Half a croissant, on a plate, with a sign in front of it saying '50c'
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Parabolic Pool Table

  (+79, -4)(+79, -4)(+79, -4)
(+79, -4)
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Like a regular table, but the surface is parabolic. It sits in the middle of a rotating carousel, the floor of which is also parabolic. The speed of rotation is such that the combined gravitational and centrifugal forces are always perpendicular to the parabolic surfaces, so the balls (and players) don’t roll off on their own.

Requires some knowledge of orbital mechanics to actually sink a ball.

ldischler, Oct 04 2004

The equations...some of them, anyway. http://www.delocorp.net/hb/pool/
[ldischler, Oct 04 2004, last modified Oct 05 2004]

(?) Drawing by Bristolz. http://bz.pair.com/fun/parab-o-pool.html
Scroll down to see it rotate. [ldischler, Oct 04 2004, last modified Aug 18 2006]

Related idea Cylindrical_20Snooker
Spacestation Snooker [Cosh i Pi, Jun 20 2007]

Nice - an elliptical pool table http://www.theguard...-ellipse-elliptical
[hippo, Jul 16 2015]

Drawing by Bristolz http://web.archive....n/parab-o-pool.html
Linked to the waybackmachine, because I refer to this occasionally (and Bristolz's drawings deserve to live on) [Worldgineer, Nov 17 2015]

[link]






       Nice. So, if I understand this correctly, if you put a ball on the table it would stay put, relative to the table. Similarly, players would be able to freely walk around the rotating parabolic floor.

Of course, players from the Southern hemisphere playing in the Northern hemisphere (and vice versa) would be disadvantaged because of the reversal of the Coriolis force affecting the motion of the balls.
hippo, Oct 04 2004
  

       Glad to see my all time favourite idea is back in recent and being voted on. May I repeat my croissant. And one for Bris.
ImNotReal, Oct 04 2004
  

       Ahhh. I am glad you reposted this idea. I got to repost mine. Thanks for the reminder.   

       Oh, and I like this idea, too.
DesertFox, Oct 05 2004
  

       Forgive me for not spending half an hour trying to get my head around your equations [ldischler], but could you give me a rough idea of the rate at which bris's table would have to spin?
wagster, Oct 05 2004
  

       [wagster] Well, let’s say you have a 44x88 inch playing surface, and you want the corner pockets to rise up by 12 inches relative to the center. Then, for centrifugal force to cancel out that slope, the table must turn at 5.4 rpm.
ldischler, Oct 05 2004
  

       Good link, Steve. So I’m thinking of trashing the pool table and selling the parabolic floor to NASA as a rotating ballroom. Dancing astronaut couples would be forced to twirl in one direction while moving to the center, and then in the opposite direction while moving away.
ldischler, Oct 05 2004
  

       Thanks [ldishcler], that sounds like an rpm I could live with. Well, for as long as it would take to finish a game of pool at any rate.
wagster, Oct 05 2004
  

       My favourite 0.5-bakery idea to date. Someone should make this...   

       <Imagines the fun you could have (after a couple of drinks) if there was a variable speed control on the table>
suctionpad, Oct 06 2004
  

       Simply would not work for the game we call pool but I am glad to see the idea back
shad, Oct 08 2004
  

       And why not [shad]?
wagster, Oct 08 2004
  

       wagster,   

       I am sorry I don't have more time to explain some of the more complicated aspects of it but here are a few points. Of course I am ignoring the Coriolis effect as one can learn to overcome this.   

       When you break, you are going to jump the ball either before you hit the rack or after, A ball will bounce on the table when it changes direction from down to up. It takes very little amount of vertical misalignment for a ball to jump when they collide, creating a wedging rather than a even hit   

       English imposed on the ball will significantly differ ccw / cw   

       With a parabolic table the relation of angle to the gravity is inconstant to the playing surface as this will always change along the distance of the table. One of the more important rules of pool is that you should keep the back end of your cue as low as possible, when the ball is on the other end of the table the back of the cue will be forced to be rather high in relation to the relative gravity. And no,a parabolic stick will not resolve this.   

       it is an intriguing thought. Though I think that this idea does not do the game justice
shad, Oct 09 2004
  

       [shad] Yes, wedging could be a problem, but remember the white on most pub tables is smaller than the coloureds, but never jumps them, even though it strikes from slightly underneath the centre. Having the cue raised could be a more serious problem.   

