Originally used within the tailoring sector, the term 'bespoke' was used to describe suits that were tailored to fit and specific to the individual wearer.

From a manufacturing standpoint, we see it as a term that says exactly the same thing, but for application solutions. There are a lot of catalogue solutions out there that will 'fit' and will do the job up to a point. When that spring or wireform reaches its limitations, by looking at the material science, the spring characteristics and the application specifics, Central Birmingham Springs can tailor parts to fit a solution that will increase lifespan, improve functionality and provide a bespoke solution to your product.

With the Manufacturing world ever changing and the expectation of continuous improvement within many 'quality' & 'analysis' systems, we know that each individual component can greatly improve a process or product. Bespoke to us, means understanding your needs and then delivering what you need, when you need it and support your application.

So whether it's a 'custom solution' or a 'bespoke solution', CBS are happy to help you get what's right and not just 'close enough'.

Talk to us about your application issues and see how we can get you the right solution, at the right cost and at the right time.

Feel free to send us any enquiries or current issues and we would be happy to discuss further and get you a cost efficient, longer lasting solution.

What is a constant force spring?

A constant force spring, also known as clock spring, is typically a roll of pre-stressed strip that can exert a mostly constant force to withstand uncoiling. This is achieved because the changes in the curvature’s radius are also constant. However, the force is just truly constant when this variation is disregarded.
Constance force springs are generally designed as a rolled ribbon of steel spring which is quite similar to a rolled-up unit when relaxed. Due to their virtual absence of inter-coil friction, constant torque, and long-extension capabilities, many designers have used them in many industrial applications which require a counterbalance against heavy-moving components such as motors or van doors.

Operation of constant force springs

A constant force spring can be tightly mounted with the terminal attached to its load force and interior layers which are coiled around itself. The interior diameter might be tied to a moving drum. During operation, the resistance is generated by the spring's effort to return to the natural, wound state. The thickness and width of the material, the drum’s diameter, and natural radius curvature all determine its extension resistance. Once the spring has been extended to 1.25 times the diameter, it will achieve a full- load rate and easily reach the loading capacity.

Technical features of constant force springs

When choosing constant force springs, keep in mind the following technical features:

Constant force springs are mostly constructed from 301 stainless steel due to its durability and low cost. It is able to attain ductility and highly tensile strength in cold working conditions. In addition, Inconel and high-carbon steel are other common materials.
The drum attracted to the interior diameter is often made of plastic, which provides coil attachment, structural integrity, as well as reduce friction compared to a metal unit.

Estimated life cycles
The life of constant force springs isn’t time-dependent. Instead, it can be determined by the relation between the material’s thickness and its diameter. A higher estimate makes the unit bigger and more expensive, but these units can also last longer.

Required force
The force of the springs should be equal to the application’s requirements. Basically, the usual tolerant should be approximately 10%.

Available space
There are a few combinations of material width and thickness which could be applied for any force values. The natural diameter of the coil will depend on the force, life, and thickness required.

Mounting methods
There is a variety of mounting options for constant force springs. These include single, dual, front-to-front dual, back-to-back dual, and back-to-back dual-dual

Common applications
As said earlier, this type of spring is applied in many industries thanks to its constant torque and long-extension capabilities. Some of the applications include door closers, hose retrievers, cable retractors, counterbalances, space vehicles, appliances, electric motors, toys, hair dryers, gym equipment, furniture & cabinet components, and other devices which require constant loads. Also, you can find these units in retail beverage racks to deliver products to the cooler door.

Extension springs are used in both heavy industry and in domestic tools and machinery; from the cars, we drive to the motorbikes or even to the pens we use. Springs are essential in the construction industry. Heavy machinery as well as minutely accurate scientific equipment use springs to provide the necessary contact pressure, to balance loads and ensure smooth and safe operation. Depending on the method of force application, springs can be divided into two main categories, Compression and Extension Springs.

Extension springs

Extension springs, also referred to as tension springs, work by resisting pulling forces of two moving parts of an application. The extension spring stretches, absorbs the energy and then will pull back to it's closed (free) position.
The variables that are considered in making extension springs include; end configuration, material, end types, length, number of coils, spring shape and diameter. Tension springs also have special hooks on their ends which are used to attach within an application. These hooks are available in various configurations; including full loops, half loops, extended hooks, machine hooks, and crossover centre loops.

Stainless steel and Music wire are the two most popular materials used in making extension springs. These materials can also be modified depending on your needs. The springs can be coated with zinc plating, or any other coating to suit your needs.


Extension Springs are also customised to fit into various forms. With the right design properties, these springs are essential throughout industry. Common uses of tension springs include:

  • Balancing heavy engineering. High load, high stress engineering products. Stamping machines, press brakes, CNC machines, drop presses. All require springs to damped the shock and force of operation.
  • Belt balancing.  Moving high, variable mass product along belts requires load balancing to ensure safe, smooth operation.  both compression and extension springs are utilised to ensure safety and efficiency.
  • Industrial vehicles and load transportation equipment. Springs are required to balance load, ensure driver or operator comfort and most importantly ensure the safety of the vehicle, operator and those around it.
  • Garage doors: Tension springs are used to ease the upward movement in garage doors.
  • Automotive uses: Tension springs are used in various vehicle parts. One of them being in carburettors.
  • Vice-grip grip tools such as pliers: This type of pliers can be tapped in a specific position where it can be used as vice grips. Extension springs are used to keep the grip tight.
  • Farm machinery: Most parts of farm machinery utilise extension springs the same way vehicles do. Extension springs are used in ploughs, graders, bulldozers and harvesters.
  • Washing devices: These springs are used in dishwashers and washing machines to keep the tub balanced. These washers are made using a specific type of extension springs known as suspension springs.
  • Medical devices: Quite a number of medical devices have extension springs. These include surgical lights stretchers, and some small handheld devices.

Even if you’re not sure of the type of Extension Springs spring you need, our experienced team at Central Birmingham Springs team can help you come up with the right spring for your requirements.


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    Central Birmingham Springs Limited
    Unit 7D. Waterfall Lane Trading Estate
    Waterfall Lane. Cradley Heath
    T: 0121 248 1112
    E: [email protected]
    Company No. 04256582