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
The Porsche 930 is a sports car manufactured by German automobile manufacturer Porsche between 1975 and 1989, known to the public as the 911 Turbo. It was the maker's top-of-the-range 911 model for its entire production duration and, at the time of its introduction, was the fastest production car available in Germany. Porsche began experimenting with turbocharging technology on their race cars during the late 1960s, in 1972 began development on a turbocharged version of the 911. Porsche needed to produce the car in order to comply with homologation regulations and had intended on marketing it as a street legal race vehicle like the 1973 Carrera 2.7 RS. The FIA's Appendix “J” rules upon which the 911 Turbo Carrera RSR 2.1 was entered into competition in 1974 changed in 1975 and 1976. The FIA announced that cars for Group 4 and Group 5 had to be production cars and be available for sale to individual purchasers through manufacturer dealer networks. For the 1976 season, new FIA regulations required manufacturers to produce 400 cars within a twenty-four month period to gain approval for Group 4.
Group 5 would require the car to be derived from a homologated model in Group 3 or 4. Porsche's Group 4 entry was the 934, homologated on 6 December 1975. For Group 5, Porsche would develop one of the most successful racing cars of the time, the 935; the 911 Turbo was put into production in 1975. While the original purpose of the 911 Turbo was to gain homologation for the 1976 racing season, it became popular among car enthusiasts. Four-hundred cars were produced by the end of 1975. Since Porsche wanted to compete in the 1976 season, they gained FIA homologation for the Porsche Turbo for Group 4 in Nr. 645 on 6 Dec 1975 and the 1,000th 911 Turbo was completed on 5 May 1976. Ernst Fuhrmann adapted the turbo-technology developed for the 917/30 CAN-AM car and applied it to the 3.0 litre flat-six used the Carrera RS 3.0, thus creating what Porsche internally dubbed as the 930. The car utilises a single KKK turbocharger. Total power output from the engine was 260 PS at 5,500 rpm and 329 N⋅m of torque at 4,000 rpm, much more than the standard Carrera it was based on.
The engine has a compression ratio of 6.5:1. In order to ensure that the platform could make the most of the higher power output, a revised suspension, larger brakes and a stronger gearbox became part of the package, although some consumers were unhappy with Porsche's use of a four-speed transmission whilst a five-speed manual transmission was available in the "lower trim" Carrera. A "whale tail" rear spoiler was installed to help vent more air to the engine and to create more downforce at the rear of the vehicle, wider rear wheels with upgraded tyres combined with flared wheel arches were implemented in order to increase the car's width and grip, making it more stable. Porsche badged the vehicle as "Turbo" and introduced the vehicle at the Paris Auto Show in October 1974 before putting it on sale in the spring of 1975; the 930 proved fast but very demanding to drive, due to its short wheelbase and rear engine layout, was prone to oversteer and turbo-lag. Porsche made its first and most significant changes to the 930 for 1978 model year, enlarging the engine bore by 2 mm to a total displacement of 3,299 cc and adding an air-to-air intercooler.
By cooling the pressurised air charge, the intercooler helped increase power output to 300 PS at 5,500 rpm and 412 N⋅m of torque at 4,000 rpm. The suspension benefitted from new anti-roll bars, firmer shock absorbers and larger diameter rear torsion bars. Porsche upgraded the brakes to units similar to those used on the 917 race car. While the increase in displacement and addition of an intercooler increased power output and torque, these changes increased the weight of the vehicle the engine, which contributed to a substantial change in the handling and character of the car compared to the earlier 3.0-litre models. Changing emissions regulations in Japan and the United States forced Porsche to withdraw the 930 from those markets in 1980, it however remained available in Canada. Envisioning the luxurious 928 gran turismo replacing the 911 as the top of the Porsche model lineup, Fuhrmann cut back further development on the model, it was not until his resignation that the company committed the financing to reregulate the car.
