Got Guts?Got Guts?

Project by:Project by:Shiko NjunoShiko NjunoHector TorrezHector TorrezLuis ZamudioLuis Zamudio

Topics to coverTopics to cover General InformationGeneral Information Types of racquet stringsTypes of racquet strings The making of the stringsThe making of the strings SRJC Lab analysis of a sampleSRJC Lab analysis of a sample

General InformationGeneral Information► Over the last two decades, racket heads Over the last two decades, racket heads

have become larger and lighter using light-have become larger and lighter using light-weight materials.weight materials.

► Wooden rackets and natural gut string were Wooden rackets and natural gut string were used up to mid 1970’s, along with leather used up to mid 1970’s, along with leather grip handles. Later, Aluminum and Steel grip handles. Later, Aluminum and Steel became highly useful materials being became highly useful materials being extremely light and providing durability.extremely light and providing durability.

► Today most racket frames are made out of Today most racket frames are made out of light weight graphite or graphite composites light weight graphite or graphite composites that include titanium, fiberglass (Kevlar) that include titanium, fiberglass (Kevlar) that provides more flexibility and yet that provides more flexibility and yet remains cost effective.remains cost effective.

► During a game, a racket can experience 140 During a game, a racket can experience 140 mph impacts. There are about two mph impacts. There are about two thousands different models available that thousands different models available that have been manufactured to withstand this have been manufactured to withstand this punishment. punishment.

► To the right is a picture of an antique To the right is a picture of an antique Spalding tennis racket.Spalding tennis racket.

Tennis Racket Periods and GenerationsPeriod 1, Formative Years, 1860s-1880s (Incunabula Rackets) [SET 1]

1st Generation, Lacross Style Rackets, 1860s

2nd Generation, Balloon Head, Sheepskin Grips, 1870s

3rd Generation, Lopsided Head, 1870s-1880s

4th Generation, Flat-Top Triangular Head, 1870s-1880s

Period 2, Early Years, 1880s-1920s (Antique Rackets) [SET 2]

1st Generation, Transitional Heads, Solid (Intrusive) Wedges, 1880s-1920s

2nd Generation, Transitional Heads, Laminated (Intrusive) Wedges, 1900s-1920s

3rd Generation, Transitional Heads, Concave (Extrusive) Wedges, 1900s-1920s

4th Generation, Transitional Heads, Shoulder Wrappings & Coverings, 1910s-1920s

Period 3, Golden Years, 1920s-1940s (Vintage Rackets) [SET 2]

1st Generation, Plied (Multiple Pieces of Wood) Frames, 1920-1930s

2nd Generation, Aerodynamic & Power Variations, 1920s-1930s

3rd Generation, Structural Reinforcements, Facing, Shoulders, Throats, 1930s-1980s

4th Generation, Smaller Handles/Grips, Leather Grips, 1930s-1980s

Period 4, Middle Years, 1940s-1960s (Traditional Rackets) [SET 3]

1st Generation, Enhanced, Painted Decorations, 1940s-1980s

2nd Generation, Laminated (Many Very Thin Strips of Wood) Frames, 1940s-1980s

3rd Generation, New Woods, Further Experimentation, 1940s-1980s

4th Generation, Fiber (Not fiberglass) Throat Overlays, Production Refinements, 1940s-1970s

Period 5, Last Years, 1960s-1980s (Modern Rackets) [SET 3]

1st Generation, Rackets as Commodities, 1960s-1980s

2nd Generation, Rackets as Classics, 1960s-1980s

3rd Generation, Composite Materials, Conventional Frames, 1960s-1980s

4th Generation, Composite Materials, Transitional Frames/Heads, 1970s-1980s

Sponsored by WOOD TENNIS RACKETS, A COLLECTOR'S GUIDE.Copyright © 1999, Clark H. Bensen. All Rights Reserved.

POLIDATA ® Collectors Guides / Clark Bensen / 3112 Cave Court, Suite T / Lake Ridge, VA 22192updated: 2002

Tennis Racket Periods and Generations

Types of StringsTypes of Strings

Natural Gut (Cow or Natural Gut (Cow or Sheep)Sheep)

