String Tension

**Pete LSD** · 05-04-2004, 11:08 PM

This topic has been extensively talked about under the proportional stringing thread. As Cooler indicated the 10% extra on the cross is a poor man's way of bringing the cross back into its original shape.

Originally Posted by taneepak

Well, you can try to visualize how a racquet will look if strung with a certain tension on the mains only and then the same type of racquet if strung with the same tension on the crosses only. Which will deform more? The mains only will deform more than the crosses only. I am sure you know why.
Maybe some of you are engineers who have designed long span bridges and who can provide some input on this.

**Pete LSD** · 05-04-2004, 11:10 PM

The amount of support from a six-point machine allows one to safely string the cross less than the main under very high-tension, e.g., 30 + lbs.

What you are talking about is string bed stiffness as it is measured in lbs or kg per unit distance.

Originally Posted by bluejeff

I will have to add some more comments to this thread

In Taiwan, there are lots of people believeing in the Main(vertical strings) should have greater tension than Cross(Horizontal strings).

For example, we string at 20x22 here, but in taiwan, they do it reversely to 22x20.

Why? Because people in Taiwan think that, since the distance of the main strings are longer and cross is shorter, therefore, you must use higher tension at the main in order to "catch up" the tension at the cross. (I am talking about the two piece strings here, not one piece.)

Personally, I don't get it and I am not a believer to that. I still string cross higher than main. However, I have seen people (my friends) with 22x20 racquets strings and I compared it to mine racquet (both are MP99), and they look the same!!

I am just not sure how stringers in Taiwan can manage to reverse the tension pattern without changing the shape of the racquet.......wow....

**cooler** · 05-04-2004, 11:17 PM

Originally Posted by taneepak

Well, you can try to visualize how a racquet will look if strung with a certain tension on the mains only and then the same type of racquet if strung with the same tension on the crosses only. Which will deform more? The mains only will deform more than the crosses only. I am sure you know why.
Maybe some of you are engineers who have designed long span bridges and who can provide some input on this.

You are placing too much reliance on engineer and scientifist.There are many task and craft that have been mastered by non-engineer and non-scientist. Having science background helps but it is experience and desire to excel to be the best make a person a master or an expert. I can give a racket to a civil engineer with PhD and he wouldn't know start on stringing a racket. On the other extreme, if I give a racket to a civil engineer with structual design experience, he/she will laugh at the 20x22 rule from yonex because it is too simplistic and identify the unbalanced stress points.

I know a mechanical engineer who knows next to nothing on basic auto mechanic and yet a high school drop out who pump gas would know more auto mechanic than this mechanical engineer.

**LazyBuddy** · 05-05-2004, 12:16 AM

Originally Posted by cooler

You are placing too much reliance on engineer and scientifist.There are many task and craft that have been mastered by non-engineer and non-scientist. Having science background helps but it is experience and desire to excel to be the best make a person a master or an expert. I can give a racket to a civil engineer with PhD and he wouldn't know start on stringing a racket. On the other extreme, if I give a racket to a civil engineer with structual design experience, he/she will laugh at the 20x22 rule from yonex because it is too simplistic and identify the unbalanced stress points.

I know a mechanical engineer who knows next to nothing on basic auto mechanic and yet a high school drop out who pump gas would know more auto mechanic than this mechanical engineer.

Totally agree.

Yonex's standard is a "safe" standard, and more like a quick instruction on "how to learn string a racket in 20 min". However, experts could implement their own thoughts and experience to figure out better (or, at least, another) way to get the job done. Such methods needs the crafty hands, special made tools and loads of experience, and could be very complicated to beginners, who will get confused, get poor result, and put valuable equipment in danger.

For example, many ppl know MicroSoft Windows could be crap, due to its bugs, especially in security control. However, why MS windows could be the "standard" for the market? Of course not because its standard is the best, just because of its market strategy and easy to use interface. Other OS, such as Unix is much more reliable (talking about better and higher standard), but due to various reasons, it could only be masterized by professionals, but not just Joe office clerk. Therefore, same thing as Yonex so call "standards" in all of its product...

