Animation of a cycloidal drive A cycloidal drive or cycloidal speed reducer is a mechanism for reducing the speed of an input shaft by a certain ratio. Cycloidal speed reducers are capable of relatively high ratios in compact sizes with very low backlash. The input shaft drives an eccentric bearing that in turn drives the cycloidal disc in an eccentric, cycloidal motion. The perimeter of this disc is geared to a stationary ring gear and has a series of output shaft pins or rollers placed through the face of the disc.
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This causes the cycloidal disc to rotate around the bearing faster than the input shaft is moving it around, giving an overall rotation in the direction opposing the rotation of the input shaft. The cycloidal disc has holes that are slightly larger than the output roller pins that go inside them. The output pins will move around in the holes to achieve steady rotation of the output shaft from the wobbling movement of the cycloidal disc. The reduction rate of the cycloidal drive is obtained from the following formula, where P means the number of the ring gear pins and L is the number of lobes on the cycloidal disc.
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Parts of a 10:1 cycloidal speed reducer mechanism The input shaft is mounted eccentrically to a Rolling-element bearing (typically a cylindrical roller bearing), causing the cycloidal disc to move in a circle. The cycloidal disc will independently rotate around the bearing as it is pushed against the ring gear. This is similar to planetary gears, and the direction of rotation is opposite to that of the input shaft. The number of pins on the ring gear is larger than the number of pins on the cycloidal disc.
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For cycloidal gears (as used in BS978-2 Specification for fine pitch gears) and cycloidal-type gears each module, ratio and number of teeth in the pinion requires a different hobbing cutter, so the technique is only suitable for large volume production. To circumvent this problem a special war-time emergency circular arc gear standard was produced giving a series of close-to-cycloidal forms which could be cut with a single hob for each module for eight teeth and upwards to economize on cutter manufacturing resources. A variant on this is still included in BS978-2a (Gears for instruments and clockwork mechanisms. Cycloidal type gears.
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The cycloidal propeller offers powerful thrust levels, and a unique ability to change the direction of the thrust almost instantly.
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An example of a transverse OAG, the so-called cycloidal OAG, is shown in Fig. 1. The optical axis in this grating is monotonously modulated in transverse direction. This grating is capable of diffracting all incident light into either +1st or −1st order in a micrometer-thick layer . The cycloidal OAGs have already been proven to be very efficient in beam steering and optical switching.
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These output shaft pins directly drive the output shaft as the cycloidal disc rotates. The radial motion of the disc is not translated to the output shaft.
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Foss Maritime developed and built an ASD Z-Drive and Voith Schneider Propulsion cycloidal tractor tugs capable of working with the largest vessels in its operating area.
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Epicyclic gearing In epicyclic gearing one or more of the gear axes moves. Examples are sun and planet gearing (see below), cycloidal drive, automatic transmissions, and mechanical differentials.
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An addendum of one gear rests inside a dedendum of the other gear. In the cycloidal gears, the addenda of the wheel teeth are convex epi-cycloidal and the dedenda of the pinion are concave hypocycloidal curves generated by the same generating circle. This ensures that the motion of one gear is transferred to the other at locally constant angular velocity. The size of the generating circle may be freely chosen, mostly independent of the number of teeth.
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Construction of a two-lobed cycloidal rotor. The red curve is an epicycloid and the blue curve is a hypocycloid. A Roots blower is one extreme, a form of cycloid gear where the ratio of the pitch diameter to the generating circle diameter equals twice the number of lobes. In a two-lobed blower, the generating circle is one-fourth the diameter of the pitch circles, and the teeth form complete epi- and hypo- cycloidal arcs.
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This condition -in most of the cases- is impractical because of involvement of vibration, and thus in most of the cases, an involute profile of the gear is used. There is some dispute over the invention of cycloidal gears. Those involved include Gérard Desargues, Philippe de La Hire, Ole Rømer, and Charles Étienne Louis Camus. A cycloid (as used for the flank shape of a cycloidal gear) is constructed by rolling a rolling circle on a base circle.
