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If you are wondering where to find torsion spring calculators look no further. Planetspring.com offers a torsion spring calculator that was constructed with you in mind. We have made the simplest and most effective torsion spring calculator on the web today. This calculator will help you from A-Z in calculating spiral torsion springs. Before you get started on your torsion spring design you will need to know how to measure a torsion spring. Please see the picture at the top of the calculator or watch our “how to measure a torsion spring” video to learn how to measure number of active coils, wire diameter, and outer diameter, because these will be the 3 inputs needed to begin the spring rate calculation. Torsion springs are often metal springs. In order to calculate your spring properly you will need to know the type of spring wire. For example, are you looking for music wire springs or a stainless steel torsion spring? Simply choose the type of wire and you are ready to calculate.

Once you have hit the calculate button you have created your torsion spring design. You have outputs such as the spring rate and the spring constant as well as any other output you will need.

In order to completely understand your spring design you will need to understand the spring rate, load, and index of your spring.

The rate of your spring is a constant. This constant will let you know how much torque (force) is needed to move the spring 360 degrees.

The load of a torsion spring is how much force in weight (pounds, ounces, grams) needed to move a spring a particular distance of travel in degrees. For example you have a torsion spring with a rate of 5 inlbs/360 degrees. You want to know what the load is if you need to travel 90 degrees plus having 45 degrees of preload. So you take the rate (5 inlbs /360 degrees) to get your torque per degree (5/360 = 0.01388 inlbs/degree). Multiply it by the degrees you are traveling (90 degrees) plus the preload (45 degrees). This will give you a total load.

Formula to determine total load (torque) is:
(Torque / degree) x (Degree of Travel + Preload) = Total Load
0.01388 (90 +45) = 1.873 inlbs

Also with a torsion spring you will have a preload (L1) and a working load (L2). For example on our spring above our preload (L1) would be 0.624 inlbs @ 45 degrees of travel. L2 would be 1.873 inlbs @ 135 degrees of travel if these are the measurements in your design.

The next thing you want to remember when designing your spring is the index. The index of your spring will let you know the stress level of your spring. This value is one of the outputs you will get from our calculator. Once you have calculated your spring take a look at the “spring index”. If the value in that column is lower than a 4 you will have a very high stress spring with small amounts of degrees of travel. This will cause the spring to become very fatigued and you will have spring failure or spring setting. If your index is a 14 or higher your spring will be very difficult to manufacture because of it's instability. This type of spring can be made but will come at a high cost to you because it is very hard to manufacture. If you would like optimum repeatability and a cost effective spring make sure your spring index is between 7 and 13.

Configuring a spring rate calculation by hand, calculating spring constant or calculating any type of spring constant physics can be tricky. However, if you would like to use the torsion springs formula to design your torsion springs or you need an explanation of torsion springs please visit our torsion springs technical article.

How to measure Torsion Springs video
See how to measure torsion springs here
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Enter Your Spring Dimensions

Please select your desired unit of measure:   English Metric
Diameter of spring wire, d: IN MM
Outer diameter of spring, Douter: IN MM
Inner diameter of spring, Dinner: IN MM
Number of active coils, na    
  Length of leg 1: IN MM
  Length of leg 2: IN MM
Please select a material: