A torsion spring is a mechanical spring that works by applying torque or torsional force when twisted along its axis. The spring is made of metal wire wound in a spiral shape, with one end of the wire connected to a fixed point and the other end connected to a rotating point. When the rotation point rotates, the spring stores energy by twisting, and when the rotational force is released, the spring will release and release the stored energy. Although the name implies other meanings, torsion springs bear bending stress rather than torsional stress. They can store and release angular energy, or statically fix the mechanism in place by causing the legs to deflect around the body's central axis.
Torque springs are usually tightly wound, but can have a pitch to reduce friction between coils. A torsion spring can resist the force exerted by torsion or rotation. Depending on the application, the torsion spring can be designed to rotate clockwise or counterclockwise, which will determine the wind direction.

The torsion spring structure is designed to store and release angular energy, or to statically fix the mechanism by causing the legs to deflect around the central axis of the body. When this type of spring is deflected in the preferred direction of the manufacturing wind, the diameter of the main body will decrease and the length of the main body will slightly increase.

Torque springs have a wide range of applications and are essential in various industries. Common application examples of torsion springs include:
Automotive industry: Torque springs are used for door hinges and vehicle suspensions, helping to ensure smooth operation of these components
Home: These springs are suitable for garage doors, clothespins, and clipboards, helping them operate seamlessly.
Electronics industry: Torque springs play a crucial role in the operation of switches and cameras, making them an essential component in electronic devices.
Toys and consumer goods: They are used for toys, clocks, and other consumer goods that require rotational force.
Mechanical: Torsion springs are commonly used in various types of machinery to facilitate the smooth operation of levers and other components.
Ship and outdoor sports industry: Twisted springs are used in life-saving devices, such as personal ship boarding steps, and their durability and corrosion resistance are crucial.

When designing a torsion spring, it is important to consider your application and whether you need circular, rectangular, or irregular wires (such as square wires). The simplest and most common torsion spring design is a monolithic torsion spring made of rectangular wire, with straight ends at both ends, but this design format can be modified through bending and forming.
Due to the fact that the position of the leg bearings/connectors must be on the left or right side during assembly, the direction of the manufacturing wind is also important for torsion spring applications. A torsion spring is usually supported by a rod (mandrel) that is aligned with the theoretical hinge line of the final product. The design of double torsion springs is more complex and requires consideration of manufacturing methods. Double torsion springs are wound from the center, while single torsion springs are wound from both ends.

