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View Full Version : Q re:spin/speed ratio (pre: tip deflection thread)



heater451
06-17-2002, 10:15 AM
<blockquote><font class="small">Quote: Anonymous:</font><hr>Tony, If the contact time of a hard tip is less then where is my thinking wrong? soft tip = more contact time = more friction = more bite = more spin.<hr></blockquote>

<blockquote><font class="small">Quote: Fred Agnir:</font><hr> The thinking breaks down when you say that more contact time = more friction. It is not necessarily true. Friction is the result from the chalk mostly. Tip hardness or tip contact time isn't part of the friction.<hr></blockquote>
Bob Jewett would probably say that contact time ("dwell") is not a factor, although I personally believe that it's just too small to be measurable.

Also, assuming a constant dwell, chalk/friction coefficient, and distance from center of ball, wouldn't the spin/speed ration then only be affected by the velocity of the cue tip at contact?

Jay M
06-17-2002, 10:47 AM
Just something to think about with regards to the effects of tip hardness on spin. Artistic billiards players, as well as many of the "trick shot artists", use a tip that is so soft that it has to be replaced for each tournament in order to maintain maximum effectiveness. This would suggest to me that those players have found through experience that the softer tips create more spin.

Jay M

heater451
06-17-2002, 02:15 PM
My guess would be that a softer tip's 'dome' compresses, yielding a larger elliptical contact section. This might add more friction, but, if there is no slippage with a smaller section, it wouldn't matter, would it?

BTW, like with the "Throw" thread, my experience doesn't alway match theory. I shot with a guy's cue once, that he said the tip was too soft for him, but I thought I got more spin on the ball, than I could with what I normally shot.

TonyM
06-18-2002, 12:11 AM
"Also, assuming a constant dwell, chalk/friction coefficient, and distance from center of ball, wouldn't the spin/speed ration then only be affected by the velocity of the cue tip at contact?"

Actually, the contact time does vary with speed (less contact time for faster speed and vice versa). The spin speed ratio doesn't vary with tip hardness because of the change in speed exactly equals the change in contact time. Thus the net force is always equal.

Spin speed ratio is affected only by eccentricity. Changing the speed affects both the spin "and" the speed, thus the ratio is maintained. To change the ratio, you have to change the tip location.

Clear?

Tony

TonyM
06-18-2002, 12:14 AM
Yes this point has been made before. However, for a given tip offset, the tip hardness cannot affect the amount of spin produced. But it is entirely possible that a soft tip could allow for a greater amount of tip eccentricity, thus changing the spin speed ratio. For "special shots" this might be crucial.

Tony
-tried a homemade rubber tip, got lots of spin, but no speed, so draw stank. Great for masse though....