Inline skates are a type of roller skate used for inline skating. Unlike quad skates, which have two front and two rear wheels, inline skates typically have two to five wheels arranged in a single line. Some, especially those for recreation, have a rubber "stop" or "brake" block attached to the rear of one or occasionally both of the skates so that the skater can slow down or stop by leaning back on the foot with the brake skate. The modern style of inline skates was developed as a substitute for ice skates, for use by a Russian athlete[who?] training on solid ground for Olympic long track speed skating events. Life magazine published a photo of American skater Eric Heiden, training for the 1980 Olympics, using such skates on a Wisconsin road. During the late 1980s and early 1990s, Rollerblade, Inc., a company founded by Scott and Brennan Olson in Minneapolis, Minnesota, widely promoted inline skating through the registered trademark Rollerb
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John Joseph Merlin experimented with single- to many-rowed devices worn on feet in 1760. Inline skates, skates designed to work like ice skates during periods of warm weather, was patented by Robert John Tyers of London in 1823, his Rolito design featured brass wheels. Louis Legrange of France created an inline design in 1849. Legrange designed the skates for an opera where a character was to appear to be skating on ice. The skates were problematic and unsuccessful as the wearer could not turn nor could they stop.
The first U.S. patent for modern in-line skates, designed to behave like ice runners with individually sprung and cushioned wheels, was granted under patent number US 2644692 in July 1953 to Ernest Kahlert of Santa Ana, CA. They were briefly described in the April 1950 issue of Popular Mechanics and again in the April 1954 issue of Popular Science in the section called "New Ideas from the Inventors". In Canada in 1972, Mountain Dew attempted to sell Mettoy's product the "Skeeler", an inline skate that was developed for Russian hockey players and speed skaters. In 1978, the German branch of SKF presented the "Speedy"-System, but the product was cancelled less than one year from market, as the management did not want a consumer product in the portfolio of the company.
The first commercially available inline skate for this form of Rollerskating is in 1987 by Rollerblade. In 1996, Jason Lewis completed the first solo crossing of the United States on inline skates, part of Expedition 360, a successful attempt to circumnavigate the globe using only human power. En route he was hit by a car in Colorado, breaking both legs. After nine months he completed the journey from Fort Lauderdale to San Francisco. In 2012, Kacie Fischer became the first woman, and the fastest person, to inline skate across the United States; she skated from California to Florida in 47 days.
A skate is composed of a boot, 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 boot. There are different types of inline skates for different types of skating such as aggressive skating, speed skating, inline hockey and artistic inline skating. Those differ in the boots, frames and wheels that are used.
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 a carbon fiber boot which provides greater support with a lower cut 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. Downhill skaters often use boots that are heat-molded to the shape of the foot, with a foam liner. Most aggressive skates use a hard boot or a hard/soft boot for increased support.
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 fiber or extruded aluminum (more expensive but more solid), magnesium, or even pressed aluminium, which is then folded into a frame (cheaper but less sturdy). Carbon fiber frames are expensive but generally more flexible, making for a smoother ride at the expense of worse power transfer between the leg and the wheels. In general, carbon fiber frames weigh about 160–180 grams (5.6–6.3 oz). Recently, high-end carbon fiber frames with a monocoque construction have been introduced. They offer the same level of stiffness as aluminum frames while weighing only around 130 g (4.6 oz). Aluminum can weigh from 170 to 240 grams (6.0 to 8.5 oz). Frame length ranges from 2 wheel framed freestyle wheels (used in aggressive skating) to around 230 mm (9.1 in) for short-framed four wheel skates (used in most inline designs), up to about 325 mm (12.8 in) for a five-wheel racing frame.
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 very important for how long bearings last. While higher rated bearings are generally better in overall quality, whether they automatically translate to more speed is questionable. Since at least 2007, Rollerblade brand amongst others have begun using their own rating system. For instance, Rollerblade brand is currently using a SG1 to SG9 rating system, whereas TwinCam brand is using its own "ILQ" (InLine Qualified) rating system and Bones brand is using its own "Skate Rated" rating system.
A mistake that is often made in purchasing bearings is that spending more translates to more speed. Generally, clean inline skate bearings contribute about 2% of the rolling resistance that the best urethane inline skate wheels produce, so there is very little opportunity in improving speed by spending more money on bearings. Newer bearings on the market have been offered that use ceramic ball bearings instead of steel, which are more expensive than traditional steel bearings but made of harder material.
Two bearings are used per wheel. The bearings slip into openings molded into each side of the wheel hub, and a flange molded into the wheel hub holds the bearings the correct distance apart. Additionally there is an axle spacer either machined into the axle or that slides over the axle (depending on the axle system used). Since the outer race of the bearing contacts the wheel spacer and the inner race of the bearing contacts the axle spacer, it is critical that the relationship between these two spacers is correct. If the wheel spacer is wider than the axle spacer the bearings will bind when the axle bolt (or bolts) are tightened.
Wheel sizes vary depending on the skating style. Note carefully that the skater's age factors in. The wheel size an adult uses shall not really be the same as a child's:
- 44–72 mm (1.73–2.83 in) for aggressive skating.
- 47–80 mm (1.85–3.15 in) for roller hockey skating.
- 68–72 mm (2.68–2.83 in) for artistic inline skating.
- 72–80 mm (2.83–3.15 in) for freestyle slalom skating and downhill skating.
- 70–90 mm (2.76–3.54 in) for urban skating.