The torsion spring structure aims to store and release energy or fix the mechanism in place by deflecting the axis around the centerline of the main body. When deflected in the correct direction, they reduce the diameter of the body and increase its length.
The winding direction of the torsion spring must meet the specific requirements of its application. When assembling, the load-bearing legs should be located on the correct side (left or right) to ensure proper alignment. The torsion spring is supported by a spindle corresponding to the hinge line of the application.
inside diameter
The inner diameter of a torsion spring is the width inside the coil helix, measured perpendicular to the central axis. This size determines the outer diameter of the shaft or mandrel that can be smoothly loaded into the spring. For optimal operation, it is recommended to include a 10% gap in the inner diameter to allow the inserted components to move freely.
outside  diameter
The outer diameter of a torsion spring is the width outside the coil helix, measured perpendicular to the centerline. This size defines the diameter of the spring insertion hole, taking into account all necessary clearances required to ensure the free operation of the spring.
Wire diameter
Wire diameter refers to the thickness of the wire used for winding and forming torsion springs.
The average diameter is calculated by subtracting the wire diameter from the outer diameter and is used for stress and spring rate calculations.
body length
The main length of a torsion spring is measured when the spring is in an unloaded state, and is determined by measuring the outer surface of the end coil. As torque is applied, the length of the main body increases while the diameter of the spring decreases.
leg length
The leg length of a torsion spring refers to the distance from the end of the spring leg to the central axis of the coil. It will affect the load or torque required to store energy in the spring. The shorter the leg, the greater the torque required to bend the coil. In addition, the legs of the torsion spring can have different lengths.
Bus Circle
The total number of coils in a torsion spring refers to the effective number of coils in the coil. An effective coil is a coil that twists or deflects under load and releases energy when the spring is released. Due to the non active coils occupied by the legs, the total number of coils on the bus is slightly less than the total number of coils. For a torsion spring with a leg angle of 0 ° in the free position, the total coil value is an integer.
Dimensions of torsion spring
bitumen
The pitch of a torsion spring is the centerline distance between two adjacent effective coils. In a tightly wound spring, the pitch is approximately equal to the wire diameter. However, dense wound springs generate significant frictional forces during the deflection process. It is usually recommended to specify the total number of turns and body length of the torsion spring, rather than the pitch.
winding direction
The winding direction of a torsion spring is specific, it can be right-handed or left-handed. When wound to the right, the coil rotates clockwise, and when wound to the left, the coil rotates counterclockwise. By observing the top of the torsion spring, the winding direction can be easily identified.
The design of torsion springs should ensure that the load and winding direction are consistent. If the load and winding direction need to be opposite, the load and angular deflection must be reduced.
Understanding the winding direction is crucial for the normal function of a torsion spring, as it determines the direction of deflection. The placement of torsion springs in applications depends on the winding direction, which can affect the positioning and movement of the front and rear legs.
For right-handed torsion springs, the hind legs will twist clockwise, while the front legs will twist counterclockwise. For left-hand torsion springs, the situation is exactly the opposite: the hind legs will move counterclockwise, while the front legs will move clockwise.
The winding direction of the torsion spring
Leg angle
The leg angle of a torsion spring is the angle between the legs when the spring is not loaded, ranging from 0 ° to 360 °. The common standard torsion spring leg angles in stores are 90 °, 180 °, 270 °, and 360 °. In addition, manufacturers can customize leg angles to meet specific customer requirements.
Leg angle
The leg angle will affect the total number of turns of the torsion spring. As mentioned earlier, the number of bus coils is slightly less than the total number of coils in the winding. The following formula describes the relationship between leg angle and the number of bus turns.
Leg angle in free position=number of inactive coils (fractional value) x 360 °
Leg direction
The leg direction of a torsion spring refers to the way the leg bends relative to the diameter of the spring. The sharp bending of the support legs can limit the load-bearing capacity of the spring, as stress is often concentrated in the bending area. Common types of leg directions include axial, tangential, radial, and radial tangential. Among them, the tangential leg configuration bears the minimum stress.
Leg direction
Leg style
The legs of a torsion spring can be twisted, bent, hooked, or looped for easy installation and operation. The following are common leg styles for torsion springs, but customized leg styles can be provided according to customer requirements.
Straight leg
Straight offset leg
Short hook end
hinged end
Circular end
Leg style
The performance of a torsion spring is determined by the following characteristics and parameters:
Spring Index
The spring index is the ratio of the average diameter to the wire diameter of a torsion spring. It provides insights into the tightness, strength, and manufacturability of spring coils. By reducing the spring index, the spring strength can be increased by increasing the wire diameter or reducing the outer diameter of the spring. Compared to thin wire springs, thick wire springs have greater strength. Lowering the spring index will tighten the coil and increase the force, but it will also increase the compressive stress on the coil. Due to increased mold wear and additional processing required to extend service life, manufacturing springs with lower indices is more challenging. Springs with an index lower than 4 or higher than 25 cannot be manufactured, and the ideal range is usually between 6 and 12.
Angular deflection
Angular deflection is the angular distance at which one leg of a torsion spring moves from a free position to a loaded state.
angular displacement
maximum deflection
The maximum allowable deflection is the maximum angular deflection that the torsion spring can achieve under load, without bending or excessive stress. If the spring exceeds this deflection, the coil may not be able to return to its original position after the load is removed due to material yielding.
The maximum angular deflection is the degree to which a torsion spring can twist under load, beyond which it will bend due to excessive stress. Generally, torsion springs with larger diameters and more coils have higher deflection ability. For example, garage door springs can withstand multiple rotations without bending due to their large number of coils and low design stress.
Maximum Load
The maximum load is the maximum torque that the torsion spring can apply to the spring leg before bending. The load-bearing capacity of a torsion spring is limited by the maximum deflection or maximum load (whichever comes first).
Spring stiffness
Spring stiffness is a measure of the rotational force applied to a torsion spring per unit angular displacement. The following formula can be used to calculate the spring stiffness of a circular spiral torsion spring:
Spring rate per degree (pounds inches/degree)=. PL/Θ = E xd^4 / 3888 x D x Na
In this equation, P represents the load, L represents the force arm, Θ represents the angular displacement, d represents the wire diameter, D represents the average diameter, Na represents the effective number of coils, and E represents the elastic modulus of the material. The constant 3888 is a theoretical coefficient used to adjust the friction between adjacent coils and between the spring body and the connected components.
The following table provides the elastic modulus of different types of torsion spring wires, which is crucial for calculating spring stiffness:
Elastic modulus of spring wire
Elastic modulus of spring wire (psi x 10 6)
Music Line 30
302, 304, and 316 stainless steel grades 28
17-7 stainless steel 29.5
Chromium Vanadium Thirty
Chromium silicon thirty
Phosphor bronze 15
The spring constant is related to torque and angular displacement, as shown in the following equation. This relationship helps determine the amount of torque required for a specific angular displacement or the amount of angular displacement required to generate a certain force.
Angular displacement=torque/spring stiffness
Torque=spring stiffness x angular displacement
pressure
The bending stress of a helical torsion spring can be calculated using the following formula:
Bending stress (psi)=32 PLK/π d ³
Here, K represents the bending stress correction coefficient. When torque is applied to the torsion spring, both the inner and outer diameters increase due to the higher bending stress on the inner surface compared to the outer surface. For circular spiral torsion springs, the bending stress correction factor for the inner diameter is calculated using the following formula developed by Wahl:
Key Information ID=[4C ² - C-1]/[4C (C-1)]
Here\ (C \) represents the spring index. The bending stress at the inner and outer diameters can be approximately calculated using the following formula:
Key Information ID=[4C-1]/[4C-4]
KOD = [4C + 1] / [4C + 4]
The torsion spring should be loaded in the direction that causes the spring diameter to decrease, as applying residual forming stress in this direction is beneficial.