Thread: Stringbed frequency to monitor string tension

1. Originally Posted by visor
@kwun

Looking at your graph, anytime after 24h is reasonably stable enough to start measuring.

Of course I understand once the racket starts to be used, there will be some gradual 10-15 Hz drop after each session but this will also eventually stabilize after several sessions. Well at least Zymax strings behave that way due to their excellent tension retention properties.
it depends on why we are collecting the data and what type of understanding we are trying to reach from the data.

in order to make any observation using the data as a whole, we need to collect them in a similar manner. if we know that playing with the string will move the stabilized point, we should avoid lumping the used and unused data into the same bucket.

it does look like that after a bit more than 24 hours, the string tension do stabilize. so i think it ok to do that, given that the racket is unused.

so my suggestion would be collect the data both right after stringing and after 24 hours. this will be meaningful coz it will tell us if some stringer's stringjob loses tension faster than another.

it would also be useful to compare, with the same stringer/racket/tension, how different string loses tension differently.

2. @kwun

Interesting points...

A few thoughts:

For the average player like me who don't string ourselves, there are a few goals I had in mind when I first started the thread.

1. To have a general consensus as to what a stringbed with a certain string at a specified tension should feel and sound like, as measured by the stringbed frequency, assuming that this correlates well with tension. (And I think you've shown that it does, at least within the 20-30 lbs range of tension that we're interested in.)

2. Why? It's because when someone says that they're playing with 26 lbs tension, it may not mean 26 lbs to me, especially if their stringer does a lousy job or uses an uncallibrated crank machine. So, when they ping it and get a frequency way lower than the general average for that string at that tension, then we'll both know why.

3. To monitor the tension fall off with use over time, so that as a player we can understand where our individual optimal tensions are, especially in regards to power and feel of the stringbed. Personally for me, once my stringbed drops more than 50 Hz from my stablized optimal, I lose both power and touch, and then it's time to cut the string. (The only few times I didn't have to cut the string was when I was using zm62 at more than 23 lbs, and we all know why... )

4. The first 24 hrs data: the average player who doesn't string their own won't be able to measure as they'll probably pick up their rackets at least a day or 2 after it's strung. And for a stringer, they're too busy stringing other rackets (making money ) rather than to spend more time measuring frequency decays every few hours on the numerous rackets they string.

5. Re how different strings lose tension differently, I think most of us know at least anecdotally or from experience the two extremes, ie. zymax strings vs. bg65/vs850. Hence, all the other strings fall within that range. One problem though is that the variation in power shots (ie. hard smashes, clears, etc) between different players' styles can affect how the rate of tension loss. And it'll be difficult to take this variable into account.
Last edited by visor; 03-04-2013 at 01:49 AM.

3. i think we are starting to converge to an agreed goal and procedure here.

1./2. totally on that. too many machines and stringers/flows and they all produce different "25lbs". there are a few standard apps on smartphones which allows players to check their tension.

3. agree.

4. that's a good point. as a stringer i have access to earlier data than my customers on their rackets. so the 24hr+ data is more realistic one for players to obtain and that's what they will see. however, from a technical point of view though, that's a decayed data. so if i string something 25lbs, give it to my customer in 24 hours, technically it is not 25lbs anymore. but that's the way it is.

5. agreed also.

it seems that we need to do some more detailed investigation for our understanding purpose and to further the goal of this whole exercise.

1. we need to characterize different strings and how their tension decay over time. we need more data points than just 0hr + 24hrs. perhaps every 2 hours so we can get a feel of how each type of string lose tension over time.

2. we need to standardize on the number data points to gather. obviously we cannot have all. some of us are stringers, and some of us have or do not have data point of the racket after it is being used. so we will end up with sparse data, but it should still be valuable.

i have some rackets in the pipeline to be strung and i have downloaded a frequency tuning apps for my phone which seems to work pretty well on testing so i can definitely help data gathering.