**taneepak** · 05-05-2004, 12:35 AM

Are we going off tangent? The simple question, which has a more meaningful bearing on what is being discussed here, is : does a racquet distort more if pulled at the same tension on the mains only vs the crosses only? And if yes, increasing the cross tension to an extent that will make both mains only and crosses only distortion equal does make sense, doesn't it? Conversely, increasing the mains only over the crosses only tension will further increase the distortion, wouldn't it? The concept must be grasped. I am not saying the 10% or 2 lbs of the crosses over the mains are gospel, but it is close and is conceptually sound. Doing it the other way will be conceptually unsound, irrespective of spurious claims to the contrary or what some may see it as fog. More importantly, the basic concept must be understood.

**Pete LSD** · 05-05-2004, 12:41 AM

Without the side supports, the 10% extra on the cross may make sense. I just can't imagine one wants to narrow the the racquet cross wise when stringing is done on a six-point machine

.

Originally Posted by taneepak

Are we going off tangent? The simple question, which has a more meaningful bearing on what is being discussed here, is : does a racquet distort more if pulled at the same tension on the mains only vs the crosses only? And if yes, increasing the cross tension to an extent that will make both mains only and crosses only distortion equal does make sense, doesn't it? Conversely, increasing the mains only over the crosses only tension will further increase the distortion, wouldn't it? The concept must be grasped. I am not saying the 10% or 2 lbs of the crosses over the mains are gospel, but it is close and is conceptually sound. Doing it the other way will be conceptually unsound, irrespective of spurious claims to the contrary or what some may see it as fog. More importantly, the basic concept must be understood.

**taneepak** · 05-05-2004, 03:45 AM

Originally Posted by Pete LSD

Without the side supports, the 10% extra on the cross may make sense. I just can't imagine one wants to narrow the the racquet cross wise when stringing is done on a six-point machine

.

No, not true. It is the other way around. Stringing the racquet cross-wise at say 2 lbs higher than the mains will not narrow the racquet. It will counter the tendency of the racquet going round from the mains' tension, to roughly equal the original shape of an unstrung racquet. If, however, the mains tension is equal to or greater than the crosses, then the racquet will have a net force towards a rounder shape.
The reason is simple. A racquet has an oval or iso shape, with the length of the 2 sides longer than the length of the head and throat. A compressive force or pulling tension on the vertical, that is from head to throat, will have the much longer sides of the racquet to deform or distort. The same compressive force on the crosses will have the much shorter head and throat distances to deform. Applying equal compressive forces to the mains and crosses will therefore result in the mains deforming more than the crosses.

**taneepak** · 05-05-2004, 10:22 AM

Originally Posted by LazyBuddy

The racket manufacture specifies the range of tension for main and cross, but not necessary the difference/ratio.

Yonex specifies their recommended tension ranges separately for the mains and for the crosses; and the crosses are always 2 lbs more than the mains, never the other way around.
For example, the AT700's recommended tension, according to Yonex is :
1. For 3U. Main : 20-23 lbs; Cross : 22-25 lbs.
2. For 4U. Main : 19-22 lbs; Cross : 21-24 lbs.

**Pete LSD** · 05-05-2004, 10:47 AM

The side supports are already holding the racquet in its original shape.
With a mold, the width of the frame will not even bulge out!

Originally Posted by taneepak

No, not true. It is the other way around. Stringing the racquet cross-wise at say 2 lbs higher than the mains will not narrow the racquet. It will counter the tendency of the racquet going round from the mains' tension, to roughly equal the original shape of an unstrung racquet. If, however, the mains tension is equal to or greater than the crosses, then the racquet will have a net force towards a rounder shape.
The reason is simple. A racquet has an oval or iso shape, with the length of the 2 sides longer than the length of the head and throat. A compressive force or pulling tension on the vertical, that is from head to throat, will have the much longer sides of the racquet to deform or distort. The same compressive force on the crosses will have the much shorter head and throat distances to deform. Applying equal compressive forces to the mains and crosses will therefore result in the mains deforming more than the crosses.

