Is it possible to bend a bank shot back (i.e., curve the OB’s post-rebound path in the short direction)?

The short answer is: Not nearly as much as many people think. For the long answer, see the following video, follow-up explanations, and the \$2000 Bank Bend Challenge.

At first, I was very disappointed that I didn’t see any bend in the OB path with any of the shots on any of the equipment or conditions I tested. It is possible to bend a bank since the cushion nose can impart massé spin (about an axis perpendicular to the rail) and topspin (about an axis parallel to the rail), both of which can curve the OB’s post-rebound path; but bending a bank a significant amount is not as easy as some people might think. One reason a large bend cannot occur is that much of the small amount of topspin or massé spin imparted to the ball during cushion nose compression has an effect or “takes” (and dissipates) only when the OB first interacts with the bed of the table when the cushion nose pushes the ball down into table. This effect can help “twist” or “shorten” the bank, but only the curving spin that remains after the bounce out of the “rail groove” can contribute to bending or curving the OB’s path to the pocket. The downward push into the table (into the rail groove) is what causes the OB to bounce into the air with fast-speed banks. While the OB is in the air, it can head only in a straight line (relative to the table). But when it lands, any remaining curving spin can start to “take” and bend the post-rebound path. On slicker cloth, less spin will be lost during the first bounce out of the rail groove, and any remaining curving spin will take longer to bend the ball’s path, making the curve more clearly visible. Once the curving spin totally dissipates, the OB heads in a straight line to the pocket.

Now, speed and reverse spin can most certainly “twist” or “shorten” or “stiffen” a bank a significant amount, allowing one to easy avoid obstacle balls or double kisses, as demonstrated in the following videos:

It is possible to bend a bank a small amount, and this could allow one to pocket a bank that could not be made otherwise, but the amount of bend possible on typical shots on typical equipment is much smaller than many people think is possible. That was one purpose for the \$2000 Bank Bend Challenge … to show people how difficult it is to bend a bank, and do so accurately and consistently. Here’s a good example (from pool101 on AZB) clearly and convincingly showing that a bank can be bent with a good hit and suitable conditions:

Here’s a small-bend example from the challenge video:

Here’s another from rob3c on YouTube showing a significant bend with a good camera angle:

Now, it is very easy to bend a bank shot forward in the long direction when the OB rolls into the rail with topspin (due to slower speed and/or greater distance to the rail). This effect is the same as with the rolling and bending kick shots demonstrated in NV H.2 – Bending, Twisting, and Stiffening Kick and Bank Shots. In fact, the main reason why fast speed is used by top bank-pool players is to limit forward bend, which varies too much with shot angle, speed, and conditions. For more info, see advantages of fast-speed banks.

The problem with anecdotal statements about what people claim they have seen in person concerning bank bending is that our eyes and brain aren’t fast enough to accurately visualize the path of the OB with fast-speed banks. There are too many visual clues that can create optical illusions and mislead us:

• the ball can compress and slide down the cushion a significant amount during rebound.
• the ball typically bounces into the air (sometimes high, with multiple subsequent bounces) after rebound.
• the ball typically has a combination of sidespin and topspin after rebound that might visually look like massé or bank-bending spin.
• the ball “turns” when it heads into the pocket if it hits the pocket point or facing first.
• we are used to seeing slower-speed banks curve long (due to incoming topspin), so a fast-speed bank might seem to curve short in comparison.

Again, when all of this happens very quickly, or if poor-quality video is being used, our eyes (and brains) can easily be fooled into thinking something is happening that is not. Freddy’s “bank benders” included and analyzed in NV H.3 – Pool Myth Buster – Bending Bank Shots are good examples of this. That’s another reason for the \$2000 Bank Bend Challenge. It totally eliminates the potential for optical illusions or deception, and it provides a direct measure of the amount of bend possible. It also rewards the person who can achieve more bend than anyone else. This will also help us figure out how much bend is possible with the best possible hit of a well-chosen shot on typical equipment.

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