An evaporative cooler is a device that cools air through the evaporation of water. Evaporative cooling differs from typical air conditioning systems, which use vapor-compression or absorption refrigeration cycles. Evaporative cooling uses the fact that water will absorb a large amount of heat in order to evaporate; the temperature of dry air can be dropped through the phase transition of liquid water to water vapor. This can cool air using much less energy than refrigeration. In dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants; the cooling potential for evaporative cooling is dependent on the wet-bulb depression, the difference between dry-bulb temperature and wet-bulb temperature. In arid climates, evaporative cooling can reduce energy consumption and total equipment for conditioning as an alternative to compressor-based cooling. In climates not considered arid, indirect evaporative cooling can still take advantage of the evaporative cooling process without increasing humidity.
Passive evaporative cooling strategies can offer the same benefits of mechanical evaporative cooling systems without the complexity of equipment and ductwork. An earlier form of evaporative cooling, the windcatcher, was first used in ancient Egypt and Persia thousands of years ago in the form of wind shafts on the roof, they caught the wind, passed it over subterranean water in a qanat and discharged the cooled air into the building. Modern Iranians have adopted powered evaporative coolers; the evaporative cooler was the subject of numerous US patents in the 20th century. A typical design, as shown in a 1945 patent, includes a water reservoir, a pump to circulate water over the excelsior pads and a centrifugal fan to draw air through the pads and into the house; this design and this material remain dominant in evaporative coolers in the American Southwest, where they are used to increase humidity. In the United States, the use of the term swamp cooler may be due to the odor of algae produced by early units.
Externally mounted evaporative cooling devices were used in some automobiles to cool interior air—often as aftermarket accessories—until modern vapor-compression air conditioning became available. Passive evaporative cooling techniques in buildings have been a feature of desert architecture for centuries, but Western acceptance, study and commercial application is all recent. In 1974, William H. Goettl noticed how evaporative cooling technology works in arid climates, speculated that a combination unit could be more effective, invented the "High Efficiency Astro Air Piggyback System", a combination refrigeration and evaporative cooling air conditioner. In 1986, University of Arizona researchers W. Cunningham and T. Thompson built a passive evaporative cooling tower, performance data from this experimental facility in Tucson, Arizona became the foundation of evaporative cooling tower design guidelines developed by Baruch Givoni. Evaporative coolers lower the temperature of air using the principle of evaporative cooling,n]] or absorption refrigerator.
Evaporative cooling is the conversion of liquid water into vapor using the thermal energy in the air, resulting in a lower air temperature. The energy needed to evaporate the water is taken from the air in the form of sensible heat, which affects the temperature of the air, converted into latent heat, the energy present in the water vapor component of the air, whilst the air remains at a constant enthalpy value; this conversion of sensible heat to latent heat is known as an isenthalpic process because it occurs at a constant enthalpy value. Evaporative cooling therefore causes a drop in the temperature of air proportional to the sensible heat drop and an increase in humidity proportional to the latent heat gain. Evaporative cooling can be visualized using a psychrometric chart by finding the initial air condition and moving along a line of constant enthalpy toward a state of higher humidity. A simple example of natural evaporative cooling is perspiration, or sweat, secreted by the body, evaporation of which cools the body.
The amount of heat transfer depends on the evaporation rate, however for each kilogram of water vaporized 2,257 kJ of energy are transferred. The evaporation rate depends on the temperature and humidity of the air, why sweat accumulates more on humid days, as it does not evaporate fast enough. Vapor-compression refrigeration uses evaporative cooling, but the evaporated vapor is within a sealed system, is compressed ready to evaporate again, using energy to do so. A simple evaporative cooler's water is evaporated into the environment, not recovered. In an interior space cooling unit, the evaporated water is introduced into the space along with the now-cooled air. A related process, sublimation cooling, differs from evaporative cooling in that a phase transition from solid to vapor, rather than liquid to vapor, occurs. Sublimation cooling has been observed to operate on a planetary scale on the planetoid Pluto, where it has been called an anti-greenhouse effect. Another application of a phase change to cooling is the "self-refrigerating" beverage.
