Natural Gut: Dynamic Tension measurement

[amoeba]

I have a racket I strung with 24kg natural gut mains and 22kg poly crosses, a coach used his ERT300 and it came up with 22 DT.

Another I strung at 26/24 came up 24 DT.

The coach thought I had it strung way too low because "you should'nt be able to get the mains to touch each other with your fingers", i.e. he could easily pinch the centre main strings together.

Is this pinch-ability just a characteristic of natural gut, or do I need to worry about my stringing ability/knowledge?

 

[SavvyStringer]

At 57lbs I don't think you should be able to get them together, even with gut.

 

[10shoe]

A real shortage of detail but generally those ERT readings are unusually low if you are talking about:
1. Freshly strung racquets
2. Midsize racquets with standard string patterns.
3. A properly calibrated stringing machine.

For starters, what model racquet?

 

[Technatic]

if you show the data of your racquet we can calculate what it should be with the Tension Advisor and including the type of string that you used.
What are the Length and the width of the stringarea and the number of mains and crosses.

 

[amoeba]

Rackets were a Angell TC105 Tour 16x19, and a Babolat Pure Drive Roddick (2012) 16x19. One was strung 2 months ago, the other ~6 months ago.

I am pretty sure the machine is calibrated correctly, as I have tried it with a weight scale and its pretty much bang on.

 

[fritzhimself]

There are several possibilities. I won't pursue all.
Based on my own experience, I can confirm that the ERT 300 with Gut/Poly Hybrid is not able to determine correct measurement values.
Measurements after 6 months are not to be connected with a cause. If the stringbed stiffness doesn't seem like a hammock to you - then play on.
It could be that your clamps let the string slip imperceptibly. Then you can never come to explainable stringbed stiffness.

 

[uk_skippy]

Those readings seem very low given the time since stringing. I use a gut/poly hybrid at ~22kg and would get a reading of ~ 36DT. Even after 6 months it wouldn't have dropped to 22DT. If you getting readings of 22 & 24DT then the starting tension would seem to be too low.

What machine are you using?

I'd also suggest getting the rqt tested with the DT as soon as you can after restringing. This will give you a base line to work with.

Based on my own experience, I can confirm that the ERT 300 with Gut/Poly Hybrid is not able to determine correct measurement values.
Measurements after 6 months are not to be connected with a cause.

An ERT will give a correct reading, unless its a faulty one. I have no problem using it either on my rqts or at tournaments. An ERT should only be used to get an initial reading, and then used to determine the drop in DT. It shouldn't be used to determine actual tension, this is where it will fall down when checking with the guide disc that is supplied with the ERT.

A measurement after 6 months can indicate an issue when stringing, ie if the DT reading is too low it would show that the initial resting was too low. I have seen this when a customer comes to me with a rqt that has meant to be strung at 55lbs. When I checked the DT it was a lot lower than expected. I restrung the rqt at a lower reference tension, 42lbs in this case, and the DT was several points higher. This would indicate that the original restring was done on a machine that was pulling too low.

 

[fritzhimself]

We have measurements with the Babolat RDC, the Pacific Multitester ERT 300, ERT 700 and ERT1000.
At Hybrid´s the ERT´s fantasy numbers have delivered themselves.
You can measure the data of a ERT´s - but they will never provide data comparable to another measuring system.

 

[uk_skippy]

We have measurements with the Babolat RDC, the Pacific Multitester ERT 300, ERT 700 and ERT1000.
At Hybrid´s the ERT´s fantasy numbers have delivered themselves.
You can measure the data of a ERT´s - but they will never provide data comparable to another measuring system.

I agree that you can't compare the readings from different measuring devices, but that doesn't make the ERT300 wrong. I would also say that it has become the defacto measuring device for DT due to its ease of use, relative cheap price, and compact design.

Any reading should be used only as way to get an initial figure, and then checking the strings loss of DT over time

 

[fritzhimself]

I would also say that it has become the defacto measuring device for DT due to its ease of use, relative cheap price, and compact design.

Basically, I am with you - the ERT delivers good, comprehensible results with single-variety strings. The weak points are hybrids - the system is lying to you.
But as you have already said - you can read off the decline with false readings. But this leaves room for misunderstandings.

 

[uk_skippy]

Basically, I am with you - the ERT delivers good, comprehensible results with single-variety strings. The weak points are hybrids - the system is lying to you.
But as you have already said - you can read off the decline with false readings. But this leaves room for misunderstandings.

