Originally Posted by j6uk
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Okay, the 3/4 ball photo looks wider than 3/4 to me. The diagram looks fine.
The 2/3 shot, maybe it is, maybe half ball - I can't honestly say. The diagram for 2/3 certainly isn't - look at the centre of the pink and the edge of the white - that's a thick half-ball.
But this really isn't my argument.
Go back to your initial set-up of the 3/4 shot with the white on the cushion half way between pink and blue. From there the potting angle on the pink is 19.5 by my calculation whereas a 3/4 ball is supposed to be 14.5. This potting angle is that between the incoming white and the path of the OB toward the pocket. I admit this may change when you slide the white toward the pink but to pot it from there you aren't hitting an exact 3/4 ball.
My calculation takes into account the correct contact point but is complicated to explain here. As an approximation it's a little easier to imagine the following.
Set your position on the cushion for a 3/4 ball pink - using your 4x4 grid the pink is 4 squares in from the cushion and the white is 2 squares along the cushion. Imagine hitting the pink full ball and the path of the white is the hypotenuse of a right angled triangle with opp/adj sides of 2 and 4. The internal angle at the pink is tan-1(2/4) which is 26.57 deg. The potting line of the OB is 45 deg across the table from corner to opposite middle so the angle between the incoming white and the desired potting line is 45-26.57 = 18.43 deg. If you aim slightly wider at the 3/4 ball hit so you actually make the pot you widen this angle and I make it 19.5 deg.
This is an approximation but it does indicate that you have to aim at more than 18.5 deg to make the pot from this setup.
Seriously, I'm not knocking your potting - I just don't think the 4x4 grid works for the pink - the 1/2 ball and 3/4 balls are very close to lying on a 3x3 grid.
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