A separate compartment ins
Skiing can be a means of transport, a recreational activity or a competitive winter sport in which the participant uses skis to glide on snow. Many types of competitive skiing events are recognized by the International Olympic Committee, the International Ski Federation. Skiing has a history of five millennia. Although modern skiing has evolved from beginnings in Scandinavia, it may have been practiced more than 100 centuries ago in what is now China, according to an interpretation of ancient paintings; the word "ski" is one of a handful of words. It comes from the Old Norse word "skíð" which means "split piece of wood or firewood". Asymmetrical skis were used in northern Sweden until at least the late 19th century. On one foot, the skier wore a long straight non-arching ski for sliding, a shorter ski was worn on the other foot for kicking; the underside of the short ski was either plain or covered with animal skin to aid this use, while the long ski supporting the weight of the skier was treated with animal fat in a similar manner to modern ski waxing.
Early skiers used spear. The first depiction of a skier with two ski poles dates to 1741. Skiing was used for transport until the mid-19th century, but since has become a recreation and sport. Military ski races were held in Norway during the 18th century, ski warfare was studied in the late 18th century; as equipment evolved and ski lifts were developed during the late 19th and early 20th centuries, two main genres of skiing emerged—Alpine skiing and Nordic skiing. The main difference between the two is the type of ski binding. Called "downhill skiing", Alpine skiing takes place on a piste at a ski resort, it is characterized by fixed-heel bindings that attach at both the toe and the heel of the skier's boot. Ski lifts, including chairlifts, bring skiers up the slope. Backcountry skiing can be accessed by helicopter, snowcat and snowmobile. Facilities at resorts can include night skiing, après-ski, glade skiing under the supervision of the ski patrol and the ski school. Alpine skiing branched off from the older Nordic type of skiing around the 1920s when the advent of ski lifts meant that it was not necessary to walk any longer.
Alpine equipment has specialized to the point. The Nordic disciplines include cross-country skiing and ski jumping, which both use bindings that attach at the toes of the skier's boots but not at the heels. Cross-country skiing may be practiced in undeveloped backcountry areas. Ski jumping is practiced in certain areas that are reserved for ski jumping. Telemark skiing is a ski turning technique and FIS-sanctioned discipline, named after the Telemark region of Norway, it uses equipment similar to Nordic skiing, where the ski bindings are attached only at the toes of the ski boots, allowing the skier's heel to be raised throughout the turn. The following disciplines are sanctioned by the FIS. Many are included in the Winter Olympic Games. Cross-country – Encompasses a variety of formats for cross-country skiing races over courses of varying lengths. Races occur on homologated, groomed courses designed to support classic and free-style events, where skate skiing may be employed; the main competitions are the FIS Cross-Country World Cup and the FIS Nordic World Ski Championships, various cross-country skiing events have been incorporated into the Winter Olympics since its inception in 1924.
The discipline incorporates: cross-country ski marathon events, sanctioned by the Worldloppet Ski Federation. Paralympic cross-country skiing and paralympic biathlon are both included in the Winter Paralympic Games. Ski jumping – Contested at the FIS Ski Jumping World Cup, the FIS Nordic World Ski Championships, the FIS Ski Jumping Grand Prix, the FIS Ski Flying World Championships. Ski jumping has been a regular Olympic discipline at every Winter Games since 1924. Freeriding skiing – This category of skiing includes any practice of the sport on non-groomed terrain. Nordic combined – A combination of cross-country skiing and ski jumping, this discipline is contested at the FIS Nordic Combined World Cup, the FIS Nordic World Ski Championships, at the Winter Olympics. Alpine skiing – Includes downhill, giant slalom, super giant slalom, para-alpine events. There are combined events where the competitors must complete one run of each event, for example, the Super Combined event consists of one run of super-G and one run of slalom skiing.
The dual slalom event, where racers ski head-to-head, was invented in 1941 and has been a competitive event since 1960. Alpine skiing is contested at the FIS Alpine Ski World Cup, the FIS Alpine World Ski Championships, the Winter Olympics. Para-alpine skiing is contested at the World Para Alpine Skiing Championships and the Winter Paralympics. Speed skiing – Dating from 1898, with official records beginning in 1932 with an 89-mile-per-hour run by Leo Gasperi, this became an FIS discipline in the 1960s, it is contested at the FIS Speed Ski World Cup, was demonstrated at the 1992 Winter Olympics in Albertville. Freestyle skiing – Includes mogul skiing, ski cross, half-pipe, slopestyle; the main freestyle competitions are the FIS Freestyle Skiing World Cup and t
A baseball glove or mitt is a large leather glove worn by baseball players of the defending team, which assists players in catching and fielding balls hit by a batter or thrown by a teammate. By convention, the glove is described by the handedness of the intended wearer, rather than the hand on which the glove is worn: a glove that fits on the left hand—used by a right-handed thrower—is called a right-handed or "right-hand throw" glove. Conversely, a left-handed glove is worn on the right hand, allowing the player to throw the ball with the left hand. Early baseball was a game played without gloves. During the slow transition to gloves, a player who continued to play without one was called a barehanded catcher; the earliest glove was not webbed and not well suited for catching but was used more to swat a ball to the ground so that it could be picked up. One of the first players believed to use a baseball glove was Doug Allison, a catcher for the Cincinnati Red Stockings, in 1870, due to an injured left hand.
