Dr. Dave, I have been practicing the 2-rail parallel line kick shots you show in your book on pages 229 & 230 and demonstrated in NV 7.9. It works fine if I set up the balls similar to what you show in your book but I am having difficulty envisioning the same shot from other set ups. I don’t think I fully understand how to determine the center line between the 2 parallel lines. Can you elaborate on this idea?
The following video demonstrates the midpoint-parallel-shift system:
Unfortunately, the action of this shot depends on sidespin, shot speed, angle, ball distances, and table (especially cushion) conditions. Obviously, when practicing, you need to try to use consistent sidespin and speed on a given table to see how the cue ball responds at different angles. Here’s a summary of the adjustments required to compensate for different effects, as demonstrated in the video above:
- slow or fast speed go short, so aim farther from pocket
- OB close to cushion goes short, so aim farther from pocket
- OB far from cushion goes long, so aim closer to pocket
- diagonal (45˚) approach into 1st rail:
- benchmark speed and spin give square hit
- less spin goes long, so aim closer to pocket
- more spin goes short, so aim farther from pocket
- shallower angle into 1st cushion (steeper angle into 2nd cushion) goes long
- aim closer to pocket or use less spin
- steeper angle into 1st cushion goes short
- aim farther from pocket or use less spin
The midpoint parallel-shift system can also be used for 2-rail bank shots, measuring between the OB and the target pocket. But with no or less running spin on the OB (even though you can impart a little with spin transfer), the OB will tend to go long, especially when coming into the 1st rail steep. But appropriate aim adjustments can be made. There is also a midpoint-parallel-shift system for aiming 1-rail kick and bank shots. It is covered on the mirror-system resource page.
from Patrick Johnson:
You have to aim a little closer to the corner than the measurement suggests – experience will tell you how much, depending on the angle to the first rail and the cleanliness of the table/balls.
In this drawing the blue line is the measured track, but the actual track will look more like the red line:
… the “Amazing Double-mirror Image Method” or ADIM for short … is explained on the second page of http://www.sfbilliards.com/articles/2004.pdf (July). Mostly, it gives you a very easy way to put up a target ball exactly where the real ball would appear for a perfect mirror system. … This lets you see immediately how pitifully awful the two-rail mirror system is, but it also allows you to try to find out where it does work and maybe how to modify it so it works for more cases.
Here’s an illustration of the mirror version of the midpoint-parallel shift system mentioned in Bob Jewett’s article above:
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