       //English imposed on the ball will significantly differ ccw / cw// - errrm... is it me or does that sentence make no sense at all...?   

       I reckon it could still be feasible with a shallow parabola and slow spin. Don't know enough about the coriolis problem to be sure though.
wagster, Oct 09 2004
  

       Bris and Jutta--that is fantastic!
ldischler, Oct 25 2004
  

       It was just a test. It's not the kind of thing the site owner has in mind as it really distracts from the idea and the overall simplicity of her carefully evolved layout.
bristolz, Oct 25 2004
  

       Rats! I thought it was cool.
ldischler, Oct 25 2004
  

       Oooh, I don't care if it works, I just wanna see the first game. +
k_sra, Oct 25 2004
  

       Have I missed something here? If there's an animation of this one I'd *love* to see it. Hope it hasn't expired.
wagster, Oct 25 2004
  

       It appears there was a brief test of the interface with an animation located on the idea page. To see [bris]'s animation, click on the second link and scroll to the bottom.
Worldgineer, Oct 25 2004
  

       3D with global illumination and low key grayscale textures and some extra tricks to get a pen line look ;-) No toon shader. Also a bit of motion blur. Done with brazil r/s.
bristolz, Oct 25 2004
  

       Slick.
wagster, Oct 25 2004
  

       Very nice indeed. Excellent illo as well, [ldischler]. Just name it something else for the purists.
absterge, Oct 25 2004
  

       2 visuals come to mind: a. An old elemetary mathematics film called Donald Duck in Mathmagicland that illustrated geometric principles using a pool table. Much more fun with this table. b. Peter Sellers with his bent pool que, on home turf, at last.
Don Quixote, Oct 28 2004
  

       this is a thing of joy, well done to you both. [bris] your rotating table is marvellous.
neilp, Dec 13 2004
  

       Wow, this is so brilliant. This shouldn't be in the halfbakery, it should be in my local pub right now. Please, someone, make this.

[Shad], I'm not sure I fully grasped your objection to this, but it sounded like you were saying that the angle of the table with relation to gravity will change over the trajectory of the ball. If this is your point, it's incorrect - the surface of the table is perpendicular to gravity at all points, just like a normal pool table. This is because you can't draw a distinction between gravity and the centrifugal force resulting from the table's rotation - they're essentially the same force, and so adding them together results in one effective force acting perpendicular to the surface of the table. (Apologies if I misunderstood your real point and just gave a poor explanation of something obvious; feel free to set me straight.)
spacemoggy, Dec 13 2004
  

       Conic sections always get my vote. Well done, and well illustrated. The orbital aspects could allow one to "hook" the cue ball around stationary balls without having to attempt English.   

       My brain hurts, but it's a good hurt.
gardnertoo, Dec 15 2004
  

       That sounds fun! Not sure that the shape would be parabolic...but...it wouldn't be hard to find.   

       And shad, I agree with the others...the ball will always feel that it is being pulled straight down relative to the table. By feel, it wouldn't know that it was on a slant at all. The force a still ball wil feel would always be perpendicular to the tangent of the tables curve at that point. If it were moving, you'd have to add the frictional force between the table and the ball. I think that's all correct.   

       Figured out the equation, just need to find the integral now :)
nomel, Dec 15 2004
  

       Let me repeat that I think that it is a good idea and it could pioneer a good game that would be challenging and would work fine in itself however it is incomparable to pool due to the intense experience and flexibility needed.   

