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An Invention for Billiards

  1. Mar 10, 2007 #1
    Billiards is a popular game with plenty of physics. Unfortunately, because it is only a game, no one has bothered to invent a relatively simple device (compared to all the other physics devices out there) that would substantially help one become better. So I have no choice but to take on the project myself.

    One of the most important skills in making a successful shot in billiards is that your cue delivery is very straight, like a piston motion. Fortunately, there has been an invention for improving that skill, called the laser cue. By feathering your laser cue back and forth, you can watch a laser spot on a wall. The straightness of your cue motion during the feathering and the cue delivery can be judged directly by watching whether the laser spot wobbles as your move your cue back and forth. So far so good.

    Unfortunately, this is where the inventions end. The problem is that during a real shot with a real cue ball, the cue ball would be blocking the laser. So this does not help during a real shot. Here are the many problems that a player can have without knowing it:
    1) His line of sight is not even in the same direction as his cue during the feathers and cue delivery. Thus, he is aiming at a spot on the target ball that his cue is not even pointing at!
    2) During the cue delivery, his cue motion veered to the left or right, and he doesn't know it. Because of this, a player can miss and blame his error in angle judgement when instead the miss might have been due to a non-straight cue delivery.

    The perfect invention is to have some sort of laser cue that would allow you to see the laser spot on the target ball during a real shot with a cue ball. This device will:
    1) Train the player to look in the same direction as his cue.
    2) Allow the player to know exactly what went wrong if a miss occurs.

    Possible inventions:
    1) A laser cue that shoots a laser beam over the cue ball and onto the object ball. The problem is that the pointing device would obstruct the player's view when he in the cuing position.
    2) Invent a translucent cue ball that allows the laser beam to pass through. The problem is that even the slightest diffraction would cause the invention to be erroneous. Also what the would the material of the ball be?

    Any other ideas? The bottom line is that I need to invent a device that will allow you to know what exactly went wrong if you miss a shot: Did you miss because you aimed at the wrong spot on the target ball? Did you aim at the correct spot but your cue delivery veered off? Or was your cue not even pointing where you were looking at to begin with? A device that reveals these errors would allow one to improve his game immensely.
    Last edited: Jan 22, 2008
  2. jcsd
  3. Mar 10, 2007 #2
    You can buy this special cue ball, it's white and chalk sticks to it more readily. It has a coordinate type design on it. If you place it on the table at the same orientation every time, and wipe it off after every shot, you can see where you hit the cue ball. This will help you hit the ball with whatever kind of spin you want.

    And if you want to practice shooting straight, you can set up a beer bottle and thrust the cue stick into and out it without hitting the sides.
  4. Mar 10, 2007 #3
    Thanks. I've actually already tried these, and let me say from experience that these controlling devices are too crude to perfect your skill (maybe good for a beginner, but not accurate enough to get you really good).

    If the've invented accurate devices to monitor golfswings, and the computerized "Hawkeye" for tennis ball trajectories and landing spots, why can't someone think of something similar for billiards in order to help players assess what went wrong? Billiards is as popular as golf and tennis, is it not?
  5. Mar 10, 2007 #4


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    How about putting a camera in the cue so every shot is recorded and can be analysed afterwards ? You could use a wireless USB connection.
    I always find a telescopic sight works well :smile:
  6. Mar 10, 2007 #5


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    Two possible solutions:
    1] Move the pointing device to a location behind the player's line of sight. You could put it a mere foot from the tail of the cue. (You could have the pointer on a gimbal mount so that it stays upright regardless of how the player rotates the cue, and it could also auto-level itself so that it points horizontally.)

    2] Make the pointing device itself transparent so the player can see right through it. How? Make the pointing device a beam-spliting prism. Place your laser at any convenient out-of-the-way spot on the cue and have the prism deflect the laser the way you want it while allowing the player to look right through it.
    Last edited: Mar 10, 2007
  7. Mar 10, 2007 #6


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    In the cue would be a problem. There would have to be a hole of some minimum diameter in the tip, which would get clogged up with glue during application and with chalk during use. I suppose that it could be filled with some optically transparent material, but that would interfere with the natural elasticity of the tip.
  8. Mar 10, 2007 #7

    D H

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    1. A device that shows where the cue ball will hit the target ball. Being able to visualize the contact point is very important since the target ball will move along the line from the contact point to the center of the target ball.

    The spot on the cue ball that will hit the target ball is not in sight (it is somewhere on the side of the cue ball facing away from the shooter). This device will be difficult to construct.

