Sealy is a city in Austin County in southeastern Texas, United States, within the Houston–The Woodlands–Sugar Land metropolitan area. The population was 6,019 at the 2010 census. Sealy is located 49 miles west of the downtown Houston area. Sealy is located at 29°46′27″N 96°9′27″W. According to the United States Census Bureau, the city has a total area of 15.5 square miles, of which, 13.38 square miles of it is land and 0.16 square miles is water. Sealy is 50 miles west of Downtown Houston. San Felipe, sold part of its original 22,000-acre township to the Gulf and Santa Fe Railroad to create Sealy in 1879. Sealy gets its name after business tycoon and majority stock holder of the GCSF RR, George Sealy of Galveston. In 1881, Daniel Haynes, a cotton gin builder, filled a request for a cotton-filled mattress which started a company, he named this the Sealy Mattress Company after the town. Business grew exponentially, which led to more innovation and several patents, such as a machine that compressed cotton.
As of the census of 2000, there were 5,248 people, 1,882 households, 1,349 families residing in the city. The population density was 759.3 people per square mile. There were 2,077 housing units at an average density of 300.5 per square mile. The racial makeup of the city was 75.1% White, 12.3% African American, 0.30% Native American, 0.55% Asian, 12.88% from other races, 1.92% from two or more races. Hispanic or Latino of any race were 30.43% of the population. There were 1,882 households out of which 38.4% had children under the age of 18 living with them, 52.6% were married couples living together, 13.7% had a female householder with no husband present, 28.3% were non-families. 24.5% of all households were made up of individuals and 11.7% had someone living alone, 65 years of age or older. The average household size was 2.75 and the average family size was 3.30. In the city, the population was spread out with 30.2% under the age of 18, 9.3% from 18 to 24, 28.9% from 25 to 44, 19.2% from 45 to 64, 12.5% who were 65 years of age or older.
The median age was 33 years. For every 100 females, there were 91.3 males. For every 100 females age 18 and over, there were 87.8 males. The median income for a household in the city was $34,277, the median income for a family was $40,348. Males had a median income of $28,720 versus $20,793 for females; the per capita income for the city was $15,986. About 11.2% of families and 15.6% of the population were below the poverty line, including 18.9% of those under age 18 and 13.5% of those age 65 or over. People who live in Sealy are zoned to schools in Sealy Independent School District; the schools in Sealy ISD are Selman Elementary School or Sealy Elementary, Selman Intermediate School, Sealy Junior High School, Sealy High School. All of the schools are in Sealy. Blinn College has a Sealy Campus located along Interstate 10 east of State Highway 36. Eric Dickerson, Pro Football Hall of Fame running back Ernie Koy, Major League Baseball player Huey Long, singer with The Ink Spots Ricky Seals-Jones, current NFL tight end for the Arizona Cardinals Sealy is served by Interstate 10, U.
S. Highway 90, Texas State Highway 36, the BNSF Railway, the Union Pacific Railroad; the Greyhound Bus Lines operates the Sealy Station at Mazac Muffler City AC. Bellville Brazos Country Brookshire Columbus Houston San Felipe Wallis City of Sealy official website Sealy Economic Development Corporation Sealy's 2016 Detailed Community Profile Sealy's 2015 "Population Quick Facts" report for 15-mile radius and 20-mile radius Sealy Chamber of Commerce Sealy Convention and Visitors Bureau Blinn College - Sealy Campus Sealy Independent School District Sealy Police Department Sealy Fire Department Austin County Austin County News Online The Sealy News Sealy Tiger Sports Network Handbook of Texas article
The Lotus Exige is a British two-door, two-seat sports car made by Lotus Cars since 2000. A more-hardcore coupé version of the Lotus Elise roadster, since the Series 3 the Exige has been the larger-engined model of the family - using a V6 engine in place of the Elise's straight 4 with convertible versions of both available; the original Exige was launched in 2000 with a aspirated 1.8 L Rover K Series Inline-four engine in VHPD tune. It produces 177 bhp at 7,800 rpm in standard form. There was a "track spec" version with 190 bhp available; the car has a five-speed manual gearbox, a claimed top speed of 219 km/h. 0–60 mph was achieved in 4.7 seconds and 0–100 km/h in 4.9 seconds. The first Exige used the round, less aggressive headlights of the first generation Elise, although the Elise was updated soon after the introduction of the Exige; the Series 1 was built until 2002, in 604 examples, was not replaced until the Series 2 of 2004. In 2004, the Series 2 Exige was introduced, it features a aspirated 1.8 L 16-valve DOHC Toyota/Yamaha engine that produces 190 bhp with the Toyota engine designation of 2ZZ-GE.