       But when you compare this game to pool or consider it an alternative for one with skills learned from pool you need to take the speed of the ball into account and what will happen when the ball changes direction (nothing to do with gravity but the forces contained in the ball imposed on it by the cue ) as it transitions from one place to another   

       FRICTION: for advanced players, friction is a very important part of the game it allows the player to create a "stop shot", masse (curve the ball) draw and a follow shot... let me explain, - - - on a flat table, to cause a stop shot, this is a shot at which the cue ball stops moving forward on the moment of impact, One must shoot the cue ball with just the perfect amount of backward spin so that at the moment of impact with the other ball the cue ball will have stopped spinning backward and be in a neutral state - - - on a parabolic table this friction will be constantly changing when the ball transitions across the table depending on where the ball is on the table and where it is going - I DO AGREE that with a parabolic table once and if a stop shot were performed (more likely on accident) that the ball will rest where it stops Friction on a table can be increased or decreased by how heavy the ball is (relatively)   

       - - -If the ball does not touch the table it will NOT be acted upon by the parabola - - - the energy stored in the ball by the rotating table is miniscule compared to the force imposed on the ball during most shots - - - it is a fact that the ball will go in the direction it is shot, regardless of the parabola you will have to aim in a place where the target ball is not when the shot is made, same principal as skeet shooting you aim where the pigeon will be when the shot arrives at the distance of the target not where the target is when you pull the trigger The one thing is the table will impose a force ( friction ) on the ball as it is rolling toward its target (similar to a cross wind in target shooting) and in turn change the trajectory of the target ball due to a force imposed by the spin on the cue ball when you hit it One of the things that the target shooting analogy doesn't take into account is that after you hit your target most advanced players would like to plan on where their ball will end up this rotating motion of the table will impart (through friction) a spin on the ball which will completely change the normal trajectory after the ball hits the target ALL of these points will vary from area to area on the table and depends on how hard you hit the ball ect.   

       oh, all of these forces that I just described will start over when the cue ball hits the target ball and every ball thereafter Quite complicated!!!   

       (keep in mind when you are swinging a gun up for an aim the amount of force that you put on the bullet by swinging the gun is almost irrelevant to the trajectory of the bullet once you pull the trigger due to the far greater force that the gun powder imparts on the on the bullet - - -the bullet doesn't curve left or right when shot unless there is sufficient force put on the bullet after it is shot - - -small amount from wind larger amount by rocks and such things - --)   

       Once again when one breaks you will have to keep in mind the above and also, due to the great force the probability of launching the ball when you break first when the ball is hit it should go in a direction that it was hit and then again when the ball bounces on the table - - it is imperative that when the ball hits the rack that it is perfectly aligned on its axis's otherwise the force will cause a ramping effect and will case balls to become airborne   

       To jump a ball (legally) the ball must be shot from above and in turn causing the ball the to compress into the felt and storing energy causing it to rebound from the felt (sounds far fetched but it is done all the time) the trajectory will change depending on the angle of incidence which will change depending on the relationship between the angle of the cue and the surface of the table causing a considerable learning curve on a table with an varying angle already imposed in it ( it is difficult for many players to make this shot predictably if not impossible for others to even get the ball off the table )   

       Even though I could keep going on about other points I will finalize with this last point   

       it is ideal to shoot a ball with the rear of the cue as low as possible as to prevent imparting a side spin into the cue ball this typically increases accuracy for people unaware of their misalignment ( right to left ) with a parabolic table the possibility of lowering the rear of the cue in a lot of shots would be impossible ( no a curved cue will not help )   

       with all of these points in mind I would not do anything to change the proposed idea I would use them as a point for the potential complexity and high level of experience achievable for this new game all of these points do not make it a bad game it makes it a game that would use the mind to it fullest and almost require the player to play at a subconscious (by feel not understood physics) level due to all that would have to be taken into account. this would also eliminate the so called "lucky players" of pool. A table run would be unheard of and people would revere it
shad, Dec 20 2004
  

