A picture speaks a thousand words.
Since I did not take any pics in my previous post (link), I snapped some while re-stringing my ProKennex Black Ace 98 with synthetic gut recently.
Below measurement was after the mains were done.
To reduce parallax error, some pics were taken from directly above the inside hoop. It spans from 1.0 cm to 26.1 cm, yielding an internal hoop width of 25.1 cm. Note the crosses were unfilled.
Here's how it looked after the crosses were completed. Racket still mounted.
From 1.0 cm to 25.4 cm, it's now 24.4 cm. The hoop narrowed 0.7 cm after the crosses were done.
The unstrung internal hoop width was 24.5 cm for this racket. So it's a 1 mm distortion.
As I mentioned in my previous post (link), my belief is no mounting would completely stop the frame from distorting. It serves more as a guide than "locking down" the hoop.
Choosing an appropriate combination of strings, tension and stringing method should take greater emphasis.
A few keen on purchasing their own stringing machines asked me the importance of 2-points mounts versus 6-points.
As with anything else, it always seem the more the better, right?
However, my experience appears otherwise.
Thinking back, I have had many rackets done by others on high-end 6-points mount stringing machines. Yet frame distortion happened. (link)
When tensioning the mains at 50 lbs on a 16 mains racket, the total stress adds up to 800 lbs (16 x 50). Each end of the racket, at 12 and 6 o'clock respectively, would be subjected to a total of 400 lbs of direct pulling force compressing the hoop together.
In my younger days, I often sat on the hoop of tennis rackets with the handle butt on the floor. None cracked. So I have good faith in my racket's construction.
But looking at the mounting posts of ANY stringing machine, can anyone believe that those posts are capable of supporting 400 lbs each?
When stringing mains, hoops often shorten from 12 to 6 o'clock and widen between 3 and 9. When the crosses were strung, the 3 and 9 often narrows back and lengthens 12 to 6 again. I saw that happen and measured it multiple times.
Moreover, other than the mounts at 12 and 6, the other 4 "mounts" are merely supporting arms not fastened to the hoop. So it functioned more like a "safety guide", to prevent the hoop from changing its shape excessively before the crosses are done.
There have also been reports of over-tightened mountings at 12 and 6 causing lots of racket squeaks during tensioning. A few experienced cracks and believed it was due to the over-tightened mounts not allowing the hoop to flex freely.
That said, I am still satisfied with my 2-points mount. YMMV!
A reader of this blog named "F" contacted me regarding my post on stringing machines (link).
F was totally intrigued by what I claimed to be significant differences in playability between stringing machines. He wanted the truth and suggested a "Myth Busters" experiment at his expense.
The plan was simple. He owns several matched rackets. He will get one strung by someone with an electronic machine and one on my dropweight.
To prevent any string biasness, he bought three packets of the same synthetic gut from the commercial stringer. One was used to string his racket electronically.
The second pack was given to me to string his other racket at the same tension and same stringing pattern (ie. 2 piece with exact tie-off holes)
After measuring the tension (by frequencies) of both stringbeds, we proceeded to hit some balls at the tennis court. Three of F's tennis partners (about ntrp 5.0 players) joined us and played with the unmarked rackets. Each had exactly 5 minutes. Only F and me knew the differences. The others were kept totally in the dark.
Unanimously, all expressed a strong preference for the dropweight strung racket. The three friends even thought the electronically strung racket had dead, old and stale strings!!!
The differences all of us felt most significant were:
1. stringbed liveliness,
2. power, and
3. spin
String tension was measured after every 30 minutes of play for 2 hours. After the session, the strings were cut out, preserving several long continuous pieces intact from the same spot in both rackets. Specifically, the centre 6 mains and between crosses 6-12.
Elasticity of the four lengths of strings were tested by holding them under tension at 50 lbs in the dropweight.
Here's our findings:
Initial String Tension
- The electronically strung racket registered a frequency about 58hz higher, translating to about 6 lbs tighter.
After Play String Tension
- At 30, 60, 90 and 120 minutes of continuous play, the dropweight strung racket (orange line) lost much less tension than the other racket (blue line). The rate of tension loss also stabilized after about an hour whereas the electronically strung continued losing tension even at 120 minutes of play.
Elasticity Test
- Both pieces from the electronically strung racket lost a lot more elasticity.
- Both dropweight strung pieces of string stretched about 2.3% more than the other string.
- The full stretch was recovered when tension was released for all the strings.