Compared to the Series 2 Elise, it has a front splitter, fibreglass hardtop roof with roof scoop, rear engine cover, rear spoiler. The sole purpose of these aerodynamic additions to the base Elise is to create more downforce. In February 2005, Lotus announced a limited production run of 50 Exiges, using the Toyota engine with a supercharger; this increased the power output to 243 bhp. These vehicles were only available in yellow or black, representing the colours of Lotus Sport, are badged 240R, they have a projected 0-60 mph time of 3.9 seconds and 0-100 mph of 9.9 seconds, with a top speed of 155 mph at a cost of £44,000. The North American Exige was unveiled at the Los Angeles Auto Show in January 2006. According to Lotus, the standard Exige Series 2 model weighs 2,016 lb and has the following specifications: Engine Toyota Supplied, 1,796 cc I4, DOHC with VVTL-i - Designed by Yamaha - Engine Code: 2ZZ-GE Bore/Stroke 82 mm × 85 mm 190 hp at 7,800 rpm 138 lb⋅ft at 6,800 rpm Compression ratio: 11.5:1Transmission 6-Speed manual built by Aisin AI, close-ratio with single-plate dry clutch Performance 0–60 mph: 4.7 seconds 0–100 mph: 12.9 seconds Top speed: 147 mph Fuel consumption: 24 mpg‑imp city / 29 mpg‑imp highway In February 2006, Lotus announced the Exige S model which used a supercharged Toyota 2ZZ-GE engine producing 220 bhp.
The S was made available in North American markets as a 2007 model. According to Lotus, the Exige S model, weighing 2,057 lb, has the following specifications: Engine Toyota supplied, 1,796 cc I4, DOHC with VVTL-i, supercharged and intercooled Bore/Stroke 82 mm × 85 mm 218 hp at 7,800 rpm 159 lbf⋅ft at 5,500 rpm Compression ratio: 11.5:1Transmission 6-speed, close ratio with single-plate dry clutch Performance 0-60 mph: 4.1 seconds 0-100 mph: 9.98 seconds Top speed: 148 mph Fuel consumption: 24 mpg‑imp city / 29 mpg‑imp highway In 2008, the Exige S was replaced by the Exige S 240. Power output increased by 9% over the outgoing model to 240 bhp; the S 240 received upgraded AP Racing brakes from the Exige Cup 240 and a larger roof scoop utilised by the Exige Cup 255. 0-60 mph times improved to 4.0 seconds. The S 240 base manufacturer suggested retail price was $65,690; the Exige S 260 produced an additional 7% power output over the S 240 resulting in 260 PS. With a full fuel tank, extensive use of weight-saving materials such as carbon fiber reduced the vehicle's gross weight to 2,020 lb compared to 2,077 lb in the S 240.