The 930 remained available in Europe, for 1983 a 335 PS performance option became available on a build-to-order basis from Porsche. With the add-on came a quad-pipe exhaust system and an additional oil-cooler requiring a remodelled front spoiler and units bearing the add-on featured additional ventilation holes in the rear fenders and modified rockers. By the 1985 model year, 928 sales had risen but the question remained as to whether it would supersede the 911 as the company's premier model. Porsche reintroduced the 930 to the Japanese and U. S. markets in 1986 with an emission-controlled engine having a power output of 282 PS. At the same time Porsche introduced cabriolet variants, both of which proved popular. Porsche discontinued the 930 after the 1989 model year when its underlying "G-Series" platform was being replaced by the 964. In that year, Porsche introduced the 930 Speedster, a variant featuring body style akin to the 356 Speedster, the Speedster featured a humped rear end with a "double bubble" roof storage compartment and a short, rak
A drive shaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement between them. As torque carriers, drive shafts are subject to torsion and shear stress, equivalent to the difference between the input torque and the load, they must therefore be strong enough to bear the stress, while avoiding too much additional weight as that would in turn increase their inertia. To allow for variations in the alignment and distance between the driving and driven components, drive shafts incorporate one or more universal joints, jaw couplings, or rag joints, sometimes a splined joint or prismatic joint; the term drive shaft first appeared during the mid 19th century. In Stover's 1861 patent reissue for a planing and matching machine, the term is used to refer to the belt-driven shaft by which the machine is driven.
The term is not used in his original patent. Another early use of the term occurs in the 1861 patent reissue for the Watkins and Bryson horse-drawn mowing machine. Here, the term refers to the shaft transmitting power from the machine's wheels to the gear train that works the cutting mechanism. In the 1890s, the term began to be used in a manner closer to the modern sense. In 1891, for example, Battles referred to the shaft between the transmission and driving trucks of his Climax locomotive as the drive shaft, Stillman referred to the shaft linking the crankshaft to the rear axle of his shaft-driven bicycle as a drive shaft. In 1899, Bukey used the term to describe the shaft transmitting power from the wheel to the driven machinery by a universal joint in his Horse-Power. In the same year, Clark described his Marine Velocipede using the term to refer to the gear-driven shaft transmitting power through a universal joint to the propeller shaft. Crompton used the term to refer to the shaft between the transmission of his steam-powered Motor Vehicle of 1903 and the driven axle.
The pioneering automobile industry company, was the first to use a drive shaft in a gasoline-powered car. Built in 1901, today this vehicle is in the collection of the Smithsonian Institution. An automobile may use a longitudinal shaft to deliver power from an engine/transmission to the other end of the vehicle before it goes to the wheels. A pair of short drive shafts is used to send power from a central differential, transmission, or transaxle to the wheels. In front-engined, rear-drive vehicles, a longer drive shaft is required to send power the length of the vehicle. Two forms dominate: The torque tube with a single universal joint and the more common Hotchkiss drive with two or more joints; this system became known as Système Panhard after the automobile company Panhard et Levassor patented it. Most of these vehicles have a clutch and gearbox mounted directly on the engine, with a drive shaft leading to a final drive in the rear axle; when the vehicle is stationary, the drive shaft does not rotate.
Some vehicles, seeking improved weight balance between rear, use a rear-mounted transaxle. In some non-Porsche models, this places the clutch and transmission at the rear of the car and the drive shaft between them and the engine. In this case the drive shaft rotates continuously with the engine when the car is stationary and out of gear. However, the Porsche 924/944/928 models have the clutch mounted to the back of the engine in a bell housing and the drive shaft from the clutch output, located inside of a hollow protective torque tube, transfers power to the rear mounted transaxle, thus the Porsche driveshaft only rotates when the rear wheels are turning as the engine-mounted clutch can decouple engine crankshaft rotation from the driveshaft. So for Porsche, when the driver is using the clutch while briskly shifting up or down, the engine can rev with the driver's accelerator pedal input, since with the clutch disengaged, the engine and flywheel inertia is low and is not burdened with the added rotational inertia of the driveshaft.
