Summer Holiday Closure: August 2 to August 10, 2008

Web orders will be processed by August 12

1. Silent Partner Electronic Stringing Machines
• The Silent Partner JIVE
• The Silent Partner DG
• The Silent Partner ARIA
• The Silent Partner OPUS
2. Silent Partner Manual Stringing Machines
• The Silent Partner SWING
• The Silent Partner HIP HOP
• The Silent Partner CRUMP
• The Silent Partner JAZZ
• The Silent Partner MAESTRO
• Accessories for racquet stringing machines
3. Frequently Asked Questions about Racquet Stringing Machines
4. Stringing Tutorial
• Getting Ready for Stringing
• Mounting the Racquet on the stringing machine
• Patterns and How to Interpret them
• Lacing and Tensioning Main Strings on a Stringing Machine
• Weaving and Tensioning Cross Strings on a Stringing Machine
• Tensioning Strings with a Stringing Machine
• Tying Knots
5. Ordering a stringing machine in the United States and Canada
6. Warranties
7. International Orders for stringing machines
8. Bargain Basement (Demo stringing machines for sale)

 1)  What is a "drop weight" stringing machine?

A drop weight stringing machine relies on a lever and a weight to tension the string.  To achieve a certain tension the weight is moved to a specific location on the lever.  The string is attached to a gripper at the base of the lever.  The lever is then tilted (to the right in this picture) to pull the string.  To achieve correct tension, the lever must come to rest in a horizontal position against the pull of the string.  For a number of reasons, drop weight stringing machines are the least convenient on the market.   The most significant problem is that accurate tensioning is only achieved when the the drop weight comes to rest in a horizontal position against the pull of the tensioned string.  Deviations from the horizontal create deviations in tension.  To achieve a horizontal end state, a specific amount of slack must be left in the string before pulling it.  The amount of slack varies with the length of the string and its composition so that an operator often needs to reposition the string in the gripper several times to achieve an end state that is close to horizontal.  To help with these problems, some drop weight machines are equipped with a ratchet or clutch mechanism, although some of these systems remain very cumbersome to use.  The clutch of the Silent Partner swing greatly facilitates tensioning. The main advantage of drop weight machines is their low cost.

2)    What is a " lockout" spring and brake stringing machine?

A machine with a spring and brake tensioner relies on a hand operated crank to pull the string. A spring deflects against the tension being applied to the string.  When the pre-selected tension is reached, a lever is tripped stopping the tensioning operation, and a brake is engaged to hold the tension in the string for this reason, these tensioners are known as "lockout" or "instant off" machines.  When properly calibrated, spring and brake tensioners are very accurate and allow fast stringing, which is why they are extremely popular in pro shops. Because these machines "lockout" as soon as they reach the reference tension, professional stringers usually set the tension about 10% higher than they do with "constant pull" machines (see FAQ 11 for an explanation of the difference between instant off and constant pull machines).
  
 

3)    What is an "electronic" stringing machine?

An electronic machine is a machine that relies on an electric motor to tension the string.  The electric motor drives a string gripper and is controlled by electronic circuitry.  When the reference tension is reached, the motor maintains that tension until the string is clamped.  The appeal of electric machines comes from the fact that they are both convenient to use and accurate.  Until the introduction of the Silent Partner e.Stringer, electric machines have ranged in price from about $800 to over $8,000 (for a machine made by Babolat  that many professional stringers lust after more than a Ferrari).

4)    Are all electronic machines based on the same technology?

Important differences distinguish the technologies used in various electronic machines. There are four types of technologies. The first consists of electronics for direct torque control of a motor so that the motor cannot pull more than the desired tension. Silent Partner holds a patent for this technology (US Patent #6,162,139) and offers it exclusively on the e.Stringer, the e.Stringer CL and the e.Stringer FL, as well as in retrofit tensioners for other brands of machines. The second type of electronic technology consists of a motor control linked mechanically to a pre-loaded spring. Tension adjustment is effected by turning a knob that compresses the spring to the desired tension so that a limit switch is tripped and the motor is stopped when the tension is reached. This type of control, which is identified by a tension control knob located to the right of the machine (see picture), does not provide constant pull because tension has to drop by more than 15 lbs for the limit switch to turn the motor on again, and this does not normally happen during stringing. Quality pre-loaded spring machines such as the Jive offer a string pre-stretch feature that achieves tension stability in the string similar to that achieved by constant pull machines. The third type of electronic technology is relies on a potentiometer monitored by a microprocessor. This technology offers the potential for many keypad controlled features as well as constant pull. This is the technology used in the e.Stringer DG. The fourth and most sophisticated technology uses a load cell and microprocessor. This is the technology used in the Silent Partner Aria and the new Silent Partner Opus.