It can accelerate from 0–60 mph in 4.0 seconds. After 2009, both the S 240 and S 260 received distinctively new and enlarged rear spoilers mounted to the rear clam instead of the motor bay cover; the base manufacturer suggested retail price for the S 260 was $74,995. The Exige 265E is a factory-built version of a Exige S optimised to run on E85 fuel, 85% ethanol; the higher octane of this biofuel allows for a higher compression ratio and/or more supercharger boost. In this model, which saw the ECU re-mapped as well as upgraded injectors and fuel pump to cope with the new fuel type, the brakes have been upgraded to four-piston AP Racing calipers with increased diameter 310 mm sport brake pads mated with drilled and vented discs at the front. Brembo single-piston sliding rear calipers with 282 mm diameter discs are fitted at the rear. Lotus says it has no intention to build the 265E as a limited number standard production car, that it is a biofuels demonstrator. According to Lotus, the Exige 265E model has the following specifications: Engine Toyota supplied 2ZZ-GE 1,796 cc inline-4, DOHC with VVTL-i, supercharged and intercooled Bore/Stroke 82 mm/85 mm 264 hp at 8,000 rpm 184 lb⋅ft at 5,500 rpm Compression ratio: 11.5:1Transmission C64 6-Speed, close
Shell Oil Company
Shell Oil Company is the United States-based wholly owned subsidiary of Royal Dutch Shell, transnational corporation "oil major" of Anglo-Dutch origins, amongst the largest oil companies in the world. 22,000 Shell employees are based in the U. S; the U. S. headquarters are in Texas. Shell Oil Company, including its consolidated companies and its share in equity companies, is one of America's largest oil and natural gas producers, natural gas marketers, gasoline marketers and petrochemical manufacturers. Shell is the market leader through 25,000 Shell-branded gas stations in the U. S. which serve as Shell's most visible public presence. At its gas stations Shell provides diesel fuel, gasoline and LPG. Shell Oil Company was a 50/50 partner with the Saudi Arabian government-owned oil company Saudi Aramco in Motiva Enterprises, a refining and marketing joint venture which owns and operates three oil refineries on the Gulf Coast of the United States. However, Shell is divesting its interest in Motiva.
Shell products include oils and car services as well as exploration and refining of petroleum products. The Shell Oil Refinery in Martinez, the first Shell refinery in the United States, supplies Shell and Texaco stations in the West and Midwest. Shell gasolines included the RU2000 and SU2000 lines but they have been superseded by the V-Power line. In 1997, Shell and Texaco entered into two refining/marketing joint ventures. One was known as Equilon; the other, known as Motiva Enterprises, combined the Eastern and Gulf Coast operations of Shell Oil and Star Enterprise, itself a joint venture between Saudi Aramco and Texaco. After Texaco merged with Chevron in 2001, Shell purchased Texaco's shares in the joint ventures. In 2002, Shell began converting these Texaco stations to the Shell brand, a process, to be completed by June 2004 and was called "the largest retail re-branding initiative in American business history". In the year 2016, Shell Nederland Raffinaderij BV said that it has started a new aromatics unit at the large Pernis refinery in Rotterdam, Netherlands.
In recent years The Shell Oil Company's Midstream, Downstream, in particular, have become limited to petroleum, chemical products. This has come as a result of Royal Dutch Shell breaking off its Natural Gas and power businesses in to a new segment named Integrated Gas; the Shell Oil Company's former Natural Gas, energy divisions are now Shell Energy North America, a integrated, but distinctive entity that runs across North America and is headquartered out of Houston. Until the mid-1980s Shell's business in the United States was independent. Limited direct involvement from the main office in The Hague and having its stock "Shell Oil" traded on the New York Stock Exchange were factors. However, in 1984, Royal Dutch Shell made a bid to purchase those shares of Shell Oil Company it did not own and despite some opposition from some minority shareholders which led to a court case, Shell completed the buyout for a sum of $5.7 billion. Despite the acquisition, Shell Oil remained a independent business.
