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44-604: Unpublished products by Mitchell Camera was the high-speed 70mm camera which was used on the SR71 plane which was manufactured in Glendale and Sun Valley California. The Mitchell Camera Corporation was founded in 1919 by Henry Boeger and George Alfred Mitchell as the National Motion Picture Repair Co. Its first camera was designed and patented by John E. Leonard in 1917, and from 1920 on, was known as

88-525: A Western Bloc (BH) professional camera, but the images will not be registered accurately. Conversely, Western Bloc (BH) camera film will not pass undamaged through a U.S.S.R. professional camera (KS), as the perforations used for registration will be damaged. 16mm and 65/70mm films were standardized late in the standardization cycle so these U.S.S.R. cameras in these gauges are indeed compatible with Western Bloc camera films. Production (sound) models in 16mm, 35mm (4- and 2-perf) and 65mm (5-perf) served as

132-406: A basis for early Panavision cameras in those gauges. Planetary gear An epicyclic gear train (also known as a planetary gearset ) is a gear reduction assembly consisting of two gears mounted so that the center of one gear (the "planet") revolves around the center of the other (the "sun"). A carrier connects the centers of the two gears and rotates, to carry the planet gear(s) around

176-784: A pin-registered background plate projector with a carbon arc lamphouse which was synchronized with the film camera. One of the first MPRPPs (Mitchell Pin Registered Process Projector) was used in Gone with the Wind . Two- and three-headed background projectors evolved for VistaVision effects. George Mitchell received an Academy Honorary Award in 1952. The Mitchell Camera Company received Academy Awards for Technical Achievement in 1939, 1966 and 1968. In 1944, unable to purchase Mitchell cameras in Pounds Sterling ,

220-442: A planet engaging both a sun gear and a ring gear is called a planetary gear train . By choosing to hold one component or another—the planetary carrier, the ring gear, or the sun gear—stationary, three different gear ratios can be realized. Epicyclic gearing or planetary gearing is a gear system consisting of one or more outer, or planet , gears or pinions , revolving about a central sun gear or sun wheel . Typically,

264-410: A planetary gear train begins by considering the speed ratio of the gear train when the carrier is held fixed. This is known as the fixed carrier train ratio. In the case of a simple planetary gear train formed by a carrier supporting a planet gear engaged with a sun and ring gear, the fixed carrier train ratio is computed as the speed ratio of the gear train formed by the sun, planet and ring gears on

308-468: Is a whole number If one is to create an asymmetric carrier frame with non-equiangular planet gears, say to create some kind of mechanical vibration in the system, one must make the teething such that the above equation complies with the "imaginary gears". For example, in the case where a carrier frame is intended to contain planet gears spaced 0°, 50°, 120°, and 230°, one is to calculate as if there are actually 36 planetary gears (10° equiangular), rather than

352-422: Is constructed from two identical coaxial epicyclic gear trains assembled with a single carrier such that their planet gears are engaged. This forms a planetary gear train with a fixed carrier train ratio R  = −1. In this case, the fundamental formula for the planetary gear train yields, or Thus, the angular velocity of the carrier of a spur gear differential is the average of the angular velocities of

396-405: Is stationary); one of the two remaining components is an input , providing power to the system, while the last component is an output , receiving power from the system. The ratio of input rotation to output rotation is dependent upon the number of teeth in each of the gears, and upon which component is held stationary. Alternatively, in the special case where the number of teeth on each gear meets

440-610: Is the lowest gear ratio attainable with an epicyclic gear train. This type of gearing is sometimes used in tractors and construction equipment to provide high torque to the drive wheels. In bicycle hub gears , the sun is usually stationary, being keyed to the axle or even machined directly onto it. The planetary gear carrier is used as input. In this case the gear ratio is simply given by N s + N r N r   . {\displaystyle {\tfrac {\,N_{\text{s}}+N_{\text{r}}\,}{N_{\text{r}}}}~.} The number of teeth in

484-729: The Rank Organisation in the UK exploited a loophole (the Mitchell company had failed to register a patent in the UK for the NC) and had the Newall company produce 200 cameras known as the Newall NC. In arrangement with Technicolor , 20 Newall cameras were modified to use bi-pack film (with double magazines) to film the 1948 Olympic Games in color, though with a limited palette. The process

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528-488: The bookwheel , a vertically revolving bookstand containing epicyclic gearing with two levels of planetary gears to maintain proper orientation of the books. French mathematician and engineer Desargues designed and constructed the first mill with epicycloidal teeth c.  1650 . In order that the planet gear teeth mesh properly with both the sun and ring gears, assuming n p {\displaystyle n_{\text{p}}} equally spaced planet gears,

572-614: The Greeks invented the idea of epicycles, of circles travelling on the circular orbits. With this theory Claudius Ptolemy in the Almagest in 148 CE was able to approximate planetary paths observed crossing the sky. The Antikythera Mechanism , circa 80 BCE, had gearing which was able to closely match the Moon's elliptical path through the heavens, and even to correct for the nine-year precession of that path. (The Greeks interpreted

616-517: The Mitchell Camera Company when it closed in 1979. Mitchell Camera Supplies were supplied by Mitchell Camera Corporation management through the late 1980's. Mitchell Camera also supplied camera intermittent movements for Technicolor 's three-strip camera (1932), and such movements for others' 65mm and VistaVision conversions before later making complete 65mm and VistaVision cameras in normal and high speed. Mitchell also made

