COIL SPRING CALCULATORS

Coil springs are mechanical elements which are elastic and used to store energy when its length changed due to an external force exerted on it. Generally coil springs are linear and obey Hooke’s law F= k Δx. Here F is exerted force on spring; k is spring rate which shows the spring resistance to length change, Δx is deflection due to force. Coil springs are usually made from spring steel.

Coil or wire springs are made to resist and deflect under  tensile, compressive, or torsional loads. Engineering calculators on mechanical coil springs were developed to calculate spring parameters of wire springs which are under compression, tension and torsion loads.

Note: Following calculators have been developed by mainly using Shigley's Mechanical Engineering Design book. For further information on subject , this reference source can be used.

CALCULATORS
COMPRESSION COIL SPRINGS
Calculator Usage
Compression Springs Design (Dimensional or Rate Based) Calculates compression springs parameters for wire springs according to dimensional or rate based inputs. Calculation results generated by the calculator are spring rate, solid height, torsional shear stress at solid height, buckling check, outer diameter expansion, load-deflection curve, stress–deflection curve, etc.
Compression Springs Calculator (Load Based Design) Calculates compression springs parameters for wire springs according to load based inputs. Load based inputs can be Load 1 @ height 1 and spring rate, Load 1 @ height 1 and free height and Load 1 @ height 1 and Load 2 @ height 2 Calculation results generated by the calculator are spring rate, solid height, torsional shear stress at solid height, buckling check, outer diameter expansion, load-deflection curve, stress–deflection curve, etc.
Critical frequency of helical springs Calculates the natural frequency of a coil spring whose one end is against flat plate and the other end is moved by a cyclic sine-wave motion.
Compression springs design for fatigue loading Calculates stresses occurred at compression springs which work under dynamic loading. Gerber, Sines and Goodman fatigue failure theories are used for the calculations.
SUPPLEMENTS
Allowable Torsional Stresses for Compression Springs Maximum allowable torsional stresses for coil compression springs in static applications.
End Conditions for Compression Springs Stability Analysis End condition constants for coil compression springs stability analysis
Formulas for Compression Springs Design List of formulas used in the compression springs design calculators.
Formulas for Compression Springs Fatigue Design Formulas for compression springs fatigue design
Compression Springs Terms and Definitions Compression springs terms and definitions
Spring Steels for Coil Springs List of spring steel materials given in calculators.
EXTENSION COIL SPRINGS
Calculator Usage
Dimensional design of extension springs Calculates dimensional parameters of extension springs with the knowledge of different parameter sets such as spring rate & free length, spring diameter & free length, preload & spring rate, spring diameter & spring rate etc. Calculation results generated by the calculator are spring height,  number of body coils,  spring body length, spring rate, spring initial preload range, spring index.
Stress analysis of extension springs for static loading Calculates shear and tensile stresses on extension springs with full twisted end for static loading case. Calculations are done with the knowledge of spring wire diameter, spring diameter and maximum working load. Calculation results generated by the calculator are shear and tensile stress at spring end, shear stress at spring body, factor of safety values for the points where the stress values are calculated.
Stress analysis of extension springs for fatigue loading Calculates fatigue resistance of ordinary extension springs with full twisted end. This calculator can be used to check critical points fatigue resistance against dynamic loading. Gerber and Goodman failure criterias are used in this calculator for the fatigue evaluation of the spring.
SUPPLEMENTS
Allowable Stresses for Extension Springs Maximum allowable stresses for helical extension springs in static and fatigue applications
Formulas for Extension Springs Static Design List of formulas used in the extension springs static design calculator.
Formulas for Extension Springs Fatigue Design List of formulas used in the extension springs fatigue design calculator.

Reference:
  • Budynas.R , Nisbett.K . (2008) . Shigley's Mechanical Engineering Design. 8th edition.  McGraw-Hill
  • F. P. Zimmerli, “Human Failures in Spring Applications,” The Mainspring, no. 17, Associated Spring Corporation, Bristol, Conn., August–September 1957.
  • Shigley J.E. , Mischke C.R. (1996), Standard Handbook of Machine Design, 2nd edition
  • EN 13906-1: 2002 - Cylindrical helical springs made from round wire and bar – Calculation and design – Part 1: Compression springsompression springs
  • Courtesy of Associated Spring (1987)., Design Handbook