This paper discusses the designs and development of human-powered vehicles (HPV). Several new records have been set with what are called HPV. In the space of three weeks, Fast Freddy Markham sets a new record for the longest hour-long ride-53.34 miles-an d Greg Kolodziejzyk put more miles under his tires in 24 hours than anyone in human-powered history, 650.5. Markham and his foes have a chance to ride their HPVs only at competitions, since they need a crew to help get them in and out of their sealed shells. Weaver has set many speed records himself and has beaten Markham in several top speed races. Markham's approach makes the most sense for an hour-long race, where there is plenty of time for experience to shine and technology to break down. It is found that while Markham's hour-long record is likely to remain unbroken for sometime Weaver still holds the US record for top speed, having hit 78.02 mph in his Cutting Edge in 2001.
Land speed record. The phrase conjures up images of humans in long, pointy vehicles tearing across salt flats. But where's all the power coming from? Just a bunch of fuel. According to one group of racers, it's a more difficult challenge to go faster than any human ever has-with human power alone.
As it happens, in the past few months, several fairly astonishing new records have been set with what are called human-powered vehicles. In the space of three weeks, Fast Freddy Markham set a new record for the longest hour-long ride-53.34 miles-and Greg Kolodziejzyk put more miles under his tires in 24 hours than anyone in human-powered history-650.5. Both men rode recumbent bikes sheathed in shiny, missile-shaped carbon fiber and Kevlar shells. But the subtle differences of their approaches to building and riding their HPVs may tell us what part of all this record breaking is the result of the word on the left side of the P in HPV and what part is owed to the word on the right.
It's H over V for Fast Freddy, a one-time Olympian. "We're about tapped out on development," he said. His HPV was designed by a sculptor, Georgi Georgiev, and although it has slowly evolved over the years, it's been essentially the same bike since 2000. "In 1990, a guy named Matt Weaver had a sleek-looking bike. It looked more like a cruise missile than anything. That spurred Georgiev."
Markham likes to say that the bike's fluid look comes from forms found in nature. "It's never seen a wind tunnel," he said. "Georgiev would look at certain shapes in the world, at fish, how they bulge here, how they taper here-a good indication of what goes fast."
But Weaver, the man who made that sleek-looking bike back in the early '90s, tells a slightly different story about the success of Markham's mold. Weaver has set many speed records himself and has beaten Markham in several top speed races. He came in third against Markham in the hour-long contest.
"It makes for good press that he's the sculptor, the artist, and I'm an engineer and that a computer spits out my design," said Weaver. But according to him, Georgiev visited him both in 1993 and 1995, and they had in-depth discussions about Weaver's bike. "I knew the pressure distribution over every square inch of the body," he said. The shape Weaver had developed was meant to achieve laminar flow-a state where there's hardly any separation of the air from the bike as it passes over the body. Avoiding the chaotic turbulence that happens with a sedan, a nonstreamlined bike, or any other moving object that's not teardrop-shaped cuts down drastically on drag .
In 1993, Georgiev came out with his first Varna, which was very similar to Weaver's bike but had a "bee tail"the rear wheel was exposed, creating unnecessary turbulence and drag at the back of the bike. When they met in '95, Weaver explained how to fix the problem by using a fin and covering the rear wheel. Georgiev didn't take Weaver's advice all at once, but over the years the Varna evolved into something that was, in essence, what Weaver had initially envisioned.
Whatever the origin of the design, the trick to Markham's success may have had a tad less to do with aerodynamics than it did with his simply knowing his bike better than other riders on the track knew theirs. Markham is now 49, and he's managed to turn his age into an asset. As he put it, "I've been riding quirky bikes for 30 years."
According to Markham, "For what I'm doing, experience and pedal finesse go a long way into making the bike work-two things I have in abundance. I'd trade them both for more horsepower or wattage, but for what I've got I do pretty well. I kinda am dialing this thing in."
Markham and his foes have a chance to ride their HPVs only at competitions, sirice they need a crew to help get them in and out of their sealed shells. Even with a crew, there's no place to test ride the bikes. You would need a flat, deserted road. Crashes in these bikes (which can go over 60 mph without much trouble) can be as lethal as an accident in a car. And renting a track is too costly for test runs.
Markham was confident enough in his abilities to commit what seemed like an unforgivable sin to his competitors at the racetrack. One of the major challenges riders face is how to keep cool. When you're pedaling at top speed inside a sealed tube, temperatures inside can reach 110D F. Markham didn't like the complex cooling solutions he saw in other bikes. "I just cut a little duct on the windscreena cardinal no-no on these bikes; it's a very aerodynamic spot-but I knew I needed wind on my face," he said.
Weaver, of course, would never sully the aerodynamics of his current HPV, called the Cutting Edge, with such a gash. In fact, Weaver was unwilling to sully the aerodynamics of his bike with even a windscreen. The Cutting Edge remained pure bullet. Weaver had planned to ride by watching a video screen with a camera in the tailfin.