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Schematic of a cycloidal pendulum. If a simple pendulum is suspended from the cusp of an inverted cycloid, such that the "string" is constrained between the adjacent arcs of the cycloid, and the pendulum's length L is equal to that of half the arc length of the cycloid (i.e., twice the diameter of the generating circle, L=4r), the bob of the pendulum also traces a cycloid path. Such a cycloidal pendulum is isochronous, regardless of amplitude.
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Cycloidal drives can start with zero backlash and high torque capacity while compact in size, unlike Involute gearboxes. They are useful in situations where low speed with high torque capacity is needed. Cycloidal drives may be designed with significantly higher contact areas for their size than any gear-based transmission such as epicyclic gears, applying force through many of the 'teeth' at once, allowing very high torque output for the size of the drive at the cost of utilising sliding contact.
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Cycloidal arches at the Kimbell Art Museum The cycloidal arch was used by architect Louis Kahn in his design for the Kimbell Art Museum in Fort Worth, Texas. It was also used in the design of the Hopkins Center in Hanover, New Hampshire. Early research indicated that some transverse arching curves of the plates of golden age violins are closely modeled by curtate cycloid curves. Later work indicates that curtate cycloids do not serve as general models for these curves, which vary considerably.
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Propulsion was by means of two Voith Schneider cycloidal propellers mounted on diagonally opposite corners of the hull, each one being driven by a Paxman 8RPHCM turbocharged V8 diesel engine of 378bhp (282kw) at 900rpm.
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Manufacturer of high precision motion control and power transmission solutions, including planetary gearboxes, cycloidal gearboxes, rotary actuators and traction drives. Products are used in the packaging, printing, machine tool, robotics, aerospace, oil & gas and semiconductor markets.
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Cyclorotor before installation on small-scale cyclogyroA cyclorotor, cycloidal rotor, cycloidal propeller or cyclogiro, is a fluid propulsion device that converts shaft power into the acceleration of a fluid using a rotating axis perpendicular to the direction of fluid motion. It uses several blades with a spanwise axis parallel to the axis of rotation and perpendicular to the direction of fluid motion. These blades are cyclically pitched twice per revolution to produce force (thrust or lift) in any direction normal to the axis of rotation. Cyclorotors are used for propulsion, lift, and control on air and water vehicles.
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Voith Schneider Propeller The Voith Schneider propeller (VSP), also known as a cycloidal drive is a specialized marine propulsion system (MPS). It is highly maneuverable, being able to change the direction of its thrust almost instantaneously. It is widely used on tugs and ferries.
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Also sometimes available are ground swirl patterns (cycloidal marks) left in the wake of a tornado. If an on site analysis is not possible, either for retrospective ratings or when personnel cannot reach a site, photographs, videos, or descriptions of damage may be utilised.
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The second pendulum clock built around 1673 by Christiaan Huygens, inventor of the pendulum clock. Drawing is from his treatise Horologium Oscillatorium, published 1673, Paris, and it records improvements to the mechanism that Huygens had illustrated in the 1658 publication of his invention, titled Horologium. It is a weight-driven clock (the weight chain is removed) with a verge escapement (K,L), with the 1 second pendulum (X) suspended on a cord (V). The large metal plate (T) in front of the pendulum cord is the first illustration of Huygens' 'cycloidal cheeks', an attempt to improve accuracy by forcing the pendulum to follow a cycloidal path, making its swing isochronous.
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If the diameter of this rolling circle is chosen to be infinitely large, a straight line is obtained. The resulting cycloid is then called an involute and the gear is called an involute gear. In this respect involute gears are only a special case of cycloidal gears.
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Due to the eccentric nature of the drive, if the cycloidal disk is not balanced by a second disk or a counterweight, it will generate vibration which will propagate through the driven shafts and the body. This will cause increased wear on the exterior teeth of the cycloidal disk, as well as component bearings. With two discs the static imbalance is corrected but a small dynamic imbalance remains, this is generally considered acceptable for most applications but to reduce vibration high speed drives use three (or more) discs to allow the imbalance to be corrected, the outer discs move in unison and in opposition to the middle one which is twice as massive.
