**Stringway – information – Questions – answers**

[onehandbh]

This discussion makes me re-think the whole concept again. I have also this MiStringer machine where racquet is literally fixed to the frame without towers, and clamps also fixed to frame with zero drawback.
It may be my imagination but I think racquet plays differently (better). I think it’s more control and more feedback from contact.

Then, in a regular machine I tried to insert a rod between 6 and 12 supports, to not allow them move during pulling mains, and I think I got a similar effect, maybe not as pronounced as with MiStringer but it’s difficult to tell.

I can't even imagine trying to string and weave strings on the MiStringer on a regular basis. The platform holding the racquet is so wide and is super close to the frame and stringbed. My fingers and hands almost hurt just from looking at that photo.

Would take me a long time to weave the crosses.

 

[villis]

Using your cross stringing tool ? They have a very simple tool to go under a cross, so you do all from the top, yes it takes time but regardless, I feel racquet plays differently. Why would it be other than frame that doesn’t bend and clamps that don’t move?

 

[Stringway Official]

Hi Guys,

Our light weight spring driven CP machine moved faster than we expected, so we have none left.

We are making new parts and assemblies at the moment but because it is a more complicated system than the drop weight the lead time is longer.

 

[jmnk]

@jmnk
Excuse me b in fig 2 was a mistake, I corrected it.

Edited for clarity/brevity.

@Stringway Official - thank you for a corrected drawing. Let's use that picture as a basis for analysis. This is not for the faint of heart, I fully realize they may not be too many readers left by the end of this post

Here are two drawings illustrating the forces in question, figure on the left when the arm is level, and figure on the right when the arm is at an angle. the formulas work for any angle, for the purpose of having practical numbers I've assumed the angle is 30 degrees. The drawing is to scale.

Two points:
1) regarding the theoretical formulas you posted as a proof that "the tension is the same for every angle"

It should be obvious that your formulas given here https://tt.tennis-warehouse.com/index.php?threads/stringway-–-information-–-questions-–-answers.673819/post-14435668 are incorrect. The formulas you want to use are the following.​

​

From the torque equality equation:​

W * a = F * b where​

W - dropdown weight in direction perpendicular to arm a​

a - distance from pivot point p to the center of weight (we are assuming that the arm itself is weightless). This never changes no matter what the angle is​

F - Force applied perpendicular to b​

b - distance from pivot point p to where force F is applied. This never changes no matter what the angle is​

​

when arm a is level W is the actual dropdown weight, and F is actual Tension force acting on a string. As such we have:​

W * a = Ts * b => Ts = W * a / b​

​

when arm a is at angle A we have:​

W' * a = F * b where W' = W * cos(A)​

however in this position F is no longer equal to Ts. Instead​

Ts = F / cos(A)​

as such we get​

W * cos(A) * a = Ts * cos(A) * b => Ts = W * a / b​

​

So indeed the force acting on a string is _the same at every angle_. Right? Right? Well, see point #2​

2) regarding practicality of what happens on an actual Stringway machine

As you can see from the figure on the right above the Ts = W * a / b is true _only as long as the force Ts acting on the string is in the direction level with the ground_.​

But unfortunately that only happens when arm a is level with the ground. On the actual Stringway machine the point where the racket's grommet ends up being is fixed. As such the direction that the force Ts acting (which is along the direction CG where the string is clamped (point C) to the grommet (point G)) changes as the arm position changes. That is unlike in a 'normal' dropdown machine where that Ts force is always along the same direction. In addition, with Concorde lift contraption that direction changes significantly.​

​

As such the actual force pulling the string ends up being as follows in various practical situations:​

1. arm a is level, with Concorde lift: set tension=48.54 actual tension=49.23. Admittedly that is not that significant of a difference between 48.54 and 49.23, but still.
2. arm a is at 30degrees vs ground, no Concorde lift: set tension=48.54 actual tension=49.69. this is (49.69 - 48.54) / 48.54 = 2.4% difference, which is not too bad still
3. arm a is at 30degrees vs ground, with Concorde lift: set tension=48.54 actual tension=57.59. this is (57.59 - 48.54) / 48.54 = 18.6% difference which is rather significant

for the interested see the derivation of those numbers below.​

*************************************************************************************************************************************************************************************************

Gory details on how the numbers are derived:

• confirmation of Ts = W * a / b when arm a is level, no Concorde lift

using sample numbers given the values from the drawings we have:​

W = 10, a=100, b=20.6 when a is level we have​

10 * 100 = Ts * 20.6 => Ts = 48.54​

when a is at 30 degree angle we have:​

W' = W * cos(30) = 10 * 0.866 = 8.66​

8.66 * 100 = 20.6 * F => F = 42.04​

Ts = F / cos(30) = 42.04 / 0.866 = 48.54​

• arm a is level, with Concorde lift

Judging from various pictures it seems that with Concorde lift the direction the force Ts is acting is about 9.5 degrees vs the level. With that, even when arm a is level, that direction is _not_ level. Based on the drawing on the left we have:​

