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Engineering a better bicycle with DBC City Bike Design

Engineering a better bicycle with DBC City Bike Design
Terrence O'Brien
Terrence O'Brien|@TerrenceOBrien|October 2, 2012 3:00 PM

My day with Dan Sorger was winding down and the photographers were out joyriding on his bicycles when he beckoned me to look at something on his tiny, age-stained LCD monitor. Nestled in between a curling collection of Post-It notes was an anecdote about a wealthy Italian man which he began to read aloud, "Once upon a time, long ago ..." According to the story he had spent an exorbitant sum of money to modify his prized Alfa Romeo. As a result, his family tried to have him declared insane and wrest control of his fortune. As the trial got underway, the judge asked to see the vehicle in question and, once he set his eyes on the custom-crafted aluminum body, he dismissed the case, declaring, "The search for beauty is the most natural thing in man." The tale is allegedly the origin of storied automobile designer Ugo Zagato, but it's the judge who is the real star and it's his words that struck a chord with Dan, the founder and owner of DBC City Bike Design.

Gallery: HP New DV Family | 22 Photos


engineering a better bicycle with DBC City Bike Design

While it might be hard to see that persistent quest for beauty at work in Sorger's basement bike shop, there is a certain elegance to its austerity. Like the Swift, the cycle he designed with the aid of about a dozen engineers from MIT and Wentworth Institute of Technology, his relatively unadorned basement headquarters is simple, functional and strangely timeless. Its walls are white and mostly free of extraneous decoration. Just beyond his tattered wood desk, a vintage Miami cruiser hangs from one of his patent-pending pedal hooks - the perfectly rusted patina on the low-riding frame is the closest thing to art on the walls. The unassuming entrance on the corner of Pearl and Purchase Streets in Boston's financial district, which he shares with a tailor, wasn't the original home of DBC. Sorger started the company in 2002 in St. Augustine, Fla. Back then, it was called the Dutch Bicycle Company and, appropriately enough, it imported Dutch commuter bikes. The unabashedly political goal of the shop, which was cofounded with his wife Maria in direct response to 9/11, was to reduce Americans' dependence on oil.

"I opened the paper and saw names I knew. Maybe they weren't my best friend or a family member or an ex-girlfriend, but I knew them," Sorger said.

He took it personally, as he puts it, but it's not all about stopping the flow of oil money - the man also has a green streak a mile wide.

There was a problem, though: European bikes were designed for European roads. They were not ideal for urban American commuting and, surprisingly enough (according to Sorger), neither were those designed here. Biking in the United States is treated primarily as a leisure activity, with 73 percent of cyclists telling the National Bicycle Dealers Association (NBDA) they ride for recreation. Only 10 percent reported commuting on their bikes in the same 2011 survey. Sorger doesn't mince words, calling most major bike manufacturers "toy companies," and looking at the numbers, he's obviously not far off. According to the NBDA, 70 percent of the bicycles sold in the country accounted for only 27 percent of the market value in 2011, with an average price of $84. What he needed was not a play thing, but a serious human-powered mode of transportation. The obvious next step, to him at least, was to create his own bike, one built exclusively for getting around the modern US city. He set about looking for engineers, designers and manufacturers nearby, but found that Florida simply couldn't provide the resources or the market he needed. So, the New York native headed north, beyond his childhood home, to the city of Boston in 2008.

engineering a better bicycle with DBC City Bike Design

It's no accident that DBC landed in Beantown. It's home to countless schools, with highly regarded engineering programs and serves as the metropolitan heart of bike-friendly New England. It didn't take long for Sorger to find co-conspirators and get to work after landing in Massachusetts. He put together a team of six engineers from Wentworth to help design a frame for men and another half dozen from MIT to tackle the women's bike. The two groups worked largely independently to avoid a common shortcut taken by many other manufacturers, which is to simply drop the top bar on a men's model and say it's for women. But, before the designers could get to work drafting a prototype, they had to figure out what exactly needed fixing.

Commuter bike design hasn't evolved much since the 1880s, at its most basic form. British engineer James Starley is, perhaps, most commonly associated with the iconic (and slightly ridiculous) Penny-farthing with its oversized front wheel, but the "safety bicycle," which his nephew developed the first commercially successful version of in 1885, is the blueprint for most modern bikes. Cycling has continued to be popular in Europe as a legitimate form of transportation ever since, but here in the States, it's something to be done in your down time, often in the form of racing or mountain biking.

