ERT 300 Tennis Computer
- Thread starter shug
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graycrait
Legend
@fritzhimself , Thanks. I had pretty much given up on caring except one has to start somewhere with a reference tension and was wondering about the value of more gadgets. For me it is just easier to stick to 3 strings that work and cut them out after a couple of on court sessions, except for Ash Kev x ZX which I play till it breaks.
lol - yeah, i am very good at pressing the button on the new ERT300 and turn the spring for the String meter... lol@esm - nope.....you are that good....
fritzhimself
Professional
@graycrait
Yes, I'm right there with you. You notice it anyway when the string becomes blunt.
My small test setup with the massive rebuilt vise is actually ONLY to reflect the relaxation of the poly. This is a string that has been pulled umpteen times and not a new one.
There the relaxation would be even more clearly to see.
The trapezoidal thread of the vise does not yield.
This only simulates what happens after clamping in the frame after a few seconds and the clamps stand tight without bending.
As I said, the developers and manufacturers of these measuring instruments know exactly what is happening inside.
Yes, I'm right there with you. You notice it anyway when the string becomes blunt.
My small test setup with the massive rebuilt vise is actually ONLY to reflect the relaxation of the poly. This is a string that has been pulled umpteen times and not a new one.
There the relaxation would be even more clearly to see.
The trapezoidal thread of the vise does not yield.
This only simulates what happens after clamping in the frame after a few seconds and the clamps stand tight without bending.
As I said, the developers and manufacturers of these measuring instruments know exactly what is happening inside.
MathieuR
Hall of Fame
This shows, even using a multitime stretched string, that fast stringers are "soft stringers" (compared with stringers using same ref.tension on an eCP or dropweight that give the string more time to relax before they clamp).
@fritzhimself , do you think the StringLab2 also "just gives a number", or can you compare this with a RDC?
I still plan to make a graph showing the dependency of the DT in relation with the depth of the "impression" of the disc. In theory you could then calculate the "bal-impression" with different ball-velocities.
Rabbit
G.O.A.T.
Wrong. A fast stringer on a lock out would clamp fast as well thereby nullifying the "relaxation" of the polyester string. It has been discussed ad nauseum that if you want a lock out to replicate an eCP you should bump up the reference tension. (Find your number.) Drop weights with flying clamps do not produce as consistent results as lock outs with fixed clamps.
Nice try, Don Quixote..... You really should learn a new song.
MathieuR
Hall of Fame
You are giving me a strawman fallacy. You should read what I wrote.
You have it wrong.
Nobody should read what you wrote!
fritzhimself
Professional
This is wrong or half the truth - no matter how you tension the string, relaxation begins immediately after you clamp the string.
Sorry -I can't say, we haven't made that direct comparison.
MathieuR
Hall of Fame
Relaxation begins immediately after you tension the string (not after clamping).
Just take this example: re-tention with a lockout same string, using same ref.tension. This is "comparable" with clamping on an eCP "blitzschnell/extreme-fast", or giving it some time before clamping.
Edit: I used "your" word relaxation. I should have used Permanent Elongation; kicks in immediately when tensioning the string.
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fritzhimself
Professional
................has translated my program wrong - yes that's what I meant!
Lockout vs. ECP......but you can't compare apples with oranges.
What should come out of it - the SBS will be different - that is obvious to everyone.
But it may also be related to the better clamps and a more stable turntable of a high-quality ECP machine.
Crazydoc
New User
What good is this test without knowing the different elasticity behaviour of each string? Basically, a string is a more or less progressive spring. The progressivity also depends on the tension weight or, if you want, on the DT value. Simply put, you can have two strings that have the same DT value at a certain deflection, but are no longer the same at twice the deflection. The only thing that would really help would be to know what power a player is able to generate at the point of impact. Then you would have to find a string that is exactly in the player's comfort zone at a certain tension weight. I imagine that would be a bit time-consuming......