Tsc = Ts / cos(9.5) = 49.23 where Tsc is the tension acting on a string when the racket is lifted​

Admittedly that is not that significant of a difference between 48.54 and 49.23, but still.​

• arm a is at 30degrees vs ground, no Concorde lift:

However the machine is very 'sensitive' to the change of angle of arm a. When the arm a is at 30 degrees vs the level, and the frame is lifted by Concorde, we have:​

with Concorde frame is raised. The distance L is L=d*sin(9.5)=13.23 where d is the distance from the pivot point to where the grommet is along the line level to the ground. Given the scaling of the drawing d is about 80.17.​

​

from basic trigonometry we have:​

b=b'+b"​

d=d'+d"​

d"=b*sin(A) = 20.6 * 0.5 = 10.3 => d' = d - d" = 80.17 - 10.3 = 69.87​

b'= b * cos(A) = 20.6 * 0.866 = 17.84 => b" = b - b' = 20.6 - 17.84 = 2.76​

tan(B) = b" / d' = 2.76 / 69.87 = 0.0395 => B = 2.262​

​

Ts' = F / cos(A+B) = 42.04 / cos(32.262) = 42.04 / 0.846 = 49.69 this is the tension force acting on the string when arm a is at 30 degree angle and racket is NOT lifted by Concorde.​

this is (49.69 - 48.54) / 48.54 = 2.4% difference, which is not too bad still​

​

• arm a is at 30degrees vs ground, with Concorde lift:

with Concorde frame is raised by angle C where​

tan(C) = (L+b")/d' = (13.23+2.76) / 69.87 = 0.2289 => C= 12.89​

Tsc' = F / cos(A+C) = 42.04 / cos (30 + 12.89) = 42.04 / cos(39.5) = 42.04 / 0.73 = 57.59 this is the tension force acting on the string when arm a is at 30 degree angle and racket is lifted by Concorde.​

(57.59 - 48.54) / 48.54 = 18.6% difference which is rather significant. It is actually so significant that it makes we wonder if that entire analysis is correct. In practice it means that when you 'think' you are pulling 48.54 of tension you are actually pulling 57.59 of tension. Granted, only some of the strings are pulled while the racket is lifted by Concorde. One can also notice that when racket is lifted by Concorde there's additional friction against the grommet (due to the string being pulled at an angle) so the fact that the machine is pulling at a greater force in that state is a 'good thing'. However estimating the actual 'contribution' of that friction is entirely different story altogether. At the very least it would vary depending on the strings properties anyway, so the 'true' tension that would be acting on a string within the frame (i.e. between the grommets) would vary.​

 

[fritzhimself]

@Stringway Official - thank you for a corrected drawing. Let's use that picture as a basis for analysis. This is not for the faint of heart, I fully realize they may not be too many readers left by the end of this post

Here are two drawings illustrating the forces in question, figure on the left when the arm is level, and figure on the right when the arm is at an angle. the formulas work for any angle, for the purpose of having practical numbers I've assumed the angle is 30 degrees. The drawing is to scale.

It should be obvious that your formulas given here https://tt.tennis-warehouse.com/index.php?threads/stringway-–-information-–-questions-–-answers.673819/post-14435668 are incorrect. What you actually want as a proof of " the tension is the same for every angle" is the following.
From the torque equality equation:
W * a = F * b where
W - dropdown weight in direction perpendicular to arm a
a - distance from pivot point p to the center of weight (we are assuming that the arm itself is weightless). This never changes no matter what the angle is
F - Force applied perpendicular to b
b - distance from pivot point p to where force F is applied. This never changes no matter what the angle is

when arm a is level W is the actual dropdown weight, and F is actual Tension force acting on a string. As such we have:
W * a = Ts * b => Ts = W * a / b

when arm a is at angle A we have:
W' * a = F * b where W' = W * cos(A)
however in this position F is no longer equal to Ts. Instead
Ts = F / cos(A)
as such we get
W * cos(A) * a = Ts * cos(A) * b => Ts = W * a / b

using sample numbers given the values from the drawings we have:
W = 10, a=100, b=20.6 when a is level we have
10 * 100 = Ts * 20.6 => Ts = 48.54
when a is at 30 degree angle we have:
W' = W * cos(30) = 10 * 0.866 = 8.66
8.66 * 100 = 20.6 * F => F = 42.04
Ts = F / cos(30) = 42.04 / 0.866 = 48.54

So indeed the force acting on a string is _the same at every angle_. Right? Right?

Well, almost. As you can see from the figure on the right that is true _only as long as the force Ts acting on the string is in the direction level with the ground_.
But unfortunately that is _never_ the case in practice. On the actual Stringway machine the point where the racket's grommet ends up being is fixed. As such the direction that the force Ts acting (which is along the direction CG where the string is clamped (point C) to the grommet (point G)) changes as the arm position changes. That is unlike in a 'normal' dropdown machine where that Ts force is always along the same direction. In addition, with Concorde lift contraption that direction changes significantly.

