On Sun, 27 Feb 2005 11:24:15 -0500, "psycholist" <[email hidden]>
Quoted message said:I'm building up a TT bike. I've got it all put together, but it's got a
very conventional seatpost. Does anyone have any good data that would point
to whether or not investing in a good aero seatpost would make any
meaningful difference? I'm considering one of the Corima carbon posts, but
I don't need to toss $125 if it's just a waste. On the other hand, my
objective is to assemble the fastest bike I can and that's one area that
remains to be addressed.
Thanks for any insights.
http://www.trinewbies.com/Printable-articles/Cycling-JCobb2-Technology.htm
"Technology: Wheels, Watts & More
by John Cobb
--------------------------------------------------------------------------------
It was a pretty day, a light westerly breeze blowing the hot summer
air out over the waters. All along the docks there were wives and
loved ones crying and holding their loved ones until the last moment.
As the very last few moments came there were pleas and shouts of fear
that these sailors would never return. These brave young men were
embarking on an adventure that was doomed, guaranteed to fail. The
wise men and the scholars had all spoken their positions and there was
no real hope, everyone knew this was the wrong direction to go. These
adventurers were off to discover new worlds, but first they had to
break over the edge, the edge of the earth because everyone new that
the earth was FLAT.
Technology has a way of making our lives uncomfortable. Technology can
seemingly complicate and confuse our lives. But technology will always
reveal the truths about objects, forcing the adventurers into more
exploration.
A few months ago I wrote an article about how Aero seat posts don’t
work. On the surface that’s a pretty big statement to make and since I
had long been a proponent of all things aero and aero seat post in
particular, those were some hard words to type. Certainly if there is
not a rider on the bike then a thin aero post does work well. But
don't forget, we must have riders to ride our bikes and that changes
things a great deal. There are several of us that continued to study
this area and we are learning a great deal about specialized air
control around the rider. And with potentially new discoveries on the
horizon, we now have a new direction into which to look which has
forced us to explore the relationship of the aero seat post verses the
rider's positioning. And as we research and discover new data we can
then provide you, the consumer, some insight into this issue so that
you make better purchasing decisions.
I have been going to wind tunnels for more than 15 years now to study
bicycle air flow. I have made every mistake possible, made most of
them twice, but have continue to push on and learn about how to make a
rider go faster. One of the biggest ingredients that I’ve found for
aero success is a willingness to admit failure, the strength to
believe in something, develop it, test it, and then get your feelings
hurt when it’s proven wrong. As I’ve continued to study different
parts of the bike, the one area that always looms as very important
is... wheels.
Wheels. Without wheels you’re not going very far. Wheels are so
interesting yet so confusing to cyclist. There’s a variety of shapes
and configurations and there is an ocean of difference in price
between two objects that appear pretty similar. If you take the money
out of the equation and just look at the technical aspects, it can get
overwhelming. If you throw in some marketing hype that is almost never
backed up by research, then wheels can become downright intimidating.
I began trying to show the difference in wheels by expressing the
energy they require to spin through the air in watts. Watts are the
amount of energy a human can generate over a given distance and since
we, as humans, have difficulty generating very many, we need to use
them carefully. Originally and still to this day, we talk about wheel
drag or the effort it takes for air to pass over a wheel. Wheel drag
can only be measured in a wind tunnel and wind tunnels are expensive
and not readily available for people to use. Drag numbers are also
hard for riders to relate to because these numbers are affected by
everything around the object. Loose clothing, long hair, tube sizes
and shapes all affect this drag number. Watts generated by wheels are
not affected by these outside factors so that makes it a better way to
express good, bad, or better. Over the years, I’ve continued to try
and enlist the help of various manufacturers to learn about wheels and
pay for some of the wind tunnel time. Most of the manufacturers are
very hesitant to get involved because it gives their competitors all
the information for free and they can’t seem to get past that.
One company, Hed wheels, did jump on the band wagon early on and has
continued to stay heavily involved in wheel research. Steve Hed has
always been an open book to the athletes and to his competitors,
trying to convey the most accurate information. Very few companies
have spent the time or money to develop products in this way. It's the
been a long hard road but it has led to great success for Hed wheels.
As I said earlier, watts are something on which we need to focus. The
engineers at Texas A&M have been working with me for the last 3-4
years to develop a way to consistently measure wheel watts. My last
trip to the wind tunnel was in Sept. ’02 and it was like sailing off
the edge of the earth only to discover that the earth was round. I
believe we have conquered wheel watts and how to measure them
correctly. This would normally be cause for great celebration, big
fireworks and much partying, except that as usual with all things in
research it trashed everything I thought I new. The next step will now
be to find a way to express watts/drag and steering torque in simple
terms that means the same thing to everyone. When we solve that
equation, and hopefully very soon, all or you will benefit a great
deal. I’m hoping to come up with an "Energy Value System" that will
take into account the drag / steering torque/ watts and give a value
verses price that the industry will maybe adopt.
Technical adventures are a lot like the old sailing adventures of
Columbus and others. You make some mistakes, you run aground every now
and then, but eventually, you find a new world.
Train Hard and be well
John Cobb
