Testing aerodynamics of elite cyclists

Lindsey Underwood is working with some of New Zealand’s elite cyclists to improve their racing times by reducing their aerodynamic drag. She works with BikeNZ and is completing her PhD at the University of Canterbury. She describes how body position, helmets and bike set-up can lower drag to save a cyclist precious seconds in a race.

Point of interest:
In this clip, you will see footage of elite New Zealand cyclists training in Montreal, just prior to the 2012 Olympic Games.

Transcript

LINDSEY UNDERWOOD
I work with BikeNZ – the organisation that pick the athletes to go to the Olympics or for specific world championships. I’d never have predicted that I would be doing a PhD in cycling aerodynamics.

I love sports, I’ve always loved sports, and I’m not actually a cyclist myself, but I love maths and physics and how can I apply this with sports. I was looking for a sports engineering career and then I saw this PhD being advertised and thought, wow, I can help athletes win gold medals at the Olympics.

I’m looking at how we can increase the velocity of the cyclist, and I’m doing sort of two different methods. So one method is I’m predicting the finishing time for an athlete for a specific race. So I can look at if the athlete uses a different bike or if they use a different strategy, we can predict the finishing time, and we can tell the athlete, “OK, if you use this bike, you are going to gain so many seconds for this particular race.” So I’m looking at how we can reduce pressure drag with different position and using different types of helmets and also reduce the skin friction drag by using different skinsuits.

The main aim is to try and find ways that all cyclists can increase their speed, but what I am doing is I’m looking at the air flow over the cyclists, and I’m trying to work out, say, why is this helmet better than another helmet for one cyclist but it might be different for another one. The position of the body, that is generally the shape of the person sitting on the bike, so if you are sitting upright, you’ve got a really big frontal area, so you are going to have a really high drag, but if we can get this cyclist so they are sitting in a more aerodynamic shape and a more streamlined shape, then we can reduce this drag.

We can change the bike set-up by the seat height and the length of the handle bars from, you know, move them further out or move them further in, and this will affect the shape of the body, but again it’s different for different cyclists. So the cyclists that we usually test are elite cyclists, and they already have their current racing position, and then we can make changes to that baseline position. Any changes that lower the drag, then we say, “Right, can you adopt this position? This is going to reduce your drag, it’s going to save you time when you race.”

Those who don’t have a very streamlined baseline position, we’ve seen up to 2 seconds time gain just from changing their position, and that is over say a racing distance of 4,000 metres, which, if you look at the Olympics and you look at the time differences between first and second, it’s milliseconds, so a 2 second time difference just by changing their position is huge.

Acknowledgements:
Lindsey Underwood
Geoff Searle
SKINS International Trading AG/Benjamin Fitzmaurice
Craig Palmer, BikeNZ