Assessment of Performance Parameters of a Series of Five
‘Historical’ Cricket Bat Designs
14th May 2014
Summary
Context and Scope
This report summarises work conducted by researchers in the Department of
Bioengineering at Imperial College London (Professor Anthony Bull, Mr Lomas
Persad, Dr Theofano Eftaxipoulou) on the request of the MCC. This work follows on
from prior work conducted at Imperial as part of a strategic collaboration between
MCC and Imperial College London.
The MCC has provided through a bat manufacturer a set of five different bat designs
from different eras. This work was conducted to address the simple question: “have
the changes in bat design over the years resulted in a performance advantage”.
Imperial’s approach has been to conduct a formal study to provide a quantitative
assessment of performance. This summary can be read in isolation and provides the
results in summary form together with an interpretation of these results.
Key Parameters
Previous work has clearly shown that the following parameters can all influence bat
performance: materials, manufacturing processes, weight distribution, and blade
design. Assumptions made in this study are that the materials are equivalent (same
type of wood, cane, rubber, twine and adhesives) and that the manufacturing
processes are equivalent, or at least do confer any performance benefit if altered.
Therefore, the other parameters would need to be quantified.
Key parameters associated with cricket bat performance are the ‘sweet spot’,
stiffness, moment of inertia and coefficient of restitution. The transfer of energy at
the sweet spot is maximal resulting in the most powerful shots, while the transfer of
energy to the hands is minimal resulting in minimum reaction force at the hands.
Imperial College has developed and published techniques to assess these key
parameters using vibration analysis (a measure of coefficient of restitution and size
of the ‘sweet spot’), and assessment of the moment of inertia (‘pick-up’ weight). One
parameter not previously addressed in great detail is the torsional moment of
inertia. This is a measure of the energy imparted at the edges of the bat and we
hypothesised that there would be a difference due to bat design modifications. This
parameter is directly related to the ability of a miss hit at the edge to travel further.
Results
The newest bat is heavier, longer (standing height), has a greater blade width, and is
much thicker resulting in a significantly greater moment of inertia (‘pick-up’ weight)
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and better sweet spot characteristics than the oldest bat. This gives a significant
performance advantage.
Performance Implications and Interpretation
Bat design can have a significant effect on performance. The newer bats, by and
large, confer a performance advantage in terms of the feel to the batsman (a likely
reduction in vibrations transmitted to the hands) which concomitantly will result in
less energy absorption by the bat and batsman and thus a greater proportion of the
energy will be imparted to the ball. This advantage is shown by the greater sweet
spot at both the centre and edge of the newer bats. Of note is the fact that the
scooped bat has the largest sweet spot, yet it is not the heaviest bat. This is a highly
optimised design for a large sweet spot. A second measure of energy ‘loss’ is the
natural frequency test which shows that all bats are similar in this regard. Of note is
the fact that the newest and oldest bats performed equally in this regard.
Pick-up weight has increased dramatically over the years. This is a function of
absolute weight, but also of geometry and balance. The results show clearly that
even if the bats were made of equal weight, the newer bats will be harder to ‘pick
up’, but for the same pick up height will impart greater energy to the ball due to the
greater moment of inertia; this results in a collision of greater energy and thus
confers a performance advantage.
Finally, the new experiment conducted here has shown that the greater torsional
stiffness of the newer bats, the scooped bat in particular, will likely confer an
advantage in the ‘miss hit’ or a short off the edge of the bat.
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Details
Bats Provided
A visual inspection of the bats confirmed that the older bats looked lighter and
smaller. In particular, the large depth of the newer bats and the more complex
varying profile was noted.
1905 'Ranjit'
1980 Powerspot
2009 Predator
2013 Perimeter (Scooped)
2013 Nemesis
Bat Dimensions
The newer bats are longer and thicker, thus confirming the visual inspection.