4. Awesome kwun. We're counting on you to help generate some data!

5. If you guys are looking at time-lapsed data, won't you also need to take into account things like consistent weather conditions that actually vary from place to place as much as 20C or more?

6. Originally Posted by cobalt
If you guys are looking at time elapsed data, won't you also need to take into account things like consistent weather conditions that actually vary from place to place as much as 20C or more?
I knew someone was going to bring that up. I had been thinking about that.

Most stringers string at a comfortable room temp, say 18-25C. Most homes are around that too, which is when we do the measurements. And most places that we play at are also in that range, with the exception of Malaysia, Singapore, Se Asia where it can go up over 30C.

Nevertheless we need to check out the significance of temp on frequency(tension).

@kwun
Has a frequency vs temperature graph been done before?
If not, I guess one of us will have to do one...preferably from 0 to 30C.
Last edited by visor; 03-04-2013 at 09:36 PM.

7. Originally Posted by visor
I knew someone was going to bring that up. I had been thinking about that.

Most stringers string at a comfortable room temp, say 18-25C. Most homes are around that too, which is when we do the measurements. And most places that we play at are also in that range, with the exception of Malaysia, Singapore, Se Asia where it can go up over 30C.

Nevertheless we need to check out the significance of temp on frequency(tension).

@kwun
Has a frequency vs temperature graph been done before?
If not, I guess one of us will have to do one...preferably from 0 to 30C.
there are theories. but actual measurements?

it is hard to do.

1. where to find a environment where we can achieve such temperature variation? we need some sort of temperature controllable oven / fridge.

2. how to do the experiment so it is fair? hard to describe but let me describe this scenario. if i string a racket at 25lbs at 30C. i move it to 0C. we know that will increase the tension. and then afterwards, we move it back to 30C. will it still be at 25lbs? the increase in tension will more effectively stretch the string and modify it's property. so how is it possible to make such measurement? do we start cold? start hot? start somewhere in the middle?

8. imho, temperature is a orthogonal variable to this experiment / data gathering. as long as we keep the temperature relatively close, ie. the racket is strung in Canada and used in Canada, strung in Singapore and used in Singapore. then it will be good enough.

the temperature experiment can be done independent of this experiment and will take a lot more thoughts to plan it in such a way to make it reliable and accurate.

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Yes agreed. we must indicate the countries when we post the data. So that members who are living in a country with the same weather condition should be able to use that data as a reference.

10. Originally Posted by kwun
there are theories. but actual measurements?

it is hard to do.

1. where to find a environment where we can achieve such temperature variation? we need some sort of temperature controllable oven / fridge.

2. how to do the experiment so it is fair? hard to describe but let me describe this scenario. if i string a racket at 25lbs at 30C. i move it to 0C. we know that will increase the tension. and then afterwards, we move it back to 30C. will it still be at 25lbs? the increase in tension will more effectively stretch the string and modify it's property. so how is it possible to make such measurement? do we start cold? start hot? start somewhere in the middle?
Just did a simple test re temp vs freq... racket (RKEP XP70 with zm62 at 22x23lbs) was placed indoor and outdoor for at least 2 hours before measuring.

1077 Hz at 20C
1075 Hz at 5C
1077 Hz at 20C again

Does that make sense? So there is no difference, and even so, the freq dropped with lower temp, meaning that the string loosened instead of contracting? Huh? I would have expected the freq to rise with lower temp due to string contraction...

In any case, if there's not much significant freq difference with a 15C drop, then can we safely assume there won't be much difference going in the other direction, with a 15C rise? Anyone in Malaysia/Singapore want to measure that?

Hmmm... I should also test vs850 tomorrow night.
Last edited by visor; 03-05-2013 at 12:58 AM.