The first confirmed glove use was by Charlie Waitt, a St. Louis outfielder and first baseman who, in 1875, donned a pair of flesh-colored gloves. Glove use caught on as more and more players began using different forms of gloves. Many early baseball gloves were simple leather gloves with the fingertips cut off to allow for the same control of a bare hand but with extra padding. First baseman Albert Spalding skeptical of glove use, influenced more infielders to begin using gloves. Spalding founded the sporting goods company Spalding, which still manufactures baseball gloves along with other sports equipment. By the mid-1890s, it was normal for players to wear gloves in the field. In 1920, Bill Doak, a pitcher for the St. Louis Cardinals, suggested that a web be placed between the first finger and the thumb in order to create a pocket; this design soon became the standard for baseball gloves. Doak sold it to Rawlings, his design became the precursor to modern gloves, enabled Rawlings to become the preferred glove of professional players.
For many years it was customary for fielders to leave their gloves on the field when their team went in to bat. This practice was prohibited by the major leagues in 1954. Baseball gloves have grown progressively larger since their inception. While catching in baseball had always been two handed gloves grew to a size that made it easier to catch the ball in the webbing of the glove, use the off-hand to keep it from falling out. A glove is worn on the non-dominant hand, leaving the dominant hand for throwing the ball; the shape and size of the baseball glove is governed by official baseball rules. Section 3.00 - EQUIPMENT AND UNIFORMS specifies glove dimensions and materials in parts 3.04 through 3.07. The structure and quality of the baseball glove has developed over the past century. Today, the production of baseball gloves is efficient; this has increased the usefulness and accessibility of baseball gloves to the general population. Easton is "experimenting with combining leather and Kevlar in a new ultra-light weight glove line".
Manufacturers have designed new, non-traditional types of gloves to suit non-traditional players. Manufacturers are personalizing gloves for high caliber players to help increase their exposure on national television. Though there have been many advancements in the design and creation of the baseball glove, the greatest came in the invention of the catcher's mitt. However, as a Wake Forest University study demonstrated through 39 minor-league players though today's catcher's mitts are state-of-the-art, they still do not offer enough protection from long-term injury to the hand and wrist; the highest-quality baseball gloves are made of heavy leather. These heavy leather gloves take more time for the player to break in; these gloves provide a tighter, more personalized fit for the player. This is an improvement from youth and recreational gloves, which tend to feature palm pads and/or adjustable velcro wrist straps; these gloves take less time to break in or they are pre-broken in, they less personal and more "one size fits all".
Baseball gloves are measured by starting at the top of the index finger of the glove and measuring down the finger, along the inside of the pocket and out to the heel of the glove. Gloves range in size from 9 inches to 12.75 inches for adult outfield play. Catcher's mitts, unlike those of other gloves, are measured around the circumference, they have 32- to 34-inch patterns; the shape and size of a glove is described by its pattern. Modern gloves have become quite specialized, with position-specific patterns: Catcher's mitts are called "mitts" because they lack individual fingers, like mittens, they have extra padding and a hinged, claw-like shape that helps them funnel fastballs into the pocket and provide a good target for pitchers. Some catchers use mitts with phosphorescent paint around the ridges to provide a clearer target for the pitcher. In addition, catcher's mitts come in single hinge and dual hinge varieties. If required to catch a knuckleball, a catcher will use an larger mitt; some knuckleball catchers have experimented with using first baseman's mitts, as described below.