The Porsche torque tube is solidly fastened to both the engine's bell housing and to the transaxle case, fixing the length and alignment between the bell housing and the transaxle and minimizing rear wheel drive reaction torque from twisting the transaxle in any plane. A drive shaft connecting a rear differential to a rear wheel may be called a half-shaft; the name derives from the fact. Early automobiles used chain drive or belt drive mechanisms rather than a drive shaft; some used electrical motors to transmit power to the wheels. In British English, the term "drive shaft" is restricted to a transverse shaft that transmits power to the wheels the front wheels. A drive shaft connecting the gearbox to a rear differential is called a propeller shaft, or prop-shaft. A prop-shaft assembly consists of a slip joint and one or more universal joints. Where the engine and axles are separated from each other, as on four-wheel drive and rear-wheel drive vehicles, it is the propeller shaft that serves to transmit the drive force generated by the engine to the axles.
Several different types of drive shaft are used in the automotive industry: One-piece drive shaft Two-piece drive shaft Slip-in-tube drive shaftThe slip-in-tube drive shaft is a new type that improves crash safety. It can be compressed to absorb energy in the event of a crash, so is known as a collapsible drive shaft
Internal combustion engine
An internal combustion engine is a heat engine where the combustion of a fuel occurs with an oxidizer in a combustion chamber, an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine; the force is applied to pistons, turbine blades, rotor or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy; the first commercially successful internal combustion engine was created by Étienne Lenoir around 1859 and the first modern internal combustion engine was created in 1876 by Nikolaus Otto. The term internal combustion engine refers to an engine in which combustion is intermittent, such as the more familiar four-stroke and two-stroke piston engines, along with variants, such as the six-stroke piston engine and the Wankel rotary engine. A second class of internal combustion engines use continuous combustion: gas turbines, jet engines and most rocket engines, each of which are internal combustion engines on the same principle as described.
Firearms are a form of internal combustion engine. In contrast, in external combustion engines, such as steam or Stirling engines, energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products. Working fluids can be air, hot water, pressurized water or liquid sodium, heated in a boiler. ICEs are powered by energy-dense fuels such as gasoline or diesel fuel, liquids derived from fossil fuels. While there are many stationary applications, most ICEs are used in mobile applications and are the dominant power supply for vehicles such as cars and boats. An ICE is fed with fossil fuels like natural gas or petroleum products such as gasoline, diesel fuel or fuel oil. There is a growing usage of renewable fuels like biodiesel for CI engines and bioethanol or methanol for SI engines. Hydrogen is sometimes used, can be obtained from either fossil fuels or renewable energy. Various scientists and engineers contributed to the development of internal combustion engines.
In 1791, John Barber developed the gas turbine. In 1794 Thomas Mead patented a gas engine. In 1794, Robert Street patented an internal combustion engine, the first to use liquid fuel, built an engine around that time. In 1798, John Stevens built the first American internal combustion engine. In 1807, French engineers Nicéphore and Claude Niépce ran a prototype internal combustion engine, using controlled dust explosions, the Pyréolophore; this engine powered a boat on France. The same year, the Swiss engineer François Isaac de Rivaz built an internal combustion engine ignited by an electric spark. In 1823, Samuel Brown patented the first internal combustion engine to be applied industrially. In 1854 in the UK, the Italian inventors Eugenio Barsanti and Felice Matteucci tried to patent "Obtaining motive power by the explosion of gases", although the application did not progress to the granted stage. In 1860, Belgian Jean Joseph Etienne Lenoir produced a gas-fired internal combustion engine. In 1864, Nikolaus Otto patented the first atmospheric gas engine.