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Pascal, Roberval and Senator Carcavy were the judges, and neither of the two submissions (by John Wallis and Antoine de Lalouvère) were judged to be adequate. While the contest was ongoing, Christopher Wren sent Pascal a proposal for a proof of the rectification of the cycloid; Roberval claimed promptly that he had known of the proof for years. Wallis published Wren's proof (crediting Wren) in Wallis's Tractus Duo, giving Wren priority for the first published proof. Fifteen years later, Christiaan Huygens had deployed the cycloidal pendulum to improve chronometers and had discovered that a particle would traverse a segment of an inverted cycloidal arch in the same amount of time, regardless of its starting point.
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Ordinary cycloids were studied by Galileo Galilei and Marin Mersenne as early as 1599 but cycloidal curves were first conceived by Ole Rømer in 1674 while studying the best form for gear teeth. Leonhard Euler claims first consideration of the actual deltoid in 1745 in connection with an optical problem.
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An aircraft using cyclorotors as the primary source of lift, propulsion, and control is known as a cyclogyro or cyclocopter. The patented application, used on ships with particular actuation mechanisms both mechanical or hydraulic, are named after the name of the German company Voith Turbo GMBH that produces them: Voith–Schneider cycloidal propellers.
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The Glen class is a series of five yard tractor tugboats designed for coastal/harbour use in Canada's major naval bases. The vessels have a standard displacement of . As built they are long with a beam of and a draught of . They are propelled by two Voith Schneider cycloidal propellers turned by two Ruston-Paxman diesel engines rated at .
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Horologium oscillatorium sive de motu pendulorum, 1673 Illustration of Huygens' 1673 experimental pendulum clock from Horologium Oscillatorium. Huygens placed cycloidal-shaped metal "cheeks" on either side of the pendulum string, to force the pendulum to move in a cycloidal path, to increase accuracy. Horologium Oscillatorium: sive de motu pendulorum ad horologia aptato demonstrationes geometricae (Latin for "The Pendulum Clock: or geometrical demonstrations concerning the motion of pendula as applied to clocks") is a book published by Christiaan Huygens in 1673; it is his major work on pendulums and horology. This work is regarded as one of the three most important works done on mechanics in the 17th century, the other two being Galileo’s Discourses and Mathematical Demonstrations Relating to Two New Sciences (1638) and Isaac Newton’s Philosophiæ Naturalis Principia Mathematica (1687).
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Each ship of the class will be long, with a beam of , and a loaded draft of . They will carry 4,500 passengers, with a crew complement of 16. They will be powered by four EMD 12-710 diesel engines arranged in two married pairs, each of which drive a cycloidal propeller at each end of the ship for double-ended operation.
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On September 1, 1993, Foss Maritime expanded into the San Francisco Bay Area, maintaining a pool of vessels and barges for Tug/Barge escort, docking, and other services in conjunction with SeaRiver maritime. Today Foss provides three large conventional SeaRiver tugs and one Foss cycloidal tractor tug. The Foss SeaRiver Tug office is located at 150A West Industrial Way, Benicia, CA .
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A prolate trochoidal mass spectrometer is a chemical analysis instrument in which the ions of different mass-to-charge ratio are separated by means of mutually perpendicular electric and magnetic fields so that the ions follow a prolate trochoidal path. These devices are sometimes called cycloidal mass spectrometers, although the path is not a cycloid (the prolate trochoid path has loops, the cycloid has cusps).
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The tornado produced very severe cycloidal ground scouring in farm fields, and damage near the town of Goessel was "extreme F5" according to NWS damage surveyors. The severity of the damage left behind by this tornado led some meteorologists to believe that the Goessel tornado was among the strongest ever documented at that time. The storm passed Goessel and then dissipated approximately from its genesis.
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Historical marker is located about east of the Village of Midlothian in U.S. Route 60. Just west of this marker, the site of the cycloidal inclined plane on the steep western slope of Falling Creek Valley is still recognizable and juxtaposes the remains of the railroad bridge at Falling Creek. The location is about east of the Village of Midlothian on U.S. Route 60.
