CCM Motorcycles Headlamp Mounting Analysis

Company Profile

Until 1998, CCM specialised in competition motorcycles, but saw its position eroded as lightweight engines were introduced into the competition market. Now the company has established a range of Trail and Supermoto models, based on the company's competition motorcycles, designed to appeal to the fast growing on-road/off-road leisure market, illustrating the company's re-direction towards a leisure audience rather than solely to motocross competitors, even though the company continues to sell into the traditional motocross market.

CCM has increased its sales team both abroad and in the UK and has developed a strong UK dealer network. The company is also rolling out distribution and dealer developments in continental Europe and Australia and is extending its product range. Restricted to the UK market until 2000, when European homologation (legal approval) was achieved, CCM has now launched its fully road-legal motorcycles into France and Germany. CCM Motorcycles' world-beating reputation is founded on machines that combine superb handling and performance with the proven reliability guaranteed by the use of the highest quality components.

Scope of Project

A customer had reported that one of the three fixities that connect the instrument panel to the headlamp mounting unit had failed in service. To prove that the fixity had been correctly designed and rated, CCM asked for a stress analysis to be performed to prove that the unit must have been subjected to an abnormally high loading.


Simulation Details

The stress analysis was performed in ANSYS. An axisymmetric model was created and subjected to two loading conditions: the first was a "torquing-up" of the connector to the "as-assembled" condition; the second was the application of the "pull-out" load.

The FE model consisted of 2-D axisymmetric solid elements and encompassed the connector and a finite length of the instrument panel and headlamp housing determined from physical measurements of the assembly.

The first loading condition was the preloading (or "torquing-up") of the connector. To simulate this process, the bolt was modelled in two separate pieces. The gap between the two was the axial length through which the "WELL-NUT" connector was "torqued-up". The "torquing-up" process itself consisted of a vertical displacement load on the lower half of the bolt that brought the two halves into contact.

The design optimisation control file was used to carry out the design optimisation process by varying the design variables, executing the model file, and evaluating the state variables and objective function. Typical design variables for Phase 1 were the width, depth and taper ratios of the shank, and the wall thickness of the small end. Typical design variables for Phase 2 were the radii of some of the big end features, the depth of the bolt hole, the radius and height of the cap web. For both phases the state variables were the maximum and minimum stresses, and the objective function was to minimise the total volume of the design. A number of random designs would be generated by varying the values of the design variables within the specified limits before the optimiser ‘homed’ in to the best design.

The macros were used to carry out single design stress analyses and also full design optimisation analyses for a number of connecting rod designs. The graphic above illustrates the von Mises stress for a design of shank and small end subjected to the compressive inertia loading. The graphic on the right illustrates the von Mises stress for the big end and cap of the same connecting rod design under the compressive inertia loading.

A bonded contact surface was described between the two halves of the bolt, such that, when they came into contact, the bolt became one solid component.

The second loading condition was the application of the "pull-out" load on the headlamp housing. This was modelled by applying a vertical displacement load to the outer diameter of the headlamp housing.

The figures show the component areas that were meshed for the model and a graphically enhanced contour plot of the (2-D axisymmetric) equivalent (or Von Mises) stress distribution at the final "pull-out" load, which far exceeded the normal service load. Even at this excessive "pull-out" load, the connector does not fail.


Benefits

As a result of this analysis, CCM Motorcycles was able to show that their original design was more than adequate and was capable of supporting a load far in excess of the load that would be expected in normal service.