This was due in part to complex legal reasons as Royal Dutch Shell feared that there could be onerous liability problems if a closer control of Shell Oil's affairs was exercised by the "parent company". One consequence of this independence was that the Shell logo used in the U. S. was different from that used in the rest of the world. In the 1980s Shell Oil's independence began to erode as the "parent company" took a more hands-on approach in running the business; the logo used in the United States is the same as that used elsewhere since June 1, 1998. Shell has companies in North and Central America: in Argentina, Barbados, the Bahamas, Brazil, Chile, Costa Rica, The Dominican Republic, Guatemala, Mexico, Panama, Puerto Rico, Suriname and Tobago, the U. S. and Venezuela. Shell has companies in Africa, the Middle East, Asia. Aera Energy —joint venture with ExxonMobil operating in California. Motiva Enterprises —joint venture with Saudi Refining. Being divested, with the second quarter of 2017 being the official date.
Shell Development Emeryville —research facility that operated from 1928–1966 in California. Pennzoil Jiffy Lube Quaker State Limejump Shell Puget Sound Refinery, Washington, was fined $291,000 from 2006 to 2010 for violations of the Clean Air Act making it the second most-fined violator in the Pacific Northwest; as of 2011, it was listed as "high priority violator" since 2008. In 2008, a lawsuit was filed against Shell Oil Company for alleged Clean Air Act violation. Shell Deer Park facility, 20 miles east of Houston, was the nation's eighth-largest oil refinery and one of the world's largest petrochemical producers; the facility was the second largest source of air pollution in Harris County, which ranked among the lowest in the nation in several measures of air quality. According to Sierra Club and Environment Texas, analysis of Shell's reports to the Texas Commission on Environmental Quality, air pollutants released at Deer Park since 2003 exceeded the EPA's emissions limits. Will Oremus from Slate magazine states, "The company's business depends on being able to anticipate and respond to seismic shifts in the energy market.
So it called scenario planners, to keep it a step ahead. In 2008 the company released a fresh pair of scenarios for how the world might respond to climate change over the coming decades. Both were predicated on what the company called
S-segment is the a European segments for passenger cars for sport coupés. The cars are described as sports cars and the equivalent Euro NCAP class is called "roadster sport". S-segment cars have a sporting appearance and are designed to have superior handling and/or straight-line acceleration compared to other segments; the most common body styles for S-segment cars are convertible. Rear passenger accommodation is not a priority for S-segment cars, therefore many models are either two-seat cars or have a 2+2 layout with cramped rear seating. Most recent S-segment cars use the commonplace front-engine design, however the majority of cars with a Mid-engine design or rear-engine design belong to the S-segment; the five highest selling S-segment cars in Europe are the Audi TT, Mazda MX-5, Porsche 911, Ford Mustang and Porsche Boxster/Cayman. In 2014, the five highest selling coupé models were the BMW 4 Series, Opel Astra GTC,BMW 2 Series, Renault Mégane Coupé and Mercedes-Benz C-Class; the five highest selling convertible models in 2014 were the Fiat 500C, Mini Hatch, BMW 4 Series, Volkswagen Beetle and Volkswagen Golf Mk6
Rear mid-engine, rear-wheel-drive layout
In automotive design, a RMR or Rear Mid-engine, rear-wheel-drive layout is one in which the rear wheels are driven by an engine placed just in front of them, behind the passenger compartment. In contrast to the rear-engined RR layout, the center of mass of the engine is in front of the rear axle; this layout is chosen for its low moment of inertia and favorable weight distribution. The layout has a tendency toward being heavier in the rear than the front, which allows for best balance to be achieved under braking. However, since there is little weight over the front wheels, under acceleration, the front of the car is prone to lift and cause understeer. Most rear-engine layouts have been used in smaller vehicles, because the weight of the engine at the rear has an adverse effect on a larger car's handling, making it'tail-heavy', it is felt. The mid-engined layout uses up central space, making it impractical for any but two-seater sports cars. However, some microvans use this layout, with a low engine beneath the loading area.
