Ultra high stiffness putter shaft
A golf club shaft used with putter type club heads for making a putting stroke on the green of a golf course is made from high-modulus fibers which results in an ultra-high stiffness putter shaft with high frequency, low tip deflection, and high torsional and bending rigidity. The ultra-high stiffness putter shaft prevents unwanted face twisting during the impact of a golf ball during a putting stroke, allowing for greater putt accuracy.
1. A putter shaft comprising:
a tubular body comprising:
a torque core formed of bias plies;
wherein: the torque core bias plies comprise a graphite composite with a modulus greater than 60 msi,
an outer portion formed of longitudinal plies;
wherein: the outer portion longitudinal plies comprise a graphite composite with a modulus value between 54 msi and 56 msi,
a tip end; and
a butt end;
wherein:
the putter shaft has a length, measured between the tip end and the butt end, that is inclusively between 32 inches and 38 inches;
the putter shaft has a shaft mass inclusively between 115 grams and 135 grams;
the torque core comprises four full-length bias plies and two partial-length bias plies;
the outer portion comprises four full-length longitudinal plies;
each bias ply and each longitudinal ply wrap around twice to form two layers within the tubular body; and
the putter shaft comprises an ultra-high stiffness as evidenced by:
a frequency value of greater than 650 cycles per minute (cpm);
a tip deflection of less than 1.0 inch (2.54 cm); and
a torsional stiffness of less than 1.5 degrees;
wherein the frequency value is the number of oscillations that the tip end undergoes per minute when a first 6 inches of the butt end is clamped, a 205 gram weight is attached onto the tip end, and the tip end has been displaced and released; wherein the frequency value is measured within the first 2 to 10 oscillation cycles;
wherein the tip deflection is the perpendicular displacement of the tip end of the putter shaft from an at-rest position of the putter shaft when a first 6 inches of the butt end is clamped and a 3.9 lb load is applied perpendicularly to the putter shaft at 1 inch inward from the tip end; and
wherein the torsional stiffness is an angle of twist when a first 6 inches of the butt end is clamped, a first 1 inch of the tip end is clamped, and a torque load of 1 ft*lb is applied to the clamped tip end.
2. The putter shaft of claim 1 , wherein:
the longitudinal plies comprise fibers oriented approximately parallel to a longitudinal axis of the putter shaft; and
the bias plies comprise fibers oriented at +/−45 degrees from the longitudinal plies.
3. The putter shaft of claim 1 , wherein:
the two partial-length bias plies are tip bias plies; and
the tip bias plies extend to 20 inches (or 500 mm) from the tip end.
4. The putter shaft of claim 1 , wherein the ratio of the distance between a center of gravity of the putter shaft and the butt end of the putter shaft and the full length of the putter shaft is greater than 45%.
5. The putter shaft of claim 1 , wherein:
the putter shaft is hollow and comprises a wall thickness defined by an inner diameter (ID) and an outer diameter (OD); and
the wall thickness ranges inclusively between 0.030 inch and 0.100 inch.
6. The putter shaft of claim 1 , wherein:
the putter shaft further comprises a tip ID and a tip OD;
the tip ID and the tip OD are measured at the furthest portion of the tip end;
the tip ID ranges inclusively between 0.06 inch and 0.20 inch; and
the tip OD ranges inclusively between 0.25 inch and 0.45 inch.
7. The putter shaft of claim 1 , wherein:
the putter shaft further comprises a butt ID and a butt OD;
the butt ID and OD are measured at the further portion of the butt end; and
the butt OD ranges inclusively between 0.5 inch and 0.7 inch.
8. The putter shaft of claim 1 , wherein:
the putter shaft comprises a characterizing ratio selected from the group consisting of:
a ratio of frequency to tip OD that ranges inclusively between 1444 cpm/inch and 3200 cpm/inch,
a ratio of torsional stiffness to tip OD that ranges inclusively between 1.0 degrees/(ft*lb*inch) and 4.0 degrees/(ft*lb*inch),
a ratio of frequency to shaft mass that ranges inclusively between 4.0 cpm/gram and 8.0 cpm/gram, and
a ratio of torsional stiffness to shaft mass that ranges inclusively between 0.003 degrees/(ft*lb*gram) and 0.010 degrees/(ft*lb*gram).
9. The putter shaft of claim 8 , wherein:
the putter shaft comprises a frequency ratio between 5.5 and 8; and
the ratio is calculated by the following equation:
R
F
=
Frequency
10
,
0
0
0
×
(
Tip
OD
)
+
Shaft
Mass
.
10. The putter shaft of claim 8 , wherein:
the putter shaft comprises a torsional stiffness ratio between 0.004 and 0.010; and
the torsional ratio is calculated by the following equation:
R
T
=
Tortional
Stiffness
10
,
0
0
0
×
(
Tip
OD
)
+
Shaft
Mass
.
11. The putter shaft of claim 1 , wherein:
the putter shaft comprises a stiffness ratio between 650 and 1600; and
the stiffness ratio is calculated by the following equation:
R
S
=
Frequency
Torsional
Stiffness
.