5)    Is it true that most brands of stringing machines are made by the same manufacturer in Taiwan?

Although one vendor of low cost stringing machines claims that its products are made by the same OEM (original equipment manufacturer) that supplies reputable brands, this is not true. Quality stringing machines are manufactured in a number of countries such as France, Holland, Japan, Canada and Taiwan. Taiwan has several manufacturers of stringing machines and reputable brands like Prince, Gamma, Alpha and Silent Partner have exclusive arrangements with their own suppliers in Taiwan. These arrangements are important because they involve close working relationships between engineers in North America and in Taiwan. One supplier of low cost stringing machines has acquired a very bad reputation for poor quality and customer service, and it is wise for customers to limit their shopping to reputable brands. The tensioners of the e.Stringer, SC and FL are made in Canada. All other components of these models as well as the complete Jazz, Maestro and e.Stringer DG are made for Silent Partner by a partner factory in Taiwan under an exclusive North American agreement .

6)    What is the difference between two-point mounting and six-point mounting?

Proper and safe stringing requires that the racquet frame be mounted securely and that it not slide while sections of strings are tensioned. It is not uncommon for the pull of the string as it is being tensioned to cause visible distortion in the racquet head.  Avoiding frame damage is therefore imperative.  Some stringing machines hold the frame at the tip and at the throat (picture on the left).  This is known as a two-point mounting system.  Other machines hold the frame at several locations and are known as multi-point (usually six-point) mounting sysems. Not all six-point mounting systems work the same way. Some system place supports inside the head at the tip and throat and four side supports on the outside (picture in the middle).  Some mounting systems provide six support points on the inside of the head and are known as "inside six-point systems" (see picture on the right).

7)    What is better, inside or outside racquet mounting?

Silent Partner produces stringing machines with multi inside supports as well as multi outside supports and believes that both systems provide excellent racquet support. To appreciate why, it is necessary to understand two critical functions of mounting systems. First, upon installing the mains (strings that run length wise), every tensioned string pulls the racquet head inwards by the selected tension (around 60 lb.). Each string alone does not cause much stress, but when more and more strings are installed, the stress builds accordingly. By the time 16 or 18 mains have been installed, the inward pull on the racquet head is well over 1000 lb. (see picture). As tension rises, the racquet head wants to get shorter and wider. Inside mounting systems fight this tendency by providing excellent distributed support to prevent the racquet from changing shape. Outside mounting systems support the center of the head and throat on the inside and counteract any tendency of the racquet getting wider with the outside side supports. The second important function of the mounting system is to prevent the racquet from sliding sideways when the cross strings are tensioned (see second picture). The force of a cross being tensioned is only about 60 lb., but it is important to prevent the racquet from moving sideways because such movement can cause damage to the head and the grommets. Inside as well as outside mounting systems provide sufficient support to prevent all sideway movement during the tensioning of cross strings.

8)    What are flying clamps, fixed clamps, glide clamps, swivel clamps, single action clamps and dual action clamps?

Racquet stringing consists of a series of steps where sections of strings are tensioned and then clamped in such a way as to retain the tension.  String clamping is, therefore, an essential element of racquet stringing. Flying clamps (also known as floating clamps and quick clamps) get their name from the fact that they hang from the strings rather than being attached to the turntable on the stringing machine.  Fixed clamps get their name from the fact that they are secured to the turntable of the stringing machine.  Fixed clamps come in two forms: glide clamps and swivel clamps.  Glide clamps move linearly on glide bars and lock in position with a single action that also secures the string.  Swivel clamps move linearly along the turntable, but they also swivel at their base.  Swivel clamps require two actions, one to clamp the string and the other to lock on the turntable.  Fixed clamps (glide clamps and swivel clamps) are more convenient to use than flying clamps. The main advantage of flying clamps is low cost.  Still, good flying clamps produce excellent results. Some machines, like the e.Stringer SC,  have one swivel clamp and one flying clamp.  The advantage of these machines is that they allow most clamping (at least half the mains, and absolutely all the crosses) to be done by means of a swivel clamp, yet they remain affordable because of the simpler design of their turntable.

9)    What type of machine is the most accurate?

