Velo-sncf

Every bicyclist has to overcome wind resistance. Most recreational bicycles in which the rider sits up have very poor aerodynamics. While newer bicycles are being designed with better aerodynamics in mind, the human body is simply not well designed to slice through the air. Bicycle racers are aware of the problem of wind resistance and over the years have developed techniques for reducing it. Bicycle designers and inventors have experimented in developing alternative bicycle designs and HPVs (human- powered vehicles) with an emphasis on better aerodynamic performance.

Wind Resistance

Every cyclist who has ever pedaled into a stiff headwind knows about wind resistance. It’s exhausting! In order to move forward, the cyclist must push through the mass of air in front of her. This takes energy. Aerodynmaic efficiency–a streamlined shape that cuts through the air more smoothly–enables a cyclist to travel much faster, with less effort. But the faster the cyclist goes, the more wind resistance he experiences, and the more energy he must exert to overcome it. When racing cyclists aim to reach high speeds, they focus not only on greater power, which has its human limitations, but also on greater aerodynamic efficiency.

Aerodynamic drag consists of two forces: air pressure drag and direct friction (also known as surface friction or skin friction). A blunt, irregular object disturbs the air flowing around it, forcing the air to separate from the object’s surface. Low pressure regions from behind the object result in a pressure drag against the object. With high pressure in the front, and low pressure behind, the cyclist is literally being pulled backwards. Streamlined designs help the air close more smoothly around these bodies and reduce pressure drag. Direct friction occurs when wind comes into contact with the outer surface of the rider and the bicycle. Racing cyclists often wear “skinsuits” in order to reduce direct friction. Direction friction is less of a factor than air pressure drag.

On a flat road, aerodynamic drag is by far the greatest barrier to a cyclist’s speed, accounting for 70 to 90 percent of the resistance felt when pedaling. The only greater obstacle is climbing up a hill: the effort needed to pedal a bike uphill against the force of gravity far outweighs the effect of wind resistance.

Reducing resistance

Frame builders and designers have been working on creating more aerodynamically efficient designs. Some recent designs have concentrated on shifting from round tubes to oval or tear-shaped tubes. There is a delicate balancing act between maintaining a good strength-to-weight ratio while improving aerodynamic efficiency. Improvements to wheels have made perhaps the biggest impact. A standard spoked wheel has been described as an “egg beater,” creating many small eddies as the tire rotates–creating drag. Disc wheels, while generally heavier than their spoked counterparts, produce less wind drag and turbulence when they spin.

While improvements to frames and components have improved aerodynamic performance, the cyclist is the largest obstacle to dramatic improvement. The human body is not very streamlined. Body positioning is important; road cyclists use “drop bars” to allow themselves to reduce their frontal area, which helps reduce the amount of resistance they must overcome. Reducing the frontal area helps riders increase their speed and their efficiency over time. In addition to positioning, small details like clothing can also make a big difference in reducing “skin friction.” Tight-fitting synthetic clothing is worn by almost every professional rider, both road and mountain. Many recreational riders are also wearing bicycle clothes for the improvement in aerodynamics as well as comfort.

Light is good, especially when you’re marketing to the cross-country crowd, but of all the components on a bike the last place for compromise is its brakes. Magura clearly recognizes that fact.

For the sake of performance, all Marta models now share brake pads with Magura’s all-mountain brake Louise. The new pads increase surface area by 20-percent. Likewise, Magura shuns the pursuit of lightweight-at-all-costs and bucks the current trend of offering a 140mm rear rotor.

“140 [mm] is just too dangerous,” said Stefan Pahl, Magura’s suspension product manager. “We have a test at Magura that all of our brakes have to pass.”

In the lab, Magura uses an 800-watt system that simulates a rider descending a 15-percent grade. The brakes have to hold up for two tests of 15 minutes, with only a couple minutes of rest between.

Besides better braking performance changing Marta’s pad puts it in line with all of Magura’s other brakes, with the exception of its most powerful, the Gustav M. That marks an improvement for Magura because it cuts down on the number of pads it manufactures, and it’s an advantage to the consumer because of the better brake performance and greater compatibility.

Aside from the larger pad, the caliper is made from forged magnesium (Marta SL Magnesium) or forged aluminum (Marta SL, Marta); only post mount calipers will be available in 2009, to fit International Standard fork and frame mounts Magura offers adaptors to fit most frames, forks and its three rotor sizes: 160mm, 180mm, 203mm.

The master cylinder is also new. It is also forged out of either magnesium or aluminum, depending on model, and features a new pivot mechanism. In the past, the Marta lever used a dual sliding pivot that relied on a single bolt, which secured the lever and provided for reach adjustment. If that one bolt backed out or failed the lever would fall out which is disastrous. This has been rectified with the new brake so that even if the reach-adjust bolt is lost the lever remains operable.

Both Marta SL Magnesium and Marta SL are produced using the company’s new carbon molding technology. In the past Magura used a common “pre-preg” carbon manufacturing method in which layers of pre-preg carbon were hand laid into lever molds. The new method incorporates a machine that stitches the shape of the lever into the carbon before resin is introduced, this allows Magura to lighten and stiffen the carbon brake lever for the 2009 models.

Magura’s Marta three-model brake line-up is new for 2009. This is the first time the brake has been redesigned since its introduction at Interbike in 2001.

While Hayes may have been the first to popularize disc brakes for mountain bikes, Magura’s Marta is responsible for making a high performance hydraulic disc brake light enough for even gram-counting cross-country racers to accept. The fact that it has had a seven-year run, without change, in such a competitive market is a testament to the strength of the original design.

