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1# Gripper Design and Anatomy 1# Gripper Design and Anatomy
2 2
3A conventional torsion-spring hand gripper has three visible parts: a coiled spring and two handles attached to the spring legs. That simple layout permits substantial variation in dimensions, materials and geometry. Those differences affect how a gripper fits the hand and how its resistance develops through the closing arc. 3A conventional torsion-spring hand gripper has three visible parts: a coiled spring and two handles attached to the spring legs. That simple layout permits substantial variation in dimensions, materials and geometry. Those differences affect how a gripper fits the hand and how its resistance develops through the closing arc.
4 4
5[![AtomGripz torsion-spring gripper showing the spring, coils and handles](https://www.grippervault.com/uploads/users/2/grippers/67eef3576acd4.jpg)](https://www.grippervault.com/grippers/819) 5[![AtomGripz torsion-spring gripper showing the spring, coils and handles](https://www.grippervault.com/uploads/users/2/grippers/67eef3576acd4.jpg)](https://www.grippervault.com/grippers/819)
6 6
7*An AtomGripz 1-band gripper from Clint Ziegler's [GripperVault collection](https://www.grippervault.com/liftyzig). Photograph by Clint Ziegler.* 7*An AtomGripz 1-band gripper from Clint Ziegler's [GripperVault collection](https://www.grippervault.com/liftyzig). Photograph by Clint Ziegler.*
8 8
9## Main components 9## Main components
10 10
11| Component | Description | Useful observations | 11| Component | Description | Useful observations |
12| --- | --- | --- | 12| --- | --- | --- |
13| Spring body | The central helical coil | Wire diameter, outside diameter, number of coils, winding direction and finish | 13| Spring body | The central helical coil | Wire diameter, outside diameter, number of coils, winding direction and finish |
14| Spring legs | The two lengths of wire leaving the coil | Shape, angle, symmetry and the transition from coil to handle | 14| Spring legs | The two lengths of wire leaving the coil | Shape, angle, symmetry and the transition from coil to handle |
15| Handles | The two surfaces pressed together by the hand | Material, length, diameter, texture, markings and mounting depth | 15| Handles | The two surfaces pressed together by the hand | Material, length, diameter, texture, markings and mounting depth |
16| Handle ends | The exposed ends opposite the spring | Stamps, engravings, stickers, plugs and wear patterns | 16| Handle ends | The exposed ends opposite the spring | Stamps, engravings, stickers, plugs and wear patterns |
17| Handle gap or spread | Distance between the handles while the gripper is at rest | Measure at a stated location, since the handles are not parallel | 17| Handle gap or spread | Distance between the handles while the gripper is at rest | Measure at a stated location, since the handles are not parallel |
18 18
19A torsion spring stores energy as its legs rotate and the wire bends. Engineers specify torsion springs using measurements that include wire diameter, coil diameter, number of coils, leg position and winding direction.[^1] A gripper is therefore not defined by wire diameter alone. 19A torsion spring stores energy as its legs rotate and the wire bends. Engineers specify torsion springs using measurements that include wire diameter, coil diameter, number of coils, leg position and winding direction.[^1] A gripper is therefore not defined by wire diameter alone.
20 20
21## Spring terminology 21## Spring terminology
22 22
23### Wire diameter 23### Wire diameter
24 24
25**Wire diameter** is the thickness of the spring wire. It is best measured with calipers or a micrometer at an accessible, undamaged section. Record this dimension precisely because a small measurement error can produce a misleading specification.[^1] 25**Wire diameter** is the thickness of the spring wire. It is best measured with calipers or a micrometer at an accessible, undamaged section. Record this dimension precisely because a small measurement error can produce a misleading specification.[^1]
26 26
27Thicker wire often appears on harder grippers, but it does not establish closing difficulty by itself. Coil diameter, active coils, material, heat treatment, free position, leg geometry and handle leverage also contribute. 27Thicker wire often appears on harder grippers, but it does not establish closing difficulty by itself. Coil diameter, active coils, material, heat treatment, free position, leg geometry and handle leverage also contribute.
