I wrote this Wind tunnel review after my session back in 2008 and posted it in the FairWheelBikes forum and thought I might as well copy it here. After my time in the tunnel, the bike has gone through quite a few iterations - mainly due to the moving goal posts courtesy of the UCI. As I still tinker with my position and equipment, the guys at the tunnel have also been busy testing quite a few riders. Also since my session, they have updated the test jig to now make on the fly yaw adjustments easy.
Hopefully you can get something from this to help you get faster!
I was fortunate to take part in Wind Tunnel testing at the Monash University, Clayton Campus recently. As much as I’d like to divulge actual values, before testing we had
to sign a legal agreement to not publish the figures. This prevents
companies from accessing valuable testing information for free;
unfortunately this also makes it harder to write up about the day! But
I’ll try to at least give a general feel for the process and the
benefits of Wind Tunnel testing for non elite cyclists like myself.
The Monash tunnel is the largest on
the Southern hemisphere and can produce wind speeds up to 180km/hr.
Often used for testing cars due to its size, the venue has also worked
with the AIS and various elite cyclists. Bikes are mounted in the centre of a rotatable plate set up with
rollers. Under the plate are four sensitive electronic pressure sensors
which interpret the loads as drag.
View of the tunnel from the control centre
Due to time constraints, testing primarily focussed for all three
riders including myself being tested on the day with positioning.
Therefore testing during the session was at Zero degrees yaw, the
Triathlete and myself limited by UCI rules tested at 40km/hr wind speed,
the track cyclist tested at 55km/hr.
My bike being fitted to the test jig
My bike was the first to be fitted and soon the fans were started
and we were away. Initial tests were with my current position and two
hand positions: first on the ends of the extensions and second closer in
as I use climbing. What was most surprising here was how unaero my
original position was when I thought it was quite reasonable. Also
surprising was how drag increased from such a subtle hand change!
Hand position one
Hand position two
Next tests involved three different helmets (two being AS approved
Limar Speed Demon and Crono 05 and also a Bell Meteor II 07) whilst
shoulder shrugging and turtling.
Some of the helmets brought in for testing
Just this alone saved approximately 10% from the initial position.
My final position change involved dropping a 2cm spacer and holding the
same head and shoulder position and with it came some additional
savings.
Final position
Difference comparing Test 1 and my final position in Test 18 which
had identical hand positions ended up saving me ~43 Watts at 40km/hr!
Additional observations
There was a little spare time at the end I could do a few additional
tests. Unfortunately not enough to rotate the test jig so all equipment
tests done were only at 0 degrees yaw…
Based on this, the Arundel bottle was no better or really worse than
no bottle on my bike, so if you need fluid it isn’t bad but won’t be
the great fairing as hoped. The Jetstream bottle was a little worse but
given you don’t have to move out of position to drink, it would be
interesting to see if not having to reach down is actually better during
a longer event, not to mention the ease of refilling on the go.
The compression tights I had actually tested a little better than
bare shaved legs, therefore deserve more investigation as to the
benefits of wearing compression clothing during racing.
Also as I was able to spend the whole day observing, from watching the other guys:
What appears aero isn’t necessarily so. The track cyclist tested a
smooth track helmet and standard road helmet in his sprint position and
the road helmet tested better.
Helmet interaction between individuals varies considerably. Just
because one helmet has tested better in a study doesn’t mean it will be
that way for you!
Depending on your build, going lower doesn’t always equal better
drag figures. Rob the Triathlete with solid swimming shoulders found
going lower made no real difference in drag. So he will stay higher for
comfort and to be able to produce maximum watts.
So was it worth it?
Definitely! The numbers don’t lie! I entered the tunnel
with what I thought was a good position and left with a major
improvement in aerodynamics. The drag savings uncovered in 1 ½ hours
could otherwise take years of hard training were gained in such a short
time. Yes it will take time to adapt, but well worth the effort given
the huge improvement available!
Thanks go to Raoul Leuscher for organising the day, and David Burton and the engineering team at the Monash tunnel who are planning to make more sessions available in the future.
(Position photos courtesy of the Monash Wind Tunnel)
