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View Full Version : how do you find your shaft's pivot point?



whipy
03-11-2007, 10:08 AM
are there any easy ways of finding the pivot point on your shaft, or do you just have to go with trial and error? i recently bought a custom cue, hence the question.

Billy_Bob
03-11-2007, 10:27 AM
See "Squirt Measurements:" on page 10.
http://www.sfbilliards.com/Shepard_squirt.pdf

Jal
03-11-2007, 02:54 PM
<blockquote><font class="small">Quote Billy_Bob:</font><hr> See "Squirt Measurements:" on page 10.
http://www.sfbilliards.com/Shepard_squirt.pdf <hr /></blockquote>It should be noted that the distances of the pivot point from the tip that people get from the aim-and-pivot test vary by as much as a factor of four! from tests done with machines (Predator, Platinum Billiards). I don't think it's been proven conclusively as to who's right.

Jim

Billy_Bob
03-12-2007, 06:54 AM
<blockquote><font class="small">Quote Jal:</font><hr>It should be noted that the distances of the pivot point from the tip that people get from the aim-and-pivot test vary by as much as a factor of four! from tests done with machines...<hr /></blockquote>

With the do-it-yourself testing, you can get more accurate by placing the cue ball and object ball near a rail and spacing them both one balls distance out from the rail. (Use a 3rd ball for this.)

So it would look like this...
http://CueTable.com/P/?@4AWwb4PWyI@

Then you can shoot dead center so the cue ball stops dead or continues forward in a straight line. Then mark with masking tape (or whatever) on the short rail exactly where the cue is lined up to make a perfectly straight shot.

So now you have a "baseline" of perfectly straight balls and a marking of where the cue should be lined up over the short rail to shoot a perfectly straight shot. (And get the cue ball to continue in a straight line after the shot.)

Then proceed with the pivot point test as discussed at the link above. Measure or mark the cue for various pivot points you want to try.

This takes a lot of patience and repeat testing, but it works for me.

Jal
03-12-2007, 12:21 PM
<blockquote><font class="small">Quote Billy_Bob:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>It should be noted that the distances of the pivot point from the tip that people get from the aim-and-pivot test vary by as much as a factor of four! from tests done with machines...<hr /></blockquote>

With the do-it-yourself testing, you can get more accurate by placing the cue ball and object ball near a rail and spacing them both one balls distance out from the rail. (Use a 3rd ball for this.)

So it would look like this...
http://CueTable.com/P/?@4AWwb4PWyI@

Then you can shoot dead center so the cue ball stops dead or continues forward in a straight line. Then mark with masking tape (or whatever) on the short rail exactly where the cue is lined up to make a perfectly straight shot.

So now you have a "baseline" of perfectly straight balls and a marking of where the cue should be lined up over the short rail to shoot a perfectly straight shot. (And get the cue ball to continue in a straight line after the shot.)

Then proceed with the pivot point test as discussed at the link above. Measure or mark the cue for various pivot points you want to try.

This takes a lot of patience and repeat testing, but it works for me. <hr /></blockquote>Sounds like a good idea. I would suggest two additional things to make the aim-and-pivot test more accurate than described in Ron Shepard's paper.

First, wet the contact area on the object ball to reduce throw to near zero. Second, don't pay attention to what the cueball does after impact. Instead, just try to get the object ball going in a straight line.

The reason is that throw acts on both the object ball and cueball, and post-impact swerve on the cueball. The cueball will not sit spinning in place after a perfectly full hit, and in fact can move several inches over to the side (more from swerve than throw). But a full hit without throw will send the object ball in a straight line. At least this is true if the cueball doesn't have much elevation (loft), which is another potential source of error.

Jim