3D mannequin helps cyclist go for gold
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[October 10, 2016]
By printing a 3D mannequin of
leading international cyclist Tom Dumoulin and testing a series of
skinsuits on his replica inside a wind tunnel until they found the
perfect fit, researchers at TU Delft believe they can help Team
Giant-Alpecin win gold at the UCI Road World Championships in Doha.
Olympic silver medalist Tom Dumoulin is confident of winning a gold
medal in the men's time trial at the UCI (Union Cycliste Internationale)
Road World Championships in Doha on October 12 - and the leading cyclist
has a secret weapon.
A skinsuit worn by the Dutchman was developed by researchers at Delft
University of Technology (TU Delft), in conjunction with his team, Team
Giant-Alpecin, using an unusual technique.
The inter-disciplinary team from TU Delft scanned Dumoulin's body using
photogrammetry, before 3D printing a full-sized replica mannequin of his
body in classic riding posture. The mannequin was then dressed in a
series of skinsuits made of various fabrics and placed on his bicycle
saddle, where it underwent tests in the university's wind tunnel.
Dr Jouke Verlinden, of TU Delft's Faculty of Industrial Design
Engineering, led the development of the mannequin, which first involved
placing 150 DSLR cameras in a room and programming them to each
simultaneously take a single image of Dumoulin sitting absolutely still
on the cycle.
![](http://archives.lincolndailynews.com/2016/Oct/10/images/ads/current/Bonanza_sda_072214.png)
Verlinden told Reuters: "You really want to have someone like that fixed
in the right position and you need to have an instant 3D scan of that.
We used a system based on photogrammetry, so taking a lot of pictures
with a high-resolution camera, an SLR camera, and we had a rig with 150
of these cameras which took one picture completely at the same time, and
from that we could reconstruct a 3D model."
The mannequin was constructed using an inexpensive 3D printing method.
This consisted of turning two household 3D printing machines on their
head, so they could print up to two meters high, producing Dumoulin's
replica in eight separate parts. It took a total of 50 hours to print,
before each part was attached via simple pin-and-hole joints.
"It (the printer) uses plastic wire, which is extruded like a glue gun
and then it's being drawn on the flat surface below, at a tenth of a
millimeter or less, and in that way layer by layer you draw these kind
of plastic curves," explained Verlinden.
The suit was originally made for Dumoulin's participation in this
summer's Tour de France and Olympic Games in Rio. Speaking before the
two events, he explained his hopes for the skinsuit. "In cycling, and
especially in time trialling, it's about seconds, and even if we get
only a little difference with a faster suit it will make a big
difference maybe in the result," he said.
Unfortunately, an accident meant Dumoulin had to withdraw from the Tour
at stage 19, but his Olympic performance was a happier experience, with
him finishing second in the time trial behind Fabian Cancellara.
Andrea Sciacchitano, assistant professor in aerospace at TU Delft, told
Reuters that aerodynamics is crucial to time trial performance.
"In order to go faster aerodynamics is very important, it's up to 90
percent of the total resistance that the guy has to overcome - and the
roughness of the fabric is very important in order to reduce drag," he
said. "One may think that in order to go faster the surface must be very
smooth. This is, in fact, not always the case. In some cases some
roughness can help the guy to go faster because it energizes the flow
close to the surface. So it allows the flow to close on the back and
therefore to reduce the aerodynamic drag."
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![](../images/101016PICS/news_m17.jpg)
(From L-R) Daan Bregman and assistant professor Andrea Sciacchitano,
from Delft University of Technology (TU Delft), and Teun Van Erp,
sports scientist at Team Giant-Alpecin, pose with a 3D-printed
mannequin replica of Dutch cyclist Tom Dumoulin wearing a special
skinsuit they co-designed, in Delft, the Netherlands October 4,
2016. REUTERS/Jim Drury
![](../images/ads/current/richardson_lda_090916.png)
Sciacchitano said a technique developed at the university called
particle image velocimetry (PIV) proved crucial in the wind tunnel
tests. Helium-filled soap bubbles were used to map the flow and
ensure good measurements.
"In the wind tunnel we can have a very controlled environment, very
specific flow velocity. Particle Image Velocimetry, is a particular
technique that we have developed at TU Delft, in which we introduce
small particles in the flow, we illuminate them by means of a laser
and we take images of these particles - and by measuring the
displacement of these particles at two time instance we can
determine the velocity field and therefore the pressure and finally
the aerodynamic drag," he said.
Dr Daan Bregman, of the TU Delft Sports Engineering Institute, said
the same techniques could be used to test other parts of Dumoulin's
equipment.
"We want to use this mannequin to test more aspects of his
aerodynamics," said Bregman. "For example, which helmet should we
use, can we use the same time trial suit when it's raining or maybe
we should use something else. So it gives us loads of opportunities
to test all the things we want without having Tom Dumoulin here in
the wind tunnel."
Bregman added that the project's multidisciplinary nature had been
of enormous benefit to the project.
![](http://archives.lincolndailynews.com/2016/Oct/10/images/ads/current/mkspink_lda_093016.png)
Teun van Erp, the scientific consultant for Team Giant-Alpecin, was
involved in the testing program, and is hopeful the innovative
skinsuit could help Dumoulin win gold in Doha. "We hope that with
ten or fifteen seconds extra gain we have with the suit he will win
the gold medal," he said.
Van Erp added that five of Dumoulin's colleagues in Team
Giant-Alpecin will also be wearing tailor-made suits in Qatar,
developed using the 3D mannequin tests.
The TU Delft team believes similar tests could be conducted on suits
worn by speedskaters and swimmers, where drag is also an important
element of sporting performance.
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