Springs - Extension, Drawbar

Part Number	Description / PDF	Quantity
S-558CS Century Spring Corp.	EXT O= .312,L= 2.25,W=.041 HD	202
5768CS Century Spring Corp.	EXT O= .437,L= 2.25,W= .064	1542
80481SCS Century Spring Corp.	EXT O= .359,L= 2.50,W= .037	262
80485SCS Century Spring Corp.	EXT O= .359,L= 4.00,W= .037	554
80445SCS Century Spring Corp.	EXT O= .359,L= .88,W= .031	284
A-54CS Century Spring Corp.	EXT O= .234,L= .94,W= .024	618
80029SCS Century Spring Corp.	EXT O= .094,L= .63,W= .010	1728
80492SCS Century Spring Corp.	EXT O= .359,L= 1.50,W= .039	816
S-547CS Century Spring Corp.	EXT O= .250,L= 2.75,W=.047 HD	210
5831CS Century Spring Corp.	EXT O= .812,L= 3.75,W= .125	416
80237SCS Century Spring Corp.	EXT O= .240,L= .75,W= .018	122
551CS Century Spring Corp.	EXT O= .500,L= 2.88,W= .091	507
80782CS Century Spring Corp.	EXT O= .625,L= 5.00,W= .063	451
136CS Century Spring Corp.	EXT O= .812,L= 8.50,W= .091	148
80626CS Century Spring Corp.	EXT O= .420,L= 2.75,W= .046	577
80743SCS Century Spring Corp.	EXT O= .500,L= 2.75,W= .069	1200
80621SCS Century Spring Corp.	EXT O= .420,L= 1.50,W= .046	549
5764CS Century Spring Corp.	EXT O= .266,L= 1.16,W= .031	443
80037CS Century Spring Corp.	EXT O= .094,L= .75,W= .011	98
80633SCS Century Spring Corp.	EXT O= .420,L= 1.75,W= .055	246

Springs - Extension, Drawbar

1. Overview

Extension springs and drawbar springs are critical mechanical components designed to absorb and store energy through axial deformation. Extension springs operate under tensile loads, providing resistance when stretched, while drawbar springs (typically compression springs) transmit force through rigid mechanical linkages. These springs are fundamental in maintaining structural integrity, controlling motion, and dampening vibrations across industries such as automotive, aerospace, and industrial machinery.

2. Main Types and Functional Classification

Type	Functional Characteristics	Application Examples
Helical Extension Spring	Coiled design with hooks/loops for tension absorption	Garage door mechanisms, trampolines
Drawbar Spring Assembly	Encased compression springs with mechanical actuation	Railway couplers, heavy machinery
Variable Rate Extension Spring	Non-linear load distribution through variable pitch	Military vehicle suspension systems
Torsion Extension Spring	Rotational force transmission with angular displacement	Industrial valve actuators

3. Structure and Components

Both spring types share common structural elements:

Coil Body: Precision-wound wire (typically ASTM A227/A229 steel) with controlled pitch
End Attachments: Hooks (S-hook, double-loop), threaded inserts, or flange mounts
Coefficient Zones: Active coils for elasticity and inactive coils for structural support
Surface Treatment: Zinc plating, phosphate coating, or powder epoxy for corrosion resistance

Drawbar springs incorporate additional mechanical components: outer housing cylinders and integrated locking mechanisms.

4. Key Technical Parameters

Parameter	Description	Importance
Spring Rate (k)	Load per unit deflection (N/mm)	Determines stiffness and energy absorption capacity
Max Working Load	Ultimate tensile/compressive force (N)	Defines operational safety limits
Wire Diameter (d)	0.5 25 mm range	Impacts fatigue resistance and load capacity
Active Coils (Na)	Number of functional windings	Controls spring flexibility and elasticity
Endurance Limit	Cyclic load threshold (10 10 cycles)	Predicts service life under dynamic loads

5. Application Fields

Automotive: Suspension systems, engine valve trains
Railway: Coupler damping systems, carriage leveling
Manufacturing: Press machines, robotic arms
Consumer Goods: Washing machine balance springs
Aerospace: Landing gear shock absorption

6. Leading Manufacturers

Manufacturer	Headquarters	Representative Product
MISUMI Group Inc.	Japan	OSPF Series Drawbar Springs
Barnes Group Inc.	USA	Acxess Spring Line
Lesj fors Spring AB	Sweden	Variforce Extension Springs
Suhner Holding AG	Switzerland	PowerLoc Spring Systems

7. Selection Guidelines

Key considerations during selection:

Determine load requirements (static vs. dynamic)
Evaluate environmental conditions (temperature, corrosion exposure)
Match end attachment geometry with mating components
Calculate fatigue life using Modified Goodman criteria
Verify dimensional compatibility (free length, solid height)

Example: Selecting a drawbar spring for railway couplers requires ISO 9001:2015 certification and EN 13298 compliance for vibration damping at 1.2 million load cycles.

8. Industry Trends

Current developments include:

Adoption of carbon fiber-reinforced polymer springs for weight reduction
Smart springs with embedded piezoelectric sensors for real-time stress monitoring
3D-printed lattice structures enabling complex load profiles
Increased demand for corrosion-resistant alloys in electric vehicle applications
Integration with Industry 4.0 predictive maintenance systems