In 1872, American George Brayton invented the first commercial liquid-fuelled internal combustion engine. In 1876, Nikolaus Otto, working with Gottlieb Daimler and Wilhelm Maybach, patented the compressed charge, four-cycle engine. In 1879, Karl Benz patented a reliable two-stroke gasoline engine. In 1886, Karl Benz began the first commercial production of motor vehicles with the internal combustion engine. In 1892, Rudolf Diesel developed compression ignition engine. In 1926, Robert Goddard launched the first liquid-fueled rocket. In 1939, the Heinkel He 178 became the world's first jet aircraft. At one time, the word engine meant any piece of machinery—a sense that persists in expressions such as siege engine. A "motor" is any machine. Traditionally, electric motors are not referred to as "engines". In boating an internal combustion engine, installed in the hull is referred to as an engine, but the engines that sit on the transom are referred to as motors. Reciprocating piston engines are by far the most common power source for land and water vehicles, including automobiles, ships and to a lesser extent, locomotives.
Rotary engines of the Wankel design are used in some automobiles and motorcycles. Where high power-to-weight ratios are required, internal combustion engines appear in the form of combustion turbines or Wankel engines. Powered aircraft uses an ICE which may be a reciprocating engine. Airplanes can instead use jet engines and helicopters can instead employ turboshafts. In addition to providing propulsion, airliners may employ a separate ICE as an auxiliary power unit. Wankel engines are fitted to many unmanned aerial vehicles. ICEs drive some of the large electric generators, they are found in the form of combustion turbines in combined cycle power plants with a typical electrical output in the range of 100 MW to 1 GW. The high temperature exhaust is used to superheat water to run a steam turbine. Thus, the efficiency is higher because more energy is extracted from the fuel than what could be extracted by the co
Dr.-Ing. H.c. F. Porsche AG shortened to Porsche AG, is a German automobile manufacturer specializing in high-performance sports cars, SUVs and sedans. Porsche AG is headquartered in Stuttgart, is owned by Volkswagen AG, itself majority-owned by Porsche Automobil Holding SE. Porsche's current lineup includes the 718 Boxster/Cayman, 911, Panamera and Cayenne. Ferdinand Porsche founded the company called "Dr. Ing. h. c. F. Porsche GmbH" in 1931, with main offices at Kronenstraße 24 in the centre of Stuttgart; the company offered motor vehicle development work and consulting, but did not build any cars under its own name. One of the first assignments the new company received was from the German government to design a car for the people, a "Volkswagen"; this resulted in one of the most successful car designs of all time. The Porsche 64 was developed in 1939 using many components from the Beetle. During World War II, Volkswagen production turned to the military version of the Volkswagen Beetle, the Kübelwagen, 52,000 produced, Schwimmwagen, 15,584 produced.
Porsche produced several designs for heavy tanks during the war, losing out to Henschel & Son in both contracts that led to the Tiger I and the Tiger II. However, not all this work was wasted, as the chassis Porsche designed for the Tiger I was used as the base for the Elefant tank destroyer. Porsche developed the Maus super-heavy tank in the closing stages of the war, producing two prototypes. At the end of World War II in 1945, the Volkswagen factory at KdF-Stadt fell to the British. Ferdinand lost his position as Chairman of the Board of Management of Volkswagen, Ivan Hirst, a British Army Major, was put in charge of the factory. On 15 December of that year, Ferdinand was arrested for war crimes, but not tried. During his 20-month imprisonment, Ferdinand Porsche's son, Ferry Porsche, decided to build his own car, because he could not find an existing one that he wanted to buy, he had to steer the company through some of its most difficult days until his father's release in August 1947. The first models of what was to become the 356 were built in a small sawmill in Austria.