28 28
29### Coil diameter and coil count 29### Coil diameter and coil count
30 30
31The **outside diameter** is measured across the outside of the coil. The **inside diameter** is the open space through its center. The **mean diameter** is the outside diameter minus one wire diameter.[^2] 31The **outside diameter** is measured across the outside of the coil. The **inside diameter** is the open space through its center. The **mean diameter** is the outside diameter minus one wire diameter.[^2]
32 32
33Coil count should be recorded consistently. A collector should state whether the figure includes only complete coils or partial turns where the legs leave the spring body. Photographs are useful when comparing grippers whose transitions are ambiguous. 33Coil count should be recorded consistently. A collector should state whether the figure includes only complete coils or partial turns where the legs leave the spring body. Photographs are useful when comparing grippers whose transitions are ambiguous.
34 34
35### Winding direction 35### Winding direction
36 36
37A spring may be wound left-handed or right-handed. Winding direction is one of the standard specifications recorded for a torsion spring.[^1] Winding direction should not be confused with the community's preferred palm-side orientation or with IronMind's separately marketed Left-Turn grippers. 37A spring may be wound left-handed or right-handed. Winding direction is one of the standard specifications recorded for a torsion spring.[^1] Winding direction should not be confused with the community's preferred palm-side orientation or with IronMind's separately marketed Left-Turn grippers.
38 38
39### Spring legs and the “dog leg” 39### Spring legs and the “dog leg”
40 40
41Gripper users call the straighter transition from one spring leg into the coil the **dog leg**. The opposite transition is usually more curved. Cannon PowerWorks attributes the difference to spring manufacture: the leading leg is braced while the coil is wound around a mandrel.[^2] 41Gripper users call the straighter transition from one spring leg into the coil the **dog leg**. The opposite transition is usually more curved. Cannon PowerWorks attributes the difference to spring manufacture: the leading leg is braced while the coil is wound around a mandrel.[^2]
42 42
43A longstanding convention places the dog-leg handle against the palm. However, Cannon PowerWorks reported that its measurements did not find a resistance difference based on orientation and said three spring manufacturers found no engineering basis for the broader claim. The earlier PDA work cited in the same article reported a difference at the beginning of movement on its apparatus, but the same final closing measurement in both orientations.[^2] The evidence therefore does not justify treating dog-leg orientation as a universal change in final closing strength. Athletes may still choose a consistent orientation for repeatability or comfort. 43A longstanding convention places the dog-leg handle against the palm. However, Cannon PowerWorks reported that its measurements did not find a resistance difference based on orientation and said three spring manufacturers found no engineering basis for the broader claim. The earlier PDA work cited in the same article reported a difference at the beginning of movement on its apparatus, but the same final closing measurement in both orientations.[^2] The evidence therefore does not justify treating dog-leg orientation as a universal change in final closing strength. Athletes may still choose a consistent orientation for repeatability or comfort.
44 44
45## Handle design 45## Handle design
46 46
47### Materials 47### Materials
48 48
49Handles have been made from aluminum, steel, plastic, wood and other materials. Modern premium grippers commonly use machined metal handles. IronMind states that it introduced knurled aircraft-grade aluminum handles to Captains of Crush in 1995.[^3] 49Handles have been made from aluminum, steel, plastic, wood and other materials. Modern premium grippers commonly use machined metal handles. IronMind states that it introduced knurled aircraft-grade aluminum handles to Captains of Crush in 1995.[^3]
50 50
51Material affects weight, corrosion behavior and how sharply a texture can be formed, but material alone does not determine the strength of the spring. 51Material affects weight, corrosion behavior and how sharply a texture can be formed, but material alone does not determine the strength of the spring.
52 52
53### Diameter and length 53### Diameter and length
54 54
55Handle diameter changes how far the fingers wrap around the gripper. Narrow handles may allow more finger overlap, while larger handles can increase the effective hand span. Handle length also changes where the user can apply force. 55Handle diameter changes how far the fingers wrap around the gripper. Narrow handles may allow more finger overlap, while larger handles can increase the effective hand span. Handle length also changes where the user can apply force.
56 56
57Comparisons should record both dimensions. Two grippers with similar spring resistance can feel different when their handle diameters, lengths or spreads differ. 57Comparisons should record both dimensions. Two grippers with similar spring resistance can feel different when their handle diameters, lengths or spreads differ.