Judging from various pictures it seems that with Concorde lift the direction the force Ts is acting is about 9.5 degrees vs the level. With that, even when arm a is level, that direction is _not_ level. Based on the drawing on the left we have:
Tsc = Ts / cos(9.5) = 49.23 where Tsc is the tension acting on a string when the racket is lifted
Admittedly that is not that significant of a difference between 48.54 and 49.23, but still.

However the machine is very 'sensitive' to the change of angle of arm a. When the arm a is at 30 degrees vs the level, and the frame is lifted by Concorde, we have:
with Concorde frame is raised. The distance L is:
L=d*sin(9.5)=13.23 where d is the distance from the pivot point to where the grommet is along the line level to the ground. Given the scaling of the drawing d is about 80.17.

from basic trigonometry we have:
b=b'+b"
d=d'+d"
d"=b*sin(A) = 20.6 * 0.5 = 10.3 => d' = d - d" = 80.17 - 10.3 = 69.87
b'= b * cos(A) = 20.6 * 0.866 = 17.84 => b" = b - b' = 20.6 - 17.84 = 2.76
tan(B) = b" / d' = 2.76 / 69.87 = 0.0395 => B = 2.262

Ts' = F / cos(A+B) = 42.04 / cos(32.262) = 42.04 / 0.846 = 49.69 this is the tension force acting on the string when arm a is at 30 degree angle and racket is NOT lifted by Concorde.
this is (49.69 - 48.54) / 48.54 = 2.4% difference, which is not too bad still

with Concorde frame is raised by angle C where
tan(C) = (L+b")/d' = (13.23+2.76) / 69.87 = 0.2289 => C= 12.89
Tsc' = F / cos(A+C) = 42.04 / cos (30 + 12.89) = 42.04 / cos(39.5) = 42.04 / 0.73 = 57.59 this is the tension force acting on the string when arm a is at 30 degree angle and racket is lifted by Concorde.
(57.59 - 48.54) / 48.54 = 18.6% difference which is rather significant. It is actually so significant that it makes we wonder if that entire analysis is correct. In practice it means that when you 'think' you are pulling 48.54 of tension you are actually pulling 57.59 of tension. Granted, only some of the strings are pulled while the racket is lifted by Concorde. One can also notice that when racket is lifted by Concorde there's additional friction against the grommet (due to the string being pulled at an angle) so the fact that the machine is pulling at a greater force in that state is a 'good thing'. However estimating the actual 'contribution' of that friction is entirely different story altogether. At the very least it would vary depending on the strings properties anyway, so the 'true' tension that would be acting on a string within the frame (i.e. between the grommets) would vary.

................wowowowoowow - what does your doctor say -are the pills off?

 

[Stringway Official]

@kmn
I really admire your dedication to this subject, but my question is the following:
I worked more than 20 years as a development engineer on the Dutch nuclear centre.
With most developments there was a cooperation between “calculators and development engineers ”. I learned that the practical end result is always a compromise between the practical solutions and the theory. That resulted in rule: “The practical test is always right”.
Is this something you subscribe or do you think that products have to work according to the theory for 100 %?
In other words: Do you work as a practical engineer or mathematician?

Concerning our tension system: The inaccuracy of +/- 1 % of the end test of our tension systems is a very satisfying practical result.

 

[villis]

practical end result is always a compromise between the practical solutions and the theory

I can ensure you that a mechanical system as simple as a stringing machine works 100% according to theory. There was no need to post a flawed theory (wrong diagram) and now there is no need to feel offended. There is no problem with this diagram on your website.

The inaccuracy of +/- 1 % of the end test of our tension systems is a very satisfying practical result.

Very well.. So - 1% error is also drop weitht lever 8° off from horizontal. I think it is obvious that maintaining 8° accuracy of lever angle is not an issue. So only advantage of your drop weight system is a certain degree of convenience.
That is not all, even your website if full of questionable and outright misleading statements.

The biggest drawback of a ratchet system is that the stringer has to maintain the tension in the string “by hand” while the lever is lifted for the next stroke

Whoever wrote this, does not know what "ratchet system" is. You simply lift the lever up, and ratchet mechanism (not stringer by hand as your website claims) keeps tension.

The tension depends upon the angle, because “H” is different for every angle while “R” remains the same.

Yes, and even 8° error will yield a "very satisfying" result.

(For Stringway machine) The tension is the same for every angle, because the distance”V” and the distance “H” both change and therefore the ratio between “V” and “H” remains the same.

Conveniently forgot to mention that this is true ONLY if the pull angle of string does not change (stays horizontal on the diagram on your website). Any change of pull angle from horizontal (like if using Concorde system), will result in same error as error in positioning weight lever for traditional drop weight system.
Also, conveniently forgot to mention that while "traditional drop weight system" is sensitive to lever angle, it is NOT sensitive to change of pull angle, unlike Stringway system.

 

[Stringway Official]

Very well.. So - 1% error is also drop weitht lever 8° off from horizontal. I think it is obvious that maintaining 8° accuracy of lever angle is not an issue. So only advantage of your drop weight system is a certain degree of convenience.