       Thank you [shad] - nice analysis. The next stage is to get a quote on building it. I should imagine slate is out of the question - for a start it levels flat very nicely but isn't very good at curves. I reckon steel is the only option for this. Engineers please - do we cast it before polishing it into a parabola, or can we steam press it? Bear in mind there must be no flex in it at all which I should imagine entails 0.25" steel at minimum. Finally - how do you felt a parabola? It shouldn't be that hard as you can make complex forms such as hats out of felt, I just don't know how to do it.
wagster, Dec 20 2004
  

       Could it not be done with resin and spinning the mold? Or maybe molten glass? Or maybe a billet of glass and ground like a telescope mirror? Or an active surface that adjusts for spin speed, akin to adaptive optics? Or make a giant wood lathe and turn it like a bowl out of a big piece of glue lam? Or a supral formed surface like Aston-Martin has used for some prototyping? Or ferro cement on wire? Or a sputtered, litho or sprayed buildup surface like rapid prototyping printers? Or blow a giant glass bubble and cut the proper section off once cool? Or just have Uri Geller do it from stainless spoon stock?
bristolz, Dec 20 2004
  

       Thanks [bris], what about the felt?
wagster, Dec 20 2004
  

       Maybe a sprayable coating like 3M Nextel black velvet? (It may not be made anymore but it was a great finish).
bristolz, Dec 20 2004
  

       Great list, [bris] - the blown glass option was genius. I vote for spun resin, which should be easy to adhere [wag]'s precious felt to.
Worldgineer, Dec 20 2004
  

       I vote for having a huge Uri Geller make it out of a huge spoon.
wagster, Dec 20 2004
  

       actually it could be made out of marble and ground to the desired shape... cannot be made out of materials that could dent break or chip. ceramics? as for felt I think that it could easily be made to fit however a tightly stretched felt will play a ball faster than a "loose" felt this could just be the characteristics of your new table   

       wagster, for the record it is not necessarily true that "in most bars the white on most pub tables is smaller than the coloureds" many bars have opted for the magnetically actuated ball return which you can probably imagine how this works or they will have a ball that is heavier than the rest and you can figure this out also. I will concede, when playing pool it is most ideal that the ball be the exact weight and size and also have the same center of gravity as the rest of the balls which does cause for a compromise in any but the best designed magnetic systems
shad, Dec 25 2004
  

       [shad] - Firstly, marble is very soft and easily chipped (as you'll know if you've ever sliced bread directly onto the surface of a good friends marble worktop...), maybe granite? I was also hoping to avoid the 'carve a dish shape out of a block' technique to avoid upping the already massive weight being placed on the bearings. Ceramics sounds interesting, as it can be moulded first. Secondly, this magnetic white sounds good - haven't come across it yet. It just occured to me though, why not just have a device that checks the colour of the ball before dropping it in to the relevant channel? Colour recognition isn't that hard these days.
wagster, Dec 26 2004
  

       that is not a bad idea I have work with optical sensors and conclude that it would be a rather simple circuit requiring minimal power (batteries and solar that charges off the pool light and the only time that the system needs to be on is when there is a ball near the sensor preferably the system could be retrofitted to table with oversized balls. I understand your opinion about marble chipping easy but think of how easily slate chips. I would agree ceramics may be the best choice and the simplest to make light
shad, Dec 26 2004
  

       //It takes very little amount of vertical misalignment for a ball to jump when they collide   

       I don't think that will be a problem, since the force the ball feels is always perpendicular to the table.   

       //English imposed on the ball will significantly differ ccw / cw   

       Isn't that the whole point?   

       //when the ball is on the other end of the table the back of the cue will be forced to be rather high in relation to the relative gravity. And no,a parabolic stick will not resolve this.   

       Valid objection. But how would a parabolic stick not resolve this?   

       //on a parabolic table this friction will be constantly changing   

       Because the force, while always perpendicular, will be stronger or weaker depending on where it is? So draw a few isoforce lines on the table and call it part of the game.   

       //Colour recognition isn't that hard these days.   

       Quite a simple circuit to make for this tightly-defined purpose. It would have to measure several points at once to make sure it wasn't measuring a striped ball as white. It could keep score for you, too.   