This makes it possible to move the driver right to the front of the vehicle, thus increasing the loading area at the expense of reduced load depth. In modern racing cars, RMR is the usual configuration and is synonymous with "mid engine". Due to its weight distribution and resulting favorable vehicle dynamics, this layout is employed in open-wheel Formula racing cars as well as purpose-built sports racing cars; this configuration was common in small engined 1950s microcars, in which the engines did not take up much space. Because of successes in racing, the RMR platform has been popular for road-going sports cars despite the inherent challenges of design and lack of cargo space; the similar mid-engine, four-wheel-drive layout gives many of the same advantages and is used when extra traction is desired, such as in some supercars and in the Group B rally cars. The 1900 NW Rennzweier was one of the first race cars with rear-wheel-drive layout. Other known historical examples include the 1923 Benz Tropfenwagen.
It was based on an earlier design named the Rumpler Tropfenwagen in 1921 made by Edmund von Rumpler, an Austrian engineer working at Daimler. The Benz Tropfenwagen was designed by Ferdinand Porsche along with Hans Nibel, it raced in 1923 and 1924 and was most successful in the Italian Grand Prix in Monza where it stood fourth. Ferdinand Porsche used mid-engine design concept towards the Auto Union Grand Prix cars of the 1930s which became the first winning RMR racers, they were decades before their time, although MR Miller Specials raced a few times at Indianapolis between 1939 and 1947. In 1953 Porsche premiered the tiny and altogether new RMR 550 Spyder and in a year it was notoriously winning in the smaller sports and endurance race car classes against much larger cars—a sign of greater things to come; the 718 followed in 1958. But it was not until the late 1950s that RMR reappeared in Grand Prix races in the form of the Cooper-Climax, soon followed by cars from BRM and Lotus. Ferrari and Porsche soon made.
The mid-engined layout was brought back to Indianapolis in 1961 by the Cooper Car Company with Jack Brabham running as high as third and finishing ninth. Cooper did not return, but from 1963 on British built mid-engined cars from constructors like Brabham and Lola competed and in 1965 Lotus won Indy with their Type 38. Rear mid-engines were used in microcars like the Isetta or the Zündapp Janus; the first rear mid-engined road car after WW II was the 1962 Bonnet / Matra Djet, which used the 1108cc Renault Sierra engine, mated to the transaxle from the FWD Renault Estafette van. Nearly 1700 were built until 1967; this was followed by the first De Tomaso, the Vallelunga, which mated a tuned Ford Cortina 1500 Kent engine to a VW transaxle with Hewland gearsets. Introduced at Turin in 1963, 58 were built 1964-68. A similar car was the Renault-engined Lotus Europa, built from 1966–1975. In 1966, the Lamborghini Miura was the first high performance mid-engine, rear-wheel-drive roadcar; the concept behind the Miura was that of putting on the road a grand tourer featuring state-of-the-art racing-car technology of the time.
This represented an innovative sportscar at a time when all of its competitors, from Ferraris to Aston Martins, were traditional front-engined, rear wheel drive grand tourers. The Pontiac Fiero was a mid-engined sports car, built by the Pontiac division of General Motors from 1984 to 1988; the Fiero was the first two-seater Pontiac since the 1926 to 1938 coupes, the first and only mass-produced mid-engine sports car by a U. S. manufacturer. Engine and driveline layout considerations
A semi-automatic transmission is an automobile transmission that combines manual transmission and automatic transmission. It allows convenient driver control of gear selection. For most of automotive history, automatic transmissions allowed some control of gear selection using the console or shifter to limit the transmission shifting beyond a certain gear and/or locking out the use of overdrive gears when towing, it enhanced such features by providing either steering wheel mounted paddle shifters or a modified shift lever, allowing the driver to enter a "manual mode" and select any available gear in a sequential "up shift/downshift" manner. Some transmissions allow the driver to have full control of gear selection, though most will intervene to prevent engine stalling and redlining by shifting automatically at the low end and/or high end of the engine's normal operating range. Hydraulically-coupled and most clutch transmissions provide the option of operating in the same manner as a conventional automatic transmission, by allowing the transmission's computer to select gear changes.
