Bob,
I think your numbers are in the right direction, but want some
reassurance on their actual values. Let's do some sanity checks on them.
At 01:50 PM 9/17/2007, Bob Barrette wrote:
I tried your wire suggestion and it worked great!
Here are the results I came up with.
(A) When I place the shaft above the cradle and under the wire ,
I get 3 S/W less than when I place it in the cradle.( D2 vs. C9 )
Theory says that the wire fixture should weigh about 11 grams if it
cuts 3 points from the reading.
Is that the case? Did you weigh it?
(B) For every 1/2 inch I extend the shaft beyond the cradle it
changes 2.5 S/W.
(C) For every one inch I extend the shaft beyond the cradle it
changes 5 S/W.
(D) For every 1 1/2 inches I extend the shaft beyond the cradle it
changes 7.5 S/W.
How did you measure this?
The only valid test*** I can think of is to sacrifice a shaft (though
you could do it with a shaft that you are going to use even shorter
than the shortest test you make here).
(1) Measure the swingweight of a club with no grip and, say, 3 inches
sticking out beyond the butt-stop of the scale.
(2) Trim away one inch, and remeasure with one inch less sticking
out. That way, you have EXACTLY THE SAME CLUB AS BEFORE on the
business end of the butt stop; the only thing you have changed is the
amount of shaft sticking out beyond the stop.
(3) Repeat step #2 until there is no more shaft sticking out beyond
the butt-stop.
(4) Look at the difference in readings for each iteration of step #2.
Is that what you did? I ask because the numbers sound quite high to
me. I get more like 1 point per inch for standard weight steel and a
half point per inch for lightweight graphite.
Actually, it sounds like you slid the whole club. I.e.- for each inch
less butt sticking out, you have one inch MORE distance between the
clubhead and the butt stop. That should give numbers similar to what
you report. But it's not the number you need.
*** Let's review what we're trying to do here. We know we can test
the FREQUENCY of a shaft with a trimmed butt without actually
trimming the butt. We just have to let the butt stick out behind the
clamp of the frequency meter.
Now we're trying to do the same thing with SWINGWEIGHT; trim the
shaft without actually trimming it. Instead, we let it stick out
beyond the end of the swingweight scale. We're smart enough to know
that we may have to make some corrections; we can't just use the raw
reading the way we did with frequency. That's because our fixture
(wire in your case, a binder clip in my case) weighs something, and
the shaft sticking out behind the swingweight scale does too. In this
thread, we're trying to find out how big the corrections are, and in
what direction.
The direction is: The actual swingweight will be MORE than what you
read on the scale. Both the fixture and the surplus shaft will cause
the measured swingweight to be lower than the swingweight you'd get
by actually trimming at that point.
The amount is: What we are now discussing. But, to find it, you need
to vary the amount sticking out behind the stop WITHOUT CHANGING the
configuration on the other side of the stop. AT ALL!
BTW, I do this with a fixture made from a small binder clip (standard
stationery item). I made this years ago and have been using it ever
since. In fact, I used it to build a couple of clubs a few weeks ago.
I used the corrections I cited above (actually, 2/3 point per inch
for middle weight graphite), and got the correct swingweight when I was done.
Thanks,
DaveT
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