Bofors 40 mm gun
The Bofors 40 mm gun referred to as the Bofors gun, is an anti-aircraft autocannon designed in the 1930s by the Swedish arms manufacturer AB Bofors. It was one of the most popular medium-weight anti-aircraft systems during World War II, used by most of the western Allies as well some captured systems being used by the Axis powers. A small number of these weapons remain in service to this day, saw action as late as the Persian Gulf War. In the post-war era, the original design was not suitable for action against jet-powered aircraft, so Bofors introduced a new model of more power, the 40 mm L/70. In spite of sharing nothing with the original design other than the calibre and the distinctive conical flash hider, this weapon is widely known as "the Bofors". Although not as popular as the original L/60 model, the L/70 remains in service as a multi-purpose weapon for light armoured vehicles, as on the CV 90. Bofors has been part of BAE Systems AB since March 2005; the Swedish Navy purchased a number of 2-pounder Pom-Poms from Vickers as anti-aircraft guns in 1922.
The Navy approached Bofors about the development of a more capable replacement. Bofors signed a contract in late 1928. Bofors produced a gun, a smaller version of a 57 mm semi-automatic gun developed as an anti-torpedo boat weapon in the late 19th century by Finspång, their first test gun was a re-barreled Nordenfelt version of the Finspong gun, to, added a semi-automatic loading mechanism. Testing of this gun in 1929 demonstrated that a problem existed feeding the weapon in order to maintain a reasonable rate of fire. A mechanism, strong enough to handle the stresses of moving the large round was too heavy to move enough to fire rapidly. One attempt to solve this problem used zinc shell cases; this proved to leave heavy zinc deposits in the barrel, had to be abandoned. In the summer of 1930 experiments were made with a new test gun that did away with controlled feed and instead flicked the spent casing out the rear whereafter a second mechanism reloaded the gun by "throwing" a fresh round from the magazine into the open breech.
This seemed to be the solution they needed, improving firing rates to an acceptable level, the work on a prototype commenced soon after. During this period Krupp purchased a one-third share of Bofors. Krupp engineers started the process of updating the Bofors factories to use modern equipment and metallurgy, but the 40 mm project was kept secret; the prototype was completed and fired in November 1931, by the middle of the month it was firing strings of two and three rounds. Changes to the feed mechanism were all that remained, by the end of the year it was operating at 130 rounds per minute. Continued development was needed to turn it into a weapon suitable for production, completed in October 1933. Since acceptance trials had been passed the year before, this became known as the "40 mm akan M/32". Most forces referred to it as the "Bofors 40 mm L/60", although the barrel was 56.25 calibres in length, not the 60 calibres that the name implies. The gun fired a 900 g high explosive 40 × 311R shell at 2,960 ft/s.
The rate of fire was about 120 rounds per minute, which improved when the barrels were closer to the horizontal as gravity assisted the feeding from the top-mounted magazine. In practice firing rates were closer to 80–100 rpm, as the rounds were fed into the breech from four round clips which had to be replaced by hand; the maximum attainable ceiling was 7,200 m. The gun was provided with an advanced sighting system; the trainer and layer were both provided with reflector sights for aiming, while a third crew-member standing behind them "adjusted" for lead using a simple mechanical computer. Power for the sights was supplied from a 6V battery. In spite of the successful development, the Swedish Navy changed its mind and decided it needed a smaller hand-traversed weapon of 13 mm-25 mm size, tested various designs from foreign suppliers. With the 40 mm well along in development, Bofors offered a 25 mm version in 1932, selected as the Bofors 25 mm M/32; the first version of the 40 mm the Navy ordered was intended for use on submarines, where the larger calibre allowed the gun to be used for both AA and against smaller ships.
The barrel was shorter at 42 calibers long, with the effect of reducing the muzzle velocity to about 700 m/s. When not in use, the gun retracted into a watertight cylinder; the only known submarines that used this arrangement was the Sjölejonet-class boats. The guns were removed as the subs were modified with streamlined conning towers; the first order for the "real" L/60 was made by the Dutch Navy, who ordered five twin-gun mounts for the cruiser De Ruyter in August 1934. These guns were stabilized using the Hazemeyer mount, in which one set of layers aimed the gun, while a second manually stabilized the platform the gun sat on. All five mounts were operated by one fire control system. Bofors developed a towable carriage which they displayed in April 1935 at a show in Belgium; this mount allowed the gun to be fired from the carriage with no setup required, although with limited accuracy. If time was available for setup, the gunners used the tow-bar and muzzle lock as levers, raising the wheels off the ground and thereby lowering the gun onto supporting pads.