The angle with the horizontal in our test rig is much bigger than plus or minus 8 degrees resulting in the 1 % inaccuracy.

 

[villis]

The angle with the horizontal in our test rig is much bigger than plus or minus 8 degrees resulting in the 1 % inaccuracy.

So?
8° change of pull angle in your test rig will cause the SAME 1% error as 8% change of lever angle in "traditional" drop weight. You have traded one error for another error that you are pretending that you do not have.
But you are changing pull angle every time when using the Concorde system, and having this error!!! Traditional drop weigh does not have error from changing pull angle, and traditional design is as it is NOT because they didn't know better, unlike what the Stringway website is trying to imply.

 

[AceyMan]

Both the drawing and the equations seem to be somewhat questionable.

LOL, someone doesn't understand something so ... that means it's incorrect ,.

 

[jmnk]

................wowowowoowow - what does your doctor say -are the pills off?

writing about physics related to tennis _is_ my pills....

 

[jmnk]

@kmn
I really admire your dedication to this subject, but my question is the following:
I worked more than 20 years as a development engineer on the Dutch nuclear centre.
With most developments there was a cooperation between “calculators and development engineers ”. I learned that the practical end result is always a compromise between the practical solutions and the theory. That resulted in rule: “The practical test is always right”.
Is this something you subscribe or do you think that products have to work according to the theory for 100 %?
In other words: Do you work as a practical engineer or mathematician?

Concerning our tension system: The inaccuracy of +/- 1 % of the end test of our tension systems is a very satisfying practical result.

@Stringway Official - I'm an engineer. There's hardly any math here, these are relatively basic machines physics wise (although they are actually fairly cool and complex mechanical wise).

As far as "The practical test is always right”. When the practical results are significantly different from theory then either theory or tests are incorrect. I do not actually own Stringway machine so I cannot try to replicate your tests. But anyone familiar with physics can try to derive theory. It is certainly possible that my analysis is somehow incorrect. In fact I was hoping that you would try to point out where the mistakes are.

Again, my intention is not to discredit your product in any way. They look like solid machines. The foot operated one, the one with the spring - that looks really cool. That is why I contacted you privately at first hoping that my questioning would perhaps make you re-do the analysis and maybe post some corrections. It would be one thing if you said 'the measurements results show that the tension is the same for every angle - and I can't explain why'. But instead you keep posting incorrect drawings, and incorrect formulas.

 

[jmnk]

LOL, someone doesn't understand something so ... that means it's incorrect ,.

@AceyMan - if you read through my posts in this thread and still think I do not understand the principle here then I do not know what to tell you. Perhaps you could point out where I'm wrong with my analysis.

 

[Stringway Official]

@villis

8° change of pull angle in your test rig will cause the SAME 1% error as 8% change of lever angle in "traditional" drop weight.

Pfff it is probably my Dutch English that makes simple statements so difficult to understand.

The inaccuracy in the test rig is smaller than 1 % for angles with the horizontal of much bigger than 8 degrees.

 

[villis]

The inaccuracy in the test rig is smaller than 1 % for angles with the horizontal of much bigger than 8 degrees.

What are you talking about? You can not have string pull angle 8degrees from horizontal (horizontal for your machine as drawn in diagram) and error less than 1%.
In your machine you of course can have weight lever at any angle, that is how ANY lever works, not only your machine. As I said, you have traded one source of error (weight lever angle) for another equally large source of error (pull angle).
It worked well without Concorde system, as pull angle was constant and there was indeed an advantage from your system. Now with Concorde system, claiming this constant pull advantage is a bit ridiculous.

 

[Stringway Official]

What are you talking about? You can not have string pull angle 8degrees from horizontal (horizontal for your machine as drawn in diagram) and error less than 1%.

@villis
I am afraid we are talking about different angles concerning the 8 degrees:
You are talking about the pull angel of the string and the horizontal I am talking about the angle of the weight lever and the horizontal in the test rig.

And we already explained that the friction with Concorde system is not zero but low because of the pull angle.

 

[villis]

I am afraid we are talking about different angles

Yes of course, except those are not “different”, those are simply angles on other side of lever, and are as important as angles on weigh side.If you are discussing a lever system, of course have to look on both sides, otherwise it may only be useful for a commercial.

 

[Stringway Official]

Every now and then we get the question: “How do the cross stringers work?”
I hope that this video answers most of the questions, if not let me know:

 

[eagle]

Every now and then we get the question: “How do the cross stringers work?”
I hope that this video answers most of the questions, if not let me know:

Love my Cross Stringer. Thank you for creating it.

 

[Stringway Official]

@tennis in Hawaii
Good to hear this.
We are both happy then because we love to create things.

 

[villis]

Interesting, using Stringway machine with electronic tensioner. Is that an option, is it possible to buy a Stringway machine without drop-weight mechanism and mount for say 2086 head?
Thanks.

Every now and then we get the question: “How do the cross stringers work?”
I hope that this video answers most of the questions, if not let me know:

 

[Stringway Official]

Interesting, using Stringway machine with electronic tensioner. Is that an option, is it possible to buy a Stringway machine without drop-weight mechanism and mount for say 2086 head?