A few allow an alternate automatic mode called "sport" mode, where gear selection is still automatic but the transmission will favor higher engine speeds by up shifting when accelerating and downshifting earlier when slowing. A clutch-less manual facilitates gear changes by dispensing with the need to press a clutch pedal at the same time as changing gears, it uses electronic sensors, pneumatics and actuators to execute gear shifts on input from the driver or by a computer. This removes the need for a clutch pedal which the driver otherwise needs to depress before making a gear change, since the clutch itself is actuated by electronic equipment which can synchronize the timing and torque required to make quick, smooth gear shifts; the system was designed by automobile manufacturers to provide a better driving experience through fast overtaking maneuvers on highways. Some motorcycles use a system with a conventional gear change but without the need for manual clutch operation. In the 1930s, automakers began to market cars with some sort of device that would reduce the amount of clutching and de-clutching and shifting required in stop and go driving.
Most a fluid coupling or a centrifugal clutch replaced the standard manual clutch to allow for stop and go driving without using the clutch pedal every time the car was brought to a stop. More sophisticated systems allowed for shifting while driving without using the clutch, some systems did away with the clutch pedal altogether. Semi-automatic transmissions were phased out as technology advanced and automatic controls were developed to take care of changing gear ratios. Smaller, lower powered cars used semi-automatic transmissions with a dry clutch because the mechanical connection offered a more efficient powertrain compared to a fluid coupling. Another early semi-automatic transmission was the Sinclair S. S. S. Powerflow gearbox. Which was applied to Huwood-Hudswell diesel mines locomotives, it was applied to some road vehicles. Improved semi-automatics appeared in the 1960s; the Automotive Products Manumatic and Newtondrive systems were known as "two-pedal transmissions". They relieve the driver of the need for skill in operating clutch and engine speed in conjunction with the gear change.
The Manumatic has a clutch servo powered by the vacuum at the induction manifold operatign the automatic clutch - a conventional clutch incorporating centrifugal operation. A switch in the gear lever operates a solenoid valve so that when the gear lever is moved, the clutch is disengaged. A control unit made throttle adjustments to keep the engine speed matched to the driven clutch plate and varied the speed of clutch operation appropriate to road speed; the Newtondrive system differed in making a provision for choke control and a cable linkage from clutch operating mechanism to the throttle. These systems could be fitted to smaller cars such as the Ford Anglia. Modern "Semi-automatic transmissions" have a automatic mode, where the driver does not need to change gears at all, operating in the same manner as a conventional type of automatic transmission by allowing the transmission's computer to automatically change gear if, for example, the driver were redlining the engine; the semi-automatic transmission can be engaged in manual mode wherein one can up-shift or down-shift using the console-mounted shifter selecter or the paddle shifters just behind the steering wheel, without the need of a clutch pedal.
The ability to shift gears manually via paddle shifters, can be found on certain automatic transmissions and continuous variable transmissions. Despite superficial similarity to other automated transmissions, semi-automatic transmissions differ in internal operation and driver's "feel" from manumatics and CVTs. A manumatic, like a standard automatic transmission, uses a torque converter instead of clutch to manage the link between the transmission and the engine, while a CVT uses a belt instead of a fixed number of gears. A semi-automatic transmission offers a more direct connection between the engine and wheels than a manumatic and this responsiveness is preferred in high performance driving applications, while a manumatic is better for street use because its fluid coupling makes it easier for the transmission to perform smooth shifts, CVTs are found in
A manual transmission known as a manual gearbox, a standard transmission or colloquially in some countries as a stick shift, is a type of transmission used in motor vehicle applications. It uses a driver-operated clutch engaged and disengaged by a foot pedal or hand lever, for regulating torque transfer from the engine to the transmission. A conventional 5-speed manual transmission is the standard equipment in a base-model vehicle, while more expensive manual vehicles are equipped with a 6-speed transmission instead; the number of forward gear ratios is expressed for automatic transmissions as well. Manual transmissions feature a driver-operated clutch and a movable gear stick. Most automobile manual transmissions allow the driver to select any forward gear ratio at any time, but some, such as those mounted on motorcycles and some types of racing cars, only allow the driver to select the next-higher or next-lower gear; this type of transmission is sometimes called a sequential manual transmission.