Two additional legs folded out to the sides, the platform was leveled with hand cranks. The entire setup process could be completed in under a minute. Orders for the land based versions were immediate, starting with
The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaiʻi in the south to northernmost Kure Atoll. The group was known to Europeans and Americans as the Sandwich Islands, a name chosen by James Cook in honor of the First Lord of the Admiralty John Montagu, 4th Earl of Sandwich; the contemporary name is derived from the name of Hawaii Island. The U. S. state of Hawaii now occupies the archipelago in its entirety, with the sole exception of Midway Island, which instead separately belongs to the United States as one of its unincorporated territories within the United States Minor Outlying Islands. The Hawaiian Islands are the exposed peaks of a great undersea mountain range known as the Hawaiian–Emperor seamount chain, formed by volcanic activity over a hotspot in the Earth's mantle; the islands are about 1,860 miles from the nearest continent. Captain James Cook visited the islands on January 18, 1778, named them the "Sandwich Islands" in honor of John Montagu, 4th Earl of Sandwich, one of his sponsors as the First Lord of the Admiralty.
This name was in use until the 1840s, when the local name "Hawaii" began to take precedence. The Hawaiian Islands have a total land area of 6,423.4 square miles. Except for Midway, an unincorporated territory of the United States, these islands and islets are administered as Hawaii—the 50th state of the United States; the eight main islands of Hawaii are listed here. All except Kahoolawe are inhabited. Smaller islands and reefs form the Northwestern Hawaiian Islands, or Hawaiian Leeward Islands: Nihoa Necker French Frigate Shoals Gardner Pinnacles Maro Reef Laysan Lisianski Island Pearl and Hermes Atoll Midway Atoll Kure Atoll The state of Hawaii counts 137 "islands" in the Hawaiian chain; this number includes all minor islands and islets, or small islands, offshore of the main islands and individual islets in each atoll. These are just a few: Ford Island Lehua Ka'ula Kaohikaipu Mānana Mōkōlea Rock Nā Mokulua Molokini Mokoliʻi Moku Manu Moku Ola Moku o Loʻe Sand Island Grass Island This chain of islands, or archipelago, developed as the Pacific Plate moved northwestward over a hotspot in the Earth's mantle at a rate of 32 miles per million years.
Thus, the southeast island is volcanically active, whereas the islands on the northwest end of the archipelago are older and smaller, due to longer exposure to erosion. The age of the archipelago has been estimated using potassium-argon dating methods. From this study and others, it is estimated that the northwesternmost island, Kure Atoll, is the oldest at 28 million years; the only active volcanism in the last 200 years has been on the southeastern island, Hawaiʻi, on the submerged but growing volcano to the extreme southeast, Loʻihi. The Hawaiian Volcano Observatory of the USGS documents recent volcanic activity and provides images and interpretations of the volcanism. Kīlauea has been erupting nearly continuously since 1983. All of the magma of the hotspot has the composition of basalt, so the Hawaiian volcanoes are composed entirely of this igneous rock. There is little coarser-grained gabbro and diabase. Nephelinite is exposed on the islands but is rare; the majority of eruptions in Hawaiʻi are Hawaiian-type eruptions because basaltic magma is fluid compared with magmas involved in more explosive eruptions, such as the andesitic magmas that produce some of the spectacular and dangerous eruptions around the margins of the Pacific basin.
Hawaiʻi island is the youngest island in the chain, built from five volcanoes. Mauna Loa, taking up over half of the Big Island, is the largest shield volcano on the Earth; the measurement from sea level to summit is more than 2.5 miles, from sea level to sea floor about 3.1 miles.. The Hawaiian Islands have many earthquakes caused by volcanic activity. Most of the early earthquake monitoring took place in Hilo, by missionaries Titus Coan, Sarah J. Lyman and her family. From 1833 to 1896 4 or 5 earthquakes were reported per year. Hawaii accounted for 7.3% of the United States' reported earthquakes with a magnitude 3.5 or greater from 1974 to 2003, with a total 1533 earthquakes. Hawaii ranked as the state with the third most earthquakes over this time period, after Alaska and California. On October 15, 2006, there was an earthquake with a magnitude of 6.7 off the northwest coast of the island of Hawaii, near the Kona area of the big island. The initial earthquake was followed five minutes by a magnitude 5.7 aftershock.
