Brandishing clubs, bats, sticks, and rackets, Design News' staffers recently
vented their frustrations by going out and whacking stuff around.
It was mere coincidence that all the field investigations involved taking one
thing and hitting another thing with it: We tested a golf club, a hockey stick,
a softball bat, and a tennis racket--which actually have more in common with
each other than you might think. Despite the widely varying objectives of each
sport, the design goals from an engineering standpoint are pretty much the same.
"The basic objective is to achieve an efficient transfer of energy," says
Bill Bishop, principal engineer at Wilson Racquet Sports Technology (Chicago,
IL). "Best case, you'd like to have a perfectly elastic collision where there is
no energy loss."
To test the effectiveness of their designs, sports equipment engineers need
to know something about the characteristics of the object being struck. One
design parameter they're interested in is the coefficient of restitution (or
COR), which is a measure of how much energy is absorbed during impact. Testing
varies by sport. For example, engineers measure the COR of a baseball by firing
it against a steel plate and measuring the speed at which it bounces back; they
measure the COR of a tennis ball by dropping it from a fixed height of 100
Different objects have different CORs, which are also a function of speed. As
rough approximations, the COR of a baseball is 0.52 to 0.57 at 88 ft/sec; the
COR for a golf ball is 0.79 at 125 ft/sec; and the COR for a tennis ball is 0.67
to 0.73 at 60 ft/sec. A COR of 1.00 indicates a perfectly elastic collision,
i.e. no energy loss.
This kind of empirical testing gives engineers insight into the relative
effectiveness of their designs. The end result? New technology that is becoming
increasingly better at compensating for a weak backhand in tennis or a wicked
slice in golf, as we amateur athletes--including two new writing talents on our
art staff--discovered during our field research.
Titanium scores in hockey stick design
Rick DeMeis, Associate Editor
A few years ago I decided to upgrade my meager hockey skills. A skating
school did help my mobility on the ice. But until now, I never gave much thought
to upgrading my equipment. Needless to say, when the chance to test the new
ProKENNEX titanium-mesh-jacketed Ti GT 8000 Pro composite-shaft hockey stick
came up, my trusty wood stick quickly became history.
The GT 8000 consists of two parts: a fiberglass-jacketed,
carbon-fiber-reinforced laminated wood blade and a short wooden upper handle.
Both sections are hot-glued into the ends of a hollow shaft, consisting of six
fiberglass and carbon-composite layers, jacketed by a titanium mesh (see diagram
The exact layer arrangement varies along the length. At the bottom, an
extra-carbon-plies reinforced flared "hosel" holds the wood blade in place. This
part of the shaft must be the strongest, because of slap-shot forces and the
need to reduce torquing on the blade.
Above the hosel is the "kick point," much like that designed into a
composite-shaft golf club. A different orientation of the composite-ply layup
here results in a distinct change in the bend profile.
The 8000 stick I tried out has a kick point two inches higher than the 6000
model, which has two fiberglass layers in place of one of the carbon-fiber
layers. Paul Kid, VP of product development at ProKENNEX, explains that the
6000's lower kick point and greater flexibility combine to angle shots higher,
allowing weaker players to achieve greater loft.
A titanium weave sheathes the shaft along its mid-length, which again changes
the bending profile by stiffening and strengthening the stick. A side-load test
on the stick-end hosel showed that it can sustain a 400-kg load before breaking.
Other sticks only went to 370-kg loads. Interestingly, sticks cannot be designed
for maximum mid-point side-load strength, to prevent players from injury.
These titanium-clad sticks are also stiff in torque. Tests with a 6.8-kg
weight on an arm extending 15 cm off the stick produced an angular deflection of
2.5 to 4.0 degrees for the 8000; 3.5 to 5.5 degrees for the 6000; 4.5 to 6.0
degrees for the composite-only 1000 model; and 9.0 to 11.8 degrees for wooden
After cutting the handle end of the stick down to the length I play with, the
first thing I noticed was its low weight. Other players commented on the same
thing, finding it almost disconcerting at first. But a light stick means less
strain on the arm or elbow, particularly when playing one-handed.
The stick's low weight and high stiffness allow putting "a lot of power" into
a shot. I found the ProKENNEX lively enough that I had to pay attention to
receiving passes with the proper technique--"catching" them with a slight "give"
and downward twisting of the blade. Otherwise, pucks tended to bounce off my
rigidly held blade.
If you're a player and inclined to a premier stick, in the same price range
you may want to consider the ProKENNEX 8000 and 6000 along with other top-end
Product:ProKENNEX Ti GT 8000 Pro hockey stick
composition: Titanium/fiberglass/carbon composite/wood
weight: 1.24 lb (comparable size all-wood stick, 1.48 lb)
Major design innovation: Titanium-mesh jacket
stiffens stick mid-shaft and protects under-layers
Performance improvement: Very good to excellent. This editor and
fellow players using it commented on the "power" it put into shots. Carrying
such a lightweight stick takes some getting used to.