If the system gives a reading, whatever that reading is, is the point we take reference from. Since the proper way to use this tool is to take an initial reading and plot future readings from that point, whatever is the actual reading is basically irrelevant. The system isn't lying, its giving a reading based on its interaction with the string during the testing process.

As long as you're comparing apples to apples, there is no issue. Even referring back to the OP, as he has 2 different rqts, the results are likely to be vary given that difference, even if they were strung at the same tension.

I'm assuming you know that even if 2 different string set-ups gave the same DT they would feel different due to string construction, but mention it for those who may not be aware of it.

These test are no more than finding ways to work with arbitory figure/specs and its the same as using the 10cm from the buttcap to get a swingweight reading, and flexing the frame at the throat on an RDC. They give us figures to work with, even if they aren't the best representation of what we're looking for.

 

[bigmatt]

Rackets were a Angell TC105 Tour 16x19, and a Babolat Pure Drive Roddick (2012) 16x19. One was strung 2 months ago, the other ~6 months ago.

I am pretty sure the machine is calibrated correctly, as I have tried it with a weight scale and its pretty much bang on.

If you have string jobs that old, they should be replaced regardless of the DT. What were the readings right after stringing, anyway?

 

[amoeba]

I dont have an ERT300 - was using a coaches. I understand that natural gut does not lose tension like other strings, so having a 6 month old stringjob shouldn't be as big a deal as other strings.

 

[10shoe]

When I see readings as low as the OP mentions my first question to the player is usually: "Do you store your racquets in the trunk of your car?"

 

[jwocky]

[snip]The coach thought I had it strung way too low because "you should'nt be able to get the mains to touch each other with your fingers" [snip]

Two likely explanations:
1. Have you checked for a misweave?
or
2. Perhaps the clamps did not hold when you started mains? However, a couple of really loose string would/should have become apparent
a) if/when tuning the mains before starting crosses, or,
b) when you installed the crosses.

 

[bigmatt]

I dont have an ERT300 - was using a coaches. I understand that natural gut does not lose tension like other strings, so having a 6 month old stringjob shouldn't be as big a deal as other strings.

No matter what kind of string you use, 6 months is forever. If you can find the original DT, it would be a good indicator of how long you can effectively use the strings.

 

[amoeba]

When I see readings as low as the OP mentions my first question to the player is usually: "Do you store your racquets in the trunk of your car?"

Yes, but I am in the UK: we dont get hot weather.[/quote][/quote]

 

[AndI]

My ERT-300 notes related to natural gut:
Racquet: Wilson ProStaff RF97 or RF97A, 16x19.

Natural gut (VS Touch 16), 55 Lbs (Sergetti) DT = 41.5 to 42
Natural gut (VS Touch 16), 52 Lbs (Sergetti) DT = 39 to 40
Natural gut (mains)(VS Touch 16) + Alu Power Rough (crosses) 16L, 55 Lbs (Sergetti) DT = 37 to 38
Natural gut (mains) (Vs Touch 16) + RPM Blast 17, 55 Lbs Sergetti DT = 39 to 40

I may have more notes somewhere, a couple of different tensions and several more racquets and several more gut-based hybrids, but cannot find them right away. They are generally consistent. Your racquet has a larger surface area, so your DTs should be scaled down somewhat, for the same tension.

Readings with ERT-300 are very stable in the center of the racquet. Translation back to target tension using ERT-300 calculator (that cardboard wheel) works best with "Mid", for RF77(A) racquet for gut, and with "Mid Plus" for hybrid.

I do not really care too much how DT translates to tension, I use it (a) to validate that my next stringing job is consistent with the previous ones, and (b) to check if it is time to restring (for me, it is 10% DT drop ideally, 15% max). This usually happens after 5-6 weeks.

You cannot make the mains touch each other with your fingers on a racquet strung to tension in the 50+ Lbs (23+ kg), not a chance, you can barely move them with your fingers. Neither with gut nor with any other string.

DT of 22 to 24 indicates totally dead strings.
Something must be wrong with your puller or clamps. Perhaps they should be tightened.
Did you use a brand name gut?

 

[uk_skippy]

Yes, but I am in the UK: we dont get hot weather.

[/quote][/QUOTE]

You should never leave rqts in car boot/trunk. Heat and Cold will affect the strings.