CTE and the 30 degree cut angle..

L

LAMas

AzB Silver Member
Silver Member
I put the OB between the long rails (2 diamonds) and 6 diamonds away from the head rail or 2 diamonds up from me. I place the CB 1 diamond close to me offset by 1/2 ball off of the center line between the long rails (right or left).

If I moved the CB 1/2 diameter to the right, the center of the CB is looking up table at the right edge of the OB and the left edge of the CB is looking at the center of the OB.

I shoot the shot hitting the CB dead center at the right edge of the OB or CTE and the OB goes into the left corner pocket. I trig this out to be 18.4 degrees. Geometrically, the cut angle should be 30 degrees so the shot was affected by cut induced throw CIT.

This 18.4 degree cut angle may be different for others who try because of other factors like cloth speed, humidity or...

For these reasons, it is futile to tie aiming to geometrically correct angles using a center ball hit on the CB - where many pivot and non-pivot aiming systems start at before the tip contacts the CB.

This could be a blessing to those that don't tie geometry to the actual cut angles achieved and only commit to memory the resulting cut angles for aiming at the edge other fractions on the OB or distances/points off of the edge of the OB.

This is also true for those that use the contact point on the OB that sends it to the pocket/target as a reference for aiming if the CB is hit at its center - english (off center) gets you closer.

Is this just me?

Be well

angle.JPG
 
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Good post.

I think you should re-check your math.
Something is off.

Just from memory I recall an 1/2 ball hit being about 28 degrees.

Have a great day
randyg
 
LAMas said:
Pj
I guess that the CB is sliding being so close to the OB.
Thanks,
Be well
Click to expand...
Have you tried freezing a "ghost ball" to the OB to be sure you're not hitting/aiming wrong? Aim the combo at 2.5 diamonds from the corner pocket (~30 degrees), then shoot it from your original CB position at pocket speed. That should produce maximum throw.

11-12 degrees of throw is about twice maximum in my experience.

pj
chgo
 
Patrick Johnson said:
Have you tried freezing a "ghost ball" to the OB to be sure you're not hitting/aiming wrong? Aim the combo at 2.5 diamonds from the corner pocket (~30 degrees), then shoot it from your original CB position at pocket speed. That should produce maximum throw.

11-12 degrees of throw is about twice maximum in my experience.

pj
chgo
Click to expand...

Pj,

I did that years ago to convince myself that CTE is 30 degrees but the GB (CB) was frozen and not a rolling or sliding CB taking the place of the GB.

Be well
 
LAMas said:
Pj,

I did that years ago to convince myself that CTE is 30 degrees but the GB (CB) was frozen and not a rolling or sliding CB taking the place of the GB.

Be well
Click to expand...
You can separate the OB and "ghost ball" slightly (just a mm or so is enough) in the direction of the CB to eliminate static friction - then it should mimic a moving CB.

I set the same frozen combo shot up just now, shot it a number of times at slow speed (to maximize throw) and it consistently throws about 1 diamond farther down the long rail (to about 1.5 diamonds from the corner pocket). This represents about 6 degrees of throw, just about what I'd expect.

I'm thinking your balls must be high-friction for some reason.

pj
chgo
 
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LAMas said:
I put the OB between the long rails (2 diamonds) and 6 diamonds away from the head rail or 2 diamonds up from me. I place the CB 1 diamond close to me offset by 1/2 ball off of the center line between the long rails (right or left).

If I moved the CB 1/2 diameter to the right, the center of the CB is looking up table at the right edge of the OB and the left edge of the CB is looking at the center of the OB.

I shoot the shot hitting the CB dead center at the right edge of the OB or CTE and the OB goes into the left corner pocket. I trig this out to be 18.4 degrees. Geometrically, the cut angle should be 30 degrees so the shot was affected by cut induced throw CIT.

This 18.4 degree cut angle may be different for others who try because of other factors like cloth speed, humidity or...

For these reasons, it is futile to tie aiming to geometrically correct angles using a center ball hit on the CB - where many pivot and non-pivot aiming systems start at before the tip contacts the CB.

This could be a blessing to those that don't tie geometry to the actual cut angles achieved and only commit to memory the resulting cut angles for aiming at the edge other fractions on the OB or distances/points off of the edge of the OB.

This is also true for those that use the contact point on the OB that sends it to the pocket/target as a reference for aiming if the CB is hit at its center - english (off center) gets you closer.

Is this just me?




