 5 to the irons whose shafts, medium, whippy or stiff are shown respectively in FIGS. II, III and IV.

The dimensions given in Table 2 relate to the medium shafts used for the woods of Example 1, the whippy shafts used in Example 2 and the stiff shafts used in Example 3. It will be seen from Table 2 that the difference between the three types of shaft lies in the different lengths of Steps A and N, the lengths of the other steps being unchanged whether for medium, whippy or stiff shafts. The various lengths of Step A are shown in Table 3.

It should be noted that in the shafts used for these woods the external diameter of the last eight inches at the end of Step A tapers uniformly from 0.335 to 0.277 inch. This taper is to facilitate the attachment of the shaft to the head of the club.

TABLE 2 - WOODS ______________________________________ Step External Diameter Length of Step (inch) (inches) ______________________________________ A 0.335 (variable see Table 3) B 0.345 4 C 0.360 2 D 0.375 11/2 E 0.390 11/2 F 0.405 1 G 0.425 1 H 0.455 7/8 I 0.485 7/8 J 0.515 5/8 K 0.545 5/8 L 0.575 1/2 M 0.600 1/2 N 0.620 depends upon length of Step A ______________________________________

TABLE 3 - WOODS ______________________________________ Length of Step A (inches) Total Length of shaft (inches) Stiff Medium Whippy shaft shaft shaft ______________________________________ 44 12.25 13.75 15.25 43.5 12.5 14 15.5 43 12.75 14.25 15.75 42.5 13 14.5 16 ______________________________________

FIGS. II, III and IV show respectively the shafts used for the irons of Examples 1, 2 and 3. The dimensions of the steps of each of those shafts are given in Tables 4 and 5 below.

It should be noted that in the shafts used for these irons the external diameter of the last two inches at the end of Step 1 tapers uniformly from 0.370 to 0.355 inch to facilitate attachment of the shaft to the club head.

TABLE 4 - IRONS __________________________________________________________________________ Step External Diameter Length of step (inches) (inch) __________________________________________________________________________ Stiff Medium Whippy Stiff Medium Whippy __________________________________________________________________________ 1 0.370 0.370 0.370 (variable see Table 5) 2 0.380 0.380 0.370 13/4 13/4 13/4 3 0.387 0.387 0.387 11/4 11/4 11/4 4 0.395 0.395 0.395 1 1 1 5 0.405 0.405 0.405 5/8 5/8 5/8 6 0.415 0.415 0.415 5/8 5/8 5/8 7 0.430 0.430 0.430 1/2 1/2 1/2 8 0.450 0.450 0.450 1/2 1/2 1/2 9 0.470 0.470 0.460 1/2 1/2 1/2 10 0.480 0.480 0.470 1/2 1/2 1/2 11 0.490 0.490 0.480 1/2 1/2 depends upon length of step 1. 12 0.505 0.500 -- 1/2 depends -- upon length of step 1. 13 0.520 -- -- depends -- -- upon length of step 1. __________________________________________________________________________

TABLE 5 - IRONS ______________________________________ Total length Length of of shaft (inches) step 1 (inches) ______________________________________ 39 61/4 381/2 7 5/16 38 83/8 371/2 9 7/16 37 101/2 361/2 11 9/16 36 123/8 351/2 13 11/16 ______________________________________

In producing the finished clubs of the Examples the thinner end of each shaft was fixed in a reamed cavity in the head. The other end of the shaft was trimmed, if necessary, to obtain the desired length of club and the grip fitted. The total length of shaft referred to above is the length of the shaft before any such trimming, and is the length of the shaft when the various tests to ascertain frequency of vibration and moment of inertia are made.

Claims

We claim:

1. A matched set of golf clubs having woods and irons, each club of said set comprising a shaft having a club head on one end and a grip on the opposite end and said set comprising a plurality of woods of decreasing shaft length and increasing loft and a plurality of irons of decreasing shaft length and increasing loft, the improvement comprising having the flexural rigidity of the shaft of any wood in the set not greater than that of the shaft of any longer wood in the set and having the flexural rigidity of the shaft of any iron in said set not greater than that of the shaft of any longer iron in said set.

2. A matched set of golf clubs according to claim 1, in which the values for flexural rigidity of the shafts of both the woods and the irons decrease progressively from the longest to the shortest shaft of the woods and of the irons.

3. A matched set of golf clubs according to claim 2, in which the shafts are of stepped metal tube and the decrease in flexural rigity from one shaft to another is obtained by use of different wall thicknesses for the various steps of each shaft.

4. A matched set of golf clubs according to claim 2, in which the shafts are of stepped metal tube and the decrease in flexural rigidity from one shaft to another is obtained by an increase in the length of the step most distant from the grip end of the clubs.

5. A matched set of golf clubs according to claim 4, in which the length of the various steps between the two terminal steps of the tube is the same for all the irons of the set.

6. A matched set of golf clubs according to claim 4, in which the length of the various steps between the two terminal steps of the tube is the same for all the woods of the set.

7. A matched set of golf clubs according to claim 1, in which at least all the woods have a common frequency of vibration.

8. A matched set of golf clubs according to claim 7, in which all the irons have a common frequency of vibration.

9. A matched set of golf clubs according to claim 1, in which the clubs are matched with respect to their moments of inertia, said moments of inertia for each club being measured about a point in the shaft which is a fixed distance from the grip, said distance being the same for each club.