 Is it just a glorified plank with roller skate wheels on it? Or is it a highly engineered device through which kids have reclaimed the urban landscape, bringing creativity and style back to the sterile asphalt spaces of sprawl? |  | The basic elements of the skateboard seem pretty straightforward. A board has three parts: the board or deck, the wheels, and the trucks, which connect the wheels to the board, and allow the board to turn. |
"Modern skateboards are made traditionally from 7 plies of sugar maple veneers, pressed together using polyvinyl glues in either aluminum, metal or concrete forms, generally taking around 300 psi to take up multiple skateboards in one closing of a press. Anywhere from 3-5 skateboards are done in one press, and after 30 minutes to an hour, the boards are removed from the press. At this point they have been stuck and laminated in the compound curve or the shape, which is the concave. Then after days of curing, the CNC routers, or hand routers depending on the woodshop, will cut out the final shape, apply the edge trimming, paint it and send it on its way."
2. Concaves, kicktails, nose
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"There's two shapes you talk about when you look at performance: of a skateboard: number one is the concave, the 3-dimensional curves that are in the board itself, nose, tail and side to side concave. Every manufacturer has their own style or philosophy. Mine is based on actual functionality; what your foot feels like when it's in the concave itself. To get there, I do a lot of prototyping in foam cutting, letting all of our pro and amateur riders have a say in what feels good and what works before we go and cut tooling to make skateboards. So our approach is based on a feel functionality first, and then secondly, when no one's looking, I slip in curves and bends engineered into this 3-d curve, the concave, that makes the board stiffer, stronger, and makes it last longer."
The other shape is called the plan form. This is the shape of the board's outline; if you put a board flat up against the wall and traced its outline, you would be drawing the plan form. According to Piumarta, this shape is largely determined by the choices of individual riders. "Now the other shape we're talking about is the plan form, or the shape outline of the board of looking at a wall. Pro riders can tell by looking and feeling with their hand, they can tell if a board is out of shape by even fifty thousandths of an inch. They can feel it, they know what they like, and what they don't like." And, as Piumarta says, all the engineering in the world means nothing if it doesn't result in a good ride. |
Skateboard wheels have gone through a dramatic change since the early 1900's when kids took roller skate wheels and nailed them to a two-by-four. Those early wheels were usually steel, which offered a rough ride, to say the least. Worse, steel wheels offered little or no traction, so riding these boards was pretty much a straight-ahead proposition. In the late 1950's, the first commercial skateboards appeared, though most boards were still homemade. By the 1960's, some advances in roller skate design led to the appearance of clay wheels. These were an improvement over metal wheels, but not by much. As one early rider described the ride, circa 1961: "It was wobblier than hell, moved way too fast, and vibrated on the asphalt enough to jar every bone in your body and loosen every tooth. It was more like getting electrocuted than anything else." (Bob Schmidt, quoted in The Concrete Wave, 1999)
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But it wasn't until the early 1970's that a pair of wheel innovations would arrive that would help turn skateboarding, "from a funky, surfing activity, what you would do when the waves were down, into a real bonafide sport," according to Tim Piumarta. The urethane wheel and the press-in precision bearing changed skateboarding forever, and led to the next big explosion in skateboard popularity.
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The first urethane wheels were the handiwork of Frank Nasworthy, who, after seeing some experimental urethane roller-skate wheels in a friend's backyard in 1970, realized that such wheels could be used for skateboards. Nasworthy and his friends tried them, and found that the old tooth-jarring ride was gone, replaced by a ride of unprecedented smoothness and stability. Skateboarding was in a dead period in the early 70's, but Nasworthy's wheels, called Cadillacs, began to catch on.Fausto Vitello explained why urethane was perfect for wheels: "Urethane has some unique properties. The first is that it has really good abrasion resistance, which means that the wheel will last a while. The second one, even more important, is that urethane gives a really good grip with the ground. It will slide if you push it hard, but it gives great traction. So that means you can control your board. And the last is that modern urethanes have a real high resiliency, or rebound, which means that although the wheels have no pneumatic tube or anything (they’re solid), they’re still able to be very fast."
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He also points out that with wheels, adding cool colors may actually weaken the wheel. "Urethane is normally a whitish clear color, when it’s poured with no other agents. Dyes or pigments take up room (in the structure of the wheel) that would normally be actual urethane. Less urethane means less resiliency in the wheel. Dyes are arguably better than pigments, which really take up a lot of space. But some people argue that dyes alter the chemical structure of the urethane itself. When people are really looking for a high-performance wheel, we recommend a clear wheel."So, as the wheel turns, the section of the wheel that is in contact with the ground is flattened a little bit by the weight of the skater pressing down. Engineers refer to this flattening as deformation. A resilient urethane wheel returns to its round shape very quickly, pressing back out against the pavement before the wheel loses contact with the ground. If the wheel rebounds more slowly, after the flattened section has rolled away from the ground, the energy that has gone into the deformation is lost, and the wheel rolls more slowly. You might think that a wheel that didn't deform at all would be better. But, as Exploratorium Physicist Paul Dougherty explained, "a wheel that is too hard would actually press on the pavement so that the pavement would deform, and more energy would be lost that way." In addition, a harder wheel loses the shock absorbing and ride-smoothening properties that were such an improvement over the early clay and metal wheels.
4. So what a heck is a "Truck", anyway ?
The skateboard steering devices on the bottom of the board are called the trucks. Trucks consist of a base plate (mounted to the base of the skateboard itself), an axle which pivots on two urethane cushions (called bushings) and a pivot point. This construction enables the wheels (which are attached to the axles) to swing in a predefined arc, which allows the skateboard to turn.
This design allows the skater to turn the board by leaning; lean right, the board goes right. Lean left, and you go left. A nut called the kingpin nut controls the ease of turning. Tightening this nut compresses the urethane bushings, stiffening the action of the truck. Tightening the kingpin nut makes the board more stable, but makes it much harder to turn. Loosen it, and the board becomes floppier, but much easier to turn.
The most popular truck of all time, and the standard for the modern skater, was the Independent Truck. As designed and produced by the combined creativity of NHS and the Ermico Foundry, the Independent was a wonder of clean design: smooth, easy turning, durable and strong. Fausto Vitello, one of the founders of Ermico and one of the originators of the Independent Truck, described the basic truck design: "The basic skateboard truck has not changed in probably fifty or sixty years. It was designed around the 1920's for ballroom roller-skate dancing,which had a big boom prior to the depression. The basic system for allowing a truck to turn is called the Chicago pivot, and all modern trucks are derived from that. What has changed in the Chicago Pivot truck is that we have refined the system to allow better turning, more stability, and certain other features that skaters demand."
Tim Piumarta agreed the skateboard truck has hardly changed at all over the years. "Trucks have barely changed at all, in fact the skateboard truck design and geometry was lovingly lifted from roller skate base plates going back to the 1950's and before that. Two elastomers sandwiching a yoke which was connected to an axle and everything pivoted on one point."
resource from http://www.exploratorium.edu/skateboarding/