First baseman's mitts lack individual fingers. They are very long and wide to help them pick or scoop badly thrown balls from infielders; these mitts have 12.5- to 12.75-inch patterns, measured from wrist t
A gel is a solid jelly-like soft material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a dilute cross-linked system, which exhibits no flow when in the steady-state. By weight, gels are liquid, yet they behave like solids due to a three-dimensional cross-linked network within the liquid, it is the crosslinking within the fluid that gives a gel its structure and contributes to the adhesive stick. In this way gels are a dispersion of molecules of a liquid within a solid in which liquid particles are dispersed in the solid medium; the word gel was coined by 19th-century Scottish chemist Thomas Graham by clipping from gelatine. Gels consist of a solid three-dimensional network that spans the volume of a liquid medium and ensnares it through surface tension effects; this internal network structure may result from physical bonds or chemical bonds, as well as crystallites or other junctions that remain intact within the extending fluid. Any fluid can be used as an extender including water and air.
Both by weight and volume, gels are fluid in composition and thus exhibit densities similar to those of their constituent liquids. Edible jelly is a common example of a hydrogel and has the density of water. Polyionic polymers are polymers with an ionic functional group; the ionic charges prevent the formation of coiled polymer chains. This allows them to contribute more to viscosity in their stretched state, because the stretched-out polymer takes up more space; this is the reason gel hardens. See polyelectrolyte for more information. A hydrogel is a network of polymer chains that are hydrophilic, sometimes found as a colloidal gel in which water is the dispersion medium. A three-dimensional solid results from the hydrophilic polymer chains being held together by cross-links; because of the inherent cross-links, the structural integrity of the hydrogel network does not dissolve from the high concentration of water. Hydrogels are absorbent natural or synthetic polymeric networks. Hydrogels possess a degree of flexibility similar to natural tissue, due to their significant water content.
As responsive "smart materials," hydrogels can encapsulate chemical systems which upon stimulation by external factors such as a change of pH may cause specific compounds such as glucose to be liberated to the environment, in most cases by a gel-sol transition to the liquid state. Chemomechanical polymers are also hydrogels, which upon stimulation change their volume and can serve as actuators or sensors; the first appearance of the term'hydrogel' in the literature was in 1894. Common uses for hydrogels include: Scaffolds in tissue engineering; when used as scaffolds, hydrogels may contain human cells to repair tissue. They mimic 3D microenvironment of cells. Hydrogel-coated wells have been used for cell culture Environmentally sensitive hydrogels; these hydrogels have the ability to sense changes of pH, temperature, or the concentration of metabolite and release their load as result of such a change. Sustained-release drug delivery systems Providing absorption and debriding of necrotic and fibrotic tissue Hydrogels that are responsive to specific molecules, such as glucose or antigens, can be used as biosensors, as well as in DDS.
Disposable diapers where they absorb urine, or in sanitary napkins Contact lenses EEG and ECG medical electrodes using hydrogels composed of cross-linked polymers Water gel explosives Rectal drug delivery and diagnosis Encapsulation of quantum dots Breast implants Glue Granules for holding soil moisture in arid areas Dressings for healing of burn or other hard-to-heal wounds. Wound gels are excellent for helping to maintain a moist environment. Reservoirs in topical drug delivery. Materials mimicking animal mucosal tissues to be used for testing mucoadhesive properties of drug delivery systemsCommon ingredients include polyvinyl alcohol, sodium polyacrylate, acrylate polymers and copolymers with an abundance of hydrophilic groups. Natural hydrogel materials are being investigated for tissue engineering. Hydrogels show promise for use in agriculture, as they can release agrochemicals including pesticides and phosphate fertiliser increasing efficacy and reducing runoff, at the same time improve the water retention of drier soils such as sandy loams.
An organogel is a non-crystalline, non-glassy thermoreversible solid material composed of a liquid organic phase entrapped in a three-dimensionally cross-linked network. The liquid can be, for an organic solvent, mineral oil, or vegetable oil; the solubility and particle dimensions of the structurant are important characteristics for the elastic properties and firmness of the organogel. These systems are based on self-assembly of the structurant molecules. Organogels have potential for use in a number of applications, such as in pharmaceuticals, art conservation, food. A xerogel is a solid formed from a gel by drying with unhindered shrinkage. Xerogels retain high porosity and enormous surface area, along with small pore size; when solvent removal occurs under supercritical conditions, the network doe
A wicket-keeper's gloves or mitt are large leather gloves worn by cricket players of the defending team which assist players in catching and fielding balls hit by a batsman or thrown by a teammate. Law 40.2, which deals with the specifications for wicketkeepers' gloves, states that: If.... The wicket-keeper wears gloves, they shall have no webbing between the fingers except joining index finger and thumb, where webbing may be inserted as a means of support. If used, the webbing shall be: a single piece of non-stretch material which, although it may have facing material attached, shall have no reinforcements or tucks; such that the top edge of the webbing- does not protrude beyond the straight line joining the top of the index finger to the top of the thumb. is taut when a hand wearing the glove has the thumb extended. Gray-Nicolls Kookaburra Sport Slazenger Steeden Cricket clothing and equipment Baseball glove a similar glove in a similar sport
Leather is a natural durable and flexible material created by tanning animal rawhides and skins. The most common raw material is cattle hide, it can be produced at manufacturing scales ranging from artisan to modern industrial scale. Leather is used to make a variety of articles, including footwear, automobile seats, bags, book bindings, fashion accessories, furniture, it is decorated by a wide range of techniques. The earliest record of leather artifacts dates back to 2200 BC; the leather manufacturing process is divided into three fundamental subprocesses: preparatory stages and crusting. A further subprocess, can be added into the leather process sequence, but not all leathers receive finishing; the preparatory stages are. Preparatory stages may include: soaking, liming, bating and pickling. Tanning is a process that stabilizes the proteins collagen, of the raw hide to increase the thermal and microbiological stability of the hides and skins, making it suitable for a wide variety of end applications.
