Case studies

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Case Study 1

Testing a new rear wheel at the velodrome:

  1. Perform at least 6 laps with current/base wheels – this is the baseline.
  2. Swap rear wheel to perform another 6 laps – this is test 1.
  3. Return to the current wheels for a final 6 laps – this is the repeat baseline.
  4.  Conclusion:
    • Looking at the data, there is a 0.4% difference between the first baseline and the repeat baseline CdA, this means that anything larger than 0.4% on test 1 can be resolved and conclusions can be taken.
    • New rear wheel test yielded a reduction in CdA of 1.3% – this is larger than the baseline confidence delta, therefore with confidence we can say that the new rear wheel reduces the rider’s CdA. Larger differences increase the confidence.

Case Study 2

Testing four different helmets on a straight, flat, quiet road:

  1. Perform 3 1000m out and back runs with a current helmet – this is the baseline
  2. For four subsequent tests, the rider changes between the four test helmets – these are tests 1-4
  3. Return to the current helmet and perform the same 3 1km out and back runs – this is the repeat baseline.
  4.  Conclusion:
    • Looking at the data, there is a large 4% increase in CdA on the repeat baseline – this baseline confidence delta is too large to draw any conclusions from the tests. Speed, distance, and wind conditions are all much less than 4% different – so something else must be at play.
    • It is noticeable that, after looking at head and chest position data from Aerobody, there has been a 15mm increase in average head position from the baseline to the repeat baseline – this almost certainly explains the large CdA increase.
    • The test helmet data also backs this up, there were expectations pre-session that all helmets would reduce drag compared to the current helmet, however that data says this is not the case, even saying the performance is worse in some cases – this is because the head positions also were different for each test, and therefore ruined the results.
    • This means the rider did not keep a consistent body position throughout the session and implies that the rider couldn’t sustain the position for that length of time – which is itself a useful conclusion for the rider.
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Case studies

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