In a manual transmission, the flywheel is attached to the engine's crankshaft and spins along with it. The clutch disc is in between the pressure plate and the flywheel, is held against the flywheel under pressure from the pressure plate; when the engine is running and the clutch is engaged, the flywheel spins the clutch plate and hence the transmission. As the clutch pedal is depressed, the throw out bearing is activated, which causes the pressure plate to stop applying pressure to the clutch disk; this makes the clutch plate stop receiving power from the engine, so that the gear can be shifted without damaging the transmission. When the clutch pedal is released, the throw out bearing is deactivated, the clutch disk is again held against the flywheel, allowing it to start receiving power from the engine. Manual transmissions are characterized by gear ratios that are selectable by locking selected gear pairs to the output shaft inside the transmission. Conversely, most automatic transmissions feature epicyclic gearing controlled by brake bands and/or clutch packs to select gear ratio.
Automatic transmissions that allow the driver to manually select the current gear are called manumatics. A manual-style transmission operated by computer is called an automated transmission rather than an automatic though no distinction between the two terms need be made. Contemporary automobile manual transmissions use four to six forward gear ratios and one reverse gear, although consumer automobile manual transmissions have been built with as few as two and as many as seven gears. Transmissions for heavy trucks and other heavy equipment have 8 to 25 gears so the transmission can offer both a wide range of gears and close gear ratios to keep the engine running in the power band. Operating aforementioned transmissions use the same pattern of shifter movement with a single or multiple switches to engage the next sequence of gear selection. French inventors Louis-Rene Panhard and Emile Levassor are credited with the development of the first modern manual transmission, they demonstrated their three-speed transmission in 1894 and the basic design is still the starting point for most contemporary manual transmissions.
This type of transmission offered multiple gear ratios and, in most cases, reverse. The gears were engaged by sliding them on their shafts, which required careful timing and throttle manipulation when shifting, so the gears would be spinning at the same speed when engaged; these transmissions are called sliding mesh transmissions or sometimes crash boxes, because of the difficulty in changing gears and the loud grinding sound that accompanied. Newer manual transmissions on 4+-wheeled vehicles have all gears mesh at all times and are referred to as constant-mesh transmissions, with "synchro-mesh" being a further refinement of the constant mesh principle. In both types, a particular gear combination can only be engaged when the two parts to engage are at the same speed. To shift to a higher gear, the transmission is put in neutral and the engine allowed to slow down until the transmission parts for the next gear are at a proper speed to engage; the vehicle slows while in neutral and that slows other transmission parts, so the time in neutral depends on the grade and other such factors.
To shift to a lower gear, the transmission is put in neutral and the throttle is used to speed up the engine and thus the relevant transmission parts, to match speeds for engaging the next lower gear. For both upshifts and downshifts, the clutch is released; some drivers use the clutch only for starting from a stop, shifts are done without the clutch. Other drivers will depress the clutch, shift to neutral engage the clutch momentarily to force transmission parts to match the engine speed depress the clutch again to shift to the next gear, a process called double clutching. Double clutching is easier to get smooth, as speeds that are close but not quite matched need to speed up or slow down only transmission parts, whereas with the clutch engaged to the engine, mismatched speeds are fighting the rotational inertia and power of the engine. Though automobile and light truck transmissions are now universally synchronized, transmissions for heavy trucks and machinery, motor