As far as F and his partners are concerned, they have found their answers.
Note:
Since this test could affect someone's livelihood, no details nor pictures were posted. Neither would any questions concerning the racket, string brand or electronic machine be answered.
I get asked very often why didn't I "upgrade" my stringing machine (link) to an electronic model. Why struggle with manual tensioning, flipping that tension arm up and down dozens of times per racket?
My answers are dualfold.
First, I am not a commercial stringer and have little interest stringing for other people. In fact, I do not even enjoy stringing rackets except for my own frames.
Second, dropweight machines are incredibly accurate, reliable and consistent. Among the three types of stringing machines (dropweights, cranks and electronics), dropweights are the most reliable and accurate.
Hard to believe? After all, electronic tensioners have been around for decades! Surely the technology is developed, proven and stable? Moreover, all the professional tour players' rackets are tensioned electronically!
Or I must be comparing the dropweight with some cheapo, DIY home-made electronic tensioner designed by some third world country's technology?
Nope!
Read for yourself:
http://tt.tennis-warehouse.com/showthread.php?t=394502
http://tt.tennis-warehouse.com/showthread.php?t=309117
http://tt.tennis-warehouse.com/showthread.php?t=298995
http://tt.tennis-warehouse.com/showthread.php?t=201369
http://tt.tennis-warehouse.com/showthread.php?t=413893&page=2
http://tt.tennis-warehouse.com/showthread.php?p=6930240
http://tt.tennis-warehouse.com/showthread.php?t=452572&page=3
http://tt.tennis-warehouse.com/showthread.php?t=323567
http://tt.tennis-warehouse.com/showthread.php?t=441450
Very few people know about the tension overshoot problem with many electronic tensioners. Since all strings have elasticity, the tensioner would keep adjusting to try to maintain constant tension.
The repeated over-pulling and over-releasing either "kills" the playability of the string or causes a very loose stringbed, depending on when the strings are clamped.
Observe the stringer when you next pass by his shop. Watch and listen to the electronic tensioner head "zipping" back and forth continuously when the tension button is pressed. The problem is worsened if the pull speed is set to fastest.
So far, I only know of a few electronic machines that does not have the overshoot problem:
1. Wilson Baiardo
2. Babolat Star 4
3. Yonex ES-5
If you have only played with rackets strung electronically, try the exact same string at the same tension strung using the same stringing pattern with a dropweight!
Feel the difference. The strings will play livelier, softer and last much longer too!
My experience with crank and electronic machines are shallow. I have owned neither. And I was using them to help the owner string rackets in return for his tutelage.
Day in day out, I was repeating the same thing on different rackets with different strings at different tensions. I did not get to try anything special or any out-of-the-world stringing methods.
So why did I settle on the Klippermate, which is merely a low-tech and manual dropweight?
I have been blessed with good hands that allowed me to pick up quite a few crafts. In my late teens, I was already taught how to strip down a vehicle engine completely for overhaul and then reinstall it.
While I was staying at a rented house, I developed "green fingers" and learnt to trim bushes, prune plants and cook my favourite foods.
Every now and then, I help my friends fix their bicycles, changing freewheels and aligning crank bearings. And re-wiring some electronic circuits was as familiar to me as spine-aligning a golf shaft.
I must thank the master mechanic that exposed me to such "hand" craft. His favourite question was "If your car breaks down in the desert, and you have no access to parts or tools other than what's available in the trunk, what are you going to do?"
What he was insinuating, was that our knowledge and our hands far exceed what tools can do for us. He taught me to think out of the box.
So, the reason for the simple dropweight is, I believe that the stringer matters more than the stringing machine. Plus, that thing is built like a tank. There are very few parts that can break down easily. Even regular calibration is not needed! Unless gravity changes of course!
Another lesser known reason is no over-tensioning. Almost all crank machines over-tensions the string before dropping off back below the poundage intended.
In other words, to string a racket at 60 lbs on a crank usually means "cranking" the string at about 65 lbs and after the crank "locks" in place, the tension drops to about 55 lbs or less.
Some electronic stringing machines suffer this problem too. Especially when impatient stringers set the pull speed to fastest. It over-tensions about 5-10% but will settle back to the intended tension since it is a "constant-pull". A good and consistent electronic tensioner does not come cheap. And neither are all expensive electronic models accurate.
Ultimately, it is up to the stringer or player to determine if the string is damaged by this "over-stretch". Is playability or durability compromised?
A few of my playing partners and myself can definitely feel the difference.