Regards
Rabbit
G.O.A.T.
Just a thought here....if everybody else is telling you that you are wrong, do you think maybe, just maybe you are? If everybody else is tired of continually hearing how good your mechanism (I didn't want to say Stringway) is, do you think maybe the message is worn out? Do you think possibly you could contribute something new?
MathieuR
Hall of Fame
All my postings in this thread had NOTHING to do with Stringway! (Just mentioned the StringLab2 as it is a DT measuring device)
Just forget your bias, and read what I wrote!
Rabbit
G.O.A.T.
My post was a comment as to the general tenor of your catalog of posts. You continually say the same thing regardless of whether or not you mention STRINGWAY.
Read what I wrote!
Crazydoc
New User
The real question is what exactly the DT value should be.
If you follow the common descriptions, it would be the force needed to push a tennis ball-sized object into the sweet spot of a racket by 1 cm.
But if you look at the devices available on the market, there is a bit of trickery everywhere:
The Stringlab presses the string bed in by a few mm with an approx. 12.6 cm² disc, measures a force and calculates something higher.
All frequency-based devices measure the resonance frequency of the string bed (Rackettune, etc.) and approximate themselves with the help of some parameters or by self-excitation (ERT). The values are then expressed, extrapolated and displayed as a credible kg or DT value.
However, all these methods have one thing in common, namely that it is possible to make comparisons of exactly one racket with exactly one string and thus to check its stringing work.
Some devices are more established and, in my opinion, often wrongly set the standard for all things.
Regards
If you follow the common descriptions, it would be the force needed to push a tennis ball-sized object into the sweet spot of a racket by 1 cm.
But if you look at the devices available on the market, there is a bit of trickery everywhere:
The Stringlab presses the string bed in by a few mm with an approx. 12.6 cm² disc, measures a force and calculates something higher.
All frequency-based devices measure the resonance frequency of the string bed (Rackettune, etc.) and approximate themselves with the help of some parameters or by self-excitation (ERT). The values are then expressed, extrapolated and displayed as a credible kg or DT value.
However, all these methods have one thing in common, namely that it is possible to make comparisons of exactly one racket with exactly one string and thus to check its stringing work.
Some devices are more established and, in my opinion, often wrongly set the standard for all things.
Regards
MathieuR
Hall of Fame
I used to use the StringLab2. Now I use a ERT700. It is especially usefull when I string a "new" string in a frame. It is easier to adjust to the "standard" DT of 34 that I use for most clients as a starting point. (My clients don't give me kilo's, I decide for them).
The ERT700 consistently gives me a DT "StringLab2 minus one".
Now that I think of it I'm mighty confused about what ERT device is actually 'measuring'. It looks like ERT and racquetTune app are similar - but they are actually not.
racquetTune measures vibration frequency of the stringbed. Then, based on physics theory plus some experiments by the author to tweak the constants of the theoretical formula (that is derived for ideal membrane) to better reflect a practical tennis racket, the app calculates what the average string tension is. And _then_, taking into consideration user provided racket head size and string pattern, it also calculates 'dynamic stiffness' of the stringbed. The app can calculate it as there's a relation between string tension, string pattern, racket head size and dynamic stiffness. While obviously some simplifications and assumptions are made that all is based on solid physics principles.
Now ERT also measures frequency of the stringbed. But what happens next is sort of opposite of what racquetTune does. ERT shows 'dynamic stiffness' value and _not_ string tension value. How can that be? There's no way to tell what the dynamic stiffness is from the frequency _alone_. Then ERT provides that disk where _you_ enter ERT-shown dynamic stiffness value to get the string tension that stiffness corresponds to (there are three string tension values shown by that disk - one per each range of racket head size. Plus there's a note that string tension 'deviations may occur based on string material' - which is very true, and it makes this whole disk thingy not that useful).