Stiffness and "kick point" (pivot point) combination produce a livelier shot.
Lighter weight relative to wood sticks makes for easier handling with less
potential elbow strain.
"Novelty" factor: Mention a
titanium-composite stick and the comments range from "The aerospace stick," to
"What'll they come up with next?"
Overall impression: A top quality
piece of equipment that allows performing at peak puck-playing skills, but the
retail price may be overkill for the below-to-average player.
Hybrid bat built for booming
John Lewis,l Northeast Technical Editor
Just as softball sluggers of the 1970s saw wooden bats give way to aluminum
ones, now they are watching aluminum bats go the way of their lumber
predecessors. Thanks to manufacturing and materials advances, a field of new
"high-tech" bats promises better swings and drives.
Take the Fusion bat I tested out. It's a composite of aluminum and graphite
from sporting-goods manufacturer Dudley, a unit of Spalding. Five ounces lighter
than conventional softball bats of the same size, this bat has a 3 to 6 mph
faster swing than aluminum bats with the same swing weight, Dudley says. On long
drives, this roughly translates into an additional 10 to 20 ft of increased
While claims of extra distance are as old as the game, and hard to
substantiate, the main determinant will always be the person doing the swinging.
Undaunted, I envisioned myself with the new bat, hitting ball after ball into
the stands to the appreciative roar of the fans at Fenway Park.
I use a 29-oz aluminum beer-league bat, and I asked Dudley to send the same
size bat so I could do a direct comparison. When the Dudley rep quizzed me about
whether I meant swing weight, or actual weight, I had no idea what he was
talking about. He explained that swing weight measures what the bat feels like
in your hands while swinging, and that actual weight is the bat's scale weight.
I went with the 29-oz swing weight.
When the bat arrived, the first thing I did was hold my old 29-oz aluminum in
one hand and the new 24-oz actual-weight Fusion in the other. No real difference
there. Then I flipped the bats over and held them by their barrel ends. The
weight difference was extraordinary. Since most of the Fusion's weight is in the
barrel, the aluminum bat's handle is actually quite heavy by comparison.
The Fusion's body and handle are graphite with a thin (0.065 inch thick)
C-405 aluminum sheath fused to the barrel area. By using composites in the
handle, explains Brian Feeney, director of product development at Spalding,
engineers were able to design a bat that is lighter in weight, yet still feels
like a heavier aluminum bat during the swing.
Graphite's higher strength, light weight, and directional properties allow
the Fusion bat to be at least 20% stiffer in bending and 15% more flexible in
hoop stiffness, and it has a better weight distribution than a single-wall
So how does all this translate into better play? "Softballs are made of foam
and are not very good at storing energy. When you deform them, you lose a lot of
that energy," explains Feeney. "That's why we built a bat that deflects, stores
the energy, and springs back during impact."
Although I did feel as though I were blasting balls into orbit with the
Fusion softball bat, its design innovations were not quite sufficient enough to
overcome all of the limitations of my hitting game. So with much anticipation,
I'm looking forward to next year's softball season and the next new crop of
Product name: Fusion 2 softball bat
C-405 graphite composite construction
Weight: 29-oz swing
weight/24-oz actual weight
Retail price: $250.00
innovation: Bladder molding process and materials of construction
Performance improvement: Excellent
Handling: Though the
Fusion is light in weight, it feels like a heavier aluminum bat during the swing
"Novelty" factor: The colors are cool
Although I had the sensation that I was blasting balls into orbit with the
Fushion, its design innovations weren't quite sufficient enough to overcome all
of the limitations of my game
Fat Shaft(TM) golf club is no slouch
William Reilly, Senior Art Director
First of all, let me say this: On the hacker's barometer, my golf game falls
somewhere between Tiger Woods and "Carl the groundskeeper" from Caddyshack. So I
desperately welcome any advantage on the course I can find--no matter how
It was with a kind of secret glee that I recently set out for the course
armed with the latest offering from Wilson: the Fat Shaft(TM) series irons.
The clubs have an unmistakable--actually let's just say weird--appearance.
The feature that earns them their name is the thick shaft that travels from the
butt to the tip of the club. While traditional clubs gradually taper to meet the
head, the Fat Shafts appear to have the same thickness throughout.
Actually, they do taper--from a standard thickness of 0.60 inch butt diameter
down to 0.50 inch at the tip. Conventional clubs, on the other hand, taper down
to 0.37 inch. According to Design Engineer Frank Garret at Wilson, the 35%
increase in diameter at the tip limits the twisting action of the club--by
providing 75% more torsional stability than its skinnier counterparts. The
trick? Optimizing the mass distribution of the shaft and head combined.
At less than 1.5 gms/inch, the hollow shaft is one of the lightest in the
business. The shaft's graphite epoxy construction (a blend of intermediate
modular and standard graphite) allowed designers to achieve low torque while at
the same time maintaining the flex distribution of a conventional shaft.
