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Timemachine model build-up

The model build-up of the Timemachine is a complex and highly engineered process, consisting of fourteen steps. Those steps range from computational fluid dynamics evaluation, to tube shape analysis, the design of the V- and Flat-Cockpits, to the use of the unique Medusa arm at the Sauber Engineering windtunnel – just to make sure the numbers add up.

Pre-processing / model build-up

Step 1 – Sub-assembly definition

The 3-D CAD of the previous Timemachine TM01 is defined by sub-assembly components to enhance the understanding of aerodynamic contributions.

Step 2 – Early CFD evaluation

The previous Timemachine TM01 model is tested against known wind tunnel performance metrics – an extensively tested wheel is referenced.

Step 3 – Mesh generation

To develop the most accurate Computational Fluid Dynamics (CFD) model, highly precise mesh generation is key. Each intersection of mesh is a point that will be used for measurement.

Step 4 – Mesh refinement

4.a The precision of the mesh is enhanced to capture maximum detail – the mesh is refined to the point where the data generated by computer simulation matches that produced in the wind tunnel.


A refined mesh of 0.5mm is used at the most complex areas, spokes for instance. 

4.b Refinement of the process leads to a simulation model with 40 million mesh cells. To process this amount of data a highly powerful computer is required.

4.c These computations enabled the assessment of 4 boundary layers on most of the tubes, and up to 6 layers at critical areas. This is the most accurate measure of boundary layers possible, and leads to an industry-leading final product.

Step 5 – Discipline weighting

Due to differences in average speeds in triathlon and time-trial performances, weighting of yaw angles is important to develop accurate, discipline-specific results. 

Step 6 – Pedal evaluation

Testing the influence of leg positions through the pedal stroke promotes a clearer understanding of potential improvement areas.

Step 7 – Rider definition

Including both the rider and the appropriate position are critical to real-world aerodynamic performance. Throughout the study, standard triathlon and time-trial positions are simultaneously evaluated.

Calculations

Step 8 – Component contribution

By isolating the sub-assemblies, having a refined mesh and an accurate and precise CFD model in operation, the definition of how all components contribute to the system is calculated for headwind and crosswind conditions.

Step 9 – Tube shape analysis

The CFD model is ready, the rider is established, the environment is set – the new bike begins with a tube shape evaluation, using all known parameters.

Step 10 – Tube shape analysis

For each frame tube (eg. headtube, downtube, toptube, seatube, seatpost, seatstays and chainstays) the system generates 16 tube shape variations tested at 9 yaw angles, and two rider positions. 

Evaluation

Step 11 – X vs Y Merit

The major goal of the tube shape study was to define the overall best performing combination of shapes for Coefficient of Drag in headwind (Cx) and crosswind (Cy) conditions.

Step 12 – Hydration evaluation

Understanding how hydration accessories and their placement affects aerodynamic performance, leads to specific downtube and seatube profiles, with two-position mounting options for the downtube.

Step 13 – Accessory evaluation

Storage impacts overall aerodynamic performance - the rear-mounted storage box enhances Cx performance without a sacrifice in Cy, even at extreme yaw. 

Step 14 – V-Cockpit & frame development

14.a From the tube shape study it was learned that higher arm pad stack conditions of most middle and long-course triathletes presented a new challenge. With taller stack height, the torso and legs are exposed, causing a back-pressure and contributing to increased overall drag. 

14.b Additionally it was observed that a disproportionate amount of turbulent airflow was created. Engineers and aerodynamicists worked together to formulate a system to minimize these effects – the end result is the patented V-Cockpit. 

14.c With cleaner air moving rearward and a decreased pressure differential the result is more free speed. In addition to aerodynamic performance, the forward offset promotes enhanced vertical compliance – the optimal balance of performance and comfort. 

Validation

Medusa Arm Application

Sauber Engineering possess one of the most cutting-edge wind tunnel and aerodynamics systems in the world. Combined with their high-performance wind tunnel is the legendary “Medusa Arm”– a real-time, real-condition, flow monitoring system that directly measures areas of high and low pressure – areas of good and bad aero performance.

This system provides accurate and precise information on exactly how frame shapes and components contribute to flow patterns. The Medusa Arm is used in development, to validate the simulation results with real-time measurements.

This is a first in the bicycle industry, and it is the foundation of the new Timemachine aerodynamics.

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