Kicking with top/bottom spin
- Thread starter hwest
- Start date
I'm glad you mention it, and I like the description "build better intuitions".
pj
chgo
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Years ago I just kicked at the ball hard and tried to get lucky, but now I look at the kick as if I'm shooting at the ball (from the rail I kick at) to see where the balls will go on how hard I kick it.
On kicks that have very little angle I think I kick those with just above center ball (who the hell knows where centerball is anyway). Kicks with angles I always use a hair of outside ( unless it's one of those kicks that you need inside english, draw, or extreme outside.
A small warning: physicists usually give the "direction" of rotation as the direction of the axis using the right hand rule. That means that the "direction" of follow on a ball headed away from you is to your left. A ball spinning in place with right english has an axis pointing up. A physicist would say that rotation perpendicular to a cushion is least affected by the cushion contact, while both the up/down spin and the parallel spin are significantly affected.
Yes, but since Patrick drew the "direction" of follow in line with the cue ball's motion, it was natural to keep the discussion in those terms. It's more natural to discuss billiards that way, as you've done many times yourself
Btw, for anyone attempting to read Coriolis, he used left-handed rotations in a right-handed coordinate system when deriving his equations. But in his beautiful constructions meant for intuitive understanding by less-techincal readers, he used vectors representing rotations in line with the motion just like we've been discussing in this thread. I think the important thing is to understand your convention and be consistent with it.
Robert
Thanks for sharing those, Dr. Dave. How are you measuring COR in these videos, and do you have a model for how COR changes versus ball state as depicted in them? I don't see anything in the TPs on your site.
Robert
In your video NV 6.7, the setup for the demonstrated shot (4th diamond to 2nd diamond bank) is incorrect. The two balls aren't set-up on the 4 diamond to 2 diamond line. When you shoot the shot, your cue crosses the rail closer to 4 1/4 diamonds.
The video doesn't show the whole picture but even though the line from the CB to the OB is not be exactly 4 to 2 the OB could be hit on the 4 to 2 track.
The video reporting COR values is:
I measured the ball speeds in (v_in) and out (v_out) of the rail by observing the time (T) it took to travel 1 ball diameter (D), with v = D/T.
COR = e = v_out / v_in
I have not studied this. I think both the normal and tangential ("throwback") CORs can vary with speed, angle, spin, English, ball conditions, cloth conditions, cushion geometry, rail/cushion conditions, etc.
Regards,
Dave
In NV 6.7 - Bank low-speed effect, I am measuring "across from the diamonds," not "through the diamonds." For a slow rolling ball, "through the diamonds" works better, but to find the true angle-in-equals-angle-out reference, you must measure across from the diamonds in the rail groove (gutter). Obviously, this "reference" is not very useful if you don't know how to adjust for all of the kick and bank effects.
Regards,
Dave
Donny, if you keep dropping nuggets of knowledge, you're going to piss off the other pros, who hold on to their secrets like they're the only ones who deserve to know them.
Some of us greatly appreciate the wisdom you share here; I just wish more pros were as forthcoming as you.
Thanks, dude. :thumbup:
