rider can take several paths for a Flying 200m. What path gives the shortest time?
- A rider can sprint hard for some amount of time. Perhaps a rider records this effort using a power measuring device and then uses the data to create a Power Function (Wingate Test). Based on this function, how far should the rider accelerate before the rider "dives"? Does it matter?
- Are the differences significant? Yes, a small difference of a 0.1s can mean several places in a match sprint seeding in even a regional competition.
- A rider should ride the turn with wheels on the measurement line. Often riders don't. This makes the path longer. How much extra time does it take?
- A rider can cross the start line anywhere on the track. Is starting close to the measurement line better than starting further away?
- A rider can "dive" from the top of the banking at various points. Is one point better than another?
- What is the effect of altitude? Air density? Rolling resistance? A different track?
- If a coach believes that a different pattern of acceleration would improve a rider's time, what does the model say about the coach's idea?
Velodromes come in all shapes and sizes. Shorter velodromes, particularly, have different typical rider paths for a flying 200m. Hence this model only applies to a 333.3m velodrome. The model assumes that the track has constant radius turns and a constant track width. It assumes that all points on the measurement line are at the same elevation (level) which often is not the case. It assumes that a rider cannot ride below the measurement line.
The time calculated by the model changes as the configuration of the velodrome changes. Set the banking in the turn and in the center of the straight to zero (a flat track) and see the difference configuration makes. This means that some tracks are inherently faster than others.
Path of Rider/Model
In a typical flying 200 the rider rides at the top of the track in turns 3 and 4, continues through the "dip" in the home straight, begins to accelerate, dives for the start line from somewhere high on the boards in turn 2, crosses the start line (where timing starts), and continues through turns 3 and 4 to the finish line.
The model assumes that the rider starts at the top of the track (actually, 0.5 m from the boards to accommodate the width of a rider). The model assumes the rider must dive for the start line after turn 1 and at or before the end of turn 2. The model allows a rider to pick a point at which the rider will begin to accelerate and pick an initial speed from which acceleration starts. This can be from anywhere after the start of turn 3. The rider can cross the start line at some distance away from the measurement line. The rider rides directly from the point at which the rider crosses the start line to the measurement line at the beginning of turn 3 . The rider can ride the measurement line to the finish or the model can show the result of riding a path in turns 3 and 4 that is higher than the measurement line.
The model is based on the differential equaitons of motion of a rider. This concept is explained in the Glossary. An explaination of wheel parameters is giving in Wheels Concepts.
A rider has a Power Function which is used to simulate the power of a rider doing a sprint. (See Wingate Test for how to create a power function.) Wheel parameters (weight, rotational inertia, and aerodynamic drag coefficient) are included so that one can estimate the effect of different wheels. Since gearing and cadence are important considerations, gearing is included, and a plot of cadence verses time shows cadence at each point along the rider's path.
Using the Model
An inexperienced rider is doing a Flying 200m for the first time. The rider starts accelerating somewhere in turn 1 and dives at the last possible moment crossing the start line near the measurement line and riding the turn 0.2 meters high for a time of 13.800 s.
The rider gets some coaching. The coach has the rider sprint as hard and as long as possible, recording the power in a power measuring device. The data from the sprint is converted to a power function. This shows the rider sprinting for 30 seconds with a maximum power of 750 watts and an average power of 500 watts. The coach plots the flying 200m time as functions of "Dive Point" and "Acceleration Point". The model shows that the optimal acceleration distance before the dive is 75 m and the optimal "Dive Point" is at 0 m. This improves the rider's time to 13.726. (Dive point and Acceleration Point are not independent variables, so this process may take several guesses.)
A plot of the cadence shows that gearing needs to be changed from the rider's initial choice of 53x15 to 48x15.
Analysis of the point at which the rider should cross the start line shows that it would be best to cross at 2.2m from the measurement line, improving the time to 13.719 s.
After some coaching and practice the rider can ride the measurement line through the turn. This improves the time to 13.673.
The coach suggests that the rider should borrow some good wheels. The rider borrows a deep section spoked wheel for the front and a light weight disk for the back. The time improves to 13.579 s.
At this point the coach suggests a period of development of sprint power. Power improves by 10%. This improves the time to 13.177.
The rider was feeling down one day when times were worse by 0.2 s. The coach pointed out that the air density had increased from the day before and that this accounted for the change, not rider performance.
The rider improved some more and was close to a qualifying time. One more ride was possible. Should the rider ride during the day or later in the evening. The temperate was expected to drop by 10 degrees from mid-day to evening. The rider choose to ride mid-day when the air was less dense. Later would have increased the time by an estimated 0.123 s.
Output from Model
Cadence vs. Time shows the cadence during the effort. It can be used to adjust gearing to the conditions. The first part of the curve shows the rider's cadence as the rider accelerates at the top of turns 1 & 2. The next part shows the rider diving down the track to the start line. The last section show cadence falling off as the rider fatigues.
Speed vs. Time shows how speed changes as the rider accelerates, dives, and completes the distance. The next to last break in the curve below is the speed as the rider rides "down hill" from high on the start line to the start of turn 3:
Flying 200m Time vs. Point At Which Acceleration Starts can be used to find the optimal point at which acceleration should start. The "saw tooth" in the curve is the rider starting at various points along the home straight:
© 2000 Tom Compton