Accuracy is a complicated issue when it comes to stringing.  This is because factors having to do with friction on the string as it passes through grommet holes and with the speed and duration of pull during tensioning have an important effect on final tension.  For example, a string that is pulled to a tension of 70 lb. for a brief period of time before being clamped will have a tension of a bit less than 50 lb. twelve hours later.  By contrast, a string that is pulled to a tension of 55 lb. for sixty seconds before being clamped will have a tension of a bit more than 50 lb. twelve hours later.   This, of course, does not mean that tension accuracy is not important  in stringing.  It must be realized, however, that accuracy has more to do with consistency over the various pulls necessary to string a racquet, and from one stringing job to another, than it does with the actual tension in a string at the end of the stringing job.

10)    How can tension consistency be assured?

The best way to insure consistent tension from one stringing job to another is to calibrate the tension mechanism of the stringing machine periodically.  Calibrators consisting of a spring loaded implement are now widely available at a cost of about $25.

11)    What's the difference between an "instant off" and a "constant pull" machine?

A string that is pulled to a reference tension such as 60 lb. and is then clamped will immediately start to lose tension as it stretches.  Instant off machines pull the string to the reference tension and then immediately stop pulling.  Constant pull machines pull the string to the reference tension and then continue pulling at that tension until the string is clamped and the tensioner is disengaged.    Because constant pull machine "take-up the slack" in the string for a longer period of time than instant off machines, they usually yield string jobs that are about 10% higher in tension than instant off machine.  This is not a trivial difference and good professional stringers will usually ask their customers about the type of machine that was used for their previous string job.  The main type of instant off machines are those that employ a spring and brake tensioning mechanism (that's because tensioning stops and the brake is engaged the moment the reference tension is reached).  Electric machines as well as drop weight machines usually provide constant pull.  This is because the motor of an electric machine and the lever of a drop weight machine continue to pull on the string for as long as it takes to clamp the string and disengage the tensioning mechanism. Note that electric machine that use a pre-loaded spring (see FAQ 4) are instant off rather than constant pull.

12)    What is string "pre stretching?"

Pre stretching is a procedure that "takes up slack" in the string prior to or during stringing with the aim of achieving more tension stability over time.  An old fashioned and rather inconvenient form of pre stretching involves tying one end of the string to a firm anchor and pulling on the other end (tug-of-war style) for a period of time.  More sophisticated pre stretching is done during tensioning with constant pull machines.  There is a number of ways of achieving  pre stretching.  One has to do with the speed at which the string is pulled to the reference tension: slow pulling results in more pre stretching.  Another has to do with the length of time constant pull is exerted once the reference tension is achieved: the longer the string is pulled, the more pre stretching.  A third form of pre stretching is achieved by sophisticated electric machines by exceeding the reference tension slightly before backing off to it.

13)    Are stringing machines that sit on a table less convenient to use than those with a pedestal?

The operator does not walk around a stringing machine while stringing, so placing the stringer on a table top does not present a problem.  What is important is for the racquet to swing 360 degrees without obstruction to allow all sides of the head to be accessible to the operator. Drop weight stringing machines and some models of spring and brake machines do not allow free rotation of the racquet under all conditions.

14)    Why are stringing machines equipped with a brake?

The brake is not used while tensioning strings.  In fact, it is important to allow the racquet to align itself against the pull of the tensioned string.  The brake is useful while tying knots and also when using a calibrator.

15)    All things considered, what's the best type of stringing machine?

The best stringing machine is one that holds the racquet securely, has reliable and convenient means of holding the string for tensioning and for clamping , and applies tension in a consistent manner.  There are many ways of achieving these characteristics, but electric machines have become the most popular in the market today.

16)    What accessories are necessary for stringing?

The awl is an essential accessory that is not likely to be found in a typical tool box.  The awl is used to guide the string to crowded grommet holes.  Some stringers also wedge the awl in the grommet hole to hold the string in place during tie off.  A diagonal cutter is also essential to snip the string neatly.  Although the diagonal cutter is a common tool, dedicating one to stringing only is a good idea to insure good cutting edges.  The same is true of needle nose pliers which are used to pull on the string in tight spots.

17)    How long does it take to string a racquet?

With a little experience an operator will string a racquet in 30 to 45 minutes.  By going at full speed very experienced professionals can string a racquet in as little as 12 minutes, but they seldom do so because the quality of the string job invariably suffers and because they are left gasping for air at the end of it.  Ironically, it is simple things that slow a beginner down.  Things, for example, like new strings that get tangled the moment they are taken out of the package (to avoid this, it is advisable to hold the coil in one hand and to use the other hand to unwind the full length of the string on the floor).  Initial uncertainty about a racquet's stringing pattern will also slow a beginner down. One area where experienced stringers  really shine compared to beginners is in weaving the crosses (see instructions below for the definition of  "cross" and "main" strings).  Weaving   is usually done by placing one hand over the string bed and the other below it.  The leading edge of the string being weaved is pinched between the middle finger of each hand and is pushed up and down in alternation across the mains.  Good operators make this process look so effortless that the string appears to glide magically across the mains.

