in-line skate

A roller skate whose wheels are arranged in a straight line.

Background

In-line skates were developed in the mid-1980s, but the basic concept of rolling wheels attached to a boot is much older. Earlier roller skates had wheels of wood, plastic, or steel, arranged in pairs. Modernday in-line skates have wheels made out of polyurethane plastic arranged in a line so that the gliding action is much like that of an ice skating blade. Sometimes this type of skate is called a rollerblade, although this is a trademark name and refers only to a specific brand of skates.

History

People in Scandinavia used ice skates as early as 1000 B.C. These skates were made of bone runners tied to boots, and they were used to travel across frozen lakes. The first roller skate is credited to Belgian inventor Joseph Merlin, who in 1760 demonstrated a pair of skates with small metal wheels. A French inventor named Petitbled patented a roller skate in France in 1819 that was some-thing like today's in-line skates. Petitbled's invention had a straight line of wooden, metal, or ivory rollers attached to a wooden sole. Soon after, Robert John Tyers of London came up with what he called the "rolito," a similar skate with five wheels placed in a row on the bottom of a shoe. Roller skates steadily gained in popularity, and the 1849 French opera "La Prophete" even featured a simulated ice skating scene where the performers used wooden-wheeled in-line skates.

These early skates became less common, however, with the 1863 invention of the "rocking skate" by American James Plimpton. Plimpton's skate had a pair of wheels in front and back, mounted on a rubber-padded plate. Roller skaters were able to skate in curves with the Plimpton skate, quite an advantage over previous models. This style of skate soon became the standard. Other innovations were incorporated: high-topped stiff leather boots were attached to metal plates; moveable parts were added to plates to allow skaters to turn corners; and a pair of wheels was attached to an axle on each assembly. Plastic wheels eventually replaced steel or wooden wheels, and basic design improvements over the years have included use of a rubber toe stop, similar to a front brake, and sturdier assembly.

In the 1980s, hockey players Scott and Brennan Olson of Minneapolis, Minnesota, were looking for a way to modify hockey boots so they could cross-train year round. While rummaging through a sporting goods store, they discovered an in-line skate and decided to improve on the design. They began assembling what would be the first "Rollerblade" in-line skate in the basement of their parents' house. The Olsons' first in-line skate had steel frames and skateboard rubber wheels that were riveted to hockey boots. Their prototype was extremely clunky and heavy, but the basic design prevailed.

Hockey players were the first to seriously use in-line skates. During the summer months, they played roller hockey games in the gym and outside on pavement. Nordic and alpine skiers also began to use in-line skates in their training. Soon the popularity of the skates spread to non-athletes as well. Scott Olson created the company that became Rollerblade, Inc. and improved on several of the in-line skate patents. But competition from other in-line skate manufacturers forced the company to adopt even more sophisticated manufacturing and marketing efforts. In 1994, Rollerblade patented the Active Brake Technology (ABT) braking system, a cuff-activated braking system that made stopping easier for beginning in-line skaters. The new brake also provides greater speed control. Rollerblade currently holds 16 U.S. patents and 200 pending patents for in-line skating products.

Parts of In-Line Skates

The modern in-line skate has polyurethane wheels aligned on a strip or truck (chassis) made out of plastic or light aluminum. The truck holds the wheels in place with bolts, and on some models the wheels can be detached and changed. The truck is attached to a molded boot, also made of polyurethane, which holds the buckles (made out of plastic, velcro straps, or cloth laces). Some in-line boot shells are leather or a combination of leather and polyurethane plastic. The brakes are made of hard rubber or polyurethane and are located on the back of the skate.

The boots are designed to provide good ankle support by extending 3-4 inches (7-10 cm) above the ankle joint. The upper and lower portions of the boot are connected on each side of the ankle by a hinge system that allows the ankle to flex. For additional comfort, boots are lined with material that absorbs sweat, usually high-density foam covered with nylon clots. Wheels vary in hardness (durometer) and size (diameter). Generally, the harder the wheels, the faster the skates. Wheels have two ball bearings per wheel that are separated by a spacer of either plastic or metal. Bearings help the wheels spin faster and more freely. The spacer helps prevent the bearings from making contact with each other.

