That's covered on Dr. Dave's website, somewhere. It depends on the condition of the balls and the speed of the shot. It's easy to do the test yourself with donuts. As I recall the test I did, which was the speed needed for a one pocket long-way bank, stun was 4 degrees and draw/follow were both 2 degrees for a half-ball cut. It's in one of my articles in Billiards Digest.BTW Bob. What do you have actual accurate numbers with cut angles where friction(CIT) is also counted? also how much difference in CIT when using slow stun vs rolling cueball?
BTW Bob. What do you have actual accurate numbers with cut angles where friction(CIT) is also counted? also how much difference in CIT when using slow stun vs rolling cueball?
That's covered on Dr. Dave's website, somewhere. It depends on the condition of the balls and the speed of the shot. It's easy to do the test yourself with donuts. As I recall the test I did, which was the speed needed for a one pocket long-way bank, stun was 4 degrees and draw/follow were both 2 degrees for a half-ball cut. It's in one of my articles in Billiards Digest.
Thanks Dave that was info i was looking for.. AND MORE!
First of all, sorry to resurrect a thread from 2020. However, I read through the replies, and while there were certainly some that explain what didn't seem clear to Chris, I wanted to add something, which might help others who see this discussion.Common fractions and their approximate degrees of cut change the closer (or the farther) the cue ball is from the object ball, for any given shot, so this fractional aiming system seems flawed to me. For instance, if the cue ball is only 6 inches away from the object ball, a half ball hit is only going to cut the object ball maybe 20° at the most. If the cue ball is 2 inches away from the object ball, a half ball hit is only going to cut the object ball maybe 10° or even less.
Not considering throw in the equation, there will come a point less than 1/4 inch between the two balls that a half ball hit or even a edge to edge hit will not result in any cut on the object ball at all. In fact if they are nearly touching, it will throw the object ball the opposite direction.
First of all, sorry to resurrect a thread from 2020. However, I read through the replies, and while there were certainly some that explain what didn't seem clear to Chris, I wanted to add something, which might help others who see this discussion.
The fractions and resulting angles given are posited to be considered with the initial cue ball position *shifted laterally* (left or right). The (wrong) tendency is to imagine/view the fractions from an unmoving cue ball, where the aim line is pivoted through the cue ball center.
So, with compass references, a South-->North shot will be full (center/center). So, for a 1/2-ball aim, cutting target right, the cue ball shifts West, but the shot/cue line remains S-->N. If one instead pivots the aim line from the CB center, to the left (counter-clockwise), it will still be a 1/2-ball aim, but now the shot/cue line is more like South-Southeast-->North-Northwest. And of course, the final path of the target ball differs, because of the differing, initial cue ball positions.
Again, this is explained by Bob (and others, but I'm too lazy to look up names for credits), but I wanted to try and describe it differently.
[Final note: I think the CB position can also be moved along a curve--pivoted from the target--but the idea that the CB *moves* is what matters.]
The "edge" changes, so the OB goes in different directions.if you are aiming the center of the cue ball at the edge of the object ball
how does that perspective change based on cue ball object ball distance?
How does the edge change?The "edge" changes, so the OB goes in different directions.
pj
chgo
Yes, but not the same half ball overlap.How does the edge change?
As long as the center of the Cue ball is in line with the edge of the object ball doesn’t that always produce a half ball overlap?
It's like this: The halfball overlap is from two different cb-ob relationships, due to the difference in cb-ob distance. This applies only when the cb remains on the centerline between cb and ob. If the cb gets moved along the aim line (center cb to ob edge), then the angle doesn't shift or change at different distances, meaning the halfball aim will produce the same result from 2 inches as it will at 60 inches.How does the edge change?
As long as the center of the Cue ball is in line with the edge of the object ball doesn’t that always produce a half ball overlap?
Yes, but not the same half ball overlap.
The cue ball's center changes position as it changes distance from the OB, so the angle of the line from its center to the OB's edge also changes.
pj
chgo
Only “special” people see the humor in it.Lol. Geometry !
Yes, but not the same half ball overlap.
The cue ball's center changes position as it changes distance from the OB, so the angle of the line from its center to the OB's edge also changes.
pj
chgo
brianIt's like this: The halfball overlap is from two different cb-ob relationships, due to the difference in cb-ob distance. This applies only when the cb remains on the centerline between cb and ob. If the cb gets moved along the aim line (center cb to ob edge), then the angle doesn't shift or change at different distances, meaning the halfball aim will produce the same result from 2 inches as it will at 60 inches.
When referencing the center to center line from cb to ob, as Poolology requires, the cut angle shifts as the distance between cb and ob changes.
This diagram shows two different halfball aim lines, one red (closer cb) and one blue (farther cb). The red one is 8° from cb-ob centerline to ob edge, while the blue one is only 3°. The angle difference between these two shot perspectives is 5° (8 - 3 = 5). This means shooting a halfball shot from the closer cb will shift the 30° resulting angle by 5° compared to shooting the halfball shot from the farther cb.
View attachment 753149
BUT
if you put the cue balls on a line from center cue ball to center object ball (yellow line)
then as the cue ball gets closer the center to edge sends the object ball to a different place (in you example brian by 5 degrees)
red line blue line shows different angles
yes?
View attachment 753158
BUT
if you put the cue balls on a line from center cue ball to center object ball (yellow line)
then as the cue ball gets closer the center to edge sends the object ball to a different place (in your example brian by 5 degrees)
red line blue line shows different angles
yes?
It doesn't, as far as your *aim*. However, if the cue ball is moved forward or back on the cue ball center-to-center line to the target ball, then the actual contact point will change, and so will the resulting path of the target ball. This is what BC21 has shown.if you are aiming the center of the cue ball at the edge of the object ball
how does that perspective change based on cue ball object ball distance?