The rack is a triangle with three 60 degree angles. If you put a object ball just far enough in front of
the rack, so the OB won't hit the rack on a 1/2 ball hit, neither the OB or CB will hit the the ball rack.

With a rolling CB, both balls separate and travel about 30 degrees, each one rolling down the sides.

The rack sides are each at 30 degrees. A ball rolling at 18.4 degrees would not clear that rack angle.
.
Click to expand...
 
A follow angle vs. fullness of hit chart from Bob Jewett's miscellaneous files.
A rolling CB on a 1/2 ball hit goes about 33 degrees and the OB goes at 30.


http://www.sfbilliards.com/Misc/follow_angle_vs_fullness.gif


If you recognize the 30 degree angle, you can use the angle to play position.
Hit the OB dead in the face, it goes straight. 1/2 ball goes 30. Between is 15.

.
 
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Ralph Kramden said:
A follow angle vs. fullness of hit chart from Bob Jewett's miscellaneous files.

http://www.sfbilliards.com/Misc/follow_angle_vs_fullness.gif
Click to expand...
Thanks.

In case anybody's interested, here are the OB Paths (cut angles), CB Paths, Tangent Line Angles (from the aim line) and CB Paths as % of Tangent Line Angles (for easier on-the-job estimation) for the CB/OB overlaps that Bob lists there (I added 1/4 Ball and 3/4 Ball).

pj
chgo

(NOTE: CB paths are my estimates of the angles from Bob's line graph chart.)

View attachment 78109
 

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Patrick Johnson said:
You can separate the OB and "ghost ball" slightly (just a mm or so is enough) in the direction of the CB to eliminate static friction - then it should mimic a moving CB.

I set the same frozen combo shot up just now, shot it a number of times at slow speed (to maximize throw) and it consistently throws about 1 diamond farther down the long rail (to about 1.5 diamonds from the corner pocket). This represents about 6 degrees of throw, just about what I'd expect.

I'm thinking your balls must be high-friction for some reason.

pj
chgo
Click to expand...

I set up the CB very close to the OB and the cut angle was closer but still less than the 30 degrees as you said. It hit the side rail before the pocket.

I tried my example again with the same result and had another shooter shoot the same set up with the same results - OB in the far corner pocket.

Perhaps dirty balls and cloth after all its a bowling alley.

Be well
 
Update

I tried the same shot as post 1 on a different table at Santa Clara Billiards with the same results.

Next I placed the OB centered between the long rails and 3.5 diamonds away from the far short rail which is geometrically an almost 30 (29.74} degrees cut angle and aimed the center of the CB at the edge of the OB (CTE) - I had to put outside English on the CB in order to pocket the OB in the far corner pocket.

30 degrees.PNG

Be well
 
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LAMas said:
I tried the same shot as post 1 on a different table at Santa Clara Billiards with the same results.

Next I placed the OB centered between the long rails and 3.5 diamonds away from the far short rail which is geometrically an almost 30 (29.74} degrees cut angle and aimed the center of the CB at the edge of the OB (CTE) - I had to put outside English on the CB in order to pocket the OB in the far corner pocket.

View attachment 400214

Be well
Click to expand...
Did you place the CB with its edge on the center line?

I think that shot should go with a rolling CB (reduces throw), unless the balls are sticky.

pj
chgo
 
LAMas said:
I tried the same shot as post 1 on a different table at Santa Clara Billiards with the same results.

Next I placed the OB centered between the long rails and 3.5 diamonds away from the far short rail which is geometrically an almost 30 (29.74} degrees cut angle and aimed the center of the CB at the edge of the OB (CTE) - I had to put outside English on the CB in order to pocket the OB in the far corner pocket.
Click to expand...

I would guess 30 degrees is about the OB angle... depending on the cleanliness of the balls, speed, humidity, amount of english, contact accuracy ....ect.

The CB should have natural roll when contacting the OB. A rolling CB 30 degree path is less dependent on contact accuracy. If it looks like a scratch.. It will.
 
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Following up on PJ's example:

I separated the CB and OB by about 1/4 inched while aiming CTE, slow hit the OB and the OB went 30 degrees into the pocket.

As I backed the CB away from the OB and the resulting cut angle decreased by about 5 degrees per diamond (13.5") until I arrived at the example in post 1.

This has improved my shot making for I aim thinner for the larger separations between the CB and OB.

This is just me on a dirty table with dirty balls.:rolleyes:

Be well.
 
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