**taneepak** · 05-05-2004, 10:56 AM

Originally Posted by Pete LSD

The side supports are already holding the racquet in its original shape.
With a mold, the width of the frame will not even bulge out!

But we are talking about the racquet after it leaves the stringing machine. That is when the compressive forces of the mains and crosses, unrestrained by any supports, will start to work immediately and over time.

**LazyBuddy** · 05-05-2004, 02:46 PM

Originally Posted by taneepak

But we are talking about the racquet after it leaves the stringing machine. That is when the compressive forces of the mains and crosses, unrestrained by any supports, will start to work immediately and over time.

With additional support, I think the final tension is no more the ones being read from scale. i.e. over stretch a rubber band 1st, then pull it with 2lb of force, the actual force within the rubber band might be 4lb, but not the 2lb read from scale.

**LazyBuddy** · 05-05-2004, 03:01 PM

Originally Posted by taneepak

Are we going off tangent? The simple question, which has a more meaningful bearing on what is being discussed here, is : does a racquet distort more if pulled at the same tension on the mains only vs the crosses only? And if yes, increasing the cross tension to an extent that will make both mains only and crosses only distortion equal does make sense, doesn't it? Conversely, increasing the mains only over the crosses only tension will further increase the distortion, wouldn't it? The concept must be grasped. I am not saying the 10% or 2 lbs of the crosses over the mains are gospel, but it is close and is conceptually sound. Doing it the other way will be conceptually unsound, irrespective of spurious claims to the contrary or what some may see it as fog. More importantly, the basic concept must be understood.

I think the major difference between u and rest of us is: Is yonex standard really the "basic concept"??? To me, a workable concept is a "basic concept" for this particular person, regardless if his idea is heavily praised by some big corporation or not. It might be a nightmare for others, if they don't know how to apply the method correctly or without the proper tools. Whether there are tons of theory behind it or not, I just believe, a long time well-proven method is a good method; on the other hand, a well writen thesis without applied in real life might just be crap.

Sorry to be off topic. Just want to show another example. Reggie Miller (NBA 3point speicalist) is known for his crazy 3 point bombs at the end of the game. Some scientists studies his upper body (waist, shoulder, arm, wrist) motion, and try to figure out if some special "smooth motion" actually benefited him in such shot. The result was the totally different way than expectation: The motion is very stiff (something like snake bent its head in a sudden motion), and totally against law of physics to be effective and accurate. Well, the truth is, Reggie is going to be a "Hall of Fame", but not some guy who can't even make a shot...

**cooler** · 05-05-2004, 07:22 PM

that extra 2 lbs tension for the cross as suggested by yonex is based on these assumptions

1. you use a 2 point machine
2. you follow yonex pattern and method of stringing
3. you stay under the recommended tensions
4. the stringer can be anybody

**taneepak** · 05-05-2004, 08:52 PM

Originally Posted by cooler

that extra 2 lbs tension for the cross as suggested by yonex is based on these assumptions

1. you use a 2 point machine
2. you follow yonex pattern and method of stringing
3. you stay under the recommended tensions
4. the stringer can be anybody

Can you back these up? By the way, I think Yonex sells only 6-point stringing machines. In Yonex's recommendation on main/cross tension, they did not say or even imply that their recommendations are based on the above assumptions. If they say so, they would look rather foolish, wouldn't they?

**LazyBuddy** · 05-05-2004, 10:04 PM

Originally Posted by taneepak

Can you back these up? By the way, I think Yonex sells only 6-point stringing machines. In Yonex's recommendation on main/cross tension, they did not say or even imply that their recommendations are based on the above assumptions. If they say so, they would look rather foolish, wouldn't they?

Safe choice, safe choice, safe choice...

1. 2 point machine is the worst case

2. "Joe stringer" (anyone) is the worst case...

"if they say so, they look foolish...": exactly why they don't say it. Exactly why ppl might believe that's the "basic standard"...