The principal difference between raw and tanned hides is that raw hides dry out to form a hard, inflexible material that, when rewetted, will putrefy, while tanned material dries to a flexible form that does not become putrid when rewetted. Many tanning methods and materials exist; the typical process sees tanners load the hides into a drum and immerse them in a tank that contains the tanning "liquor". The hides soak while the drum rotates about its axis, the tanning liquor penetrates through the full thickness of the hide. Once the process achieves penetration, workers raise the liquor's pH in a process called basification, which fixes the tanning material to the leather; the more tanning material fixed, the higher the leather's hydrothermal stability and shrinkage temperature resistance. Crusting is a process that lubricates leather, it includes a coloring operation. Chemicals added during crusting must be fixed in place. Crusting culminates with a drying and softening operation, may include splitting, dyeing, whitening or other methods.
For some leathers, tanners apply a surface coating, called "finishing". Finishing operations can include oiling, buffing, polishing, glazing, or tumbling, among others. Leather can be oiled to improve its water resistance; this currying process after tanning supplements the natural oils remaining in the leather itself, which can be washed out through repeated exposure to water. Frequent oiling of leather, with mink oil, neatsfoot oil, or a similar material keeps it supple and improves its lifespan dramatically. Tanning processes differ in which chemicals are used in the tanning liquor; some common types include: Vegetable-tanned leather is tanned using tannins extracted from vegetable matter, such as tree bark prepared in bark mills. It is the oldest known method, it is supple and brown in color, with the exact shade depending on the mix of materials and the color of the skin. The color tan derives its name from the appearance of undyed vegetable-tanned leather. Vegetable-tanned leather is not stable in water.
This is a feature of oak-bark-tanned leather, exploited in traditional shoemaking. In hot water, it shrinks drastically and congeals, becoming rigid and brittle. Boiled leather is an example of this, where the leather has been hardened by being immersed in hot water, or in boiled wax or similar substances, it was used as armor after hardening, it has been used for book binding. Chrome-tanned leather, invented in 1858, is tanned using chromium other chromium salts, it is known as "wet blue" for the pale blue color of the undyed leather. The chrome tanning method takes one day to complete, making it best suited for large-scale industrial use; this is the most common method in modern use. It is more supple and pliable than vegetable-tanned leather and does not discolor or lose shape as drastically in water as vegetable-tanned. However, there are environmental concerns with this tanning method. Aldehyde-tanned leather is tanned using oxazolidine compounds, it is referred to as "wet white" due to its pale cream color.
It is the main type of "chrome-free" leather seen in shoes for infants and automobiles. Formaldehyde has been used for tanning in the past. Chamois leather is a form of aldehyde tanning that produces a porous and water-absorbent leather. Chamois leather is made using marine oils that oxidize to produce the aldehydes that tan the leather. Brain tanned leathers are made by a labor-intensive process that uses emulsified oils those of animal brains such as deer and buffalo, they are known for their exceptional washability. Alum leather is transformed using aluminium salts mixed with a variety of binders and protein sources, such as flour and egg yolk. Alum leather is not tanned. In general, leather is produced in the following grades: Top-grain leather includes the outer layer of the hide, known as the grain, which features finer, more densely packed fibers, resulting in strength and durability. Depending on thickness, it may contain some of the more fibrous under layer, known as the corium. Types of top-grain leather incl
A bicycle called a cycle or bike, is a human-powered or motor-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A bicycle rider is called bicyclist. Bicycles were introduced in the late 19th century in Europe, by the early 21st century, more than 1 billion were in existence at a given time; these numbers far exceed the number of cars, both in total and ranked by the number of individual models produced. They are the principal means of transportation in many regions, they provide a popular form of recreation, have been adapted for use as children's toys, general fitness and police applications, courier services, bicycle racing and bicycle stunts. The basic shape and configuration of a typical upright or "safety bicycle", has changed little since the first chain-driven model was developed around 1885. However, many details have been improved since the advent of modern materials and computer-aided design; these have allowed for a proliferation of specialized designs for many types of cycling.
