Alan,
No, half asleep, I'm not sure about reading any small graphs correctly. :-)
So, I'm sending a couple of them for you to read.
One thing I've noticed in looking at all these graphs is that there is no
increase in acceleration in about the last 40° before impact (in fact, a
considerable drop in the last 10°), yet there is a velocity increase until the
last 20°. Could this be a reason why the clubhead is always
leading just before impact?
----- Original Message -----
Sent: Tuesday, January 21, 2003 2:53
AM
Subject: Re: ShopTalk: 20 min talk
Are you sure about those numbers? A 40-ft/sec change in
velocity in the half millisecond I have read the ball is in contact with the
club is an average acceleration of 80,000 ft/sec/sec (a delta-V of 40 divided
by a delta-t of 0.0005). Seems a bit high. A 90-mph club head is
about 132-ft/sec (60-mph is 88-ft/sec). A change in velocity due to
impact of 40-ft/sec is about a 30% velocity change and I thought it was much
smaller than that (about 10%).
Is there any reason a strong 'hitter'
with a soft shaft could not have the shaft bent back at impact? I would
think that this would lower the effective loft of the club. Also (and
this depends on your frame of reference) if the shaft appears to bend back
after impact it is a consequence of the club head suddenly slowing and the
shaft not. The shaft over runs the club head. The other way of
looking at this is that if you put your reference frame on the shaft and let
the ball hit the club head at 100-mph the shaft is clearly going to bend
backward (or try to). If the shaft is 'oscillating' and the club head is
actually going faster than the shaft then the shaft may simply appear to
straighten or be bowing forward more slowly. I sure hope this makes
sense 'cause it's late and I'm going to bed now.
Night
all,
Alan
At 08:19 PM 1/20/03 -0500, you wrote:
Graham, Several of
the full-swing BJ photos show the shaft is actually bending forward before
the clubhead strikes the ball. Then, the impact does indeed reverse the bend
before it rebounds forward again. Think I also sent you a couple of BJ's
acceleration/velocity circle graphs. They'll give you some numbers on the
"negative" acceleration...and note how the shaft rebounds from the negative
to the positive as the ball leaves the face. Velocity drops about 40'/sec at
impact and acceleration goes a couple thousand feet/sec/sec negative before
it rebounds to about zero. Guess that's the shaft suddenly bending back at
impact. Might be something to add to your
talk. Bernie Writeto: [EMAIL PROTECTED]
- ----- Original Message -----
- From: Graham Little
- To: [EMAIL PROTECTED]
- Sent: Monday, January 20, 2003 7:02 PM
- Subject: ShopTalk: 20 min talk
- I've taken up Tom Wishon's suggestion about preparing a 20 minute talk
about what happens when the club strikes the ball and I've been doing a
bit of homework. Bernie sent me a series of photos that show the full
swing including the point of contact. Thanks for the photos Bernie. One of
the more interesting things about two of the photos is the fact that the
shaft bends back at contact. We are used to seeing photos of the shaft
bending forward slightly just before impact. However, these photos show
that the shaft is not just straightened at the point of contact it is
actually bent back. Will this have any affect on the ball flight or is it
too late to matter? Do we have to rethink issues like the shaft flex
taking this into account?
-
- Any comments? Does anyone have other photos of this sequence that may
shed some light on this matter?
-
- Cheers
- Graham
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