A new spin on an old design engineering a better bicycle with DBC City Bike Design

To find out what it is about their bikes that drives Americans to see them as fitness tools or recreational distractions, as opposed to modes of transportation, the teams blanketed Boston with questionnaires. Both avid and reluctant cyclists were interviewed to find out where current designs needed the most work. The results shocked even Sorger. A "laundry list" of complaints was analyzed and the decision was made to approach the various problems quantitatively. Each area of improvement was given a point value and each potential solution was scored appropriately. Some solutions introduced new problems or exacerbated existing ones, so trade-offs had to be made to find the proper balance. And balance, it turns out, was one of the key issues. Most bikes distribute a rider's weight evenly over both wheels, but this is neither ideal nor efficient. Resting too much weight on the upper body and forcing riders into a hunched position may be more aerodynamic, but it also puts undue strain on the human body. Increasing the weight placed over the front wheel also decreases stability, which is why it will wobble if you slam on the brakes (your body's momentum continues forward, shifting weight on to the handlebars). Sorger took a page from his days as a pilot and applied a weight and balance equation to the design, shifting a larger percentage of the load toward the rear wheel, which improved both handling and stability dramatically.

"We didn't 'design' the bike, we tweaked it. We tweaked it a lot."

For a year, the design phase pushed on as the teams tweaked angles, working to get the geometry just right. And "tweaked" is the word Sorger prefers to use. "We didn't 'design' the bike, we tweaked it. We tweaked it a lot," he insists, but still he uses the term that indicates a minimal break from tradition. Looking at the Swift, it doesn't appear terribly different from most other bikes on the market. It has two wheels, a fork, a chain and the diamond-shaped frame that is the industry standard. But those subtle, almost invisible, visual differences are actually dramatically removed from what is considered "normal." The "tweaks" were enough that the company had to abandon tools built with bicycle design in mind. "There's nothing wrong with BikeCAD," Sorger emphasizes, "it's a great program." But, it has its limitations and he says it simply wasn't going to work for DBC's purposes. Specifically he says some of the angles couldn't be handled by the narrowly focused software package. The team ended up settling on the far more robust and general purpose SolidWorks, a suite with a starting price about 10 times that of BikeCAD Pro, which retails for CAD$350.

Engineering a better bicycle with DBC City Bike Design

One advantage gained from switching to a more fully featured design program was the ability to perform simulations and virtual stress tests. Since Sorger wants his bikes to be a mode of transport, durability and reliability were paramount. Toyota kept coming up in our conversations as an exemplification of his goal. The Japanese car company is famous for touting that 80 percent of its Corollas sold over the last two decades are still on the road - the Swift is designed with that sort of longevity in mind. To wit, the engineers opted for 4130 chrome alloy steel, an aircraft-grade metal. While aluminum may be more popular with many bike designers for its lighter weight (and the Swift is not exactly petite at around 34lbs), DBC's engineers put more value in the steel's shock-absorbing power. Most aluminum alloys are much more rigid, which not only transfers more road vibrations to the rider, but also tends to crack easier under stress. The comparative flexibility of steel makes for a more comfortable ride and a vehicle that can sustain more wear and tear before coming apart at the welding seams.

"There's no magic bullet," Sorger tells me. "There's one hundred small magic bullets."

What's shocking in talking to Sorger about the work that went into creating the roughly $2,700 Swift, is how simple some of the solutions he has adopted are. "It's basic physics" he shouts when discussing the issue of weight distribution. But it's not just high school physics that come into play; it's also secondary school chemistry and math. For example, brass washers and other non-ferrous metals are placed between the chromoly frame and the stainless steel bolts to slow electrolysis. Wander into any eighth-grade science fair and you're likely to see an example of this destructive process at work - place two dissimilar metals in an electrolyte solution and one of the materials will slowly steal ions from the other, causing it to oxidize, become brittle and eventually break apart. Preventing this process using an iron-free, corrosion-resistant alloy barrier is particularly important in a city like Boston, where the air is damp and laden with salt water.

It's an odd dichotomy that so many Ivy League engineers and designers were required to develop what, from a distance, seem like incredibly simple solutions to problems that many feel plague bike design. "There's no magic bullet," Sorger tells me. "There's one hundred small magic bullets." And many of those tiny changes, once you've had them explained to you, seem like they should be common sense.

Engineering a better bicycle with DBC City Bike Design

Unlike a bike from a larger manufacturer, each Swift is custom built. You are fitted for the frame like it was a fine bespoke suit. Your height, inseam and weight are all taken into account - even the possibility that you'll be toting around a toddler in a child seat on the rear rack is considered in the equation that decides the final shape of the frame. Those measurements are then fired off to legendary bike builder Ted Wojcik, who has been hand-welding and bending award-winning frames for over 25 years. Of course, the big boys like Trek and Giant can't be faulted here, the nature of mass production makes it impossible for them to finely tune a frame for each individual. But what makes Sorger's method stand out is the difference in how it approaches the problem of scaling to the human body: the Swift scales, where other bicycles may simply get taller without increasing the wheel base. To compensate, some manufacturers will even slightly alter the geometry of a commuter cycle, perhaps tilting the seat post at a different angle, but that could potentially lead to shorter riders being forced into a more hunched or horizontal position.

