BOA/Bevelled Oval Application

Durable tension springs made of oval wire are designed for highly dynamic uses. The oval wire profile is 36 % flatter than a round wire with the same resisting torque, and this means:
oval wire with the dimensions 1.00 x 1.54 is just as strong as a round wire of d = 1.30.

With a side ratio of 1.54, the oval wire profile offers you the best relation of spring force to spring deflection. The default resistance torque is bigger, thus more elasticity than an ellipse and a tension distribution that is 30 % more even than that of a rectangle. The spring deflection of the oval is correspondingly greater, with the homogeneous tension distribution having an extremely positive effect on fatigue strength. The eyelet is the typical weak point of tension springs.

Here, too, the oval profile has several advantages:

The bending stress on a typical eyelet falls by 43 % – this means that the eyelet is more stable than the spring body itself, the service life rises by 1,000 times. As a result, the advantages of tension springs can also be used in practice: in comparison to compression springs, they work torque-free, in a straight line and completely without the risk of kinking. Thanks to the pre-tension in the coils, tension springs do not need to be pre-tensioned as much, meaning that flatter characteristic curves are realised. We finish dynamically stressed springs with shot blasting under pre-tension so that they are absolutely durable and completely relaxation free.

Take a look at the advantages of our patented new developments for yourself, watch our film about these high-performance tension springs:

The advantages of oval wire high-performance tension springs:

  • 36 % flatter construction than round wire
  • Best ratio of spring force to spring deflection
  • More elasticity
  • More even tension distribution
  • Greater spring deflections
  • 1000x service life
  • Flatter characteristic curves thanks to higher pre-tensioning
  • They work torque-free, in a straight line and without the risk of kinks
  • Thanks to the finishing, they are absolutely durable and completely relaxation-free

We have expanded our range of standard BOA high-performance tension springs They now comprise a:
nominal force range of 21-1600 N (up to 2015 > 44 – 1130 N)
working lengths: of 14 – 1120 mm (up to 2015 > 20 – 1120 mm)

On specific feature of the BOA high-performance tension springs also increases their utility. Thanks to the high pre-tension in the coils, even from Lo there is 2x to 3x the initial force in comparison to standard springs.

Force/deflection comparison of BOA high-performance tension springs versus round wire tension springs.
Both springs have the same dimensions: De = 26, Lo = 50
Thanks to the high pre-tension, the BOA high-performance tension spring effectively achieves more force earlier, in spite of 35% lower spring rate (R=3.2 instead of 4.32).