The Human Power Team is a student team co-operative between the Delft University of Technology and the VU University of Amsterdam, with the objective to design and build an aerodynamic recumbent that is meant to break the world speed record.
The team was founded in September 2010, and in September 2011 it obtained a European and student record with a speed of 129 km/h, and in September 2013 that new world record was placed at 133.78 km/h, both by the cyclist Sebastiaan Bowier. This happened at the yearly World Human Powered Speed Challenge event in Battle Mountain, Nevada, United States of America.
At this moment, the fourth team of students is preparing for the new world record attempt with a new high-tech recumbent: the VeloX IV. The technical part of the project is in the hands of the students from the TU. Just as important, is the guidance and training of the cyclists, which is in the hands of the VU students. This co-operation makes the Human Power Team a unique student team.
Thursday, 24 July 2014 12:04
The first day of the record weekend on the Dekra track in Klettwitz, Germany was a day of travelling. With 800 kilometres between Delft and the track, it was going to be a long day. We decided to gather in Delft at 05.30 in the morning. Since the bus and trailer were already loaded on Tuesday, we could leave at 6 o'clock after some last bags were packed. With a fully loaded bus, trailer and an extra car we drove off to Germany.
We will spare you the details of the ride itself, but after some traffic jams the car was first to arrive at our guest-house. After checking in and inspecting all the rooms we waited a while for the rest of the team and of course the VeloX to arrive. Luckily, this didn't take too long. The trailer was unloaded and all the equipment and the VeloX were placed in a separate room, everybody got a chance to unpack their personal belongings and food for the coming days was bought in the supermarket.
Rik and Christien were done sitting all day, so they decided to take their recumbents an go for an easy ride around Senftenberger See to loosen up their legs. Back at the guesthouse a nutrias sports meal was waiting for them. The rest of the team enjoyed a nice barbecue. After some discussions about that day and the days to come, we went to bed quite early to charge ourselves for the coming days.
Saturday, 19 July 2014 13:57
Yesterday we tested the aerodynamics of the VeloX IV in the wind tunnel for the second time. This was necessary since some problems came up during the first wind tunnel test. For example, we noticed separation across the entire back of the bike. This led to an elevated CDA-value of 0.033 [m²].
We were not able to explain this immediately, but eventually we thought that it could be caused by the shape of the back of the bike, as it was different from the scale model we used in the wind tunnel test at an earlier time this year. The first thing we did to try fix the separation was using vortex generators and Nagano strips (see pictures below). On the tail we fixed a few tufts in order to examine the airflow of the bike during cycling. This configuration has been tested once at the RDW track and at that time it seemed to work.
As a back-up we also decided to make an elongated tail of carbon fiber in order to compensate the shape of the bike. The first tail we made turned out to be a little too short when we tested it at the RDW track. That is why we made a second one as well. This one had not been tested yet. Today then, it was time to test every configuration we had come up with.
We learned a lot from this test, but at the same time we didn’t learn anything at all. The day ended with some surprising conclusions. The VeloX IV was tested in its original state, as well as with each of the elongated tails. From all these tests de CDA-value seemed to stay the same, but at this time the value was 0.025 [m²] instead of 0.033 [m²]. There were no notable differences between the configurations. An elongated tail then didn't seem to give any advantage. On top of that we weren't able to find any form of separation on the bike whatsoever. We still don’t know how this is possible.
Even though the values have dropped greatly in comparison to last wind tunnel test, we still have our doubts about them because we noticed a lot of fluctuation in the measurements. Therefore, the wind tunnel measurements do not seem to be very accurate. Eventually the record attempts will have to show us what the real values are. But for now we do know that we can probably leave the VeloX the way it is, without making use of an elongated tail.
Next week the first record attempt will finally take place. This will happen at the Lausitzring in Germany. Keep following us, because it is really going to be exciting!
Thursday, 29 May 2014 19:06
Yesterday, it was time to test the VeloX IV in the Open Jet Facility (OJF) of the faculty of Aerospace Engineering at the Delft University of Technology in order to measure its aerodynamic performance. It promised to be an interesting and exciting day.
At 9 o’clock in the morning we went to the wind tunnel with the VeloX. A lot needed to be prepared there, which took about the whole morning. After that we could finally start testing!
First the resistance of the platform needed to be measured, the so called control measurements. These would be compensated later with the data of the VeloX IV. After that it was time to test the VeloX! It was polished well first so it would be as smooth as possible.
The airflow passing the VeloX was mainly measured with a microphone. This way we could hear where the airflow turned from laminar into turbulent. This transition was marked on the bike. With a wind speed of 100 km/h this was quite a challenge!
Meanwhile the press and sponsors were greeted at the Faculty of Aerospace Engineering where they were provided with a presentation. Ton Büchner from AkzoNobel started off by telling about the good collaboration they had with the Human Power Team. We are also very pleased with how everything is going! After this introduction Toine and Dennis gave a presentation on the production of the VeloX IV and about what we were doing in the wind tunnel.
Of course it is even more interesting to witness the test itself, so after the presentation the press and sponsors were invited to join us in the wind tunnel! Here we tried to show them the airflow passing the bike by using smoke. Unfortunately the machine did not work the way it should so we could show it only for a very short time. Eventually then we showed them the airflow by using a thread.
In the meantime the press got really interested in Christien as well. This even happened to turn into a short photo shoot!
At the end of the day, after everyone had left, it was finally time to look at the results. The flow of the air was exactly as predicted trough the computer simulations and 1 in 2 scale wind tunnel test. Even some areas we weren’t really sure of, for instance the seam of the horizontal split, gave no problems at all. Although we had a lot of good results, not all areas of the VeloX were perfect, at the back of the bike there were some troublesome areas and the flow on the lower part of the body became turbulent in a very early stage because of the boundary layer of the wind tunnel itself. Fortunately, the cause of these problems is known and we are busy solving them. The coming months we will be doing drag tests during our testing days at different tracks throughout the Netherlands in order to see if the bike is getting better. We also opted for another chance to test the VeloX IV in de wind tunnel to test the entire aerodynamics once again later in the year.
The coming months will be all about testing the bike, both mechanically as well as aerodynamically, and will also give Rik and Christien the chance to get used to driving the VeloX. So keep following us through our website, facebook and twitter in order to miss nothing in our hunt for even more world records!
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