With the introduction of ultra-high strength (UHS) steels it has been possible to reduce wall thicknesses, down to 0.38mm with Columbus Spirit tubing. In the past material and production limitations restricted the minimum wall thickness achievable with steel. In theory, it would be possible to build identically handling bikes in any material, matching relative material stiffness through appropriate tubing choice. The elastic modulus, coupled with tubing dimensions is what will influence the stiffness of a frame. However, there is a limit to how thin tubing walls can be made before they become susceptible to damage, denting and more importantly buckling.īicycle frame design is about selecting tubing dimensions to appropriately tailor the stiffness and compliance to the desired ride characteristics. To maintain the same stiffness for a lighter weight, we could use less material in a larger diameter, thinner walled tube. Doing this, doubling the diameter results in four times the stiffness. For a given amount of material (and weight), we can increase the diameter of a frame tube but must simultaneously reduce its thickness.
That doesn't mean you should listen to people who claim aluminium frames are much more prone to failing in the real world however by designing frames to minimise the maximum stress levels experienced, the lifetime of the frame will be more than long enough to cover a normal lifetime of use.Ĭontrol the geometries and dimensions of the tubing used to build the frame also has a very large influence on ride characteristics. As tubing diameter increases, so does its stiffness. However, aluminium has no limit and given enough loading cycles, will fail under very small stresses. Steel and titanium have a fatigue limit, a maximum stress below which the material can be loaded an unlimited number of times without failing. Repeated loading of materials can lead to fatigue failure. A tougher material is able to absorb more energy before failing, meaning it will bend rather than breaking in a brittle way. However material toughness is essential in ensuring damage resistance. By designing a frame to be stiff enough, it will also usually be strong enough to withstand cycling loads.
Young’s Modulus is similar for metals made from the same alloy.Ĭontrary to what you might expect, outright strength is less important. This describes the material’s stiffness – the tendency for it to return to its original shape under load. The main property of importance for bike frame design is Young’s Modulus.
0 kommentar(er)
