Torsion springs explained
Our aim is to help you understand torsion springs and the role they play in applications. This will help you choose the right solutions for your designs. In this guide, we’ll cover:
What are torsion springs?
A torsion spring is also known by different names:
- Torque spring
- Rotary spring
- Rotational spring
- Torsion spiral spring
- Spiral torsion spring
- Torsional spring
No doubt you see the pattern in these various names to help you understand what these helical springs do. Torque springs, rotary springs, rotational springs – call them what you will. They’re helical-shaped, exerting torque or storing rotational energy
Standard springs need a linear force to work, but torsion springs, work on another principle.
The torsion spring stores and releases rotational energy through torque. Ironically, it’s bending stress and not torsional stress that affect torsion springs.
Torsion springs are typically close wound. Typically, but not always. They can have a pitch to reduce friction between each coil, resisting twist or applied force. Springs are designed around a certain number of turns over a specific length, which generates a given torsion spring constant, also called constant spring or torsional spring constant.
Both ends of a torsion spring can be configured in various ways, from bent to twisted. These ends attach to other components – let’s say the application is a warehouse overhead door or lighting units fitted in ceiling tiles in commercial settings.
When the components turn around the spring’s centre, the spring attempts to push the components back into its original position. A spring can either work in a clockwise or counter-clockwise turn, which is the deciding factor for the direction of the wind.
When high torque is needed for an application, two torsion springs can be configured, with a space between them. This is called a double torsion spring. Double torsion springs involve two sets of coils, with one wound clockwise and the other counter-clockwise.
What are torsion springs used for?
A torque spring is used in applications that need resistance to torque or rotary force, versus tensile or axial compression forces.
Compression springs
Compression springs, shown here, are extremely efficient at storing energy. When force is applied, the compression spring shortens – or compresses – and stores energy. When the spring returns to its original length, the energy releases, pushing back against the load. Common applications include automotive engines, medical devices and electronics.
You can check out these compression springs now.
- Conical
- Closed-end, shown here
Extension springs
There’s also an extension spring, which resists tensile forces. Tensile forces are those that pull the spring. Extension springs, also called tension springs, are coiled with an initial tension. The spring lengthens when it’s pulling, which creates force as it returns to its normal shape. These springs have loops or hooks on the ends, which are attached to components. The spring’s force holds these components together.
Examples of applications that use extension springs include off-road machinery, medical devices and automotive uses.
Which spring should you use?
- If you need the spring to push back, then you should consider a compression spring.
- If you need a pulling motion that extends and retracts, then look at extension springs
- If your components rotate, then your application will work best with rotational force. Use spiral torsion springs. You’ll mount the spring to a mandrel. Mandrel sizes should be equal, or a little less than, 90% of the spring’s interior diameter when the spring is completely deflected (minimum diameter). Avoid mandrels that are too small, as this will result in buckling during deflections.
Torsion spring parameters
Rotary spring types – all torsion spring types, really – are defined by multiple diametric numbers.
Inside diameter (ID):
Also called internal diameter. Specified when the spring has to slip over a mandrel with enough clearance to operate as needed.
Outside diameter (OD):
Typically, a reference dimension that’s specified when the spring needs to fit into a hole with enough clearance, or if outer-housing clearance scenarios exist.
Diameter (D):
The mean diameter is used to calculate the stress and deflection. It equals half the sum of the inside and outside diameters.
Wire diameter (d):
The diameter of the coiled wire that makes the torsion spring. The mean diameter (D) is equal to the outer diameter minus the wire diameter used in stress and the torsion spring rate calculation.
Body length:
The spring coil’s length when unloaded, or at rest.
Spring rate:
The change in load per unit of deflection. This is typically expressed in pounds per degree. The amount of force, in pounds, needed to rotate a spring by one degree determines the spring rate.
Maximum deflection:
The maximum rated deflection angles of springs to overstress.
Maximum load:
The rated load at the rated maximum deflection.
Wind:
A torsion spring should always operate in the opposite direction to the wind direction.
You can see our own range of torsion springs in a variety of sizes and torques. For your convenience, the mandrel size needed is specified for each spring.
Applications that use torsion springs
Whether a heavy-duty torsion spring or a small torsion spring, you’ll find these components in a variety of applications. These include:
- Automotive industry: gear shifters, clutches, automotive valves and vehicle suspension systems.
- Agricultural industry: tractors, sprayers, plows and fertiliser equipment
- Medical equipment: immobilisation devices, hospital beds, and wheelchair lifts
Also, you’ll find them used in:
- Doors and hinges
- Ratchets
- Ceiling light fittings
- Digital cameras
- Watches
- Garage doors
- Hatches and lids
Check out our entire range of torsion springs.
Download free CADs and try before you buy
Free CADs are available for most solutions, which you can download. You can also request free samples to ensure the solutions you’ve chosen are exactly what you need. If you’re not quite sure which product will work best for your application, our experts are always happy to advise you. Whatever your requirements, you can depend on fast despatch.
Request your free samples or download free CADs now.
Questions?
Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.