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This had two outer ring gears, each half the thickness of the other gears. One of these two ring gears was held fixed and had one tooth fewer than did the other. Therefore, several turns of the "sun" gear made the "planet" gears complete a single revolution, which in turn made the rotating ring gear rotate by a single tooth like a Cycloidal drive.
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Voith‐Schneider propeller The Voith Schneider Propeller, also known as a cycloidal drive is a specialized marine propulsion system. It is highly maneuverable, being able to change the direction of its thrust almost instantaneously. It is widely used on tugs and ferries. From a circular plate, rotating around a vertical axis, a circular array of vertical blades (in the shape of hydrofoils) protrude out of the bottom of the ship.
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"...it is affected by either the intemperance of the air or any faults in the mechanism so the crutch QR is not always activated by the same force... With large arcs the swings take longer, in the way I have explained, therefore some inequalities in the motion of the timepiece exist from this cause...", , translation by Ernest L. Edwardes (December 1970) Antiquarian Horology, Vol.7, No.1 To make its period isochronous, Huygens mounted cycloidal-shaped metal 'chops' next to the pivots in his clocks, that constrained the suspension cord and forced the pendulum to follow a cycloid arc (see cycloidal pendulum).Andrewes, W.J.H. Clocks and Watches: The leap to precision in This solution didn't prove as practical as simply limiting the pendulum's swing to small angles of a few degrees. The realization that only small swings were isochronous motivated the development of the anchor escapement around 1670, which reduced the pendulum swing in clocks to 4°–6°.
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In a marine situation, this provides for a drive which can be directed in any direction and thus does away with the need for a rudder. It is highly efficient and provides for an almost instantaneous change of direction. These drives are becoming increasingly common in work boats such as fireboats and tugboats where extreme manoeuvrability is needed. Azimuth thrusters (and Kort nozzles) have both advantages and disadvantages when compared to cycloidal drives.
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Spur gear Spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with teeth projecting radially. Though the teeth are not straight-sided (but usually of special form to achieve a constant drive ratio, mainly involute but less commonly cycloidal), the edge of each tooth is straight and aligned parallel to the axis of rotation. These gears mesh together correctly only if fitted to parallel shafts.
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Supercharging boost control was achieved by varying the ratio of this drive. In contemporary use, the Beier variator is most widely used as part of an industrial motor drive. An electric induction motor is driven at its ideal speed, derived from the electrical line frequency, and the variator drive is used to manually adjust its output speed. These are often coupled with a cycloidal drive to provide an extra-low speed output.
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For surface radar purposes, an AN/SPS-64(V)9 is used. They also use the AN/SLQ-48 mine neutralization system, which is tethered to the ship by a long cable. They have two AN/UYQ-31 operator data terminals, which are identical. They are propelled by two Isotta Franschini ID 36 SS 8V AM diesel engines which drive two Voith Schneider cycloidal propellers generating , and have three Isotta Fraschini ID 36 diesel generators.
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The back part of the city of New Orleans was completely inundated. It was simultaneously felt at Pensacola, Florida and Mobile, Alabama, and extended to Natchez, Mississippi up the Mississippi river. Its duration was six days from the time it commenced in Barbados and its course cycloidal; the distance passed over by the storm from Barbados to New Orleans is , and the average rate of its progress fourteen miles (21 km) an hour.
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Generation of the involute of the cycloid unwrapping a tense wire placed on half cycloid arc (red marked) The involute of the cycloid has the property of being exactly the same cycloid it originates from. This can otherwise be seen from the tip of a wire initially lying on a half arc of cycloid describing a cycloid arc equal to the one it was lying on once unwrapped (see also cycloidal pendulum and arc length).
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East of Lindenwood, further weakening occurred as the tornado damaged homes and outbuildings at EF1 strength, and a brief EF0 satellite tornado was observed. The tornado re-intensified to high-end EF3 strength as it devastated the small town of Fairdale, where the two fatalities occurred. Every structure in town sustained some type of damage, and multiple poorly anchored homes were leveled and swept away. Intense cycloidal marks were observed in farm fields outside of town.