Sorger has plenty of competition in the custom bike market, some of it more affordable than his own offering. But those lower-priced models are generally "custom" in paint and detailing, not in sizing. Truly tailored frames are often fitted using complicated stationary bikes with adjustable components that require the assistance of a professional ... a professional that demands to be paid. Those frames run anywhere from $2,000 to $5,000, and that's before any of the essential components have been added. Some shops will "fit" you for a bike by taking basic measurements, such as your inseam, but they're generally only used to select a prefabricated frame with the correct height. DBC straddles a strange line somewhere between the "custom" shops geared towards the fashion-focused and the serious cycling dens populated by aspiring Tour de France racers.

Perhaps the most important element of any bicycle is the human one. They are, ultimately, a human-powered mode of transport, and maximizing the efficiency of the engine (read: the rider) is the only way to turn biking from something people do for exercise, into a viable method for navigating a modern metropolis. (Obviously, sufficient infrastructure to enable safe and easy travel also helps, but thankfully Boston has that in spades.) Engineers and designers from top universities might have some idea how to reduce strain on the human body, but for real insight Sorger turned to doctors at Massachusetts General Hospital and sports medicine researchers at Tufts. The key problem that needed to be solved was that of fatigue. No one is going to want to pedal to work if, at the end of a relatively short 4-mile ride, they're sweaty and exhausted. The medical brain trust encouraged Sorger to do two things: first reduce the amount of vibration transferred to the rider. The choice of steel was a good starting point, but by opting for a longer wheelbase, the team was able to smooth out the ride even more. The discussion also informed his choice of other components. Cork grips were selected for the handle bars and, in a compromise of his goal to minimize the use of polymers; he opted for plastic platforms over metal ones because of their shock-absorbing properties. Secondly, he was told to limit the amount of weight being supported by the arms. He had already shifted the center of gravity closer to the rear wheel, but it became imperative that the Swift encourage an upright posture.

Engineering a better bicycle with DBC City Bike Design

By design, the Swift is relatively nondescript. There's no model number emblazoned on the top bar or a company badge on the front post. In fact, branding is all but non-existent. Probably the best way to identify one is by its lights. The finned taillight and streamlined headlight are also custom built. Sorger hired his friend and electrical engineer Dave Mroz to create a system that would be as reliable as the head and taillights of a car. That meant no batteries and rarely, if ever, changing bulbs. The second part of the equation was simple - opt for LEDs. The headlight even has a large reflector installed to maximize its brightness. Ditching batteries, however, meant putting a dynamo in the hub, and using the strength of the rider's legs to not only power the bike, but also the lights. So, they decided on an acceptable amount of resistance that could be added - almost none at all - then hooked up a multimeter and Sorger rode around Boston for weeks, measuring the amount of electricity he generated. Mroz took those numbers and figured out how to get the most out of the small amount of electrical current produced. As a testament to the DIY mentality and focus on locally produced products, all the lighting assemblies are built right in the DBC basement shop. In fact, while I was standing around pelting Sorger with questions a box of parts from electronic component supplier Digikey was delivered.

While DBC isn't about to change course and suddenly start slapping large logos on their bikes, there is a desire to improve brand recognition. For that, Sorger is working with new teams of designers, also sourced from the many universities nearby, to create more immediately recognizable frames. The basic geometry might not change, but aesthetically the company is heading into far more adventurous territory. He sees the beauty in the simplicity of his creation, but the part of him that also obsesses over classic car design desperately yearns to create something truly iconic.

Engineering a better bicycle with DBC City Bike Design

As we're wrapping up, in the midst of urgently encouraging me to take a black Swift out for a ride, Sorger gets a call. The details at the moment are very hush-hush, but the gist of the news he eagerly shares is that the Swift will be getting electrified ... sort of. An unidentified company has just agreed to order at pair of frames from DBC as testbeds for a new electric bicycle it's developing. The highly configurable frames, or mules, are slightly longer than the standard design, have many more attachment points and might not look quite the same, but all the same design and engineering expertise will be present in the final form. Sorger's excitement about the project is clear. As he explains, power-assisted bikes are either great electric bikes or great pedal bikes, but rarely both. He's confident enough in his own product and has high hopes for the unique motor being developed by his collaborators. The final version may not sport DBC branding, but the quiet recognition of being chosen as the platform for this new project seems to be enough for him.

Photographs by Ken Richardson

This article was originally published in Distro Issue #59.