What this calculator does
A barrel spring is wound with a larger middle diameter and smaller ends. The shape improves lateral stability and keeps the spring centred in a bore, which is useful where a straight cylinder would buckle. The calculator computes rate from the varying mean diameter and flags contact with the bore.
Inputs and outputs
Inputs
- End mean diameter and middle mean diameter
- Wire diameter
- Number of coils
- Free length
- Bore diameter
- Working load
Results
- Spring rate
- Deflection and stress
- Maximum outer diameter
- Bore clearance
- Stability check and curve
Typical applications
- Shock absorbers
- Pneumatic valves
- Pen mechanisms
- Medical devices
- Small pumps
Design notes
The middle diameter should clear the bore by at least 5% at full compression. Barrel springs are harder to grind square, so specify closed and ground ends only where the application needs a flat bearing surface.
The interactive calculator interface is currently in Chinese. Enter your values there, or send us the load, travel and space constraints and our engineers will return a checked calculation sheet in English.
Frequently asked questions
How is a barrel spring different from a tower spring?
A barrel spring is widest at the centre and narrow at both ends; a tower spring is widest at one end. The barrel shape centres itself in a bore, while the tower shape nests to a very short solid height.
Does the varying diameter change the rate?
Yes. The active coils have different diameters, so stiffness is calculated from the effective mean diameter and the coil sequence rather than a single value.
Can the ends be ground flat?
Yes, closed and ground ends are available. They add cost, so they are normally specified only when a flat bearing surface is required.
Related calculators
Need this spring manufactured?
Send a drawing, a sample or the parameters from this calculator. We will review manufacturability and reply with a quote and a sample lead time.