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One of the most remarkable features was a cycloidal inclined plane, a drum and rope device by which loaded coal- carrying cars lowered down the steep western slope of Falling Creek Valley pulled by two empty cars traveling up the slope. On the eastern side, the loaded cars were then raised over a distance, with power supplied by animals. After completing that movement, the roadbed was mostly a gradual downhill slope over relatively level terrain towards Manchester.
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A large tornado developed shortly after, touching down two miles south of Aplington in Butler County at 4:48 pm CDT. East of Aplington, the tornado traveled through a series of farm fields, leaving distinct cycloidal marks in the corn stubble. It then tracked toward Parkersburg, becoming extremely violent, intensifying to EF5 strength, and growing into a large wedge-shaped tornado as it tore through the southern part of the community just before 5:00 pm CDT.
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An EF5 tornado can rip well- anchored homes off their foundations, leaving them bare, and can even deform large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler radar data, photogrammetry, and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and assign a rating. Tornadoes vary in intensity regardless of shape, size, and location, though strong tornadoes are typically larger than weak tornadoes.
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To be time independent, the path must be cycloidal. To minimize the effect with amplitude, pendulum swings are kept as small as possible. It is important to note that as a rule, whatever the method of impulse the action of the escapement should have the smallest effect on the oscillator which can be achieved, whether a pendulum or the balance in a watch. This effect, which all escapements have to a larger or smaller degree is known as the escapement error.
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The tornado re-intensified to EF4 strength further to the northeast as it passed between Dibble and Washington. Numerous well-built homes were leveled in that area, and some were swept completely away. Unusual cycloidal debris impact scars were noted in open fields as well. One well- built home in this area with numerous anchor bolts was reduced to a bare slab, though a metal fence immediately next to the house remained standing and grass on the property was not scoured.
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The cycloidal propeller (see below) was developed prior to World War II and was occasionally used in tugs because of its maneuverability. After World War II it was also linked to safety due to the development of the Voith Water Tractor, a tugboat configuration which could not be pulled over by its tow. In the late 1950s, the Z-drive or (azimuth thruster) was developed. Although sometimes referred to as the Aquamaster or Schottel system, many brands exist: Steerprop, Wärtsilä, Berg Propulsion, etc.
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The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler radar data, photogrammetry, and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and award a rating. Formation of numerous waterspouts in the Great Lakes region. (North America) A flash flood caused by a severe thunderstorm Waterspouts have similar characteristics as tornadoes, characterized by a spiraling funnel- shaped wind current that form over bodies of water, connecting to large cumulonimbus clouds.
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Since 2000 Kim has been doing research on the cyclocopter with 4 rotors. In 2012 he held an outdoor flight demonstration of the cyclocopter for the first time in the world. The cyclocopter is a new VTOL (Vertical Take-Off and Landing) air vehicle that employs a unique propulsion system of cycloidal blades to generate the propulsion and lift for a VTOL maneuver. The rotor system consists of several blades rotating about a horizontal axis that is perpendicular to the direction of normal flight.
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In addition to damage to structures and vegetation, radar data, photogrammetry, and cycloidal marks (ground swirl patterns) may be utilized when available. The scale was used for the first time in the United States a year after its public announcement when parts of central Florida were struck by multiple tornadoes, the strongest of which were rated at EF3 on the new scale. It was used for the first time in Canada shortly after its implementation there when a tornado developed near the town on Shelburne, Ontario on April 18, 2013, causing up to EF1 damage.
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Three vessels were built in Dundee in 1963 by the Caledon Shipbuilding & Engineering Company to replace the paddle steamers, and were each named after prominent local politicians: James Newman (mayor of Woolwich, 1923–25), John Burns, and Ernest Bevin. These ferries featured Voith/Schneider Electric propulsion systems for manoeuvrability. A cycloidal propeller is fitted centrally at either end, each driven by a 500bhp 6-cylinder Mirrlees Blackstone diesel engine. Transport for London introduced an Art On The River scheme in 2014, showing decorative artwork on the ferry vessels.