Minor-to-moderate damage was reported on most of the Big Island. Several major roadways became impassable from rock slides, effects were felt as far away as Honolulu, nearly 150 miles from the epicenter. Power outages lasted for several hours to days. Several water mains ruptured. No deaths or life-threatening injuries were reported. On May 4, 2018 there was a 6.9 earthquake in the zone of volcanic activity from Kīlauea. Earthquakes are monitored by the Hawaiian Volcano Observatory run by the USGS; the Hawaiian Islands are subjec
Boston Navy Yard
The Boston Navy Yard called the Charlestown Navy Yard and Boston Naval Shipyard, was one of the oldest shipbuilding facilities in the United States Navy. It was established in 1801 as part of the recent establishment of the new U. S. Department of the Navy in 1798. After 175 years of military service, it was decommissioned as a naval installation on 1 July 1974; the 30-acre property is administered by the National Park Service, becoming part of Boston National Historical Park. Enough of the yard remains in operation to support the moored USS Constitution of 1797, built as one of the original six heavy frigates for the revived American navy, the oldest warship still commissioned in the United States Navy. USS Cassin Young, a 1943 World War II-era Fletcher-class destroyer serving as a museum ship, is berthed here; the museum area includes a dock, a stop on the MBTA Boat water transport system. Among local people in the area and the National Park Service, it is still known as the Charlestown Navy Yard.
The South Boston Naval Annex was located along the waterfront in South Boston. The earliest naval shipbuilding activities in Charlestown, Massachusetts across the Charles River and Boston harbor to the north from the city of Boston, began during the American Revolutionary War; the land for the Charlestown Navy Yard was purchased by the United States government in 1800 and the yard itself established shortly thereafter. The yard built the first U. S. ship of the line, "USS Independence", but was a repair and storage facility until the 1890s, when it started to build steel ships for the "New Navy". By it was called the Boston Navy Yard. On 24 June 1833, the staff and dignitaries including Vice President Martin Van Buren, Secretary of War Lewis Cass, Secretary of the Navy Levi Woodbury, many Massachusetts officials, witnessed "one of the great events of American naval history": the early United States frigate Constitution was inaugurating the first naval drydock in New England designed by prominent civil engineer Loammi Baldwin, Jr.
The ropewalk supplied cordage used in the Navy from the time it opened in 1837 until the Yard closed in 1975. After the Civil War, the Yard was downgraded to an Recruit Facility. In the late 1880s and 1890s, the Navy began expanding again bringing into service new modern steel hulled steam-powered warships and that brought new life to the Yard. In the first years of the 20th century, a second drydock was added. During World War II, it worked to fix British Royal Navy warships and merchant transports damaged by the Nazi Germans when crossing the North Atlantic Ocean. On 27 September 1941—Liberty Fleet Day—Boston launched two destroyers, the USS Cowie and the USS Knight. Before the U. S. entered the Second World War after the Pearl Harbor attack on December 7th, 1941, a month before in November, Boston was one of four United States naval shipyards selected to build Captain class frigates under the Lend-Lease military assistance program for the Royal Navy. Since the United States was at war when these ships were completed, some were requisitioned and used by the United States Navy as destroyer escorts.
In the post war period, the shipyard modified World War II ships for Cold War service through Fleet Rehabilitation and Modernization. The Korean War, Vietnam War did not bring much work to the Yard since it was so far from the fighting. 1814: USS Independence War of 1812.
Boston is the capital and most populous city of the Commonwealth of Massachusetts in the United States. The city proper covers 48 square miles with an estimated population of 685,094 in 2017, making it the most populous city in New England. Boston is the seat of Suffolk County as well, although the county government was disbanded on July 1, 1999; the city is the economic and cultural anchor of a larger metropolitan area known as Greater Boston, a metropolitan statistical area home to a census-estimated 4.8 million people in 2016 and ranking as the tenth-largest such area in the country. As a combined statistical area, this wider commuting region is home to some 8.2 million people, making it the sixth-largest in the United States. Boston is one of the oldest cities in the United States, founded on the Shawmut Peninsula in 1630 by Puritan settlers from England, it was the scene of several key events of the American Revolution, such as the Boston Massacre, the Boston Tea Party, the Battle of Bunker Hill, the Siege of Boston.