1905 'Ranjit'
1980 Powerspot
2009 Predator
2013 Scooped
2013 Nemesis
Overall standing
height
(mm)
854.00
852.00
853.00
857.00
860.00
Length
549.00
554.00
547.00
558.00
557.00
Blade dimensions (mm)
Maximum
Maximum
Width
Edge
Thickness
thickness
109.25
45.00
14.36
108.48
55.00
18.48
107.76
59.00
29.25
109.34
47.10
34.20
109.40
69.00
41.01
Weight and Mass Distribution
The table below shows that the newer bats are not only heavier, but also have the
mass distributed closer to the toe. This means that the newer bats preferentially will
transfer more energy to the ball when hit closer to the toe. However, no firm
conclusions can be drawn without the further test shown below
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1905 'Ranjit'
1980 Powerspot
2009 Predator
2013 Scooped
2013 Nemesis
Weight
(kg)
Distance to centre of
mass from bat toe
(mm)
Distance as a
% of total
height
1.03
1.15
1.15
1.17
1.21
350.00
355.00
343.25
348.00
330.00
40.98
41.67
40.24
40.61
38.37
Frequency Analysis
We present data from our vibrational energy tests that are performed as per our
previously described work. The full paper describing this has been appended to this
report for information (Eftaxiopoulou T, Narayanan A, Dear J, Bull AMJ. A
performance comparison between cricket bat designs. Proc. IMechE Part P Eng. Med.
225(P), (2011), 1078-1083).
We present the normalized vibrational energy absorbed per unit impulse at each
impact position for the first three bending modes only. The results are normalized
since the energy absorbed for the other points are calculated relative to impact
point at the toe.
The first graph below shows the energy profile for ball impact along the midline of
the blade and therefore representative of a clean cricket shot. The second graph
shows the energy profile for ball impact 2 cm inside the edge of the blade and would
indicate the performance for a poor shot during power hitting.
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Middle
1.6
1.4
Energy/J
1.2
1
0.8
0.6
0.4
0.2
0
0
10
20
Distance from toe (cm)
Ranjit 1905
Powerspot 1980
Perimeter 2013
Nemesis 2013
30
40
Predator 2009
Edge
1.6
1.4
Energy/J
1.2
1
0.8
0.6
0.4
0.2
0
0
10
20
30
40
Distance from toe (cm)
Ranjit 1905
Perimeter 2013
Powerspot 1980
Nemesis 2013
Predator 2009
The shape of the energy profile for each bat follows a similar trend where, the
highest energy absorbed is at the toe, decreasing as you move along the blade to a
minimum, indicating the sweet spot, then gradually increasing. This shows clearly
that to hit at the toe will not only transmit significant energy to the batsman, but will
also therefore dissipate energy and therefore loses energy transmission to the ball.
The energy absorbed is mainly dissipated as sound and vibrations, therefore higher
energy absorption indicates greater amplitude of vibration and greater discomfort to
the batsman during the shot. In contrast, the energy absorbed at the sweet spot is a
minimum resulting in greater energy transferred to the ball and a higher post-impact
speed of the ball.
The data above were further analysis to quantify the size and location of the sweet
spot.
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Sweet Spot Analysis
The sweet spot region here is defined as region of minimum energy absorption taken
to be less than 0.2J.
BAT
1905 'RANJIT'
1980 POWERSPOT
2009 PREDATOR
2013 SCOOPED
2013 NEMESIS
MIDDLE
Size of sweet
Location
spot region
from bat toe
(mm)
(mm)
80
140
120
160
165
220
215
180
160
180
EDGE
Size of
Location
‘sweet spot’ from bat
region (mm) toe (mm)
60
140
90
160
70
160
165
200
130
200
Powerspot and Predator bats are comparable in weight, therefore the major factor
that would affect performance is the blade profile and how the weight is distributed.
The results show that the Predator blade design is better for improving the size of
the sweet spot region but has the worst region of minimum energy absorption for
shots hit off centre. The results also indicate that the sweet spot location is
dependent on the location of maximum blade thickness.
The Perimeterweighted (scooped) and Nemesis blade designs are unique and very
different. Distribution of the weight along the edges in the scooped design results in
the largest sweet spot region of all the bats, while the Nemesis bat has a region
similar to the Predator. This might be due to the dramatic change in blade cross
section and thickness that occurs as you move away from the sweet spot towards
the handle in the Nemesis design.