12. A putter shaft comprising:
a tubular body comprising:
a plurality of bias plies and a plurality of longitudinal plies;
wherein: the plurality of bais plies comprise a graphite composite with a modulus greater than 60 msi and the plurality of longitudinal plies comprise a graphite composite with a modulus value between 54 msi and 56 msi,
a tip end; and
a butt end;
wherein:
the putter shaft has a length, measured between the tip end and the butt end, that is inclusively between 32 inches and 38 inches;
the putter shaft has a shaft mass inclusively between 115 grams and 135 grams;
the putter shaft comprises at least 6 full length plies;
at least 4 of the full length plies comprise a modulus value of at least 60 msi; and
the putter shaft comprises an ultra-high stiffness as evidenced by:
a frequency value of greater than 650 cpm;
a tip deflection of less than 1.0 inch (2.54 cm); and
a torsional stiffness of less than 1.5 degrees;
wherein the frequency value is the number of oscillations that the tip end undergoes per minute when a first 6 inches of the butt end is clamped, a 205 gram weight is attached onto the tip end, and the tip end has been displaced and released; wherein the frequency value is measured within the first 2 to 10 oscillation cycles;
wherein the tip deflection is the perpendicular displacement of the tip end of the putter shaft from an at-rest position of the putter shaft when a first 6 inches of the butt end is clamped and a 3.9 lb load is applied perpendicularly to the putter shaft at 1 inch inward from the tip end; and
wherein the torsional stiffness is an angle of twist when the putter shaft a first 6 inches of the butt end is clamped, a first 1 inch of the tip end is clamped, and a torque load of 1 ft*lb is applied to the clamped tip end.
13. The putter shaft of claim 12 , wherein:
the putter shaft is hollow and comprises a wall thickness defined by an inner diameter (ID) and an outer diameter (OD);
the wall thickness ranges inclusively between 0.030 inch and 0.100 inch;
the putter shaft further comprises a tip ID and a tip OD;
the tip ID and the tip OD are measured at the furthest portion of the tip end;
the tip ID ranges inclusively between 0.06 inch and 0.20 inch; and
the tip OD ranges inclusively between 0.25 inch and 0.45 inch.
14. The putter shaft of claim 12 , wherein:
the putter shaft further comprises a butt ID and a butt OD;
the butt ID and butt OD are measured at the further portion of the butt end; and
the butt OD ranges inclusively between 0.5 inch and 0.7 inch.
15. The putter shaft of claim 14 , wherein:
the putter shaft comprises a characterizing ratio selected from the group consisting of:
a ratio of frequency to tip OD that ranges inclusively between 1444 cpm/inch and 3200 cpm/inch,
a ratio of torsional stiffness to tip OD that ranges inclusively between 1.0 degrees/(ft*lb*inch) and 4.0 degrees/(ft*lb*inch),
a ratio of frequency to shaft mass that ranges inclusively between 4.0 cpm/gram and 8.0 cpm/gram, and
a ratio of torsional stiffness to shaft mass that ranges inclusively between 0.003 degress/(ft*lb*gram) and 0.010 degrees/(ft*lb*gram).
16. The putter shaft of claim 14 , wherein:
the putter shaft comprises a characteristic ratio selected from the group consisting of: a frequency ratio (R F ), a torsional stiffness ratio (R T ), and a stiffness ratio (R S );
the frequency ratio (R T ) ranges inclusively between 5.5 and 8;
the frequency ratio (R T ) is calculated by the following equation:
R
F
=
Frequency
10
,
0
0
0
×
(
Tip
OD
)
+
Shaft
Mass
;
the torsional stiffness ratio (R T ) ranges inclusively between 0.004 and 0.010;
the torsional stiffness ratio (R T ) is calculated by the following equation:
R
T
=
Torsional
Stiffness
10
,
0
0
0
×
(
Tip
OD
)
+
Shaft
Mass
;
the stiffness ratio (R S ) ranges inclusively between 650 and 1600; and
the stiffness ratio (R S ) is calculated by the following equation:
R
S
=
Frequency
Torsional
Stiffness
.
17. A putter shaft comprising:
a tubular body comprising:
a plurality of bias plies and a plurality of longitudinal plies;
wherein: the plurality of bais plies comprise a graphite composite with a modulus greater than 60 msi and the plurality of longitudinal plies comprise a graphite composite with a modulus value between 54 msi and 56 msi;
a tip end; and
a butt end;
wherein:
the putter shaft has a length, measured between the tip end and the butt end, that is inclusively between 32 inches and 38 inches;
the putter shaft is hollow and comprises a wall thickness defined by an inner diameter (ID) and an outer diameter (OD);
the putter shaft further comprises a tip ID and a tip OD;
the tip ID and the tip OD are measured at the furthest portion of the tip end;
the putter shaft comprises an ultra-high stiffness as evidenced by a frequency value of greater than 650 cpm and a frequency ratio (RF) between 5.5 and 8;
the frequency value of the putter shaft is the number of oscillations that the tip end undergoes per minute when a first 6 inches of the butt end is clamped, a 205 gram weight is attached onto the tip end, and the tip end has been displaced and released; wherein the frequency value is measured within the first 2 to 10 oscillation cycles; and
the frequency ratio is calculated by the following equation:
R
F
=
Frequency
10
,
0
0
0
×
(
Tip
OD
)
+
Shaft
Mass
.
18. The putter shaft of claim 17 , wherein:
the putter shaft has a shaft mass inclusively between 115 grams and 135 grams;
the tip ID ranges inclusively between 0.06 inch and 0.20 inch;
the tip OD ranges inclusively between 0.25 inch and 0.45 inch.
19. The putter shaft of claim 17 , wherein:
along at least 50% of the putter shaft length, the OD of the putter shaft varies according to the following equation:
y= 0.011 x+ 0.345
with x equaling the distance from the tip end; and
with y equaling the OD of the putter shaft.