58 58
59### Knurling and surface finish 59### Knurling and surface finish
60 60
61**Knurling** is the repeated cut or formed texture that improves purchase on a handle. Its depth, pitch and pattern vary widely. Smooth handles demand more control and may rotate more readily, while very sharp knurling can improve purchase at the cost of comfort. 61**Knurling** is the repeated cut or formed texture that improves purchase on a handle. Its depth, pitch and pattern vary widely. Smooth handles demand more control and may rotate more readily, while very sharp knurling can improve purchase at the cost of comfort.
62 62
63Paint, anodizing, plating and bare metal can alter feel and provide identification clues. Finish color alone is weak evidence of model or age because manufacturers have issued special colors and owners may modify handles. 63Paint, anodizing, plating and bare metal can alter feel and provide identification clues. Finish color alone is weak evidence of model or age because manufacturers have issued special colors and owners may modify handles.
64 64
65### Mounting depth 65### Mounting depth
66 66
67**Mounting depth** describes how far a spring leg extends into its handle, or conversely how close the handle begins to the coil. Deeper mounting shortens the exposed lever arm and can change the resting spread and the geometry of the close. This is one reason two grippers using apparently similar springs may not feel identical. 67**Mounting depth** describes how far a spring leg extends into its handle, or conversely how close the handle begins to the coil. Deeper mounting shortens the exposed lever arm and can change the resting spread and the geometry of the close. This is one reason two grippers using apparently similar springs may not feel identical.
68 68
69When documenting mounting, photograph both handle tops and measure from a repeatable point on the coil or spring leg. Visible mounting asymmetry should be recorded rather than automatically interpreted as damage. 69When documenting mounting, photograph both handle tops and measure from a repeatable point on the coil or spring leg. Visible mounting asymmetry should be recorded rather than automatically interpreted as damage.
70 70
71## Spread and closing geometry 71## Spread and closing geometry
72 72
73**Spread** is the resting distance between the handles. Because the handles form an angle, a measurement near the spring will differ from one near the ends. Record the measuring point, commonly the inside edges at the handle ends, and note whether the gripper was new, used or restrained before measurement. 73**Spread** is the resting distance between the handles. Because the handles form an angle, a measurement near the spring will differ from one near the ends. Record the measuring point, commonly the inside edges at the handle ends, and note whether the gripper was new, used or restrained before measurement.
74 74
75A wider spread increases the hand opening required for a no-set attempt. Once a gripper is positioned with a block, card or deeper set, the starting geometry changes. See [Gripper Closing Techniques](/Gripper_Closing_Techniques) for the distinctions among set styles. 75A wider spread increases the hand opening required for a no-set attempt. Once a gripper is positioned with a block, card or deeper set, the starting geometry changes. See [Gripper Closing Techniques](/Gripper_Closing_Techniques) for the distinctions among set styles.
76 76
77The resistance experienced by the hand is not constant through the motion. Athletes commonly divide the close into: 77The resistance experienced by the hand is not constant through the motion. Athletes commonly divide the close into:
78 78
79- **Sweep**, movement from the starting position toward near-parallel handles 79- **Sweep**, movement from the starting position toward near-parallel handles
80- **Transition**, the approach to the final portion of the close 80- **Transition**, the approach to the final portion of the close
81- **Close**, bringing the handle ends into clear contact 81- **Close**, bringing the handle ends into clear contact
82 82
83These terms describe portions of a movement, not independently measured properties. A gripper may feel comparatively stiff early or late because of its combined spring and handle geometry. 83These terms describe portions of a movement, not independently measured properties. A gripper may feel comparatively stiff early or late because of its combined spring and handle geometry.
84 84
85## Ratings and manufacturer poundage 85## Ratings and manufacturer poundage
86 86
87Numbers engraved or printed on grippers may be model names, nominal poundage or marketing designations. They are not automatically comparable across brands. Even specimens of the same model can vary because a finished gripper is an assembly of parts with manufacturing tolerances. 87Numbers engraved or printed on grippers may be model names, nominal poundage or marketing designations. They are not automatically comparable across brands. Even specimens of the same model can vary because a finished gripper is an assembly of parts with manufacturing tolerances.