The scooped bat also had the largest region of minimum energy absorption for ball
impacts away from the centre further highlighting the advantages of its design.
Even though the Nemesis and Predator designs have similar sweet spot sizes, one
key difference is the location of the sweet spot. The Nemesis has its sweet spot
located 40mm closer to the toe than predator, so both bats are expected to behave
differently when trying located the sweet spot in executing a good shot. Hitting
closer to the toe is more effective with the Nemesis than with the Predator. Hitting
lower will result in a high impact velocity of the bat to the ball (increasing the
distance from the centre of rotation of the bat during the swing will increase the
impact velocity). This will then result in a higher ball velocity. This is a subtle point,
but clearly shows that not only do the bats perform differently, but they will also
require a slightly different technique to optimise their performance.
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Nemesis results show that increasing bat weight is not sufficient on its own to
improve the sweet spot region. The blade profile plays an important role and so the
optimisation of the blade can have a large effect even without increase bat weight.
Natural Frequencies
The natural frequency analysis is important, because it is desirable if a bat can be
made with one or more of the natural frequencies outside the range of excitation.
This will reduce the energy absorption profile and increase performance, i.e. less
energy will be lost in impact and so more will be transmitted to the ball.
Impact from a cricket ball at 126 km/h will excite frequencies up to 1200 Hz.
Modes one two and three are bending while four and five are torsional.
1905 Ranjit and 2013 Nemesis both have a 5th mode that is excited and is expected
to have a negative impact on performance.
This all means that the bats are very similar and, surprisingly, the Ranjit and the
Nemesis have some slight additional negative performance characteristic due to the
exciting of the 5th mode.
1905 'Ranjit'
1980 Powerspot
2009 Predator
2013 Scooped
2013 Nemesis
1st
116
137
132
129
126
Bending modes (Hz)
2nd
3rd
4th
394
632
1004
425
690
1069
404
667
1039
388
650
1034
410
702
1069
5th
1106
1146
Y
Moment of Inertia
Moment of inertia (MOI) about two different axes is calculated and
used to indicate the differences in rotation characteristics for different
bat designs.
A
A
MOI pick-up weight is calculated about the AA axis of the bat which is
located at the midpoint of the handle indicative of where the batsman
would grip the bat. This is a measure of the resistance of rotating the
bat about the AA axis where the plane of the bat face is perpendicular
to the direction of movement which is typical of many shots in cricket.
A heavier bat means the moment of inertia will be higher. The pick-up
will therefore take more energy, but the momentum applied to the
ball will also be greater. The mechanism for achieving this is simply to
increase the proportion of the weight (mass of material) further away
from the axis of rotation, i.e. to distribute more mass near the toe.
Y
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The polar MOI calculates the resistance to rotation of the bat about the YY axis. In
this case a larger value would mean greater torsional stability which can reduce
twisting of the bat during ball impact off-centre and thus impart more energy to the
ball when hit off-centre (‘edge’).
MOI 'Pick-up weight'
0.2
MOI/ Kg m2
0.15
0.1
0.05
0
1905 'Ranjit'
2009 Predator
2013 Nemesis
1980 Powerspot
2013 Perimeterweighted
MOI ‘pick-up weight’ increases with weight. This is expected. Nemesis bat has the
highest value as it is the heaviest while Predator and Powerspot bats have similar
values as they have the same weight.
Further research may be needed to determine how the increase in MOI is perceived
by the batsman, but it is clear that the greater MOI in this case will result in greater
momentum transmitted to the ball, i.e. the ball will travel further.
Polar MOI 'Torsional stability'
MOI/ Kg m2
0.0013
0.0011
0.0009
0.0007
1905 'Ranjit'
1980 Powerspot
2009 Predator
2013 Perimeterweighted
2013 Nemesis
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As expected, the Perimeter has the highest value since its mass is distributed along
the edges meaning it has the highest resistance to twisting. The Predator blade
profile is better than the Powerspot design. It is conceivable that this profile may still
be able to be ‘tuned’ even more effectively to increase the hitting power of the bat
off the edge.
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