So - what magic does ERT use to figure out 'dynamic stiffness' of the stringbed based the frequency of vibrating strings alone??
racquetTune measures vibration frequency of the stringbed. Then, based on physics theory plus some experiments by the author to tweak the constants of the theoretical formula (that is derived for ideal membrane) to better reflect a practical tennis racket, the app calculates what the average string tension is. And _then_, taking into consideration user provided racket head size and string pattern, it also calculates 'dynamic stiffness' of the stringbed. The app can calculate it as there's a relation between string tension, string pattern, racket head size and dynamic stiffness. While obviously some simplifications and assumptions are made that all is based on solid physics principles.
Now ERT also measures frequency of the stringbed. But what happens next is sort of opposite of what racquetTune does. ERT shows 'dynamic stiffness' value and _not_ string tension value. How can that be? There's no way to tell what the dynamic stiffness is from the frequency _alone_. Then ERT provides that disk where _you_ enter ERT-shown dynamic stiffness value to get the string tension that stiffness corresponds to (there are three string tension values shown by that disk - one per each range of racket head size. Plus there's a note that string tension 'deviations may occur based on string material' - which is very true, and it makes this whole disk thingy not that useful).
So - what magic does ERT use to figure out 'dynamic stiffness' of the stringbed based the frequency of vibrating strings alone??
Crazydoc
New User
The Ert has always measured frequency, just not displayed it until now.
The displayed string tension is always a fictitious value. Nobody would have anything to gain from setting 25 kp on the machine and then measuring 17 kp. This would confuse more than it helps, even if it would be physically better
I think the expectations of such devices are a little too exaggerated.
Basically, the DT value as described above is a fictitious value. What unit does the DT value have?
......befor someone now throws N/mm or something similar into the room, I would like to ask you to consider that, as far as I know, there is actually no device that measures this value by pressing the string bed in by 1cm (definition point is 1cm). In order to arrive at the tension weight of a string by measuring the frequency of the string membrane, approximations and some parameters are necessary. Practically speaking, this is too complicated and not really necessary for the intended use of such devices. I find the interpretation to be able to compare strings or string properties with such devices as the Ert to be a false fallacy. However, such devices are always good for checking one's stringing work.
Alternatively, you can simply note down the frequency of the string bed of a racket with exactly one string. There is no comparison with other setups possible, but it would be enough to check your work if you just want to know if everything worked as it did last time.
regards
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read the above posts.
i am starting to think why did i bother with the new ERT300, as the DT value and its disc will give me 2 figures, but at the end of the day, what do they tell me, if (lets say, for myself) i always use the same type of string and use the same machine and same method, then i should be golden as long as i keep the consistency, which at my rec level, i have been prior the arrival of he new ERT300, anyway.
same for others - keep the same consistency, but it may vary if i am asked to use different string(s)/tension(s).
i think it will make some one look good with one, whether it is on the tennis court or next to his/her stringing machine... but who really knows?!?
anyone one heard anything/read any reviews from the ones promoting it and/or he stringers at tennis events?
anyway.... all i got from my wife was her rolling her eyes when i showed her my new ERT300... lol
i am starting to think why did i bother with the new ERT300, as the DT value and its disc will give me 2 figures, but at the end of the day, what do they tell me, if (lets say, for myself) i always use the same type of string and use the same machine and same method, then i should be golden as long as i keep the consistency, which at my rec level, i have been prior the arrival of he new ERT300, anyway.
same for others - keep the same consistency, but it may vary if i am asked to use different string(s)/tension(s).
i think it will make some one look good with one, whether it is on the tennis court or next to his/her stringing machine... but who really knows?!?
anyone one heard anything/read any reviews from the ones promoting it and/or he stringers at tennis events?
anyway.... all i got from my wife was her rolling her eyes when i showed her my new ERT300... lol
not sure what you mean. I agree it always _measured_ frequency but the device does not _show_ measured frequency. It shows 'dynamic tension' value. At least that is what the manual says that number is.
https://www.sportinngerritsen.nl/media/wysiwyg/ERT_300_quick_guide_en.pdf
the strung tension value shown by racquetTune is _not_ a fictitious value. It is an approximate value of an actual averaged string tension. The value shown by ERT may indeed be fictitious as there's no way it can be a correct (or even approximated) 'dynamic tension' - which is my entire point.
