FINITE ELEMENT ANALYSIS

The Client’s Need

Since the 1990s, full-suspension mountain bikes have gained popularity, with several styles of rear suspension now on the market. However, most rear suspension systems pose problems of energy loss during travel. A boutique mountain bike company had patents on technology based around a rocker-style suspension link that had lower potential energy loss than other models, but unfortunately, some of the rockers were failing. The bike company engaged NOVO to optimize the rocker by determining the cause of failure, implementing design changes to eliminate it, and applying those design changes while incorporating new cosmetic elements from an updated rocker on a different bike model. The final design had to be stronger, lighter, and more visually appealing than its predecessor.

The Technical and Design Challenges

Finite element analysis (FEA) was used to analyze stress and reduce stress concentrations on the rocker while lowering the part weight and ensuring adequate stiffness. NOVO engineers applied an in-depth understanding of the geometry of the bike, the rocker material properties, and the forces applied to set up the FEA and create an accurate use model. To achieve this, the engineers determined the boundary conditions for the part by calculating the x– and y-components of force according to worst-case loading at maximum suspension travel. After the FEA was validated by matching the real-life failures of the original rocker, the engineers began optimizing a new design based on the cosmetically enhanced rocker from the other bike model. Using the FEA as a guide, the engineers worked through many iterations of the part, adding and removing material and including enough safety factor to compensate for a lifetime of stresses.

The Engineering Behind Great Products

Besides applying the FEA, the engineers ensured the design was manufacturable and rugged. The stress distribution indicated where wall thicknesses could be reduced, which yielded at part weight below the client’s target without compromising durability. The client machined and fabricated NOVO’s design, assembled it onto a bike, and then sent it to a separate facility for life-cycle testing. The design passed all tests and has been in constant production since 2009.