The Marta series has a new flagship for 2009, the Marta SL Magnesium, which continues to showcase Magura’s impressive brake performance to weight ratio; it weighs less than 300 grams. That 300-gram figure includes the master cylinder, caliper, 700mm line, fluid, rotor and all of the hardware ─ much of it titanium ─ required to install the system using a post-mount.

Tour de Cure is a series of fund-raising cycling events held in 40 states nationwide to benefit the American Diabetes Association.

The Tour is a ride, not a race, with routes designed for everyone from the occasional rider to the experienced cyclist. Whether participants ride 10 miles or 100 miles*, they will travel a route supported from start to finish with rest stops, food to fuel the journey and fans to cheer them on!

Last year, more than 32,000 cyclists in 78 Tour events raised nearly $13 million to support the mission of the ADA: to prevent and cure diabetes and to improve the lives of all people affected by diabetes.

Take the Ride of Your Life. Sign up today.

Register or Request More Information online, or by calling your local American Diabetes Association office at 1-888-DIABETES.

Venus de Miles Opens Registration

Venus de Miles, Colorado’s 1st Women’s-Only bike ride, announces registration and the launch of their web site www.venusdemiles.com. Venus de Miles is a celebration of women and community designed to empower women through cycling, the world’s most popular sports, and give back to community youth through Greenhouse Scholars.

COURSE
Venus de Miles will take place on Sunday, August 17, 2008, and has two length rides - 35- and 65-miles. Both courses start at Prospect Park/Prospect New Town in Longmont and wind through the rural towns of Longmont, Hygiene and Niwot, with the longer course continuing on to the scenic and quaint towns of Lyons and Jamestown. Event coordinators estimate that ~500 women that will participate in this inaugural year.

BENEFACTOR
All event proceeds will go to Greenhouse Scholars (GHS), a nonprofit organization that supports high-performing, under-resourced college-bound students with personal, academic, and professional support as well as a significant financial scholarship. This unique Whole Person© approach to providing scholarships is designed to help ensure that students succeed in college and become community leaders that make a difference. Venus de Miles has set a goal of raising at least $17,000 for GHS.

The wheel is the most crucial element of the bicycle: it allows the rider to roll over the ground with great speed and efficiency. Historians believe the wheel originated in Mesopotamia sometime around 3,500 BC. While the Sumerians did not pedal their way through ancient Mesopotamia, animal-powered wheeled chariots and carts helped haul goods and people for thousands of years. During the industrial revolution in the 19th century, advances in materials and engineering made it possible to use the wheel effectively in human-powered machines. The modern bicycle, complete with a steel frame, a chain drive, steel wheels and spokes, and pneumatic tires, would emerge in the late 1800s.

On the Road

While the use of the wheel was widespread in ancient times, it did have limitations. The resistance to the motion of a wheel can vary tremendously depending on the surface on which it is traveling. A rough road is much harder to roll over than a smooth one. The Romans were aware of this and developed a massive network of paved roads. While this may have been the first time in history that roads were improved to facilitate the wheel, it certainly wasn’t the last. In the United States in the 1890s, cyclists successfully lobbied for improvements in roads nationwide, and with cycling the nation’s most popular sport at the time, legislators listened.

The Ordinary

When most people think about early bicycles, the high-wheelers of the late 1800s come to mind. These early models had names such as the “Ordinary” or “Xtraordinary.” In England, these bicycles were also known as “penny farthings” because the large and small wheels were reminiscent of the large one-penny coin and the smaller farthing coin.

The pedals were attached directly to the front wheel of the high-wheelers. The larger the front wheel on an “Ordinary,” the farther the cyclist would travel with each turn of the pedals. Exploratorium Senior Scientist Paul Doherty explained, “Every time the pedals would go around once, that whole giant front wheel would go around once. So, for one cycle of the bicyclist’s legs he might go 140 inches (3.556 meters), a tremendous distance forward.” This made pedaling up hills quite difficult, but allowed for great speed on the flats.

While the high-wheels were quite efficient, they were also dangerous: the cyclist was very high off the ground and perched precariously over the front wheel. So, while the high- wheelers broke new speed and distance records, they quickly gained notoriety for the dangers involved in riding them. The slightest obstacle in the road could result in a nasty head-first fall. “Headers” or “taking a header” were common terms used to describe an all-too-frequent problem. With a high center of gravity and narrow tires made of solid rubber (which occasionally could roll off their rims), high-wheeled bicycles were designed for speed, not for safety.

Rob Hayles is undergoing testing to prove he has naturally high haematocrit levels.

The UCI is allowing British track cyclist Rob Hayles to return to competition, two weeks after he was disqualified from the world track championships for having a high hematocrit level, the British cycling federation says.

British Cycling is very pleased that Rob has regained his license from the UCI and will be able to continue his racing program. We can now continue to concentrate on preparation for the Olympics in Beijing,” British Cycling performance director Dave Brailsford said in a statement released Friday.

Hayes, who has said he has a naturally high hematocrit level, is voluntarily undergoing two-weeks of additional screening in an effort to get a certificate from the UCI to avoid future disqualifications. He also is waiting for results from a urine test that he expects to show that he did not use EPO or other drugs to increase the hematocrit level, according to The Guardian newspaper.

Hayles told The Guardian he intends to return to racing on Sunday in the Thames Valley road race in Oxfordshire.