That I fully agree with. Whether the value shown by racquetTune or ERT has any practical usefulness - we can certainly debate that. But at least racquetTune value has a theoretical meaning based on physics. The value shown by ERT does not.Nobody would have anything to gain from setting 25 kp on the machine and then measuring 17 kp. This would confuse more than it helps, even if it would be physically better
I think the expectations of such devices are a little too exaggerated.
Dynamic Tension has a fairly established meaning. The unit is N/mm or kg/cm. You do not need a device that presses a string bed by exactly 1cm to get that value. Just like you do not need to measure the speed of a car for an hour to get 'miles per hour' value. You _do_ need to understand that because dynamic tension is not linear vs the applied force, for the tennis racket stringbed measurement you should use pressing force similar to what is commonly encountered when you hit a tennis ball.Basically, the DT value as described above is a fictitious value. What unit does the DT value have?
FWIW, ERT is, in my experience, much more repeatable.
In that sense, I'd call it more "accurate" for the common user.
When i had one, it kicked out numbers that i expected over time.
I gave up on racquet tune early on, just too subject to too many variables
for me to bother with. The ERT is just to simple to use.
ERT may not be TRULY "accurate", but in the hands of a single user it's prime for
what is.
In that sense, I'd call it more "accurate" for the common user.
When i had one, it kicked out numbers that i expected over time.
I gave up on racquet tune early on, just too subject to too many variables
for me to bother with. The ERT is just to simple to use.
ERT may not be TRULY "accurate", but in the hands of a single user it's prime for
what is.
the point is that ERT claims to show what 'dynamic tension' of the strung racket is. By measuring vibration frequency of the string bed, and (presumably) doing some sort of calculations to get DT from that frequency. _but it is theoretically impossible to do so_. It is as if one measured the distance a runner covered and claimed that runner was running at 2 miles per hour _without knowing how long it took a runner to cover that measured distance_.
admittedly _my_ point only
. I'm saying that it is theoretically impossible for ERT to show a number that is a 'dynamic tension' of the stringbed. As such ERT manual is basically incorrect (i.e. it is lying). Whatever this number is
- it is _not_ a dynamic tension of a sringbed.
Crazydoc
New User
https://www.sportinngerritsen.nl/media/wysiwyg/ERT_300_quick_guide_en.pdf
Sorry translation error. I meant that it measures frequency and then outputs a calculated value
Agree.
That is a matter of opinion. Of course, you don't have to push the stringbed in 1cm. But it would be better. The reason for this is the different behaviour of the string mixtures. The N/mm curve is not linear. It may be that two strings with the same density have a different elasticity behaviour. This means that two such strings may have the same value at the measuring point, but not when pressed in by 1 cm.
shug
Rookie
My reference tension (showing on my constant pull stringing machine) 77 lbs, however it seems, my dynamic tension (ERT 300) is coming up as 79+ lbs (sometimes beyond the ERT300 range). Video will be posted this weekend. I contacted the company, and we both agreed, this is due to the hyper-tension I use in my personal racquets.
Another racquet I strung at 54 lbs reference tension registered at 54 Dynamic Tension with the ERT 300.
Another racquet I strung at 54 lbs reference tension registered at 54 Dynamic Tension with the ERT 300.
MathieuR
Hall of Fame
This is a coincidence. When you use a higher ref.tension, the DT will be higher. But DT equal to ref.tension....
Just think of using same ref.tension in a 95sq.i. frame, and a 110 sq.i frame. The latter will have a lower DT.