18)   Where can I learn more about stringing and stringing machines?

The United States Racquet Stringers Association (USRSA) is an organization dedicated to supporting professional and private racquet stringers with educational and resource materials that include a yearly stringer's digest, a monthly magazine (RacquetTech), and an interactive web site. The USRSA also offers a certification program that is the recognized standard of excellence for racquet stringers and racquet technicians. Silent Partner supports the USRSA and recommends that all enthusiast with an interest in tennis equipment (racquets, strings, stringing machines, stringing technique, etc.) consider joining the organization. The cost of a one year membership is reasonable and gives access not only to a wealth of authoritative information about racquet and string technology, but also to material benefits such as free marketing samples of products like strings and grips. Though the free samples help offset the cost of membership, Silent Partner believes that the educational resources offered by the USRSA more than justify the cost of membership. For this reason, Silent Partner offers the service of accepting membership requests on behalf of the USRSA. If you would like to join the USRSA, call us at 1-800-662-1809.

19) When were stringing machines introduced and what important developments took place through the years?

A good way to learn about the history of stringing machines is by looking at US patents. One of the first patents for a complete racquet stringing machine was awarded in 1932 to Jaffe. This tennis stringing machine consisted of a turntable, a crank and, in the lower section of the machine, a weighted scale. Tension in this stringer was applied by turning the crank until balance was reached with the weight.

Other designs for tennis stringing machines soon followed. A patent awarded in 1933 (Tauber et al.) shows a large cradle for securing the tennis racquet at the grip, and on the two sides of the head. This stringer had two tensioners operated by levers, one on each side of the racquet, a feature that was necessary because the racquet did not rotate on a turntable. A patent published in 1936 (Rolston et al.) is interesting because it shows an awl inserted in one of the string holes to hold the string under tension. None of the patents of that era show a string clamp.

By 1940 a patent awarded to Serrano and another awarded in 1943 to Kausal et al. show what are rather contemporary renditions of string clamps in racquet stringing machines. The string clamps on these stringers ride on glide bars. Also of interest is the appearance in Kausal et al.'s invention of a linear string gripper equipped with a drum (now known as a diablo). Tension in Kausal et al.'s stringing machine was applied by a complex pressurized system operated by a foot pedal. Serrano's design was of greater long term significance in the history of tennis stringing machines. Today you can still hear old timers speak fondly of their Serranos, and these stringing machines occasionally surface in classified ads and on eBay. Of particular interest is the foot operated drop weight. This is the first rendition of a drop weight that looks like those in use in contemporary tennis stringing machines, and it is a testament to the significance of the Serrano that foot operation of a drop weight is found today in an expensive stringing machine from Holland.

The next significant development in stringing machines came in the late 1970's with the introduction of lockout tensioners that utilized a spring to provide a reference tension, and a brake to hold that tension once it had been reached. A patent for such a device was granted to Balaban in 1981, and the spring and brake tensioner was implemented with substantial commercial success by Ektelon. An important element of this tensioner is the linear string gripper that consists of two jaws that ride on ball bearings and that squeeze the string progressively as tension is applied, an invention patented by Halbrook in 1978.

Also significant in the 1970's and 80's is the development of inexpensive stringers for personal use. A patent was awarded in 1974 to the Tremont stringer, a small crank operated machine that enjoyed commercial recognition for about two decades. And while the Klippermate does not appear to have secured patent protection, two US patents were awarded to close imitations from Taiwan! The string clamps in these low cost stringing machines were invariably of the "floating" or "flying" variety, labels suggested by the fact that the clamps were suspended from the strings. A patent for such a clamp was awarded to Ray in 1977.

The 1990's ushered the era of sophisticated electronic tennis stringing machines. The leading innovator in this field is Babolat who was awarded patents in 1991 and 1992. Babolat's tennis stringing machine innovated not only with a reliable and accurate constant pull tensioner but also with a mounting system that cradles the racquet from the outside, and with string clamps that swivel.

Perhaps the most significant recent patent for tennis stringing machines was awarded in 2000 for the tensioner of the Silent Partner e.Stringer. This low cost tensioner has allowed thousands of private tennis stringers to enjoy the convenience of fully electronic tensioning.

Note to reader: If you have information relevant to what is presented here, please do not hesitate to write sptennis@on.aibn.com