Category Archives: Distortion

String Tension Testers…Friend or Foe?

The StringMeter is a device used to check the tension of an individual string. There are other versions of similar functionality, but this is what we use, and I will start with that.

Interestingly, this device traces its design to a tool that is used to check mainstay tension on a sailing vessel.

It is clear that our devices are well used, so they must be a “friend,” not a “foe”! And to that, I would say yes! The two (2) units shown here are “calibrated” units. One device is “free string,” and the other is “strung string.” These are different scales and very important for accurate information.

String Tension Tester

When we evaluate string or stringing machines, one of the most important values is the string tension with only the main strings installed. Using the “free string” scale, we check every main string and record the number.

Once the racquet is fully strung, we can check some center main strings and center cross strings with the “strung string” scale and see the variation. The difference between the two is the “natural ratio” of the racquet.

In addition to the stringing machine review use of the StringMeter, we also use it to calculate our “accuracy index.”

For this, we use the “strung string” scale and check each main string tension from left to right and every cross string tension from top to bottom and compare the actual numbers to the calculated numbers based on a non-distorted racquet. This spreadsheet shows how accurately the ball will come off of the racquet face.

The “efficiency index” tells us how much the racquet needs to change shape to reach that “index.”  

These are all essential functions of the StringMeter and String Tension Tester from Gamma Sports.

But, what if the StringMeter or other device is used without knowing what it is telling the user?

This is the “foe” part!

This would be the case if a customer with such a device has a racquet strung at say a reference tension of 55 pounds. The customer then uses the method to check the tension and finds that it is not 55 pounds or even close! The customer is not going to be happy!

If the customer knows what to do, they can check the main string tension as soon as they can after stringing, then, later on, to see how much the string has stretched without regard to the reference tension.

It is what it is!

When the racquet is no longer performing it would tell the customer how much the tension can deteriorate before stringing is required.

So, these devices are very useful for individual string tension but no so much for “string bed stiffness,” which is the total string bed as a ball impacts it.

We will look at some of the “string bed stiffness” devices in a future post.

 

 

Head Graphene 360+ Prestige Tour

When we do the testing and “number taking” for our demo racquets, we try to think as the consumer may think and include comments that may help the consumer make the best decision.

We do not want to make these posts so dull that you go to sleep, but data is essential, so we are going to include it…so stay awake!

Data is particularly relevant to the Prestige Series from Head.

This review is for the Prestige Tour, and it points to the differences between Prestige racquets that may go unnoticed or misunderstood.

The Prestige Tour is a 99 (645 cm²)square inch racquet with an 18 x 19 string pattern. If you have read the post on the Prestige MP, you may wonder, what’s the difference?

You may notice that the Prestige Tour has one (1) fewer cross string. Not a big deal. You may see that the Prestige Tour has one (1) square inch larger head size. Also, not a big deal. What you may not notice is the Prestige Tour has an in-plane stiffness of 400, and the Prestige MP has an in-plane stiffness of 359. That is a big deal! Even with a bigger head and fewer strings, the Prestige Tour has a higher string bed stiffness than the Prestige MP. The higher the in-plane stiffness, the less the racquet will “bend” during impact.

The Prestige Tour is more stiff overall (62 v 58) than the Prestige MP, and the 21.5mm beam contributes to that stiffness.

So, take a look at the numbers for this racquet to see if you can find other exciting differences!

 

 

 

ManufacturerHead
Racquet ModelHead Graphene 360+ Prestige Tour
Reference Tension55 lbs - 24.9 kg
String
Victrex PEEK fiber Experimental 7718
Machine UsedTrue Tension Professional
Static
ASPS, RDC55
ASPS, FlexFour71
Racquet Flex, RDC62 - After stringing
Racquet Flex, FlexFour49
Weight, Grams325
Weight, Ounces11.46

Balance, mm327
Balance, Inch12.87
Length, Cm68.6
Length, Inch27.008
Head Width9.56
Head Length13.12
Head Area, cm2635.3
Head Area, Sq. Inch98.5
Beam Width, mm, Shaft, Center, Tip21.5, 21.5, 21.5
In Plane Stiffness, Pounds/In400.0 Lbs/In.
In Plane Stiffness, Kg/cm181.4 Kg/cm
Number of Main Strings18
Number of Cross Strings19
Ratio Cross/Mains.690
Main String Grid7.81
Cross String Grid10.00
Density (% of head filled with string).724
Average Cross String Space.526
Average Main String Space.396
Dynamic
Dynamic Tension, Kp, ERT35
Dynamic Tension, Lbs/in195.7
First Moment, Nm.819
Polar Moment334
Torsional Stability18
Swing Weight, Kg/cm2316
Swing Weight, Ounces11.15
Swing Weight Calculated347.5
Power, RDC46
Control, RDC55
Manueverability, RDC76
Power, Calculated 1929.2
Head Points4.88 (negative = head heavy)
Head Weight, %47.7%
Center of Percussion20.8
Dwell Time, ms, No Swing8.58
Efective Stiffness - lbs29.1
K, Lb/In (SBS) RDC176.3
Recoil Weight150.9
Twist Weight222.7
End Weight 131.7
Tip Weight 195.3
9 O'Clock100.7
3 O'Clock101.4
Butt Cap124.0