Hollow Coil springs

[Jozo]

I read somewhere that coil springs made of hollow wire/rod could be used to reduce weight. Most of the torsion of a coil spring affects the outer parts of the spring while the core is essentially unstressed. So, the core is not really of any use. Does anyone know about use of hollow coil springs in racing?

[enzo]

Yes, it could be done, but I've never heard of anyone trying to do so.

[Stacy]

Originally posted by Jozo
I read somewhere that coil springs made of hollow wire/rod could be used to reduce weight. Most of the torsion of a coil spring affects the outer parts of the spring while the core is essentially unstressed. So, the core is not really of any use. Does anyone know about use of hollow coil springs in racing?

I think you're right, but the only application I've heard of in that area is hollow roll bars. There the weight is worth saving over a solid iron bar, but springs are so light anyway I suspect it wouldn't be worthwhile except at top levels if at all.

Stacy

[yelwoci]

It would be probably cheaper to use exotic materials for lightness rather than trying to form hollow springs.
The X-section of the tube has a major bearing on the spring performance. The risk would be for the hollow coil to become ovalloid, this reducing its effective diameter, leading to overwork in this area and ultimately failure. It would also be more susceptible to external damage.

IanC

[Jozo]

If 'exotic' materials can be used, then you could make hollow springs out of them as well and save even more weight! I may be wrong here, but I think for components that are subjected to cyclic elastic deformation you need to use a metal. The reason for this is that the deformation generates heat which, in the case of polymers, leads to failure. So the alternatives are basically metals with high yield strength, i.e. steel and titanium alloys.

Buckling, the risk for the coil cross-section to become ovaloid, could be a limiting factor in the design of such springs, but only with fairly thin walls.

[joseff]

Slightly off-topic: if you're that obsessive about weight in the first place, why not use torsion bar suspension?

[wuzak]

Hi, everyone. I'm new to this great site, and have spent the last couple of hours checking it out.


Joseff is right about using trosion bar suspension. Many F1 teams (Ferrari is one) use torsion bar springing, particularly on the front suspension. The reason for this may actually be less to do with weight, but more to do with compactness of the design. (As an aside, I think Ferrari have even done away with conventional pivots on their front suspension and actually use a flexing joint instead.)

As for the composition of spring components, I don't believe they have to be metal, but cannot be made from brittle materials.

Composite material springs do exist. Chevrolet's Corvette uses a single transverse FIBREGLASS leaf spring, and have for many years. I don't know much about fibreglass, but I wouldn't have thought it a suitable material for springing.

Also, I belive one of the leading manufacturers of carbon brakes has been developing a type of carbon fibre spring