88 88
89An [RGC rating](/Gripper_Rating_Info/Rating_Types/RGC) records the load shown by one established rating procedure near handle contact. It is useful for comparing measured specimens, but it does not fully describe spread, handle texture, sweep or how a gripper fits a particular hand. See [Gripper Rating Info](/Gripper_Rating_Info) for rating methods and limitations. 89An [RGC rating](/Gripper_Rating_Info/Rating_Types/RGC) records the load shown by one established rating procedure near handle contact. It is useful for comparing measured specimens, but it does not fully describe spread, handle texture, sweep or how a gripper fits a particular hand. See [Gripper Rating Info](/Gripper_Rating_Info) for rating methods and limitations.
90 90
91## Documenting a gripper 91## Documenting a gripper
92 92
93A useful collection record should include: 93A useful collection record should include:
94 94
951. Brand and exact model marking 951. Brand and exact model marking
962. Photographs of both sides, both handle ends and the spring transitions 962. Photographs of both sides, both handle ends and the spring transitions
973. Handle material, diameter and length 973. Handle material, diameter and length
984. Resting spread and the location where it was measured 984. Resting spread and the location where it was measured
995. Spring wire and outside coil diameters 995. Spring wire and outside coil diameters
1006. Coil count and winding direction 1006. Coil count and winding direction
1017. Mounting depth or a clear photograph of both handle tops 1017. Mounting depth or a clear photograph of both handle tops
1028. RGC rating, rating method and rater, if known 1028. RGC rating, rating method and rater, if known
1039. Packaging, purchase history and provenance 1039. Packaging, purchase history and provenance
10410. Modifications, damage, corrosion or unusual wear 10410. Modifications, damage, corrosion or unusual wear
105 105
106Do not file, bend, heat or disassemble an unidentified gripper merely to investigate it. Such work can change its resistance, erase evidence and damage a collectible example. 106Do not file, bend, heat or disassemble an unidentified gripper merely to investigate it. Such work can change its resistance, erase evidence and damage a collectible example.
107 107
108## External resources 108## External resources
109 109
110- [GripperVault](https://www.grippervault.com/) preserves collector photographs, specifications, ratings and provenance. 110- [GripperVault](https://www.grippervault.com/) preserves collector photographs, specifications, ratings and provenance.
111- [Cannon PowerWorks: The Myth of the Dog Leg](https://cannonpowerworks.com/blogs/grip-strength/the-myth-of-the-dog-leg) examines the history and measurement claims surrounding spring-leg orientation. 111- [Cannon PowerWorks: The Myth of the Dog Leg](https://cannonpowerworks.com/blogs/grip-strength/the-myth-of-the-dog-leg) examines the history and measurement claims surrounding spring-leg orientation.
112- [Acxess Spring: Torsion Spring Design](https://www.acxesspring.com/torsion-spring-design.html) explains standard torsion-spring dimensions and terminology. 112- [Acxess Spring: Torsion Spring Design](https://www.acxesspring.com/torsion-spring-design.html) explains standard torsion-spring dimensions and terminology.
113 113
114[^1]: Acxess Spring, [“Torsion Spring Design”](https://www.acxesspring.com/torsion-spring-design.html), definitions of wire, outside and mean coil diameters, winding direction and spring rate. 114[^1]: Acxess Spring, [“Torsion Spring Design”](https://www.acxesspring.com/torsion-spring-design.html), definitions of wire, outside and mean coil diameters, winding direction and spring rate.
115[^2]: Matt Cannon, [“The Myth of the Dog Leg”](https://cannonpowerworks.com/blogs/grip-strength/the-myth-of-the-dog-leg), Cannon PowerWorks, September 29, 2023. 115[^2]: Matt Cannon, [“The Myth of the Dog Leg”](https://cannonpowerworks.com/blogs/grip-strength/the-myth-of-the-dog-leg), Cannon PowerWorks, September 29, 2023.
116[^3]: IronMind, [Captains of Crush Grippers](https://ironmind.com/product-info/grip-strength-training-tools/captains-of-crush-grippers/), product history and design description. 116[^3]: IronMind, [Captains of Crush Grippers](https://ironmind.com/product-info/grip-strength-training-tools/captains-of-crush-grippers/), product history and design description.

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