11. The string probably didn't loosen as much as the metal on the frame would have contracted...

A lot of places in Malaysia/Singapore/Indonesia etc etc do away with air conditioning (or limited a/c) so the temperature is probably consitently above 25C... prolly 30C in some places. Now, if a racquet was strung at say 26/28 and remained at the same temperature for a couple of days, would it return a significantly different frequency to one (same racquet preferably) strung at 26/28 in say, Edmonton in winter?

12. Originally Posted by cobalt
The string probably didn't loosen as much as the metal on the frame would have contracted...

A lot of places in Malaysia/Singapore/Indonesia etc etc do away with air conditioning (or limited a/c) so the temperature is probably consitently above 25C... prolly 30C in some places. Now, if a racquet was strung at say 26/28 and remained at the same temperature for a couple of days, would it return a significantly different frequency to one (same racquet preferably) strung at 26/28 in say, Edmonton in winter?
Last time I checked my racket frame is not made of metal. Perhaps you're still using an old Yonex B500.

But in any case, the frame whether metal or graphite is a closed loop of an oval... there's no room for it to expand or contract. In other words, the surface area remains the same, whether it's hot or cold, whether it's under 36 lb tension or 0 lb tension.

Now your second part is where I want people with accurate tensions to provide their frequency readings from all over the world, at different temperatures. My guess is within 15-35C, there's not much difference...
Last edited by visor; 03-05-2013 at 02:17 AM.

13. Nanomeasure would leave nothing to chance! Who are you, imposter???!!! What have you done with Nanomeasure!!!

14. Originally Posted by cobalt
Nanomeasure would leave nothing to chance! Who are you, imposter???!!! What have you done with Nanomeasure!!!
Wait... I'm working on something in the head wt thread...

15. Originally Posted by visor
But in any case, the frame whether metal or graphite is a closed loop of an oval... there's no room for it to expand or contract. In other words, the surface area remains the same, whether it's hot or cold, whether it's under 36 lb tension or 0 lb tension.
i have to disagree. the head will expand and contract under heat/cold and result in a bigger/smaller oval.

16. the temperature experiment is interesting and reveals something that we didn't take into account and that's the expansion and contraction of the frame due to temperature. if the rate of expansion and contraction of the frame is similar to the string, then there is nothing to worry about. however, it looks like the rate of contraction is actually higher on the frame resulting in a almost negligible change in the observed frequency.

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There is a lot of good info and insight here. I also notice the relationship between the frequency droppage vs time elapsed after stringing. It seems to me that there is few consensus among our observations.

1. Frequency loss is the greatest during the 1 week. It will stabilize after 1 week if unused.
2. Frequency loss will further deepen with use even after 1 week.
3. Factors such as strings, stringers, temperature, humidity may play a role in affecting frequency loss but it is hard to quantify at the post with our scale or set up.

If the object of this exercise is to fine the best tension for our string, one can ignore all other factors and just focus on the frequency. It is best to test your new tension after 1 week when it is stabilized and test it again after use. Or, use the Carltune the measure the frequency of the racquet at the session that you feel you have the best tension. Use the frequency to determine the tension you need to achieve and the time you need to wait for it to achieve that frequency.

For example, for your racquet and string, you best frequency is 1000 Hz. The string will achieve that 1000 Hz at 24lbs after 1 week OR at 26 lbs after 1 week and 1 or 2 session of play. Then we should only judge our play with the same frequency every time to find any subtle differences with other changes in our game (etc, changing to a different string).

This may explain the psychological feelings that new string is better only the 1 week and it degrades after 1 or 2 sessions. Just measure the frequency to confirm.

Use the frequency as a guide can give us an objective measurement and tell us if the 2 racquets are identical in tension even if they are stringed by different stringers, machine, etc. (ie. if they have the same frequency)

By keeping the one factor constant (frequency/tension) stable, it enables us to perform a better judgment if we are going to alter any other part (ie. racquet, string type) in our equipment.

I won't be surprised if Yonex engineers also possessed a complete data for all the strings.

Hope this helps.

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