tennisbike
Professional
This is a "conversation" I started with TW Professor. I thought I share it here.
Hello TW Professor (Lindsey?),
Thank you for your work in the experiments and sharing the analysis related to our beloved sport, tennis.
was searching through the book "The Physics and Technology of Tennis" and the web pages on Tennis Warehouse for "HARDNESS" data of tennis strings.
As a physics teacher, tennis coach in high school, a mechanical engineer and a general hack, I ponder on my two recent string jobs. Both having Kevlar fishing string about 18 or 19 gauge on the main, between 60 to 65 in reference tension. One used Prince Warrior Response, a hard poly outer layer, and the one a black textured synthetic gut/multi-filament, I assume is Head Rip control, at 45 lbs. While stringing, this black string is so slippery that my fingers had problem pinching it while pushing it through the weave string the cross. In the first hitting session, I found that this slipperiness did not translate to snapping back to original position. The hard surface on the Warrior Response on the other hand stays straight.
While the result is not surprising, i.e. SG/MF cross stucks and Poly cross stays straight, the mechanism is not clear in my head. What about the slickness of the black string before installation?
This is my visualization: The friction between surface is caused by the interaction between the microscopic peaks and valleys. In the standard friction equation the friction force is equal to coefficient of friction times the normal force. At a given normal force, which is related to strung tension, then the coefficient of friction between each possible combination of strings then needs to be tested and measured. This is a nearly impossible job, since new strings are flooded to market faster than tests can be done. (is there another way?)
There were test already done about "stiffness" of the strings, but what about surface "hardness"?
This is what I envision in string to string interaction. At the impact, the 2 strings are stretched from the ball, and the already stretched from the installed tension/weaving. While the lubricated black string seemed easy to move back and forth, there are more energy in the sliding of the compressed softer material dissipated than the sliding on "hard" surface that compressed little. Another image is that the peaks and valleys expand then squeeze during the impact cycle, like a mountain bike knobby tire on a dirt surface squeeze the dirt gaining friction/grip. The softer string squeeze onto the other string and does not want to let go. Thus these are the two things that keeps the softer string from returning from the snap-back.
Assuming my model is on the right track, then having a set of table listing the surface hardness of all the strings would then be a useful tool to determine string's ability to snap back.
Am I full of **** or is there something to this idea, string hardness table. I love to hear your thoughts on this matter.
Hello TW Professor (Lindsey?),
Thank you for your work in the experiments and sharing the analysis related to our beloved sport, tennis.
was searching through the book "The Physics and Technology of Tennis" and the web pages on Tennis Warehouse for "HARDNESS" data of tennis strings.
As a physics teacher, tennis coach in high school, a mechanical engineer and a general hack, I ponder on my two recent string jobs. Both having Kevlar fishing string about 18 or 19 gauge on the main, between 60 to 65 in reference tension. One used Prince Warrior Response, a hard poly outer layer, and the one a black textured synthetic gut/multi-filament, I assume is Head Rip control, at 45 lbs. While stringing, this black string is so slippery that my fingers had problem pinching it while pushing it through the weave string the cross. In the first hitting session, I found that this slipperiness did not translate to snapping back to original position. The hard surface on the Warrior Response on the other hand stays straight.
While the result is not surprising, i.e. SG/MF cross stucks and Poly cross stays straight, the mechanism is not clear in my head. What about the slickness of the black string before installation?
This is my visualization: The friction between surface is caused by the interaction between the microscopic peaks and valleys. In the standard friction equation the friction force is equal to coefficient of friction times the normal force. At a given normal force, which is related to strung tension, then the coefficient of friction between each possible combination of strings then needs to be tested and measured. This is a nearly impossible job, since new strings are flooded to market faster than tests can be done. (is there another way?)
There were test already done about "stiffness" of the strings, but what about surface "hardness"?
This is what I envision in string to string interaction. At the impact, the 2 strings are stretched from the ball, and the already stretched from the installed tension/weaving. While the lubricated black string seemed easy to move back and forth, there are more energy in the sliding of the compressed softer material dissipated than the sliding on "hard" surface that compressed little. Another image is that the peaks and valleys expand then squeeze during the impact cycle, like a mountain bike knobby tire on a dirt surface squeeze the dirt gaining friction/grip. The softer string squeeze onto the other string and does not want to let go. Thus these are the two things that keeps the softer string from returning from the snap-back.
Assuming my model is on the right track, then having a set of table listing the surface hardness of all the strings would then be a useful tool to determine string's ability to snap back.
Am I full of **** or is there something to this idea, string hardness table. I love to hear your thoughts on this matter.