Sure we can supply the SW machine without the tensioner. The supplier of the Wise head should deliver the adaptor though.
Question can be: What advantage do you expect to get for so much extra money?

 

[onehandbh]

Love my Cross Stringer. Thank you for creating it.

It looks like it cannot be used for the last few cross strings near the throat. Is that true? Those are the hardest ones for me to weave.

 

[Stringway Official]

It looks like it cannot be used for the last few cross strings near the throat. Is that true? Those are the hardest ones for me to weave.

That is a quite true but it depends on the way you work:
- When you pre-weave the last crosses you can do more.

 

[Irvin]

That is a quite true but it depends on the way you work:
- When you pre-weave the last crosses you can do more.

Pre-weaving the last cross using a cross string tool? I’d like to see that video do you have one?

 

[USMC-615]

It looks like it cannot be used for the last few cross strings near the throat. Is that true? Those are the hardest ones for me to weave.

That is a quite true but it depends on the way you work:
- When you pre-weave the last crosses you can do more.

A friend of mine has both sizes of the Stringway cross stringing tools and I've tried both and they absolutely work as intended...pretty good concept behind the device. And yes, the last few weaves are difficult for the tool from what my buddy said...I only used it throughout several of the middle crosses and works like a champ there.

 

[Stringway Official]

Pre-weaving the last cross using a cross string tool? I’d like to see that video do you have one?

@Irvin
Hi Irvin
No we do not have video because we do not advise it. We experimented with it in order to see if it is a good idea. I think that is more complicated than weaving the last 2 or 3 without the tool.

 

[jmnk]

Last week we got this question from a Stringlab 2 user: My customer wants to know the RA value of his squash racquet.
The difference between the Stringlab test and the RA test is that the ST2 measures from ‘0’ upwards and the RA test from 100 downwards.

The ST2 can measure the stiffness of a badminton racquet which is 1 – 1,5 kg/cm and the Squash racquest, measured by the Customer, are 3,52 to 2,95 kg/cm.

When we use this conversion table there is no usefull RA value for these stiffnesses.
Therefore we are looking for some one who really measured squash racquets on his RDC or RA system.

@Stringway Official - regarding that chart. I do not have Babolat RDC machine - so perhaps there's something I do not quite understand. But on all videos showing people measuring racket flex the RDC machine shows RA value in natural numbers only. There's no decimal ever. Your chart maps Stringlab 2 values to RDC RA values that have decimal precision. How did you manage to get such precision out of RDC machine?

 

[Stringway Official]

@Stringway Official - regarding that chart. I do not have Babolat RDC machine - so perhaps there's something I do not quite understand. But on all videos showing people measuring racket flex the RDC machine shows RA value in natural numbers only. There's no decimal ever. Your chart maps Stringlab 2 values to RDC RA values that have decimal precision. How did you manage to get such precision out of RDC machine?

@jmnk
The graph is coming out of an Excel sheet.
This sheet works with the formula RA=(100- 151,8/Sf)

The formula is based on the fact that the RA value is measured from 100 downwards which was the way the old RA tester works.
Sf is the stiffness in kg/cm,
151,8 is the constant calculated from measurements done on the Stringlab and the RDC
IF there is interest I can make an English version of the Excel.

 

[jmnk]

The graph is coming out of an Excel sheet.
This sheet works with the formula RA=(100- 151,8/Sf)

The formula is based on the fact that the RA value is measured from 100 downwards which was the way the old RA tester works.
Sf is the stiffness in kg/cm,
151,8 is the constant calculated from measurements done on the Stringlab and the RDC
IF there is interest I can make an English version of the Excel.

Thank you. I for one would be very interested in those "measurements done on the Stringlab and the RDC", and the spreadsheet. If you don't mind sharing I would really appreciate it.

 

[Stringway Official]

Hereby the link to download the Excel sheet.
Stringlab2 -RDC frame stiffness

http://www.stringway-nl.com/pdf/Stringlab-RDC-ERT-ENG.xlsx

If there are questions just let me know.

 

[jmnk]

Hereby the link to download the Excel sheet.
Stringlab2 -RDC frame stiffness

http://www.stringway-nl.com/pdf/Stringlab-RDC-ERT-ENG.xlsx

If there are questions just let me know.

many thx!
Maybe converting from Excel to google sheets messed up something, so I apologize in advance. When I open the spreadsheet it shows:
three tabs - but there's data only in the first tab. I'm assuming that is OK, right?
I'm assuming columns B, C, D, and E show stringbed dynamic stiffness values as measured using respective tool, right?
and columns I and J show frame stiffness as measured by stringlab2 and RDC machines respectively, correct? And I'm assuming these frame stiffness values are for strung rackets, correct?

 

[Stringway Official]

Yes you are right no info on tab 2 and 3.
To make it easier for others it should look like this.

All racquets were strung.

