it is hard to find a lot of tension stabilized data points. mainly because i don't always get to see the client again at the appropriate time after the racket is strung. if i use my own racket, then the sample size will be very small. and also the tension loss is gradual and continuous until the string snaps, it is hard to pin point exactly the equivalent moment in the decay curve to measure the frequency. right after stringing is more reliable imho.
[QUOTE =kwun;2048344]sorry. as these are clients' rackets, they are measure right after stringing. [/QUOTE] Nooooooooo! That's too bad... as the frequency will drop another 50-100 Hz after stringing before stabilizing.
Sorry, kwun but I've seen the frequency drop 50 Hz 1 hr after stringing, then another 50 Hz after 1 day, then another 50 Hz over the next few days before plateauing... all this without playing with it! For consistency and repeatability purposes, I'd much rather measure at the plateau phase (even though there is still a slight gradual decay from playing and string creep) than the initial steep drop phase where a few hours make a huge difference.
i assume you have seen these graphs from a previous thread: this is the thread: http://www.badmintoncentral.com/for...tension-last-Here-is-the-answer-(maybe)/page2 yes. it does look like it plateaus, but if you look at the (first) plateau, it is not flat, even over time, it is still dropping. assuming unused, it will eventually stop, but we do use the racket and each time used it will get a big bump down. the question then is where do we sample our data point?
i think ideally yes, we should let it sit for a week or so and measure where it eventually plateaus. but that's unpractical as we can only get many data points if we use clients' rackets and most clients won't wait around for so long.
@kwun Yes, thanks for pulling that graph up... that was the one I was thinking about. So, as you see, I'd much rather have quality data points, than quantity. I believe that since frequency is a reflection of tension, then some time must be given to allow it to stabilize before we can have any meaningful measurements. After all, tension (and our indirect measurement of it) will affect how the string performs in repulsion, power, touch, control, so we want to make it as reproducible as possible from person to person across the world.
i agree on quality over quantity. but i have doubts on the exact condition required to achieve that quality. as you can see from the graph i obtained through an actual racket, with 70 hours of stringing, the tension/frequency seems to have settled on around 1135Hz level. at this state, there are no external force acting on the racket. so it will eventually reach the equilibrium point of ~1135Hz. however, at around 70 hours, i brought the racket to the gym, now with all the hitting, external forces (stretching) on the strings forced the string into another equilibrium point around 1110Hz. i don't believe the racket will reach the 1110Hz equilibrium point if i hadn't brought the racket to play. it would've stayed at around 1135Hz for quite a few weeks. it may reach 1110Hz if left around for months. i suspect so because the internal tension force is not strong enough to shift the equilibrium quickly. so what's my point? my point is that we must standardize on how long the racket may stay and whether we should allow it to be played. if we really do want it to plateau, i believe we must leave it unplayed otherwise it will reach a different equilibrium/plateau that is not equivalent to the one when we leave the racket unplayed. so my suggestion is if we do want it to plateau, leave it for N number of days. we can pick what N would be.
SW35 with BG80 @29lbs: 1197 Hz, strung @Yonex German Open with EsPro, measurement at 6-8 hours after stringjob.
[MENTION=1]kwun[/MENTION] 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.
I measured using Carltune My Victor BS12 with VS-850 is at 1040 Hz @ 6 Octave. It was strung digitally 6 month ago @ 23 lbs by an experienced stringer. My Yonex Nanospeed 200 with BG-66 is at 1000 Hz @ 5 Octave. It was strung digitally 1.5 years ago @ 23 lbs by the same stringer. Octave should be mentioned. That Nanospeed is a full octave lower.
Thanx SSSSNT. Your 6 months old vs850 correlates to my 1015 Hz vt80 with the same string at 24 lbs after 1yr. And after whacking some plastic birds it dropped further to 980 Hz. Plastic birds are really murder on strings!
Don't worry about the octave thing... its just a designation for piano tuning. Just look at the frequency.
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.
@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.
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.
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?
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.