Raw Materials

The in-line skate is a product of modern technology. High-grade polyurethane, copolymer plastics, or carbon fiber Kevlar (material used to make bulletproof vests) are used to make the majority of in-line skating shells or boots. Wheels are also made of polyurethane. Harder nylon or urethane plastic or steel is used for the chassis and brake components. Frames that hold the wheels can be made of aluminum, carbon fiber, or titanium. Cloth or plastic foam is used to line the inside of the boot. Steel is also used for ball bearings, buckles, and other attachments on the in-line skate itself.

The Manufacturing
Process

Separate companies worldwide manufacture the individual in-line skate components. For example, manufacturers of skate-board wheels also make in-line skate wheels. Another company makes the boot shell and chassis; another manufacturer provides the braking system. In-line skates are manufactured using an assembly line process whereby all components move down a conveyor belt and are assembled piece by piece.

Making the boot shell

• In-line boot shells are made by a process called injection molding. Urethane plastic is injected into a mold to form the boot shell, much like a ski boot. Dye may be added for color. When the mold has cooled, the injection-molding machine ejects the finished boot.

Inserting the liner

• Soft cloth or plastic foam is cut to various sizes and inserted into the boot shell. The dimensions of the liner should conform to the skater's foot.

Adding the attachments

• The remaining shell cuff (as well as the tongue), metal buckles, and plastic or velcro fasteners are attached to the shell. Most of these pieces are bought prefabricated.

Assembling the wheels

• The frame, including wheels and bearings, is attached to the boot shell by rivets or by a coupling system. The frame is often assembled ahead of time. The wheels are placed in a row and attached to the frame. On inexpensive models, the boot and frame are injection molded as one unit.
• Once the in-line skate has been assembled, it is boxed and delivered to stores.

The Future

In 1990, Rollerblade reported retail sales of more than $100 million and in 1991 controlled about 70% of the in-line skating market. Ultra-Wheels claims about 20% of the market. Since its heyday, however, Rollerblade has lost market share to many competitors, an indication of the widespread popularity of in-line skates. Industry analysts have predicted that the market for in-line skates could reach $1 billion in 1995, compared to $200 million in 1992. The future for the product is highly favorable and newer models that are faster, lighter, and more comfortable are being developed every year.

Where To Learn More

Books

Powell, Mark and John Svensson. In-Line Skating. Human Kinetics Publishers, 1993.

Rappelfeld, Joel. The Complete Blader. St. Martin's Press, 1992.

Periodicals

Fassett, Wayne. "Blade Runners." Popular Mechanics, November 1991, p. 49.

Macnow, Glen. "New Ideas Get a Sporting Chance." Nation's Business, December 1992, pp. 62-63.

"Synergy Standouts." Sporting Goods Business, February 1994, p. 74.

[Article by: Evelyn S. Dorman]

The noun has one meaning:

Meaning #1: a shoe with rollers fixed to the sole in a line
  Synonym: roller blade

Bont ZX2 inline speed skates

Inline skates are a type of roller skate, used for inline skating. Unlike quad skates which have a configuration of 2 wheels in the front and 2 wheels in the back, inline skates have two, three, four or five wheels arranged in a single line. Some inline skates, especially those used for recreation, have a "stop" or "brake" which is used to slow down while skating; most inline skates have a heel stop rather than the toe stop, particularly indispensable for Inline Figure Skating.

The earliest roller skates were of the inline design, but these were later superseded by quad skates, the design of which made skating curved edges easier. During the late 1980s and early 1990s, the popularity of inline skates had a strong resurgence, led by the company Rollerblade, Inc. founded by Scott and Brennan Olson in Minneapolis, Minnesota. After the brothers sold the company in about 1984, Rollerblade promoted and popularized inlines, and their skates became so successful that the term "Rollerblades" has become synonymous with "inline skates."^[1]

Parts

A skate is composed of a boot, which is worn on the foot. To the boot is attached a frame, which holds the wheels in place. Bearings allow the wheels to rotate freely around an axle. Finally, the rubber brake typically attaches to the frame of the right foot.