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The ships were launched between March 1991 and June 1997, and were commissioned between November 1993 and December 1998. The Osprey class ships are larger than the other Lerici designs: they displace 918 tons fully loaded, are long, wide, and with a draught of . The ships are fitted with two diesel motors driving two Voith Schneider Propellers; these cycloidal propellers eliminate the need for the aft two active rudders. The ships use a Raytheon/Thomson Sintra SQQ-32 VDS sonar for minehunting, and Alliant SLQ-48 remote vehicles for mine disposal.
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The cycloidal propeller is a circular plate mounted on the underside of the hull, rotating around a vertical axis with a circular array of vertical blades (in the shape of hydrofoils) that protrude out of the bottom of the ship. Each blade can rotate itself around a vertical axis. The internal mechanism changes the angle of attack of the blades in sync with the rotation of the plate, so that each blade can provide thrust in any direction, similar to the collective pitch control and cyclic in a helicopter.
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Minehunters are generally small, shallow-draught vessels, as they are often called upon to work in enclosed bodies of water such as shipping channels or harbours. As manoeuvrability in such areas is critical the Voith-Schneider cycloidal propulsor is commonly used, allowing the engine thrust to be transmitted in any direction. A number of modern vessels use catamaran hulls to provide a large, stable working platform with minimal underwater contact; this reduces draught whilst lowering acoustic transmission and reducing the fluid pressure generated by the moving hull that may otherwise detonate mines with a hydraulic pressure trigger.
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Whitley (1985), p. 159 Two Voith-Schneider cycloidal propeller- rudders were to be installed in the forward bow of the ship along the center- line. These were intended to assist in berthing the ship in harbor and also in negotiating narrow waterways such as the Kiel Canal where, due to the carrier's high freeboard and difficulty in maneuvering at speeds below , gusting winds might push the ship into the canal sides. In an emergency, the units could have been used to steer the ships at speeds under and, if the ships' main engines were rendered inoperable, could propel the vessel at a speed of in calm seas.
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Beulah was estimated to have achieved its peak intensity shortly thereafter as a Category 5 hurricane with winds estimated at 160 mph (260 km/h). Regarded as the third- largest hurricane on record at the time, Beulah moved along a slowing, erratic, and somewhat cycloidal path. Slight weakening ensued as it neared land and Beulah ultimately made its final landfall south of Brownsville, Texas near the mouth of the Rio Grande River around 13:00 UTC on September 20\. No direct measurements exist at the core of the hurricane as it moved ashore; however, based on a minimum pressure of 951 mbar (hPa; 28.09 inHg) in Brownsville, the hurricane likely struck land at an intensity below that value.
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R/V Knorr was named in honor of Ernest R. Knorr, a distinguished hydrographic engineer and cartographer who was appointed Chief Engineer Cartographer of the U.S. Navy Hydrographic office in 1860. Chief Engineer Knorr was one of the leaders of the Navy’s first systematic charting and surveying effort from 1860 to 1885. She was launched in August 21, 1968 at the Defoe Shipbuilding Company in Bay City, Michigan, Knorr was delivered to Woods Hole on April 15, 1970. The ship was built with Cycloidal propulsion that was replaced during a 1989-1991 midlife refit at which time propulsion was changed to two azimuthing stern thrusters and a retractable bow thruster as well as the hull being lengthened from to .
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The cycloidal gear profile is a form of toothed gear used in mechanical clocks, rather than the involute gear form used for most other gears. The gear tooth profile is based on the epicycloid and hypocycloid curves, which are the curves generated by a circle rolling around the outside and inside of another circle, respectively. When two toothed gears mesh, an imaginary circle, the pitch circle, can be drawn around the centre of either gear through the point where their teeth make contact. The curves of the teeth outside the pitch circle are known as the addenda, and the curves of the tooth spaces inside the pitch circle are known as the dedenda.