The bicycle's invention has had an enormous effect on society, both in terms of culture and of advancing modern industrial methods. Several components that played a key role in the development of the automobile were invented for use in the bicycle, including ball bearings, pneumatic tires, chain-driven sprockets and tension-spoked wheels; the word bicycle first appeared in English print in The Daily News in 1868, to describe "Bysicles and trysicles" on the "Champs Elysées and Bois de Boulogne". The word was first used in 1847 in a French publication to describe an unidentified two-wheeled vehicle a carriage; the design of the bicycle was an advance on the velocipede, although the words were used with some degree of overlap for a time. Other words for bicycle include "bike", "pushbike", "pedal cycle", or "cycle". In Unicode, the code point for "bicycle" is 0x1F6B2; the entity 🚲. The "Dandy horse" called Draisienne or Laufmaschine, was the first human means of transport to use only two wheels in tandem and was invented by the German Baron Karl von Drais.
It is regarded as the modern bicycle's forerunner. Its rider sat astride a wooden frame supported by two in-line wheels and pushed the vehicle along with his or her feet while steering the front wheel; the first mechanically-propelled, two-wheeled vehicle may have been built by Kirkpatrick MacMillan, a Scottish blacksmith, in 1839, although the claim is disputed. He is associated with the first recorded instance of a cycling traffic offense, when a Glasgow newspaper in 1842 reported an accident in which an anonymous "gentleman from Dumfries-shire... bestride a velocipede... of ingenious design" knocked over a little girl in Glasgow and was fined five shillings. In the early 1860s, Frenchmen Pierre Michaux and Pierre Lallement took bicycle design in a new direction by adding a mechanical crank drive with pedals on an enlarged front wheel; this was the first in mass production. Another French inventor named Douglas Grasso had a failed prototype of Pierre Lallement's bicycle several years earlier.
Several inventions followed using rear-wheel drive, the best known being the rod-driven velocipede by Scotsman Thomas McCall in 1869. In that same year, bicycle wheels with wire spokes were patented by Eugène Meyer of Paris; the French vélocipède, made of iron and wood, developed into the "penny-farthing". It featured a tubular steel frame on; these bicycles were difficult to ride due to poor weight distribution. In 1868 Rowley Turner, a sales agent of the Coventry Sewing Machine Company, brought a Michaux cycle to Coventry, England, his uncle, Josiah Turner, business partner James Starley, used this as a basis for the'Coventry Model' in what became Britain's first cycle factory. The dwarf ordinary addressed some of these faults by reducing the front wheel diameter and setting the seat further back. This, in turn, required gearing—effected in a variety of ways—to efficiently use pedal power. Having to both pedal and steer via the front wheel remained a problem. Englishman J. K. Starley, J. H. Lawson, Shergold solved this problem by introducing the chain drive, connecting the frame-mounted cranks to the rear wheel.
These models were known as safety bicycles, dwarf safeties, or upright bicycles for their lower seat height and better weight distribution, although without pneumatic tires the ride of the smaller-wheeled bicycle would be much rougher than that of the larger-wheeled variety. Starley's 1885 Rover, manufactured in Coventry is described as the first recognizably modern bicycle. Soon the seat tube was added. Further innovations increased comfort and ushered in a second bicycle craze, the 1890s Golden Age of Bicycles. In 1888, Scotsman John Boyd Dunlop introduced the first practical pneumatic tire, which soon became universal. Willie Hume demonstrated the supremacy of Dunlop's tyres in 1889, winning the tyre's first-ever races in Ireland and England. Soon after, the rear freewheel was developed; this refinement led to the 1890s invention of coaster brakes. Dérailleur gears and hand-operated Bowden cable-pull brakes were developed during these years, but were only adopted by casual riders; the Svea Velocipede with vertical pedal arrangement and