The prototype car was shown to German auto dealers, when pre-orders reached a set threshold, production was begun by Porsche Konstruktionen GesmbH founded by Ferry and Louise. Many regard the 356 as the first Porsche because it was the first model sold by the fledgling company. After the production of 356 was taken over by the father's Dr. Ing. h.c. F. Porsche GmbH in Stuttgart in 1950, Porsche commissioned a Zuffenhausen-based company, Reutter Karosserie, which had collaborated with the firm on Volkswagen Beetle prototypes, to produce the 356's steel body. In 1952, Porsche constructed an assembly plant across the street from Reutter Karosserie; the 356 was road certified in 1948. Porsche's company logo was based on the coat of arms of the Free People's State of Württemberg of former Weimar Germany, which had Stuttgart as its capital; the arms of Stuttgart was placed in the middle as an inescutcheon, since the cars were made in Stuttgart. The heraldic symbols were combined with the texts "Porsche" and "Stuttgart", which shows that it is not a coat of arms since heraldic achievements never spell out the name of the armiger nor the armigers home town in the shield.
Württemberg-Baden and Württemberg-Hohenzollern became part of the present land of Baden-Württemberg in 1952 after the political consolidation of West Germany in 1949, the old design of the arms of Württemberg now only lives on in the Porsche logo. On 30 January 1951, not long before the creation of Baden-Württemberg, Ferdinand Porsche died from complications following a stroke. In post-war Germany, parts were in short supply, so the 356 automobile used components from the Volkswagen Beetle, including the engine case from its internal combustion engine and several parts used in the suspension; the 356, had several evolutionary stages, A, B, C, while in production, most Volkswagen-sourced parts were replaced by Porsche-made parts. Beginning in 1954 the 356s engines started utilizing engine cases designed for the 356; the sleek bodywork was designed by Erwin Komenda, who had designed the body of the Beetle. Porsche's signature designs have, from the beginning, featured air-cooled rear-engine configurations, rare for other car manufacturers, but producing automobiles that are well balanced.
In 1964, after a fair amount of success in motor-racing with various models including the 550 Spyder, with the 356 needing a major re-design, the company launched the Porsche 911: another air-cooled, rear-engined sports car, this time with a six-cylinder "boxer" engine. The team to lay out the body shell design was led by Ferry Porsche's eldest son, Ferdinand Alexander Porsche; the design phase for the 911 caused internal problems with Erwin Komenda, who led the body design department until then. F. A. Porsche complained. Company leader Ferry Porsche took his son's drawings to neighbouring chassis manufacturer Reuter. Reuter's workshop was acquired by Porsche. Afterward Reuter became today known as Keiper-Recaro; the design office gave sequential numbers to every project (See Porsche
Water cooling is a method of heat removal from components and industrial equipment. Water may be a more efficient heat transfer fluid. In most occupied climates water offers the thermal conductivity advantages of a liquid with unusually high specific heat capacity and the option of evaporative cooling. Low cost allows rejection as waste after a single use, but recycling coolant loops may be pressurized to eliminate evaporative loss and offer greater portability and improved cleanliness. Unpressurized recycling coolant loops using evaporative cooling require a blowdown waste stream to remove impurities concentrated by evaporation. Disadvantages of water cooling systems include accelerated corrosion and maintenance requirements to prevent heat transfer reductions from biofouling or scale formation. Chemical additives to reduce these disadvantages may introduce toxicity to wastewater. Water cooling is used for cooling automobile internal combustion engines and large industrial facilities such as nuclear and steam electric power plants, hydroelectric generators, petroleum refineries and chemical plants.
Other uses include cooling of lubricant oil in pumps. The main mechanism for water cooling is convective heat transfer. Water is inexpensive, non-toxic, available over most of the earth's surface. Liquid cooling offers higher thermal conductivity than air cooling. Water has unusually high specific heat capacity among available liquids at room temperature and atmospheric pressure allowing efficient heat transfer over distance with low rates of mass transfer. Cooling water may be recycled through a recirculating system or used in a single pass once-through cooling system. Water's high enthalpy of vaporization allows the option of efficient evaporative cooling to remove waste heat in cooling towers or cooling ponds. Recirculating systems may be open if they rely upon evaporative cooling or closed if heat removal is accomplished in heat exchangers with negligible evaporative loss. A heat exchanger or condenser may separate non-contact cooling water from a fluid being cooled, or contact cooling water may directly impinge on items like saw blades where phase difference allows easy separation.