 

[Stringway Official]

We updated the dollar / euro rate for the US market.
We did not realize that the change is so big

 

[Stringway Official]

We received a question about the bending stress mentioned on this picture, therefore an explanation:

The narrow supports of many 6-point mountings cause 2 problems for the racquet:
- The racquet is bent around the support by the tensions of the main strings.
- The pressure between the racquet and the centre supports is huge because of the small service. This may cause damage of the racquet.

t would be a great improvement if suppliers of these mounting systems would provide a “load spreader” which lowers both the pressure and the bending stress. Like those supplied for badminton racquets.

This speader could look like our Babolat retainer.

 

[Stringway Official]

Stringway clamp overhaul.

We received an order for a fixed clamp for the T92 system.
This is quite exceptional because not much can go wrong with these clamps.
In 90 % of the cases a simple overhaul of the clamp is enough to let it work “as new” again.

This document describes this overhaul
http://www.stringway-nl.com/pdf/EN/STRINGWAY-CLAMP-OVERHAUL.pdf

 

[Dags]

The narrow supports of many 6-point mountings cause 2 problems for the racquet:
- The racquet is bent around the support by the tensions of the main strings.
- The pressure between the racquet and the centre supports is huge because of the small service. This often causes a damaged spot on the racquet.

I honestly think that nonsense like this harms your brand. Where are all these damaged racquets? This statement would have us believe that the mounting system used by every major brand is deeply flawed and that damaging racquets is rife. Real world evidence very clearly shows otherwise.

That resulted in rule: “The practical test is always right”.

Just my opinion of course, but when someone makes extreme statements that have no credibility, it makes it difficult to take much else they say seriously.

 

[Stringway Official]

I honestly think that nonsense like this harms your brand. Where are all these damaged racquets?

IMO You can proof that this is a problem in 3 ways:
1. By logical thinking:
The main strings cause a total force on the racquet of the tension multiplied by the number mains. Even on low tensions of 40 lbs this is a total of 640 lbs with 16 mains. Most of this force should be "supplied" by the 6 and 12 o'clock mounts.
So the pressure between the racquet and the support per square millimeter is huge.

2. Because load spreaders are supplied to prevent this problem

6 and 12:00 load spreader

Do any of you run a load spreader like you see on the bay? I have a 6 point machine. I see it for mostly badminton but I only do tennis racquets right now.

tt.tennis-warehouse.com

Mike Cottrill/Gaines: Apex and load spreader pictures??

Some images were posted to this forum a while back showing the installation of load spreaders on an Alpha Apex. Unfortunately, the links to those images in the old threads are now broken. Mike/Gaines, is it possible for you to repost those images?

tt.tennis-warehouse.com

This one is for tennis and badminton:

https://www.amazon.com/Baosity-Protector-Stringing-Badminton-Accessories/dp/B07CVJVYV9?th=1&psc=1

3. By googling 12’clock damage of racquets:

Concerning tennis:

Babolat aero team cracked at 12 o'clock

Hi, My friend's son has a babolat aero team racket, there is a small crack on the inside of the frame at 12 o'clock. I wandered if this could have been caused by the support whilst stringing and appeared later. It's difficult to spot but if you remove the grommet you can see it going through the...

tt.tennis-warehouse.com

cracked frame at 12 o'clock

what's the effect of playing with a cracked frame? I mean, i have a pair of head pro lite tours that still play well even though i noticed that there is a crack at the 12 o'clock of each frame. I noticed that the 2 center mains (LM1 & RM1) are a lot looser, but other than that, the stick still...

tt.tennis-warehouse.com

Concerning badminton:

At 900-t Cracked @ 12 O'clock

I have 2 At900-T SP buy at singapore both this 2 racket got crack at 12 O'clock!!!!!!:crying::crying::crying: Anyone got this problem ??

www.badmintoncentral.com

 

[Dags]

I’m also a fan of logical thinking. Some of the possibilities as to why a racquet might crack at 12:

• Contact with a solid surface, such as the court
• Manufacturer defect
• Incorrect technique by the person stringing it
• A fundamental flaw in the design of the mounting system

This is not an exhaustive list. In my experience, contact with a solid surface would equate for almost all of them.

Googling as you suggest results in a handful of forum posts reporting cracked racquets at 12. I read through a few (including those you linked), and there’s no evidence to associate the cracks with the stringing process.

Within tennis, this is a non-issue. Yet you claim that it ‘often’ occurs when trying to justify why you felt the need to be different to every manufacturer in the world. To me, that’s simply fabrication.

 

[USMC-615]

I honestly think that nonsense like this harms your brand. Where are all these damaged racquets? This statement would have us believe that the mounting system used by every major brand is deeply flawed and that damaging racquets is rife. Real world evidence very clearly shows otherwise.

Just my opinion of course, but when someone makes extreme statements that have no credibility, it makes it difficult to take much else they say seriously.

I'm taking my flawed machines listed in my sig and putting 'em in the bass boat tomorrow and sentencing them to a permanent nap in about 40-50 feet of water...might as well leave those turd Wise tensioners on as well. If you want 'em you better come get 'em, or meet me at the boat ramp one.

