HaHa...lol Donny
clean vs dirty balls
- Thread starter TURTLE
- Start date
Since when?
Interesting idea, but I think it could still work in 'my' favor (assuming the effect is there at all.) Since the rail is above the ball's center, as the ball rose, the cushion would likely give an impulse closer to its center than if it stayed on the table.
This would be right until the ball rises more than 1/8" or so, then the effect I described would begin to come into play. But generally I think you're closer to correct than I am.
There are high speed videos of ball/cushion interaction, but I haven't taken the time to look for them during this thread.
Yes, there are multiple effects and countereffects, making it complicated to predict the overall outcome. I think empirical observations are needed, and I guess the best we have right now are what Donny and Chris have seen. As I think this through (with your help, thanks) I'm more inclined to believe it isn't a perceptual trick, but I'd still like to see more.
I buy that - in fact, I wonder if a bouncing ball might travel farther before slowing down to its (I assume you mean initial) rolling velocity.
pj
chgo
sausage
Banned
this has been my experience too. i believe that the newly polished balls do not lose their top spin momentum when they hit the rail and therefore will have some backspin coming off. dirty balls hit the rail and the friction stops their rotation so they come off faster.
I think for the most part your statement is true. However I think rail cloth condition, meaning dirty or clean cloth is equally as important. Even polished balls retain hardly any overspin/draw effect on dirty sticky rails. I hate dirty sticky cloth, just as much as dirty balls.
Rod
I prefer Brazilian ball cleaners myself...
Ooops, wrong thread....
BTW Steve Jobs is a cool rich dude, Bill Gates is the anti Christ
Hello:
If you are looking for a good ball cleaner for a lot less $$$$ check ours out at www.abctables.com You won't be sorry.
Thanks
Ron
Here are some pertinent resources:
http://billiards.colostate.edu/threads/draw.html#effects
http://billiards.colostate.edu/threads/balls.html#Silicone
http://billiards.colostate.edu/threads/balls.html#Silicone
This is the only pertinent video I can think of:
Regards,
Dave
Thanks, Dave.
Here's a summary of what this video shows:
In other words, dirty conditions do not produce faster rebounds; in fact the opposite is true.
Slick conditions produce rebounds that are:
- 1/3 faster with follow
- the same with stun
- almost 2/3 faster with draw
pj
chgo
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we need john s
Only in humidity between 22-27%, with the room temperature between 66-74 degrees. Only with a Moori tip with no tapping done prior, with 1/67ths of chalk, and definitely only Master. You guys kill me.
I picture Earl stopping in between shots to check with some sort of micrometer the density of the dirt on the balls to adjust his stroke by 1/3. Wow.
Well I have known a few good ball cleaners in my day.
I can check and see any of them are still available. Dont hold your breath though they tend to go fast.
On a serious note.
By a BallStar. Run you about $450.00.
I have one. Nice unit. Cheap enough.
http://www.pooldawg.com/product/ballstar-pool-and-billiards-ball-cleaner?source=trafficleader
http://www.billiards.com/ball-cleaners/automatic-ball-cleaner-polisher
For $450.00 i can rub my own balls!
Let me simplify the takehome message for you and Earl:
Balls rebound farther with slick conditions.
pj <- wouldn't want to cause any headaches
chgo
By "slick conditions", you mean that the CB is juiced with silicone spray? Is that right?
"slick" = low coefficient of sliding friction
This occurs with new, clean, polished balls on "slick" cloth. It also occurs with dirty balls on "sticky" cloth, if the balls are sprayed with Silicone.
Dave
We think alike, Patrick: a version of that chart has been sitting by my desk since Dave posted the video link
I was using the Coriolis model in my analysis, which assumes a constant cushion efficiency for all interactions that is independent of the friction coefficient. I know it's a simplified model, but it makes good predictions on the more slippery carom tables that I tend to play 3-cushion on. Apparently, it doesn't hold up as well under very sticky conditions (and Dave's table is especially so without silicone, as you can see by the short distance it takes for NR to develop. It's even surprisingly sticky with the silicone, but my intuitions are calibrated more for fast carom tables.)
His video suggests that COR can vary quite significantly for different ball states. A 15-25% variance in COR is huge, and I'd like to see a good model for why friction could alter the normal component of the ball's velocity so significantly. (I assume Dave strictly controlled where he was striking the rail each time for consistency, and this is just a representative case of a larger sample set - preferably on different equipment, too.) Are little inter-molecular 'springs' in the rubber being reoriented before releasing their energy due to cushion deformation? How do you imagine the interaction happening to explain this?
At first I was surprised that the siliconed ball's stun reaction was so different than its follow and draw. Now I think the two stun versions are practically the same because the relative contact point velocity is nearly zero for both so the ball adheres to the cushion instead of sliding against it (and sliding friction is what silicone alters.)
Also, notice there is kind of a symmetry between the draw and follow cases relative to stun even though the above-center contact might suggest otherwise. It would be interesting to see just how symmetrical they get when the exact amount of draw is tightly controlled (not nearly as easy to do as a rolling ball, of course.) Seeing how the symmetry breaks is probably a clue on how to attack the problem of a more complex model.
What I don't like about using COR like that is it's a lumped parameter that disguises the underlying processes. Saying it varies with friction, speed, etc isn't saying much other than we don't really understand it that well. It also makes it tough to generalize to different conditions. 1000FPS just doesn't seem like enough resolution to observe the transition properly (it looks like ~3ms to reach full cushion compression, and there's only so much you can squeeze out of 3 blurry frames even if you could see them on youtube
) I'd also like to see a simultaneous overhead view to help guide formation of a better 3D model.Thanks again for the video, Dave. Have you posted the parameters for your equipment anywhere for reference? Table model, cushion profile, nose height, etc?
Robert
I once had a desire to try to model cushion interaction, but then I was frightened by how much experimentation would be required to calibrate and validate the model. There are many important parameters (friction between ball, bed cloth, and cushion nose, cushion normal rebound efficiency, cushion tangential "throwback" rebound, cushion vertical stiffness as a function of deformation, etc.), and they all might vary with some or all of: angle, speed, English, spin, ball conditions, cloth type and conditions, cushion nose height, cushion type and condition, etc.). I don't have enough desire, time, or resources for such a study; although, I would still be very interested in the results of such an exhaustive study.
BTW, in the video, the ball did hit the same spot on the rail each time (within 1-2 mm), and I ran the Silicone-free tests first so residue left on the cushion wouldn't corrupt the results. The ball was wiped clean (with or without Silicon) before each trial.
I don't have simultaneous views, because I only have one high-speed camera. If you want to purchase additional HSV cameras for me, I'd be happy to provide simultaneous views.
I do have different views (although not simultaneous) in HSV 7.13-7.20. I also have additional trials, on a different table (9' Brunswick) in HSV A.117-A.120.You're welcome. I aim to squerve.
8' Connelly Redington, Titan cloth, full-profile K-66 cushions, nose height=1 3/8"=35mm.
Regards,
Dave