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Numerous headstones were toppled at the New Hartford Cemetery, and shrubs and trees were completely debarked. Past New Hartford, the tornado weakened dramatically and passed just north of Waterloo and Cedar Falls, shrinking to about 1/4 mile (400 m) in width as it continued to impact rural areas. Damage along this section of the path was mostly minor, though a few farms sustained EF2 damage. Intense cycloidal marks were again noted in farm fields in this area. As the tornado approached Dunkerton, it turned to the east-northeast, missing the town and growing up to 1.2 miles (2 km) wide. Some re-intensification occurred in this area, as consistent high-end EF2 damage was noted at multiple farms.
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The horizontal cross-section of the region bounded by two cycloidal arcs traced by a point on the same circle rolling in one case clockwise on the line below it, and in the other counterclockwise on the line above it, has the same length as the corresponding horizontal cross-section of the circle. N. Reed has shownN. Reed, "Elementary proof of the area under a cycloid", Mathematical Gazette, volume 70, number 454, December, 1986, pages 290-291 how to find the area bounded by a cycloid by using Cavalieri's principle. A circle of radius r can roll in a clockwise direction upon a line below it, or in a counterclockwise direction upon a line above it.
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Damage surveys in this area showed a complex damage pattern, with evidence of sub-vortices developing well away from the main damage path, before either being pulled in and absorbed by the central tornadic circulation, or intensifying and becoming the primary circulation themselves at times. Aerial flyovers revealed extensive cycloidal scouring marks in farm fields outside of Marysville. EF3 damage continued to the east of Marysville as several homes and double-wide mobile homes were destroyed, with debris from the mobile homes was scattered up to a mile downwind. The tornado then briefly entered Scott County, regaining EF4 intensity and killing a man in the complete destruction of his frame home, obliterating five mobile homes, and severely damaging two other frame homes.
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The Fujita scale (F-Scale; ), or Fujita–Pearson scale (FPP scale), is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation. The official Fujita scale category is determined by meteorologists and engineers after a ground or aerial damage survey, or both; and depending on the circumstances, ground-swirl patterns (cycloidal marks), weather radar data, witness testimonies, media reports and damage imagery, as well as photogrammetry or videogrammetry if motion picture recording is available. The Fujita scale was replaced with the Enhanced Fujita scale (EF-Scale) in the United States in February 2007. In April 2013, Canada adopted the EF-Scale over the Fujita scale along with 31 "Specific Damage Indicators" used by Environment Canada (EC) in their ratings.
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A horizontal CNC Gear Hobbing Machine A horizontal hobbing machine A horizontal hobbing machine Hobbing machines, also known as hobbers, are fully automated machines that come in many sizes, because they need to be able to produce anything from tiny instrument gears up to diameter marine gears. Each gear hobbing machine typically consists of a chuck and tailstock, to hold the workpiece or a spindle, a spindle on which the hob is mounted, and a drive motor. For a tooth profile which is a theoretical involute, the fundamental rack is straight-sided, with sides inclined at the pressure angle of the tooth form, with flat top and bottom. The necessary addendum correction to allow the use of small-numbered pinions can either be obtained by suitable modification of this rack to a cycloidal form at the tips, or by hobbing at other than the theoretical pitch circle diameter.
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W. N. Hess, Blaisdell Publishing Co 1968 However, for particles which mirror at safe altitudes, (in yet a further level of approximation) the fact that the field generally increases towards the center of the Earth means that the curvature on the side of the orbit nearest the Earth is somewhat greater than on the opposite side, so that the orbit has a slightly non-circular, with a (prolate) cycloidal shape, and the guiding center slowly moves perpendicular both to the field line and to the radial direction. The guiding center of the cyclotron orbit, instead of moving exactly along the field line, therefore drifts slowly east or west (depending on the sign of the charge of the particle), and the local field line connecting the two mirror points at any moment, slowly sweeps out a surface connecting them as it moves in longitude. Eventually the particle will drift entirely around the Earth, and the surface will be closed upon itself. These drift surfaces, nested like the skin of an onion, are the surfaces of constant L in the McIlwain coordinate system.
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