It is one of the key defining moments in any competition vehicle development, F1 car or bike it doesn’t matter, when the engine fires up or the rider clips into the pedal that first impression of ‘is it fast?’
Two test athletes will ride their current bike (Felt iA and Cervelo P5 Disc) in their normal personal bike set-up. The rider is required to ride at a constant power (wattage), speed and body posture for a minimum of 10 laps within each 20 laps-run.
For both athletes a Kú TF1 bike has been built based on the bike fitter’s prescription. For each athlete, their current personal bike fit co-ordinates have been exactly replicated on a rider specific built Kú TF1 bike. The rider position co-ordinates have been exactly transposed from their current bike onto a Kú TF1
bike and therefor position wise, the athlete should feel or experience no difference in bike setup.
Secondly all other variables in terms of components and wheels have also been eliminated as much as possible by using the exact same components, wheels and tires on both bikes. By having replicated all bike fit co-ordinates from a current bike to the new Kú TF1 and minimizing every possible variable (i.e. wheels, components or accessories) that could influence air resistance, the test helps isolate and focus entirely on the bike frame air resistance.
It is one of the key defining moments in any competition vehicle development, F1 car or bike, it doesn’t matter, when the engine fires up or the rider clips into the pedal that first impression of ‘is it fast?’
In order to maintain test integrity Kú Cycle hired two independent companies specializing in velodrome-based performance testing
HYCYS (formally STAPS) specialize in velodrome based aerodynamic testing.
GebioMized specialize in the biomechanical characteristics of the rider on the bike.
Aerotesting is the ultimate end stage optimisation of bike and athlete for improving triathlon performance. By measuring the rider drag we can investigate ways to manipulate airflow and influence the resulting loads with the goal of reduced drag. Performance comes down to Watts (power input of the rider) per coefficient of drag (CdA) and the ability to maintain that power input and aerodynamic position.
The test is performed on a multi-test event in a velodrome. The measuring runs are randomized and integrated into an overall run list. Specialists from HYCYS and gebioMized are in charge of the execution of the performance test and test technology.
Before the first test run the athlete is asked for the individual race pace (in watts) to determine a specific target pace for the test runs. The pace is set slightly below race pace to minimize the effect of fatigue.
The athlete performs an individual warm up to confirm the test pace, familiarize to the track and test the measuring technology.
The athlete does a short warm up until a constant level of wattage, speed and body posture is reached. From there on, the aerodynamic and biomechanic data is recorded over the duration of approximately 20 laps. Corrections are provided acousticly, if the athlete is off pace or doesn’t ride in the correct line on the track. Laps with a correcting advice aren’t taken into account for the data processing. The run is ended by the scientist with a loud acoustic signal, as soon as 10 correctly performed laps are recorded.
Three athletes of different physical characteristics and varying race level were invited to attend the performance test.
The performance test provided correct and complete data on which solid analysis could be performed with excellent results of the Kú TF1
1. Over 2 test days and including all runs, the mean difference in CdA between the Felt iA (0.235) and Kú Cycle TF1 (0.218) was 0.017m2
2. The athlete was fitted as closely as possible identically on both bikes.
3. Both bikes were set up closely as their standard ‘as supplied’ configuration would allow.
1. Mean CdA of Cervelo P5 Disc compare to mean CdA of Kú TF1 bike result in a difference of 0,002m2.
2. Like for like comparison of test: same athlete fitted identically to both bikes.
3. The Kú Cycle TF1 demonstrated highly consistent and repeatable results for CdA over both days of the test.
4. No positional optimisation was performed on the Kú TF1.
5. Further development to reduce CdA from the optimisation of rider position has the potential to demonstrate considerable improvement of the Kú TF1
The answer to the question “is it fast?” based on the performance test was an overwhelming “yes it is!”
During the CFD testing the Kú TF1 showed decreased rider drag and increased bike drag in comparison to the Cervelo P5 Disc. The CFD results were validated during the performance test and demonstrated consistency
The Kú Cycle TF1 demonstrated and improvement in CdA of 8% over the Felt iA in a straight swap of rider across the two bikes.
The Kú Cycle TF1 demonstrated a CdA of between 0.9% and 2.2% of the Cervelo P5 disc. Considering the estimated maximum margin of error for the test of 3%, the result validates the early design stage simulation CFD results.