 

[Stringway Official]

I'm taking my flawed machines listed in my sig and putting 'em in the bass boat tomorrow and sentencing them to a permanent nap in about 40-50 feet of water

I’m also a fan of logical thinking. Some of the possibilities as to why a racquet might crack at 12:
Contact with a solid surface, such as the court
• Manufacturer defect
• Incorrect technique by the person stringing it
• A fundamental flaw in the design of the mounting system

Of course I understand that stringers who have a machine with the narrow centre support deny the problem for their own confidence.

And there are reasons why most stringers do not have to worry about the problem with the 12 oçlock damage nowadays:
- Tensions are much lower than 15 years ago.
- Racquets are much stronger than before.
- Manufacturers enforced the 12 and 6 o’çlock positions in the racquets to avoid damage.

The facts which remain are:
- Load spreaders are not invented without a reason.
- The mechanical load on the centre support is very high at the moment that all the mains are tensioned. This is a much more critical situation for a racquet than during play.

For a mechanical designer this means that he will try to find the solution which causes the lowest stress and pressure in the racquet.

 

[Dags]

Once again, these are your words:

This often causes a damaged spot on the racquet.

They are untrue. A traditional mounting system does not often cause a damaged spot on the racquet.

You've engineered a different support system, well done you. I am not criticising this design. What I am criticising is your marketing strategy: you are peddling a fictitious scenario where your competitors are not only damaging racquets, but doing so 'often'. It's dishonest.

 

[Stringway Official]

“

This often causes a damaged spot on the racquet.”
They are untrue. A traditional mounting system does not often cause a damaged spot on the racquet.

I agree with this because the damage does not happen often anymore because of the stronger racquets and lower tensions.
The reason for my statement is probably that I am living with old experiences. The narrow support caused a lot of damage when it was introduced by Babolat, with the higher tensions and the more vulnerable racquets.
But I agree that this is not todays situation anymore.
I changed the statement in: “This may cause damage of the racquet.”

What I am criticising is your marketing strategy: you are peddling a fictitious scenario where your competitors are not only damaging racquets, but doing so 'often'. It's dishonest.

I can understand this, in my feeling I compare technical solutions and not machine brands. The large number of available load spreaders illustrate that it is better to avoid the high pressure on the racquet?
Or not?

 

[villis]

Or not?

Is it really THAT simple?
If you mount with 3 points that perfectly contact racquet and during the tensioning towers move ~5mm inwards, are you sure you are still contacting racquet at same 3 points at the top? Plus, your racquet is not restricted from expanding sideways (getting wider), this may be a good or not so good thing. From your posts I have an impression that your modeling has been done only for static supports, not supports that move during stringing.

With 6 point mount everything is even more complicated. When towers move inwards, side supports are pushing towards the frame at it's wider part, so it should reduce pressure at centre support. Again, your model appears to be only for static supports. Have you seen any actual pressure measurements with a real racquet?

Regarding load spreaders, if they can sell something they will. Haven't seen any pro stringer using one though. It may very well be that racquet arch is a better load spreader.

P.S. I do not really believe posted results of modeling either. When I did not have any access to the stringing machines, I have strung wooden racquets manually (with a metal pipe as tensioner, stringing as tight as possible, adjusted by pipe diameter) and improvised support at 3 and 9 (worst support ever according to modeling?) and not able to detect any deformation of the racquet or issues after stringing. Later for a short time there were larger racquets with modern shape but made from wood, and those even being very fragile, didn't break during this manual stringing either.

 

[onehandbh]

I've never seem a properly mounted and strung modern racquet on a 2 point mounting system stringer damage a racquet.

Perhaps it was more of an issue with older racquets (and wood racquets). Logical reasoning (and science) would, however, lead me to believe that a 2 pt mount is more stressful on a racquet -- but not enough to damage a modern racquet easily.

 

[Stringway Official]

Hi Villis, thanks for your dedicated reply hereby some more about our thoughts when we designed our 5 point support system:

If you mount with 3 points that perfectly contact racquet and during the tensioning towers move ~5mm inwards, are you sure you are still contacting racquet at same 3 points at the top?

I do not see why the contact between the 3 head support would change during stringing. The principle of the direct support is that they work against the forces of the main strings exactly in the position where these forces pull the frame inwards.

Plus, your racquet is not restricted from expanding sideways (getting wider), this may be a good or not so good thing.

This is a good thing of the direct support:
In words: If the racquet does not get shorter it does not get wider either. So on the perfect direct support there is no widening so no need for outside support.
In the perfect direct support there is a support at every position of string.

The 3 point support with very wide support is a good compromise so that it will fit all racquet shapes.

Mechanically:

This graph shows the stress in an oversize racquet for different support systems. As it shows the stress with 6 point mounting depends strongly on the position of the supports. With 2 and 3 point support the stress can be lower and depends less on the position of the supports

I've never seem a properly mounted and strung modern racquet on a 2 point mounting system stringer damage a racquet.

This is very true, the simple direct support of the old Ektelon with 2 supports at the head and a banana support at the throat never damaged racquets even at high tensions as 72 lbs.