Synthetic Synthetic

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Types of Strings UsedTypes of Strings UsedNatural Gut: is made of cow or sheep Natural Gut: is made of cow or sheep gut. Allows for a very sensitive game but gut. Allows for a very sensitive game but is very susceptible to environmental is very susceptible to environmental conditions and is not very durable. It is conditions and is not very durable. It is also more expensive than synthetic also more expensive than synthetic string. This is the type of string preferred string. This is the type of string preferred by the professionals. by the professionals. Synthetic Fiber Strings: are made of Synthetic Fiber Strings: are made of Nylon and are almost as good as natural Nylon and are almost as good as natural gut due to technological improvements. gut due to technological improvements. They come in two subtypes: They come in two subtypes: 1)Monofilament: the string consists of 1)Monofilament: the string consists of only one filament. This is typically used only one filament. This is typically used in cheaper hobby grade metal racquets.in cheaper hobby grade metal racquets.2)Multifilament: the strings consist of 2)Multifilament: the strings consist of many thin filaments braided together. many thin filaments braided together. For example: ASHAWAY Flex 21 For example: ASHAWAY Flex 21 consists of approx. 750 filaments and consists of approx. 750 filaments and the Vantage 20 of approx 3000 separate the Vantage 20 of approx 3000 separate filaments.filaments.

Natural GutNatural Gut

Made of the serosa of the Made of the serosa of the intestine of the cow.intestine of the cow.

Its got an internal structure that is Its got an internal structure that is very elastic which makes it with- very elastic which makes it with- stand a larger number of impacts stand a larger number of impacts without fatiguing.without fatiguing.

Process ofProcess of makingmaking the gut the gut stringstring

The serosa is removed from the The serosa is removed from the 120 feet long intestine, it is cut 120 feet long intestine, it is cut into long ribbons in order to clean into long ribbons in order to clean them.them.

Ribbons are inspected Ribbons are inspected for blemishes in a for blemishes in a control ultra violet control ultra violet room.room.

Next the ribbons are Next the ribbons are counted to determine counted to determine the gauges and then cut the gauges and then cut for length.for length.

The ribbons are bundled and The ribbons are bundled and put in a salt solution. They put in a salt solution. They are refrigerated for 30 days are refrigerated for 30 days to get rid of bacteria.to get rid of bacteria.

The bundles go through a The bundles go through a multistep washing to clean multistep washing to clean off the impurities. The off the impurities. The bright lines in middle of bright lines in middle of image are a reflection from image are a reflection from overhead lighting.overhead lighting.

The ribbons are attached The ribbons are attached to a twisting machine to to a twisting machine to make into a set of make into a set of Natural GutNatural Gut

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Natural Gut String Vs Synthetic StringNatural Gut String Vs Synthetic String

Elastic Internal Elastic Internal StructureStructure

Fatigue resistantFatigue resistant

Large performance lifeLarge performance life

Very toughVery tough

High Tensile Strength High Tensile Strength

Break resistanceBreak resistance

“Gut has the integrity to retire before its game starts to suffer”

Types of tests operated on StringsTypes of tests operated on Strings

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Data:  

Length (cm) 96.5

Lo (mm) 16.49

Diameter (mm) 1.12

Area (m2) 3.94E-06

Results:          

Weight (g) L f (mm) Force (N) ∆l (mm) Stress,σ (N/m2) Strain,Є (m)

100 16.59 0.981 0.1 2.49E+05 6.06E-06

200 16.95 1.962 0.46 4.98E+05 2.79E-05

300 17.34 2.943 0.85 7.47E+05 5.15E-05

400 17.68 3.924 1.19 9.96E+05 7.22E-05

500 17.98 4.905 1.49 1.24E+06 9.04E-05

600 18.24 5.886 1.75 1.49E+06 1.06E-04

700 18.63 6.867 2.14 1.74E+06 1.30E-04

800 18.9 7.848 2.41 1.99E+06 1.46E-04

900 19.32 8.829 2.83 2.24E+06 1.72E-04

1000 19.64 9.81 3.15 2.49E+06 1.91E-04

1100 20.04 10.791 3.55 2.74E+06 2.15E-04

1200 20.46 11.772 3.97 2.99E+06 2.41E-04

1300 20.83 12.753 4.34 3.24E+06 2.63E-04

1400 21.22 13.734 4.73 3.49E+06 2.87E-04

1500 21.54 14.715 5.05 3.73E+06 3.06E-04

1600 21.97 15.696 5.48 3.98E+06 3.32E-04

1700 22.43 16.677 5.94 4.23E+06 3.60E-04

Stress-Strain Curve for a Wilson Raquet string

σ= 9E-11Є - 2E-05

0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

2.50E-04

3.00E-04

3.50E-04

4.00E-04

0 1000000 2000000 3000000 4000000 5000000

Strain, Є (m)

Str

es

s, σ

(N

/m2

)

Any Questions??Any Questions??