Environmental regulations emphasize the reduced concentrations of waste products in non-contact cooling water. Water is an ideal cooling medium for vessels as they are surrounded by water that remains at a low temperature throughout the year. Systems operating with sea water need to be manufactured from cupronickel, titanium or corrosion-resistant materials. Water containing sediment may require velocity restrictions through piping to avoid erosion at high velocity or blockage by settling at low velocity. Water is a favorable medium for biological growth. Dissolved minerals in natural water supplies are concentrated by evaporation to leave deposits called scale. Cooling water requires addition of chemicals to minimize corrosion and insulating deposits of scale and biofouling. Water is a favorable environment for many life forms. Flow characteristics of recirculating cooling water systems encourage colonization by sessile organisms to use the circulating supply of food and nutrients. Temperatures may become high enough to support thermophilic populations.
Biofouling of heat exchange surfaces can reduce heat transfer rates of the cooling system. Biofouling may create differential oxygen concentrations increasing corrosion rates. OTC and open recirculating systems are most susceptible to biofouling. Biofouling may be inhibited by temporary habitat modifications. Temperature differences may discourage establishment of thermophilic populations in intermittently operated facilities. Biocides have been used to control biofouling where sustained facility operation is required. Water contains varying amounts of impurities from contact with the atmosphere and containers. Manufactured metals tend to revert to ores via electrochemical reactions of corrosion. Water can accelerate corrosion as both an electrical conductor and solvent for metal ions and oxygen. Corrosion reactions proceed more as temperature increases. Preservation of machinery in the presence of hot water has been improved by addition of corrosion inhibitors including zinc and phosphates; the first two have toxicity concerns.
Residual concentrations of biocides and corrosion inhibitors are of potential concern for OTC and blowdown from open recirculating systems. With the exception of machines with short design life, closed recirculating systems require periodic cooling water treatment or replacement raising similar concern about ultimate disposal of cooling water containing chemicals used with environmental safety assumptions of a closed system. Total dissolved solids or TDS is measured as the mass of residue remaining when a measured volume of filtered water is evaporated. Salinity measures water conductivity changes caused by dissolved materials. Probability of scale formation increases with increasing total dissolved solids. Solids associated with scale formation are calcium and magnesium carbonate and sulfate. Corrosion rates increase with salinity in response to increasing electrical conductivity
Tatra is a Czech vehicle manufacturer in Kopřivnice. It is owned by the Tatra Trucks company, based in Ostrava, is the second oldest company in the world producing cars with an unbroken history, surpassed only by French automaker Peugeot; the company was founded in 1850 as Ignatz Schustala & Comp. in 1890 renamed Nesselsdorfer Wagenbau-Fabriksgesellschaft when it became a wagon and carriage manufacturer. In 1897, Tatra produced the first motor car in the Präsident automobile. In 1918, it changed its name to Kopřivnická vozovka a.s. and in 1919 changed from the Nesselsdorfer marque to the Tatra badge, named after the nearby Tatra Mountains on the Czechoslovak-Polish border. During World War II Tatra was instrumental in the production of trucks and tank engines for the German war effort. Production of passenger cars ceased in 1999, but the company still produces a range of all-wheel-drive trucks, from 4×4 to 18x18; the brand is known as a result of Czech truck racer Karel Loprais: in 1988–2001 he won the off-road race Dakar Rally six times with a Tatra 815.