In the next post I will try to explain why the outside support introduce stress in the racquet which is not there at all with direct supports.

 

[fritzhimself]

Hi Villis, thanks for your dedicated reply hereby some more about our thoughts when we designed our 5 point support system:



I do not see why the contact between the 3 head support would change during stringing. The principle of the direct support is that they work against the forces of the main strings exactly in the position where these forces pull the frame inwards.



This is a good thing of the direct support:
In words: If the racquet does not get shorter it does not get wider either. So on the perfect direct support there is no widening so no need for outside support.
In the perfect direct support there is a support at every position of string.

The 3 point support with very wide support is a good compromise so that it will fit all racquet shapes.

Mechanically:

This graph shows the stress in an oversize racquet for different support systems. As it shows the stress with 6 point mounting depends strongly on the position of the supports. With 2 and 3 point support the stress can be lower and depends less on the position of the supports

Oh -oh........just once for explanation!
As I know this graphic, the quoted oversize could be a wide body from the 80's - this type is no longer produced today.
Most have normal frame sizes up to 100 in². It would be time to think about repeating this test with current models.
There I am sure that the graph will look different.
But I still love you dear Fred.

 

[Stringway Official]

Oh -oh........just once for explanation!
As I know this graphic, the quoted oversize could be a wide body from the 80's - this type is no longer produced today.
Most have normal frame sizes up to 100 in². It would be time to think about repeating this test with current models.
There I am sure that the graph will look different.

Yes Fritz you are right for the outside support system, the best position will be closer to the centre than 175 mm for the 100 in^2 frame.

This is exactly the disadvantage of the outside support system; The best position of the outside supports is different for every size of racquet.

That is why it is so bad to string badminton rackets on a "tennis machine" with fixed outside supports.
The graph shows that the tension in the racket gets higher the closer the supports come to 3 and 9 o'clock .

For direct inside supports, the graph for 100 sq in will not be much different than for 110.

 

[villis]

@ Stringway Official

First, I think it is quite safe to assume that discussing mounting systems (excluding the frame) has almost no practical purpose, and it is very likely that your stringer will not string any better than say some Wilson machine, as far as mounting system is concerned. This same also applies to tensioner, it is just a matter of convenience, mostly.
If we can agree on that, then we have to forget the sales pitch and discuss it as a theoretical matter and present better arguments than quotes and diagrams from Stringway website, because those are advertising materials are mostly not true. Need proof?

Most Important Factor of the Stringway Mounting Table: It does not Blend!

Of course it does Bend, which I will assume was the intended spelling. For example in a test of "Stringway ML 100"by RacquetQuest, racquet shortened by 0.439cm with mains only strung at 60 pounds. This is not bad, but in a similar test of Wilson Biardo, racquet shortened 0.279cm with same conditions.

It is very important to understand that minimum deformation during stringing does not mean minimum stress in the racquet material. (Proof needed?)

Oh yes, very needed! Because this is simply not true. There is NO stress without deformation, because absolutely rigid materials do not exist and yes, more stress means more deformation.
Diagrams below this false statement are even more ridiculous, showing a bent beam, pointing at a straight part of it and claiming "no stress at all"!

Given few examples above, I hope you can forgive for also not trusting the posted graph of stress vs. position of support. No idea how the simulation was done and what were the assumptions.

I do not see why the contact between the 3 head support would change during stringing.

See the test result above (4.39mm). If the racquet got shorter, it changed shape. If it changed shape then 3 points on the racquet body will not match between initial shape and changed shape. As a minimum, pressure will be unevenly distributed between 3 points.

If the racquet does not get shorter it does not get wider either.

It may be a Stringway sales advertisement, but in reality it DOES get shorter (see the test) test

This graph shows the stress in an oversize racquet for different support systems.

As I said above, I do not trust such graphs, sorry. It is not clear how the data was obtained, and it is not repeatable, therefore not suitable for a discussion.

Finally, one practical advantage to your internal support that I can see is Head Prestige with it's bumper grommets. External supports tend to somewhat push on the grommet making it more difficult to string.

 

[Stringway Official]

If we can agree on that, then we have to forget the sales pitch and discuss it as a theoretical matter and present better arguments than quotes and diagrams from Stringway website, because those are advertising materials are mostly not true. Need proof?

@villis
I do not agree with this because it is true as long as the situation is not critical and stringing tennis racquets in 2023 is far from critical so nothing goes wrong on any machine. But stringing badminton racquets is a completely different matter with 25 to 30 lbs tension.’
Furthermore I am a mechanical engineer and when all my information is seen as sales promotion because it is on the Stringway website this makes my information useless.

The graph that you doubt about is a computer calculation of the stress in the racquet. We made this when we designed our support.

It is very important to understand that minimum deformation during stringing does not mean minimum stress in the racquet material. (Proof needed?)

With this statement I mean that outside supports create zero deformation but high stress. So zero deformation does not mean zero stress.

Just have a look at this “beam in the wall theory” .
The question is: What support is best for the beam?

I understand that you will doubt this explanation also.