Upon gaining U. S. independence from Great Britain, it continued to be an important port and manufacturing hub as well as a center for education and culture. The city has expanded beyond the original peninsula through land reclamation and municipal annexation, its rich history attracts many tourists, with Faneuil Hall alone drawing more than 20 million visitors per year. Boston's many firsts include the United States' first public park, first public or state school and first subway system; the Boston area's many colleges and universities make it an international center of higher education, including law, medicine and business, the city is considered to be a world leader in innovation and entrepreneurship, with nearly 2,000 startups. Boston's economic base includes finance and business services, information technology, government activities. Households in the city claim the highest average rate of philanthropy in the United States; the city has one of the highest costs of living in the United States as it has undergone gentrification, though it remains high on world livability rankings.
Boston's early European settlers had first called the area Trimountaine but renamed it Boston after Boston, England, the origin of several prominent colonists. The renaming on September 7, 1630, was by Puritan colonists from England who had moved over from Charlestown earlier that year in quest for fresh water, their settlement was limited to the Shawmut Peninsula, at that time surrounded by the Massachusetts Bay and Charles River and connected to the mainland by a narrow isthmus. The peninsula is thought to have been inhabited as early as 5000 BC. In 1629, the Massachusetts Bay Colony's first governor John Winthrop led the signing of the Cambridge Agreement, a key founding document of the city. Puritan ethics and their focus on education influenced its early history. Over the next 130 years, the city participated in four French and Indian Wars, until the British defeated the French and their Indian allies in North America. Boston was the largest town in British America until Philadelphia grew larger in the mid-18th century.
Boston's oceanfront location made it a lively port, the city engaged in shipping and fishing during its colonial days. However, Boston stagnated in the decades prior to the Revolution. By the mid-18th century, New York City and Philadelphia surpassed Boston in wealth. Boston encountered financial difficulties as other cities in New England grew rapidly. Many of the crucial events of the American Revolution occurred near Boston. Boston's penchant for mob action along with the colonists' growing distrust in Britain fostered a revolutionary spirit in the city; when the British government passed the Stamp Act in 1765, a Boston mob ravaged the homes of Andrew Oliver, the official tasked with enforcing the Act, Thomas Hutchinson the Lieutenant Governor of Massachusetts. The British sent two regiments to Boston in 1768 in an attempt to quell the angry colonists; this did not sit well with the colonists. In 1770, during the Boston Massacre, the army killed several people in response to a mob in Boston.
The colonists compelled the British to withdraw their troops. The event was publicized and fueled a revolutionary movement in America. In 1773, Britain passed the Tea Act. Many of the colonists saw the act as an attempt to force them to accept the taxes established by the Townshend Acts; the act prompted the Boston Tea Party, where a group of rebels threw an entire shipment of tea sent by the British East India Company into Boston Harbor. The Boston Tea Party was a key event leading up to the revolution, as the British government responded furiously with the Intolerable Acts, demanding compensation for the lost tea from the rebels; this led to the American Revolutionary War. The war began in the area surrounding Boston with the Battles of Concord. Boston itself was besieged for a year during the Siege of Boston, which began on April 19, 1775; the New England militia impeded the movement of the British Army. William Howe, 5th Viscount Howe the commander-in-chief of the British forces in North America, led the British army in the siege.
On June 17, the British captured the Charlestown peninsula in Boston, during the Battle of Bunker Hill. The British army outnumbered the militia stationed there, but it was a Py
Oerlikon 20 mm cannon
The Oerlikon 20 mm cannon is a series of autocannons, based on an original German 20 mm Becker design that appeared early in World War I. It was produced by Oerlikon Contraves and others, with various models employed by both Allied and Axis forces during World War II, many versions still in use today. During World War I, the German industrialist Reinhold Becker developed a 20 mm caliber cannon, known now as the 20 mm Becker using the Advanced Primer Ignition blowback method of operation; this had a cyclic rate of fire of 300 rpm. It was used on a limited scale as an aircraft gun on Luftstreitkräfte warplanes, an anti-aircraft gun towards the end of that war; because the Treaty of Versailles banned further production of such weapons in Germany, the patents and design works were transferred in 1919 to the Swiss firm SEMAG based near Zürich. SEMAG continued development of the weapon, in 1924 had produced the SEMAG L, a heavier weapon that fired more powerful 20x100RB ammunition at a higher rate of fire, 350 rpm.
