History of the Development of Brakes
The first brakes were drum brakes. They were metal upon metal, and
made a terrible noise, although they did work. Since then, brakes have
been made with asbestos, which is heat resistant, hard wearing, and
relatively silent.
Drum Brake (1890s~1980s)
The working parts of a drum brake are contained in a hard
metal drum that is attached to the hub of a wheel and revolves with
it. Inside, but unattached to the drum, are a pair of stationary
curved brake shoes that are normally held away from the drum by
springs. When the brake pedal is depressed, fluid is forced through
the brake lines and into the wheel cylinder. Pushrods in the cylinder
then apply pressure to both shoes, overcoming the spring tension and
pressing the shoes against the drum. Hydraulic drum brakes can also be
mechanically activated as parking brakes by a cable attached to the
lever. When pressure is removed from the brake pedal, springs on the
brake shoes force the shoes back to their normal released position.
This movement of the shoes forces the pistons inward, returning the
fluid to the master cylinder reservoir.
Power Brakes (1940s~present)
Power brake units used on passenger cars are of four general
types: vacuum suspended; air suspended; hydraulic booster, and
electro-hydraulic booster. Most power brakes use vacuum suspended
units, which contains a large vacuum-powered booster device to provide
the added thrust to the typical power-brake. Pressure on the brake
pedal pushes forward a rod connected to the pistons of the two master
cylinders. The pistons begin forcing fluid into the front and rear
brake lines. At the same time, the brake-pedal pushrod positions the
vacuum-control valve so that it closes the vacuum port and seals off
the forward half of the booster unit. The engine vacuum line then
draws off the air, creating a low-pressure vacuum chamber. Atmospheric
pressure in the control chamber then pushes against the diaphragm,
dividing the two chambers. The pressure on the diaphragm, which is
locked to the pushrod, forces it forward, supplying even more pressure
on the pistons. The safe driver is always ready to apply the total
force needed to stop their vehicle, even if the engine quits (removing
the power assist).
Disc Brake Disc (1970s~present)
Brakes use a clamping action to produce friction between the
wheel and the suspension members which hold the wheel. Firmly mounted
to the spindle, the caliper works like a c-clamp to pinch the rotor
which is attached to the spinning wheel. "Floating" calipers allow
themselves to move slightly when the brakes are applied, because only
one pad moves (in relation to the caliper).
Starkey, Marion L. The Devil In Massachusetts: A Modern Inquiry Into The Salem Witch Trials. London: Robert Hale Limited.
Insert the key, turn, and vroom. And down the road you go. Most people take for granted the strange conglomeration of metal and plastic under that sheet of metal either in front or back of their vehicle. The engine as you may have guessed, is modern marvel- so to speak. They’re found in cars, trucks, boats, airplanes…All with various power outputs.
Imposing even when not in motion, monster trucks of today are high-octane mechanisms of mayhem. The evolution of these arena-filling creations garners great interest within the auto culture, given the capacity for performance today’s formidable monster trucks possess. Modified trucks emerged as sideshow entertainment, but today the industry’s grandest machines fill some of the nation’s most sizable venues with their gravity-defying feats, as families marvel at the bedlam on display when truck capabilities are put to the test.
Godbeer, Richard. The Salem Witch Hunt A Brief History with Documents. Boston, New York: Bedford/St. Martins 2011
Hinds, Maurene J. Witchcraft on Trial: From the Salem Witch Hunts to the Crucible. Library ed. Berkeley Heights, NJ: Enslow, 2009. Print.
The notorious witch trials of Salem, Massachusetts occurred from June through September. It is a brief, but turbulent period in history and the causes of the trials have long been a source of discussion among historians. Many try to explain or rationalize the bizarre happenings of the witch hunts and the causes that contributed to them. To understand the trials and how they came to be, we must first examine the ideals and views of the people surrounding the events. Although religious beliefs were the most influential factor, socioeconomic tensions, and ergot poisoning are also strongly supported theories. A combination of motives seems the most rational explanation of the frenzy that followed the illness of the two girls. This paper looks closely at the some of the possible causes of one of the most notable occurrences in history.
Starkey, Marion L. The Devil in Massachusetts: A Modern Inquiry into the Salem Witch Trials. Alexandria, VA: Time-Life, 1982. Print.
McBain, J. ‘The Salem Witch Trials: A Primary Source History of the Witchcraft Trials in Salem, Massachusetts’, (Rosen Publishing Group, New York, 2002)
According to Top inventions and technical innovations of World War 2, “Saying that World War II completely changed the world sounds like either a massive understatement or a trivialization of the entire conflict.” Back in the 1900s, new ideas shaped and changed the world. During WWII, there were many inventions that gave each side of the war advantages. In the following paragraphs, it will tell you some of the major inventions of WWII. Hope you enjoy!
From Ancient Mesopotamia came a revolutionary tool that has crystallized the world into the complex civilization it is today, the wheel. The wheel has commutated the very way we live and think about the world and all credit goes to Ancient Mesopotamia for providing this life changing invention. Wheels are everywhere we look and in places that you wouldn't even think. Wheels are used everyday in some way or another and come in many sizes and innumerable different materials and purposes. This prodigious invention has helped ancient Mesopotamians work, move, and live and still helps us today.
6. Aleksander, Igor, and Piers Burnett. REINVENTING MAN: The Robot Becomes Reality. New York: Holt, Rinehart and Winston, 1983. p 25.
What is a black hole? How are black holes formed? And who first discovered black holes? Are all excellent questions that will be answered in this research document. However, before you are fed information on the history of black holes, you must first know the definition: A black hole is a region of space having a gravitational pull so intense that matter or light can escape. Black holes can be classified into 3 three categories based on their method of creation and size. These types are called: stellar, supermassive, and miniature black holes.
Imagine an angry hive of bees. Now, put that under the hood of the beautifully curvy body of a mid 90s Japanese sports car and crank the revs up to 9000. The rotary engine, a Mazda classic, is one of the most satisfying, temperamental,and rev happy engines of all time. The Wankel/Rotary engine is an internal combustion engine that uses an eccentric rotary design to convert pressure into rotating motion. Instead of the more common reciprocating piston designs, the Wankel engine has the advantages of simplicity, smoothness, compactness, high revolutions per minute, and a high power-to-weight ratio primarily because three power pulses per rotor revolution are produced compared to one per revolution in a two-stroke piston engine and one per two revolutions in a four-stroke piston engine.
First, at 1960s Dr.Engelberger invented the first robotic hand and the function of this hand is similar to the human hand. However, some researchers are trying to develop on it so it can be easily used by people with disabilities to do certain tasks. Robotic hands can give back hope to those who lost it. Moreover, it can be used by normal people to perform their tasks like doing house chores or helping them with drinking a juice etc. Also, robotic hands can be made from iron, wood, and cardboard. To make us work in a team, we we’re asked to make a robotic hand that can hold a fork and eat.
Back in time a long time ago, around 500 B.C. the Egyptians and Indians made ice on cold nights by setting water out in earthenware pots and keeping the pots wet. In the 18th century England, servants collected ice in the winter and put it into icehouses, where the sheets of ice were packed in salt, wrapped in strips of flannel and stored underground to keep them frozen until summer. Before the refrigerator or "ice box" was introduced people used snow and ice to keep their food cool, which was either found locally or brought down from the mountains. Cellars and caves were also used to refrigerate food. Meat and fish were preserved in warm weather by salting or smoking. The first cellars were holes dug into the ground and lined with wood or straw and packed with refrigeration for most of history.