Posted by: tom.guerry (tom.guerry@kp.org) on Sat Jan 4 15:23:09 2003

I believe the desired wrist action is different between golf(double
pendulum) and hitting(more smooth lessening of angle
between lead forearm and bat as swing proceeds).Has anyone
measured this?
> > > >
> > > > I did a google search on "double pendulum" and
"golf".The assumption is made that double pendulum is
desirable for golf and hitting as in this article
> > > >
> > > > http://carini.physics.indiana.edu/E105/swing.html
> > > >
> > > > Any sciencey types out there ?
> > > >
> > > > Does skilltechnologies demo address this ?
> > >
> > > Sounds like they are talking about flail only at first with
torque between the hands only coming into play at the last
moment? In any case, I don't see Bonds hitting with his arms at
full extension. No doubt you can hit with the double pendulum
action and make contact at full extension with great batspeed
(assuming you employ torque and flail all the way through), but I
don't think it would result in the high BA Bonds showed to go
along with his power. This is just after a quick read of the link but
it doesn't sound right to me.
> > >
> > > Mark H.
> >
> > After looking at the quicktime clip, my reaction is this is what
happens if you don't use top hand torque in your swing. You start
the swing with a static bat (second part of the double pendulum),
and sure, the bat will try to swing back against you at shoulder
rotation launch. This is exactly what you don't want. This, if I have
him right, results in Nyman's "wasted frames" (correct me if I got
that wrong). The bat should be set up to start swinging out
immediately (receiving rotational energy)(flail?) by using top
hand torque. How much depends on pitch location. More to set
up a wider radius for the outside pitch, very very little for the
inside pitch (of course if you use Tom's belly up to the plate
approach (Bonds) then everything is a middle in pitch?).
> >
> > I prefer Jack's model of smooth strong acceleration without
jerks, snaps etc instead of the double pendulum thing. Now if
you are talking about hitting a stationary ball, this might be
different. I know beans about golf.
> >
> > Mark H.
>
> Hey
> Tht in a golf swing would be a bad idea. As described by many
golf-pros casting out causes an outside to inside handpath
witch causes you to cut the ball and have a huge slice. If the golf
club didn't have a graphite shaft and weigh ten times less than a
baseball bat then tht would have an effect on clubhead
acceleration. A golf club uses a whip affect due to its lighter club
and more vertical handpath than baseball. From my
experiences in golf the more I cock my wrists the farther i hit the
ball, and in baseball the shorter I hit the ball. Keeping your
wrists hinged in golf is a good idea so u can conserve
momentum for the whip effect, but obviously not in baseball

Hitman-

I think you are on the money.

I think comparing mechanics across sports using Jack's
theories is very enlightening.

Following Jack's theory,what makes a swing rotational is
generation of rotational body energy(sequential hip/torso rotation
with separation/"X-factor" around a stationary axis including
transfer of momentum) and efficient transformation of this
energy into club/batspeed via tight connection and a circular
handpath perpendicular to the axis of torso rotation.Therefore
golf and hitting would both be rotational,but with different details
of transfer mechanics which make the golf swing longer(less
quick/wider radius) with higher max speed via the design of the
club/shaft and a "double pendulum" connection of shoulder to
arm to club.This requires the wrist action that gives about a 90
degree angle at the top which remains at this angle into the
downswing,then cocks more(angle becomes more acute than
90 degrees)before uncocking late in the downswing just prior to
contact.

Transfer mechanics in hitting on the other hand get the bat
arcing(THT) before the torso launches while a variable swing
radius is set at "launch"(torso tuns)which can "hook"(shorten
radius)before contact.Timing of the hip uncocking adjusts for
inside out,setting swing radius at launch.Up/down adjustment
and plane of swing are set by lean of axis and degree of bend at
waist at launch.Angle of wrist(lead arm/bat angle)uncocks at a
steadily increasing rate as the bat starts(before "launch") and
proceeds to contact.This produces a short,quick rotational
swing.

The absence of THT slows swing quickness/acceleration.

A longer swing radius at launch creates a higher load.

Extension of the handpath after launch and prior to the bat nearly
lining up with the lead forearm creates a "linear" swing which is
not efficiently powered by body rotation(slow) and which is
shaped poorly for plate coverage.

Jack's ideas thus allow a logical classification of swings into
long,short,rotational,and linear.That is quite an accomplishment.

Furthermore,the latest tape shows a nice way to teach it from the
end back.

The most confusing aspect has always been exactly what is THT
and how/when is it taught.The one hand back arm swing
demonstrated on the tape is the answer to this using the
following back arm biomechanical details:

Hold the bat vertical as in the stance with the top hand only.

Internally rotate the back arm and pinch back shoulder
blade.Back/top hand hides behind torso as seen from
pitcher.Back elbow goes up.Bat cocks toward pitcher.

Externally rotate back arm.This uncocks bat and requires elbow
to drop some,but otherwise keep elbow/upper arm extended
and up as much as possible.This will fix elbow in slot.

Elbow drop should happen as hips uncock.Torso should launch
as elbow fixes in slot.Swing with crcular handpath into heavy
bag.

This is the cure for "top hand dominance" or pushing the back
arm so it extends the handpath and ruins transfer mechanics.

Up to a certain age(?10+) it's fine for kids to just go out and hit
small objects with a dowel as much as possible.When it's time
to teach the rotational swing,this is the last piece going from
contact back to the beginning.How to cock the hip as the bat is
cocked by internal rotation is the last step of teaching and the
first part of the swing.

Give it a try.