In 1924 SEMAG failed. The Oerlikon firm, named after the Zürich suburb of Oerlikon where it was based acquired all rights to the weapon, plus the manufacturing equipment and the employees of SEMAG. In 1927 the Oerlikon S was added to the existing product line; this fired a still larger cartridge to achieve a muzzle velocity of 830 m/s, at the cost of increased weight and a reduced rate of fire. The purpose of this development was to improve the performance of the gun as an anti-tank and anti-aircraft weapon, which required a higher muzzle velocity. An improved version known as the 1S followed in 1930. Three sizes of gun with their different ammunition and barrel length, but similar mechanisms, continued to be developed in parallel. In 1930 Oerlikon reconsidered the application of its gun in aircraft and introduced the AF and AL, designed to be used in flexible mounts, i.e. manually aimed by a gunner. The 15-round box magazine used by earlier versions of the gun was replaced by drum magazine holding 15 or 30 rounds.
In 1935 it made an important step by introducing a series of guns designed to be mounted in or on the wings of fighter aircraft. Designated with FF for Flügelfest meaning "wing-mounted", these weapons were again available in the three sizes, with designations FF, FFL and FFS; the FF fired a larger cartridge than the AF, 20x72RB, but the major improvement in these weapons was a significant increase in rate of fire. The FF weighed 24 kg and achieved a muzzle velocity of 550 to 600 m/s with a rate of fire of 520 rpm; the FFL of 30 kg fired a projectile at a muzzle velocity of 675 m/s with a rate of fire of 500 rpm. And the FFS, which weighed 39 kg, delivered a high muzzle velocity of 830 m/s at a rate of fire of 470 rpm. Apart from changes to the design of the guns for wing-mounting and remote control, larger drums were introduced as it would not be possible to exchange magazines in flight. For the FF series drum sizes of 45, 60, 75 and 100 rounds were available, but most users chose the 60-round drum.
The 1930s were a period of global re-armament, a number of foreign firms took licenses for the Oerlikon family of aircraft cannon. In France, Hispano-Suiza manufactured development of the FFS as the Hispano-Suiza HS.7 and Hispano-Suiza HS.9, for installation between the cylinder banks of its V-12 engines. In Germany, Ikaria further developed the FF gun as firing 20x80RB ammunition, and the Imperial Japanese Navy, after evaluating all three guns, ordered developments of the FF and FFL as the Type 99-1 and Type 99-2. The incorporation of the improvements of the FFS in a new anti-aircraft gun produced, in 1938, the Oerlikon SS. Oerlikon realized further improvements in rate of fire on the 1SS of 1942, the 2SS of 1945 which achieved 650 rpm. However, it was the original SS gun, adopted as anti-aircraft gun, being widely used by Allied navies during World War II; this gun used a 400-grain charge of IMR 4831 smokeless powder to propel a 2,000-grain projectile at 2,800 feet per second. The Oerlikon FF was installed as armament on some fighters of the 1930s, such as the Polish PZL P.24G.
Locally produced derivatives of the Oerlikon cannon were used much more extensively, on aircraft, on ships and on land. In the air, the Ikaria MG FF was used as armament on a number of German aircraft, of which the most famous is the Messerschmitt Bf 109; the Japanese Navy used their copy of the FF, designated the Type 99 Mark One cannon on a number of types including the Mitsubishi A6M Zero. In the war, they equipped fighters including the Zero with the Type 99 Mark Two, a version of the more powerful and faster-firing Oerlikon FFL; the French firm of Hispano-Suiza was a manufacturer of aircraft engines, it marketed the moteur-canon combination of its 12X and 12Y engines with a H. S.7 or H. S.9 cannon installed between the cylinder banks. The gun fired through the hollow propeller hub, this being elevated above the crankcase by the design of the gearing; such armament was installed on the Morane-Saulnier M. S.406 and some other types. Similar German installations of the MG FF were not successful.
The Oerlikon became best known in its naval applications. The Oerlikon was not looked upon favorably by the Royal Navy as a short-range anti-aircraft gun. All through 1937-1938 Lord Louis Mountbatten a Captain in the Royal Navy, waged a lone campaign within the Royal Navy to set up an unprejudiced trial for the Oerlikon 20 mm gun, but it was all in vain, it was not until the Commander-in-Chief of the Home Fleet, Admiral Sir Roger Backhouse, was appointed First Sea Lord tha