Jul 14, 2016 | By Tess

Within the world of sports, and in the wake of an exciting Euro football Cup and Wimbledon final, all eyes are on the historical Tour de France bike races. The tour, which began early July, is now in full swing and spectators are undoubtedly eager to see the results of the upcoming individual time trials, which will take place tomorrow, July 15th. If you tune in for the time trials, be sure to keep an eye out for Dutch cyclist Tom Dumoulin, who will be sporting a new biking skinsuit made with the help of 3D scanning and 3D printing technologies.

The skinsuit was designed as a joint effort between Team Giant-Alpecin (Dumoulin’s team) and The Delft University of Technology (TU Delft) in an effort to give the professional cyclist a competitive edge against his competitors in the upcoming race. For those less familiar with the sport of biking, race results are often determined by fractions of a second, so having any sort of advantage, such as an extra aerodynamic suit, could be the deciding factor.

The custom designed skinsuit was made using a novel approach through which a team from TU Delft were able to 3D scan Dumoulin’s body in a biking position, 3D print a life-size replica of him, and test a number of different materials and suit designs on the 3D printed mannequin within a wind tunnel. Through this process, the team of researchers along with Team Giant-Alpecin were able to design an optimized and custom fitted skin suit for the Dutch athlete.

The first step in creating the skinsuit was to 3D scan Dumoulin’s body. This was necessary seeing as having the athlete himself around for all the testing was virtually impossible due to scheduling. For the scanning process, the researchers enlisted the help of 3D scanning company th3rd, who captured a detailed and accurate scan of the cyclist using a photogrammetry method. The whole process, which involved 150 DSLR cameras capturing photos of Dumoulin from all angles, took only about 30 minutes.

The next step was 3D segmenting all the data from the 3D scan to create a workable 3D model of Dumoulin’s body. Dr. Jouke Verlinden, part of TU Delft’s Faculty of Industrial Design Engineering, explains, “It’s key to use the data correctly, for example by splitting up the files in a smart way: the so-called 3D segmenting. You should also determine where the accuracy of the scan and the resulting print is somewhat less important. In those areas you can strongly reduce the amount of data you need. If you aim to make a model that is accurate to the micrometre throughout, you’ll end up spending way too much time printing the mannequin.”

Once the 3D model was prepared, the team of researchers began the 3D printing process. Of course, to create a life-size model of the cyclist, they had to break the print up into eight separate parts. The parts were printed using multiple FDM printers, and took a total of 50 hours to manufacture. The 3D printed body parts were then assembled with easy-to-use pin and hole joints into the athlete’s biking position.

To test different materials and suits, the mannequin was given to Wouter Terra, a PhD student in the Faculty of Aerospace Engineering at TU Delft, who recorded results from a number of wind tunnel tests. The material testing process, for its part, was not as simple as one might expect. Terra explains, “You would expect a smoother fabric to induce less drag. But this isn’t always the case—especially when looking at the airflow around a rounded, blunt, non-streamlined shape, like the body of a cyclist.”

According to Terra, sometimes a ridged surface can actually be more beneficial in an aerodynamic design because of the two types of drag at work: drag through friction and drag through pressure. “Through the roughness of the ribbed pattern, the drag through friction will increase, but the drag through pressure can drastically drop. The net drag will then decrease,” he continued. “An inventive combination of rough and smooth spots on the suit might only result in a decrease in drag of half a percent, but this could potentially deliver those precious seconds that make the difference between winning or being in the top 10.”

Initially, materials supplied by Etxeondo, a cyclist clothing supplier, were tested in order to give insight into which types of materials were the most efficient for the race per body part. In the end, a number of suits were made using a variation of both smooth and textured materials and tested for drag within the wind tunnel. Using a Particle Image Velocimetry (PIV) method, airflows were mapped and measured to see which combination of materials provided the best results.

The skinsuit that resulted from the research testing will be worn by Tom Dumoulin in his upcoming time trial race and researchers expect it will help shave a few seconds (or fractions of a second) off of his total time. According to the team, “We measured a clear difference in drag between the various materials. A difference of just one percent in drag, to name but a number, might not seem much, but can result in a time saving of about ten seconds in a hour-long time trial.” The advanced skinsuit will undoubtedly also give Dumoulin an extra psychological boost, perhaps improving his overall performance. Of course, we’ll have to wait and see with the results of the race tomorrow.



Posted in 3D Printing Application



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