An inline skate designed for artistic roller skating

There are different types of inline skates for different types of skating such as aggressive skating, speed skating, and artistic inline skating. Those differ in the boots, frames and wheels that are used.

The boot

For most skating a high boot is used, which provides more ankle support and is easier to skate in, particularly for beginners. Speed skaters often use lower boots allowing more ankle flexion.

For recreational skating a soft boot is used for greater comfort, but many other disciplines prefer a harder boot, either to protect the foot against impact or for better control of the skate. The boot may also contain shock absorbent padding for comfort.

Most aggressive skates use a hard boot or a hard/soft boot for increased support.

The frame

The frame and wheels of an inline skate.

Typical recreational skates use frames built out of high-grade polyurethane (plastic). Low-end department or toy store skate frames may be composed of other types of plastic. Speed skate frames are usually built out of carbon fibre or extruded aluminum (more expensive but more solid), magnesium, or even pressed aluminum, which is then folded into a frame (cheaper but less sturdy).

Carbon fibre frames are expensive but more flexible, making for a smoother ride at the expense of worse power transfer between the leg and the wheels. In general, carbon fibre frames weigh about 160-180 grams. Aluminum can weigh from 170 to 220 grams. Frame length ranges from around 230 mm for short-framed four wheel skates (used for example in inline hockey), up to about 325 mm for a five wheel racing frame.

Bearings

Axles, bearings and spacers.

Ball bearings allow the wheels to rotate freely and smoothly. Bearings are usually rated on the ABEC scale, a measure of the manufactured precision tolerance, ranging from 1 (worst) to 9 (best) in odd numbers. The ABEC standards were originally intended for high-speed machinery, not skating applications, and do not account for the quality of steel used, which is also important. While higher rated bearings are generally better in overall quality, whether they automatically translate to more speed is questionable^[2].

The vast majority of skate bearings on the market are produced in China, and tend to be of much lower quality and durability than bearings produced in Japan, Germany, Switzerland, Canada, or the USA. Newer bearings on the market now use ceramic ball bearings instead of steel, the merits of which have yet to be determined.

Wheels

Diagram of inline skate wheels with different diameter and profile.

Wheel sizes vary depending on the skating style:

• 48-60 mm for aggressive skating.
• 68-72 mm for artistic inline skating.
• 72-80 mm for general recreational skating.
• 59-80 mm for roller hockey skating and slalom.
• 80-110 mm for speed skating.

In general the bigger the wheel, the faster the skate. However, large wheels take more energy to start rolling. Smaller wheels allow faster acceleration, maneuverability, and a lower center of gravity. Wheel hardness is measured on the A scale (see Durometer) and usually ranges between 78A-93A (higher numbers are harder). Harder wheels are faster and more durable, but soft wheels may have better grip (grip is determined by many factors, and wheel manufacture is arguably more important than durometer) and less affected by road bumps. Wheel profiles and thicknesses again vary by application. Elliptic profiles minimise friction for a faster ride; more rounded profiles have better grip and are more stable.

Brakes

A hard rubber brake is typically attached to the heel of the frame. Brakes allow for skaters to bring themselves to a stop. Learning how to use the heel brake thus is crucial for beginners. The heel brakes can interfere with a useful technique called crossover turn (when a skater crosses one leg over another to make a sharp turn without losing much speed), which is why some users prefer not to use them.

Notes

1. ^ Lemelson-MIT (August 1997). Inventor of the Week Archive: Scott & Brennan Olson (spelling corrected per rowbike.com -ed.). MIT School of Engineering. Retrieved on 2007-02-25.
2. ^ ABEC = HYPE?

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