    2. A device to help with bank shots. The shooter places this little contraption on the rail the cue ball or target ball off of which the ball is to bounce. A laser level will make it possible to align the device parallel to the rail. Something as simple as a mirror combined with the laser on the cue will show where the ball will bounce (ignoring spin, of course).
  9. Mar 10, 2007 #8
    The target ball will actually move a few degrees off from this line due to ball-to-ball friction and spin on the cue ball (the less rolling motion on the cue ball upon impact, the greater the "throw" on the target ball). I've attached a diagram below.

    But nevertheless, there is a theoretical correct aiming point on the target ball. What we need is a device that allows us to be able to know how accurately the center of the cue ball moved towards the chosen aiming point (and to be able to point the cue correctly in this direction before the cue delivery). For example, if the device reveals that the cue ball did go towards the chosen aiming point, and the target ball did not go into the pocket, then we know that the aiming point was wrong.

    We have invented devices for other sports much more complicated than this.
    Last edited: Jan 22, 2008
  10. Mar 10, 2007 #9

    A totally new idea altogether is to forget about aiming at a target point on the target ball (not all pool players use this aim method), and simply try simply to establish the correct cue direction before the backswing and cue delivery (this is probably the other common method that players use when making a shot). Using this method, we no longer need a laser beam (since we are not aiming at a specific point anymore), but rather invent a cue that somehow is prevented from veering left/right or up/down during the cue delivery?

    Is it possible to create such a mechanism that would prevent the cue's axis from moving during the cue delivery? Using this special cue, the correctness of the direction can be assessed correct or incorrect according to whether the pot was made or not. With this cue you still choose your spin, cue delivery force, and cue delivery direction, and presto, the cue ball moves exactly in the direction you had lined up your cue. If the pot is made, then you had lined up your cue correctly. If the target ball was deflected too much to the right, then your cue direction was too much to the left. etc... Also, with a perfect cue motion guaranteed, you also develop the "muscle memory" to be able to create a perfect cue delivery on your own. So much you can learn with this "piston cue", if it existed.

    This idea is new. Is it possible? Such a cue would have to be connected to a machine of some sort. I remember hearing about a physics experiment in billiards from American Journal of Physics where they had to make the cue ball move in a very specific direction.
    Last edited: Mar 10, 2007
  11. Jul 3, 2008 #10


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    I know someone who invented something like this - he showed it to us when we interviewed him for a consultancy job.
    It was a fairly complicated analogue computer mounted on the bool cue like a rifle scope, you aligned one laser with the pocket, one with the target ball and a third spot showed you where on the cue ball to strike. All done with cams and gears!

    He claimed to have sold some and had a sponsorship/endorsement deal from a famous US pool player - unfortuantely I can't remember his name.
  12. Jul 3, 2008 #11
    What is the maximum displacement from its center one can strike the cue ball while maintaining transfer of energy from the cue stick?

    I'm rather uncoordinated, but my knowledge of physics makes me a substantial pool player.
  13. Jul 3, 2008 #12


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    That sounds awesome.
  14. Jul 3, 2008 #13
    Having just got done playing pool not 5 minutes ago I feel inclined to answer this. First off, I believe there is no special tool or piece of information that will improve game drastically. I believe that pool like everything else out there is an acquired skill that is gained from long hours of practice and readjustments to methods.

    But to answer the question I would say that you could somehow scan the laser. When I say scan I mean that the laser beam would be projected by a simple device that could be round glass or even a spinning mirror (too big for this application). A scanned line could be seen on the cue ball and go up far enough to where it is seen on the object ball. This system could be placed under the cue as to not disrupt the players view. The only problem I can think of is size and the fact that the cue can't be twisted as the vertical line scanned would go diagonal.
  15. Jul 3, 2008 #14


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    It may not teach you to do it well, but it may help you comprehend what you're supposed to do.

    When I took foxtrot lessons, no amount of practice would cause me to get better until I understood the beat I was supposed to be following - slow slow quick quick slow slow quick quick...
  16. Jul 7, 2008 #15
    Regarding the annalog computer aiming device-was it mounted on a "piston"-like cue stick device that could shoot w/no arm motion or was this simply an aiming device mounted on a standard cue stick?
    Last edited: Jul 7, 2008
  17. Jul 7, 2008 #16
    Regardind the annalog computer laser aiming device, was this mounted on some revolutionary "piston" powered cue stick or just an aiming device for a standard cue stick?
  18. Jul 7, 2008 #17
    Come to think of it, If you want to line up two balls you could use something as easy as glasses that you wear with lines down the center.
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