Reaching critical speed causes first-order bending. This complex formula is used to calculate the critical speed for every driveshaft. All driveshafts have a critical speed, depending on their length and diameter. The shaft material elasticity is an important part of the equation. This is the material's ability to resist non-permanent elastic deformation. For a driveshaft, this translates into bending. The higher the modulus of elasticity (MOE), the less it bends. Getting these numbers can be a little tricky because most shops keep the specific numbers they use as trade secrets. For steel, the basic MOE is 30, aluminum is 10, and carbon fiber depends on the manufacturing processes used, so no general numbers are available.
{}