reduce smoke London Taxi
Public benefits - using a car
In countries deprived from wide door-to-door public transport and with low density, such as Australia, the automobile plays an important role on the mobility of citizens. Public transport, by comparison, becomes increasingly uneconomic with lower population densities. Hence cars tend to dominate in rural and suburban environments with public economic gains.
The automobile industry, mainly in the beginning of the 20th century when the high motorization rates were not an issue, had also an important public role, which was the creation of jobs. In 1907, 45,000 cars were produced in The United States, but 28 years later in 1935 3,971,000 were produced, nearly 100 times as many. This increase in production required a large, new work force. In 1913 13,623 people worked at Ford Motor Company, but by 1915 18,028 people worked there.10 Bradford DeLong, author of The Roaring Twenties, tells us that, "Many more lined up outside the Ford factory for chances to work at what appeared to them to be (and, for those who did not mind the pace of the assembly line much, was) an incredible boondoggle of a job.10" There was a surge in the need for workers at big, new high-technology companies such as Ford. Employment largely increased.
Starting at TDC
Main article: 2-stroke engine
The defining characteristic of this kind of engine is that each piston completes a cycle every crankshaft revolution. The 4 processes of intake, compression, power and exhaust take place in only 2 strokes so that it is not possible to dedicate a stroke exclusively for each of them. Starting at TDC the cycle consist of:
Power: While the piston is descending the combustion gases perform work on it?as in a 4-stroke engine?. The same thermodynamic considerations about the expansion apply.
Scavenging: Around 75Â° of crankshaft rotation before BDC the exhaust valve or port opens, and blowdown occurs. Shortly thereafter the intake valve or transfer port opens. The incoming charge displaces the remaining combustion gases to the exhaust system and a part of the charge may enter the exhaust system as well. The piston reaches BDC and reverses direction. After the piston has traveled a short distance upwards into the cylinder the exhaust valve or port closes; shortly the intake valve or transfer port closes as well.
Compression: With both intake and exhaust closed the piston continues moving upwards compressing the charge and performing a work on it. As in the case of a 4-stroke engine, ignition starts just before the piston reaches TDC and the same consideration on the thermodynamics of the compression on the charge.
While a 4-stroke engine uses the piston as a positive displacement pump to accomplish scavenging taking 2 of the 4 strokes, a 2-stroke engine uses the last part of the power stroke and the first part of the compression stroke for combined intake and exhaust. The work required to displace the charge and exhaust gases comes from either the crankcase or a separate blower. For scavenging, expulsion of burned gas and entry of fresh mix, two main approaches are described: Loop scavenging, and Uniflow scavenging, SAE news published in the 2010s that 'Loop Scavenging' is better under any circumstance than Uniflow Scavenging.6
Car - etymology
The word "car" is believed to originate from the Latin word carrus or carrum ("wheeled vehicle"), or the Middle English word carre (meaning cart, from Old North French). In turn, these originated from the Gaulish word karros (a Gallic chariot). The Gaulish language was a branch of the Brythoic language which also used the word Karr; the Brythonig language evolved into Welsh (and Gaelic) where 'Car llusg' (a drag cart or sledge) and 'car rhyfel' (war chariot) still survive.1112 It originally referred to any wheeled horse-drawn vehicle, such as a cart, carriage, or wagon.1314 "Motor car" is attested from 1895, and is the usual formal name for cars in British English.3 "Autocar" is a variant that is also attested from 1895, but that is now considered archaic. It literally means "self-propelled car".15 The term "horseless carriage" was used by some to refer to the first cars at the time that they were being built, and is attested from 1895.16
The word "automobile" is a classical compound derived from the Ancient Greek word autÃ³s (?????), meaning "self", and the Latin word mobilis, meaning "movable". It entered the English language from French, and was first adopted by the Automobile Club of Great Britain in 1897.17 Over time, the word "automobile" fell out of favour in Britain, and was replaced by "motor car". It remains a chiefly North American usage.18 An abbreviated form, "auto", was formerly a common way to refer to cars in English, but is now considered old-fashioned. The word is still used in some compound formations in American English, like "auto industry" and "auto mechanic".