- 72–100 mm (2.83–3.94 in) for general recreational skating.
- 80–90 mm (3.15–3.54 in) for downhill inline skating.
- 100–125 mm (3.94–4.92 in) for tri-skating, mushroom blading, and speed skating.
- 125–150 mm (4.92–5.91 in) tires for off-road skating.
Wheels are nowadays almost universally made of polyurethane (a kind of durable plastic). Most other plastics and rubber either wear down too quickly or have too much rolling resistance. In general, the bigger the wheel, the faster the skate. A bigger wheel rolls over road imperfections smoothly thus the less bumpy the skating. On top of that, an inline skater trips far less on large wheels. 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 72A-93A (lower numbers are softer, higher numbers are harder). Harder wheels are not necessarily faster but tend to be more durable; soft wheels may have better grip and are generally less affected by road bumps. Harder wheels (which grant minimal elastic hysteresis energy absorption) maintain rolling speed far better while softer wheels (because they grip the surface) accelerate more straightforwardly when striding. In the 1990s, wheel rolling resistance (CRR – coefficient of rolling resistance) tended to be minimized with wheel hardness in the 78A durometer range, with rolling resistance dramatically increasing below 75A durometer and above 85A durometer. In the early 2000s, urethane compounds improved significantly, allowing skaters to use harder compounds to get better wheel life, and get the lowest rolling resistance in the 82A–84A durometer range.
Wheel profiles and thickness again vary by application. Elliptic profiles were thought to minimize friction for a faster ride; however, they were intended to mimic the knife-like properties of an ice blade. They helped define the inner, central and outer edges. Elliptic profiles made the wheel quite maneuverable when turning or otherwise crossing over. More rounded profiles provided lower rolling resistance due to the greater "belly" or tire that increased resilience (or "rebound"); and these wheels were perceived as having better grip and being more stable (less like an ice blade), but were heavier than elliptical-profiled wheels and were often used in downhill racing (such as the Hyper Downhill racing wheels) and in recreational skates. Another advantage of rounded profile wheels is longer wear life due to the increased urethane amount on the tire. To increase stability at high speed, skates intended for downhill skating usually have five or six wheels, in contrast with recreational skates, which typically have four wheels. This advantage of more wheels having less rolling resistance has been largely negated by the 100–110 mm (3.9–4.3 in) diameter wheels with 4-wheel trucks. A flat profile allowed the wheel to be even far stabler than the rounded profile. This profile is almost exclusively used on aggressive skate wheels. On the flip-side, the squared-off shape caused cornering to be tremendously harder, seeing how edges are non-existent with a flat profile. In fact, a flat profile has only a center edge preventing the skater from leaning over.
The core's general design i.e. material, shape, and flexibility/sturdiness degree at the wheel's hub determine the wheel's properties as well. In a classical point of view, wheels on older skate models (during the 1980s and early 1990s) contained no core feature whatsoever. The core is a result of the gradual technological improvement inline skating underwent. Above all else, a wheel lacking a core is prone to deformation. This deformation is a hindrance to the skater's striding ability since in such a case it minimizes the skater's top speed. The core is inserted to hold the polyurethane firmly in place. Despite the setback, markets still distribute special wheels without a core. Core designs vary among open, full or semi-open. 'Spokes' are an element seen in wheels whose cores are open which generally increase overall wheel lightness. These are inserted into the hubs of wheels for inline speed skates, fitness skates, recreational skates, some slalom skates and artistic/figure inline skates. Apart from spokes, other open-cores can be hollowed out internally. The main disadvantage about an open core is that their design does not permit sturdiness hence they are highly likely to snap under too much pressure i.e. when jumping. Another trade-off with open cores is the lesser amount of polyurethane around it to compensate for the spoked or hollow shape meaning they last shorter. Full cores are entirely solid, akin to a pipe's cross-section. This core design is mostly favored amongst aggressive skaters whose leaps off higher levels strain the wheels when landing. Of course, these cores (alongside the extra polyurethane) tend to add weight on the wheel. Some even disfavor the full core design for its rigidity that feels uncomfortable. The question still stands on whether a full core improves power transfer. Semi-open cores are a hybrid between the two previously mentioned cores seen on wheels for urban skates, slalom skates and inline hockey skates. Minuscule holes are typically punctured into these solid cores to provide a semi-open design.
Heel brakes or toe stops
A hard rubber brake attached to the heel of the frame allows the skater to stop by lifting the toes of the skate, forcing the brake onto the ground. Learning how to use the heel brake is very important for beginners, as it is the easiest way to stop in emergencies and to control speed on downhills. Also, with practice, beginners realise if the heel brakes are better placed for them on the left/right foot.
Heel brakes can interfere with a useful technique called a crossover turn, in which a skater crosses one leg over another to make a sharp turn without losing much speed; for this reason, most intermediate to advanced users prefer not to use heel brakes. Skaters in the freestyle slalom and aggressive inline skating disciplines do not use heel brakes, since they limit the skater's ability to perform tricks effectively. Aggressive inline skates and racing skates generally have no heel brake, thereby permitting extra speed and control.
Inline skaters lacking a heel brake can use various other methods to stop, such as the T-stop in which the skater moves one skate perpendicular to the other, making a "T" shape to increase friction and reduce speed, or the more advanced maneuver of a hockey stop/snow plow stop, in which the skater quickly moves both skates perpendicular to the path of motion.For artistic roller skating purposes, inline figure skates can also feature a "toe stop" which aids in performing figure skating jumps.