       //batteries and solar that charges off the pool light and the only time that the system needs to be on is when there is a ball near the sensor   

       Just plug it into the wall, silly. :-) If you really want to have it self-powered, power the sensor and selector mechanism with the falling weight of the ball. The energy would be provided by people lifting the balls out of the... "collection area"? and putting them on the table.
omegatron, Jul 31 2005
  

       Silly?? Don't scorn me omegatron   

       //""//It takes very little amount of vertical misalignment for a ball to jump when they collide   

       I don't think that will be a problem, since the force the ball feels is always perpendicular to the table.""//   

       omegatron, It WILL be a problem   

       //"//when the ball is on the other end of the table the back of the cue will be forced to be rather high in relation to the relative gravity. And no,a parabolic stick will not resolve this.   

       Valid objection. But how would a parabolic stick not resolve this?"//   

       The force delivered by the cue is a straight line between your two hands, the cue could make a figure eight between your hands and the action would still be straight.   

       //"//batteries and solar that charges off the pool light and the only time that the system needs to be on is when there is a ball near the sensor   

       Just plug it into the wall, silly. :-) If you really want to have it self-powered, power the sensor and selector mechanism with the falling weight of the ball. The energy would be provided by people lifting the balls out of the... "collection area"? and putting them on the table."//   

       SILLY?? omegatron, if you just plug a pool table into the wall, in a bar environment someone will just unplug it. Not to mention, you would have a relatively complex arraignment of slip rings and brushes to bring the power through the "rotating carrousel" to the table. omegatron, I do admit your idea of a ball powered generator would work and I am sure it would work great however I think it would be far more complex than an already baked solar panel that has no moving parts (unless of course you count electrons and photons)
shad, Jul 31 2005
  

       Love this idea and Bristolz' illustration of it. If you drink enough beer you can get a similar effect. However with the spinning table maybe you could offset the beer effect and continue drinking and playing?
sk8illogical, Aug 18 2006
  

       [ldischler]Is ok with you if I make this
dev45, Dec 05 2006
  

       Is ok, dev. Just don't complain about the equations.
ldischler, Dec 06 2006
  

       Thank you   

       And Math is my best subject.
dev45, Dec 07 2006
  

       You get a croissant simply for making something that spins.
Abusementpark, Dec 10 2006
  

       You don't have to have the table centred on the axis of rotation - as long as the surface of the table forms part of a paraboloid whose axis is the axis of rotation. Personally I like the idea of an off-axis table.   

       The Coriolis Effect in this case isn't due to the rotation of the Earth (which is much too slow to be of significance to a pool table sized system), it's due to the rotation of the table itself, and is the same for Northerners or Southerners - it depends whether the table is rotating clockwise or anticlockwise, not which hemisphere you're in.   

       I think a key point would be to have a shallower curve than a 12" lift at the corners and correspondingly a 5.4 rpm rotation - as [shad] says, you'd always be cuing downwards. With a relatively shallow curve and slower rotation, I think this would be playable - and still different enough from ordinary pool to be - erm - _interesting_.   

       The 5.4 rpm rotation version would be very tiring to play, too - standing near the corner pockets (a little further from the axis than them) you'd weigh about 50% more than normal.
Cosh i Pi, Jun 19 2007
  

       New poster - I saw this and had to add my comments!   

       I think a couple points have been over analyzed, in regards to actual game play for trajectory of the ball once stricken during the break, the cue ball would be traveling at a speed where the spin of the table would have very little bearing on the balls trajectory. As for the angle of the cue when striking the cue ball, if you are hitting the center of the ball relative to the angle of the cue, you will not have the cue leave the table. Obviously the mind that first came up with this is not only creative, but quite brilliant! This could work! Yes, it does put a big twist on the game of pool! I am an avid pool shooter and see a learning curve difficult for the novice player, but anyone with the passion for the game would find it a refreashing update to the sport!
Zogeman, Jun 20 2007
  
      
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