When i had mine, my rackets strung NG/Poly at 60/56......my ERT showed high 30's, the expected range as i recall. Maybe as high as 41? it's been awhile, i recall 34 was too low.
Rabbit
G.O.A.T.
@struggle I think @shug may be referring to the final number after using the handy dandy wheel ERT provides. I take it all back to this: you send a racket into be strung you get it back. You use the ERT to verify that the result you received was the same result as other string jobs. I do not, nor have I ever, seen the DT number as an absolute. It is merely a guide to consistency in results.
Ok, if that's a translation via the wheel, makes sense i reckon...
I remember reading that the average player can't cipher plus or minus 5 pounds, so a 10 pound range.
from their requested/preferred/normal reference tension. Seems plausible to me, i played my frames from
35-40 or so DT with no ill effects until they dropped to low.
I hear you on jaberwocky, but the numbers are real, repeatable and relative....so the unit can be useful.
We mostly agree on these gadgets, and we both sold them, haha!!
Rabbit
G.O.A.T.
Don't disagree one bit. I think that it is in the application of those numbers that most folks on here miss the mark. I owned one and liked it. I sold it because I found myself paying more attention to it than my strokes.
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So I checked one of the GPros yesterday with the new ERT300. Same Angell Halo Multi string as my other racquets.
placed the ERT at the centre (10th cross down), the DT was 38.
placed at the top of the string bed (12 o’clock), the DT was 45
placed at the sides of the string bed (3/9 o’clock), the DT was 51.
I thought it was a fun exercise. Lol
placed the ERT at the centre (10th cross down), the DT was 38.
placed at the top of the string bed (12 o’clock), the DT was 45
placed at the sides of the string bed (3/9 o’clock), the DT was 51.
I thought it was a fun exercise. Lol
David at Unholy Rackets
New User
I have just received my ERT300, so I was very interested to read this thread. I quite agree that the actual tension of string in a racket will not be the tension at which the stringer pulled that string. However, all other things being equal (and the relevant things are equal, I would argue) the actual tension will bear a constant relationship to the pulled tension (constant, but not necessarily linear). If you ask for a new car to be delivered in red, and it turns up painted blue, you will have good reason to be dissatisfied: if you ask for your racket to be strung at 55lbs, whether you are dissatisfied depends on how it feels when you play with it. And if you have always had your rackets strung at 55lbs (instruction to stringer) and you have always been satisfied with the result, then you are unlikely to be dissatisfied. You will think that the string tension in the racket you are happily playing with is 55lbs: of course we know (and you may also, vaguely) that it is not 55lbs because of tension loss and other factors - but that doesn't matter. The important thing is that you like the feel of a racket that you asked the stringer to string at 55lbs. Your green car, on the other hand, does not satisfy, because you know it is not red and the colour it is is what you either like or don't like. If tension showed as string colour (there's an interesting idea, by the way: a string that changed colour according to its tension) and you asked for red but it came as blue you would not be happy. If you happened to know that a string at 55lbs tension was red, you might ask for red string and be dissatisfied when it arrived in blue. As it is you can't tell from appearance what the tension is.
fritzhimself
Professional
This is also the reason why I always refer to the tractive force as a reference.
However, this does not mean that all machines and stringers will have the same result.
However, this does not mean that all machines and stringers will have the same result.
David at Unholy Rackets
New User
I suggest that it doesn't matter what the ERT (or any other similar device) actually measures as long as it is intuitively something that varies as the string tension varies. You can then measure the DT (or whatever you want to call it) and record that figure together with the tension that the strings were pulled. Do this for every string job and you build up a database of DT vs tension measurements: you can group these by string brand/material/gauge etc and by racket model (as detailed or as lumped-together as you wish) which you can use to gauge the tension drop in a stringbed since it was strung, if you know what tension it was strung at.
ClownCar96
Semi-Pro
ERT 300 back in stock as of this morning FYI