The increased stability also provides a large sweet spot on the club face,
ostensibly allowing for better results on missed hits. A low center-of-gravity
also helps to get the ball airborne more easily. And, of course, the advantage
of the oversized cast steel head is its larger moment of inertia--so if you do
hit it off center, less rotation occurs.
My results backed these claims up. I tested a set of irons (3 iron through
pitching wedge). Like many golfers, I have a bit of a slice, which I generally
factor into my aim. With the Fat Shafts, I not only lost my tendency to slice,
but actually managed a truer, straighter shot with greater distance.
This was particularly evident with the long irons (3-6). When reaching for
the short irons, the 9 iron and pitching wedge especially, I noticed a loss of
touch. It seemed as though the same technology that improved the distance and
accuracy in the long irons robbed me a little of the feel of the club. My shots
were straight, but gauging the distance was an adventure. This made my game a
little unpredictable at times.
I didn't test the woods, but it would seem to hold true that the same shaft
design that results in longer and more accurate shots in the irons would net the
same results in a set of woods. Now, if only Wilson would only develop a
technology that would help golfers like me avoid three-putting--then they'd
really be on to something!
Product: Wilson Fat Shaft golf irons
composition: Graphite-epoxy shaft and cast steel head
weight: Graphite shaft--395 gms; Steel shaft--415 gms
price: $1,060 (3-iron through pitching wedge)
innovation: A larger tip diamaeter of 0.50 (35% larger than conventional
shafts), providing greater torsional stability
Performance improvement: Very good
Handling: Very good
"Novelty" factor: The distinctive look of the Fat Shaft clubs got a
lot of notice around the course. Many golfers had heard of them, but had yet to
Overall impression: The unconventional look of the clubs
gave me the initial impression that they would be heavy and lacking in any
aerodynamic qualities. The reality is that this set of clubs is more forgiving,
allowing me to swing easier with longer drives and more accurate results.
Titanium racket serves up an ace
Michelle Barbera, Associate Art Director
As luck would have it, I had just purchased a new tennis racket when I had a
chance to test out Wilson's Hammer 3.0 Titanium racket. Now, I'm considering
getting the Hammer and using my first racket as a spare.
Coming from a tennis family, the competitive pressure is pretty intense, as
you might imagine. Fortunately, I immediately noticed a dramatic difference with
the new racket, especially on my forehand.
My two-handed backhand has always been my better stroke, but my one-handed
forehand was greatly aided by the lightness of the Hammer. I no longer have to
worry about dropping the head of the racket--I just concentrate on hitting
through the stroke. I have found this to be particularly helpful in mid-match,
at about the time my wrist and arm begin to tire.
I was surprised that even though the racket is lighter (8.5 oz unstrung) than
the racket I was using, I was able to hit the ball harder--but not at the
expense of control. In fact, the Hammer provides more control than other rackets
with oversized heads (118 inches) that I have used. It is important to hit the
ball with a good deal of top spin, but Hammer allows for some leeway in the
According to Bill Severa, a design engineer at Wilson Sporting Goods, the two
elements that make the racket a standout are its power and torsional stability.
Essentially, designers strategically redistributed the weight of the racket,
placing more mass in the head.
It's this mass at the point of impact that, says Severa, provides more
efficient delivery of energy and helps to keep the ball in play longer. "What we
have essentially done is move the sweet spot up to the top half of the frame,
which is where average players hit the majority of their balls," says Severa.
Designers also maintained the same moment of inertia, so that the racket
swings more like a traditional light-weighted-head racket. Moving the balance
point further away from the tip of the handle also makes the racket easier to
In fact, the weight distribution made the racket feel like an extension of my
arm. The effort involved in getting the ball to go over the net at a good clip
is so minimal it almost feels like magic. With any other kind of racket, the
same impact would cause the ball to drop to the ground short.
The racket frame is made of 100% graphite epoxy with a titanium bonding agent
in the resin to strengthen the bonding between the regular and high-modulus
graphite used. The patented dual-taper beam design limits the amount of energy
going into the bending of the racket frame, which means more energy imparted to
Bottom line, my play has improved. And with players like Conchita Martinez
and Todd Martin using Hammer rackets, I almost feel like I'm ready for the
Product name: Hammer 3.0 Titanium
Material makeup: 70%
graphite/30% high-modulus graphite with titanium as a bonding agent in the resin
Weight: 8.5 oz unstrung
Retail price: $239.99
design innovation: Dual-taper frame design that stabilizes head higher up in
the racket face, strategic weight redistribution, and use of titanium as a
Performance improvement: Great
Handling: The weight
distribution made the racket feel like an extension of my arm
factor: The oversize head is deceptive, as you actually have more control
with this racket than similar rackets
Overall impression: Great
because I no longer have to worry about dropping the head of the racket--I just
concentrate on hitting through the stroke.