Ignác Šustala, founder of the company "Ignatz Schustala & Comp" in Kopřivnice, started the production of horse-drawn vehicles in 1850. In 1891 it branched out into railroad car manufacture, naming the company "Nesselsdorfer Wagenbau-Fabriksgesellschaft", employed Hugo Fischer von Roeslerstamm as technical director in 1890. After the death of Šustala, von Roeslerstamm took over running the company and in 1897 he bought a Benz automobile. Using this for inspiration, the company made its first car, the Präsident, under the direction of engineers Hans Ledwinka and Edmund Rumpler, exhibited in 1897 in Vienna. Orders were obtained for more cars, until 1900, nine improved cars based on Präsident were made; the first car to be designed by Ledwinka came in 1900 with the Type A with rear-mounted 2714 cc engine and top speed of 40 kilometres per hour, 22 units were built. This was followed by the Type B with central engine in 1902 but Ledwinka left the company to concentrate on steam engine development.
He returned in 1905 and designed a new car, the Type S with 3308 cc 4-cylinder engine. Production was badly hit in 1912 with a 23-week strike and Hugo Fischer von Roeslerstam left the company. In 1921 the company was renamed to "Kopřivnická vozovka", in 1919 the name Tatra was given to the car range. Leopold Pasching took over control and in 1921 Hans Ledwinka returned again to develop the revolutionary Tatra 11; the new car, launched in 1923 featured a rigid backbone tube with swinging semi-axles at the rear giving independent suspension. The engine, front-mounted, was an air-cooled two-cylinder unit of 1056 cc. In 1924 the company was renamed to "Závody Tatra"; the Tatra 11 was replaced in 1926 by the similar Tatra 12. A further development was the 1926 Tatra 17 with a 1,930 cc water-cooled six-cylinder engine and independent suspension. In 1927 the company was renamed "Ringhoffer-Tatra". Tatra's specialty was luxury cars of a technically advanced nature, going from air-cooled flat-twins to fours and sixes, culminating with the OHC 6-litre V12 in 1931.
In the 1930s, under the supervision of Austrian engineer Hans Ledwinka, his son Erich and German engineer Erich Übelacker, protected by high tariffs and absence of foreign assemblers, Tatra began building advanced, streamlined cars after obtaining licences from Paul Jaray, which started in 1934 with the large Tatra 77, the world's first production aerodynamic car. The average drag coefficient of a 1:5 model of the fastback Tatra 77 was recorded as 0.2455. It featured a rear-mounted, air-cooled V8 engine, in technical terms sophisticated for the time. Both Adolf Hitler and Ferdinand Porsche were influenced by the Tatras. Hitler was a keen automotive enthusiast, had ridden in Tatras during political tours of Czechoslovakia, he had dined numerous times with Ledwinka. After one of these dinners Hitler remarked to Porsche, "This is the car for my roads". From 1933 onwards and Porsche met to discuss their designs, Porsche admitted "Well, sometimes I looked over his shoulder and sometimes he looked over mine" while designing the Volkswagen.
There is no doubt that the Beetle bore a striking resemblance to the Tatras the Tatra V570. The Tatra 97 of 1936 had a rear-located, rear-wheel drive, air-cooled four-cylinder boxer engine accommodating four passengers and providing luggage storage under the front bonnet and behind the rear seat. Another similarity between this Tatra and the Beetle is the central structural tunnel. Tatra launched a lawsuit against VW. At the same time, Tatra was forced to stop producing the T97; the matter was re-opened after World War II and in 1965 Volkswagen paid Tatra 1,000,000 DM in an out of court settlement. After the 1938 invasion of Czechoslovakia by Nazi Germany, Tatras were kept in production because Germans liked the cars. Many German officers died in car accidents caused by driving the heavy, rear-engined Tatras faster around corners than they could handle. At the time, as an anecdote, Tatra became known as the'Czech Secret Weapon' for the scores of officers who died behind the wheel; the factory was nationalised in 1945 three years before the Communist Party came to power and in January 1946 was renamed to "Tatra Národní Podnik".
Although production of prewar models continued, a new model, the Tatra 600 Tatraplan was designed—the name celebrating the new Communist planned economy and the aeroplane inspiration (Colloq