"People told me peripheral vision was fundamental for balancing, said it won't work, won't work," Weaver said. "But on my first ride, I took off riding like it was a video game, like it was old hat." As there would be no air coming into the small space where Weaver would be pounding his legs with fury, he developed an elaborate system to pump ice over him and cool airto his mouth.
Unfortunately, the mask that was meant to bring air to his face slipped seconds before he started. "It was jammed up against my face. I hadn't even done the initial acceleration and I was choking." Weaver had to pedal slowly until he calmed down and was able to breathe. Then he'd go all out until he was choking again.
"Basically, I went from one lap to the next to the next," he said. "1 almost went 49 miles in spite of that" -a distance that would have beeri a world record just eight years ago.
Although Markham has often joked about the complexity of Weaver's design, he admits that watt for watt it's superior. "Theoretically, it is the faster bike," Markham said. "It's just not easy going 80 watching a video. It's not user-friendly. The most aerodynamic shape is not always the fastest. The fastest is the one that gives the rider the confidence to start stomping on the pedal."
It may be that Markham's approach makes the most sense for an hour-long race, where there's plenty of time for experience to shine and technology to break down. While Markham's hour-long record is likely to remain unbroken for some time, Weaver still holds the U.S. record for top speed, having hit 78.02 mph in his Cutting Edge in 2001.
Twenty-four hours, however, is yet another problem. When you plan on riding for a full day without stopping in the hopes of cracking 634.644 miles, your bike had better be as streamlined as science will allow. But it had also better not be so complicated that it breaks at the 11 th hour-or the 18th hour, or the 23rd.
Greg Kolodziejzyk designed his Critical Power using a CAD program called SolidWorks, which includes a virtual wind tunnel. "We started taking photographs of me in my ideal position. The shell fit perfectly around my shoulders with just enough space around the top and bottom of my pedal stroke," Kolodziejzyk said.
With those basic measurements Kolodziejzyk and his team dreamt up several different designs and let the computer do the choosing. "We ran those ideas through the program to predict the drag coefficient, then picked the best one," he said.
To their surprise, the best one was not cambered. Most HPVs are made with the assumption that it's better to push the airflow down as it leaves the frame. "There wasn't any difference, so we went for complete symmetry." That meant they would save money, as the rightand left-hand sides could be made with the same mold.
Another important change is that Kolodziejzyk's bike is a bit higher off the ground than other HPVs to give extra stability for the long haul. "But the biggest difference between Critical Power and something Matt would build is the level of the technology," Kolodziejzyk said. "His technology is so extreme he hasn't done an event without a technical problem. For a shorter event it isn't as crucial. Maybe you can get an hour in and set a record, but for 24 .hours, you just can't take a chance."
Kolodziejzyk, like Weaver, had initially planned to maintain the purity of his aerodynamics by riding with a camera and video screen. In the end, he rejected it.
"For anything less than five hours, video might be the way to go," he said. "You only take off and land once." Kolodziejzyk got out of his bike only once, when his legs were cramping up, but landed every three hours for food and water. "With the constant up and down, I didn't want to risk a crash. We tested the video monitor, and I didn't get a feeling I could get used to it for 24 hours." The designers added a windshield, and accepted the extra drag as the price of simplicity.
So, as sleek as Critical Power is, Kolodziejzyk didn't bother with things like laminar flow. "It's tricky," he said. "Some believe that it doesn't really exist for the most part, because of the vibration of the road." When they finally tested the real thing, they found that the virtual wind tunnel had been off by no more than 10 percent.
Designers of a Formula 1 racecar consider an engine well designed if it falls apart the second it crosses the finish line-meaning there was no extra weight and that everything was only as durable as necessary. But in a 24-hour ride, that kind of thinking is tossed out the window. Redundancy is favored over lightness.
"Minimize the things that would be deal killers," Kolodziejzyk said. All the electronics? "Nothing was crucial, and I ended up losing them all by the end." Similarly, Kolodziejzyk chose a two-stage manual process to extend his landing gear-a kind of skateboard that emerged out of a hatch on the side of the bike-rather than complicate things with an electrical design that was easier and faster.
Perhaps the most important piece of engineering was Greg's Ipod-at least for the first 18 hours. The tremendous humidity that Greg worked up that caused his electronics to fail eventually killed the MP3 player, too. "Kind of a drag," he said. "That's basically what kept me going."
News of Kolodziejzyk's feat just may have whetted Markham's appetite for trying something similar, but in his own fashion. "Who knows, I might make an attempt," Markham said. "In an hour record, no matter how hard you go, you still have to go for an hour-can't go any harder to get it done sooner. For 24, my idea would be to go so frickin' fast, I could maybe stop at 21 hours and call it a day."
But true to Markham's style, he said he wouldn't change the bike he used to set the hour record.
"If I'm going to do it, it would have to be a fast bike, and it's going to be this one," he said. "But I'll let him bask in his glory for a while before I go after it."