660-575: The Mitchell Standard Studio Camera. Features included a planetary gear -driven variable shutter U.S. patent 1,297,703 and a unique rack-over design U.S. patent 1,297,704 . George Mitchell perfected and upgraded Leonard's original design, and went on to produce the most beloved and most universally used motion picture cameras of the Golden Age of Hollywood under the name of The Mitchell Camera Company. The company

704-597: The Mitchell-designed rackover focusing mechanism and the Mitchell-designed side viewer. Though the Eastern Bloc standard for camera film is Kodak Standard perforations, that standard was rejected by the very Bloc which proposed it. U.S.S.R. professional cameras consequently require film stocks that are incompatible with Western Bloc camera film, which always uses Bell & Howell perforations. Eastern Bloc (KS) camera film will pass undamaged through

748-759: The broader Asia-Pacific region, the Middle East , Latin America , and Africa with histories of anti-Soviet , anti-communist and, in some cases anti-socialist , ideologies and policies. As such, the bloc was opposed to the political systems and foreign policies of communist countries, which were centered on the Soviet Union , other members of the Warsaw Pact , and usually the People's Republic of China . The name "Western Bloc" emerged in response to and as

792-406: The fixed carrier. This is given by In this calculation the planet gear is an idler gear. The fundamental formula of the planetary gear train with a rotating carrier is obtained by recognizing that this formula remains true if the angular velocities of the sun, planet and ring gears are computed relative to the carrier angular velocity. This becomes, This formula provides a simple way to determine

836-399: The following equation must be satisfied: where N s , N r {\displaystyle N_{\text{s}},N_{\text{r}}} are the number of teeth of the sun gear and the ring gear , respectively and n p {\displaystyle n_{\text{p}}} is the number of planet gears in the assembly and A {\displaystyle A}

880-682: The following three types of structures: meshed-planet (there are at least two more planets in mesh with each other in each planet train), stepped-planet (there exists a shaft connection between two planets in each planet train), and multi-stage structures (the system contains two or more planet sets). Compared to simple planetary gears, compound planetary gears have the advantages of larger reduction ratio, higher torque-to-weight ratio, and more flexible configurations. The axes of all gears are usually parallel, but for special cases like pencil sharpeners and differentials , they can be placed at an angle, introducing elements of bevel gear (see below). Further,

924-414: The following: and only if ω r ≠ ω c   . {\displaystyle \omega _{\text{r}}\neq \omega _{\text{c}}~.} In many epicyclic gearing systems, one of these three basic components is held stationary (hence set ω ... = 0 {\displaystyle \omega _{\text{...}}=0} for whichever gear

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968-477: The four real ones. The gear ratio of an epicyclic gearing system is somewhat non-intuitive, particularly because there are several ways in which an input rotation can be converted into an output rotation. The four basic components of the epicyclic gear are: The overall gear ratio of a simple planetary gearset can be calculated using the following two equations, representing the sun-planet and planet-ring interactions respectively: where from which we can derive

1012-401: The internal gear mate that is typical of a ring gear. Some epicyclic gear trains employ two planetary gears which mesh with each other. One of these planets meshes with the sun gear, the other planet meshes with the ring gear. This results in different ratios being generated by the planetary and also causes the sun gear to rotate in the same direction as the ring gear when the planet carrier is

1056-468: The motion they saw, not as elliptical, but rather as epicyclic motion.) In the 2nd century AD treatise The Mathematical Syntaxis (a.k.a. Almagest ), Claudius Ptolemy used rotating deferent and epicycles that form epicyclic gear trains to predict the motions of the planets. Accurate predictions of the movement of the Sun, Moon, and the five planets, Mercury, Venus, Mars, Jupiter, and Saturn, across

1100-466: The other, not with meshed teeth but with a pin inserted into a slot on the second. As the slot drove the second gear, the radius of driving would change, thus invoking a speeding up and slowing down of the driven gear in each revolution. Richard of Wallingford , an English abbot of St. Albans monastery, later described epicyclic gearing for an astronomical clock in the 14th century. In 1588, Italian military engineer Agostino Ramelli invented

1144-705: The planet gear is irrelevant. From the above formulae, we can also derive the accelerations of the sun, ring and carrier, which are: In epicyclic gears, two speeds must be known in order to determine the third speed. However, in a steady state condition, only one torque must be known in order to determine the other two torques. The equations which determine torque are: where: τ r {\displaystyle \tau _{r}} — Torque of ring (annulus), τ s {\displaystyle \tau _{s}} — Torque of sun, τ c {\displaystyle \tau _{c}} — Torque of carrier. For all three, these are

1188-472: The planet gear(s) about its axis. Rotation of the planet gears can in turn drive the ring gear (not depicted in diagram), at a speed corresponding to the gear ratios: If the ring gear has N r {\displaystyle \,N_{\text{r}}\,} teeth, then the ring will rotate by N p N r {\displaystyle \,{\tfrac {\,N_{\text{p}}\,}{N_{\text{r}}}}\,} turns for each turn of

1232-463: The planet gears are mounted on a movable arm or carrier , which itself may rotate relative to the sun gear. Epicyclic gearing systems also incorporate the use of an outer ring gear or annulus , which meshes with the planet gears. Planetary gears (or epicyclic gears) are typically classified as simple or compound planetary gears. Simple planetary gears have one sun, one ring, one carrier, and one planet set. Compound planetary gears involve one or more of

1276-533: The planetary gears. For instance, if the ring gear has 64 teeth, and the planets 16 teeth, one clockwise turn of a planet gear results in ⁠ 16 / 64  ⁠ , or ⁠ 1 / 4  ⁠ clockwise turns of the ring gear. Extending this case from the one above: So, with the planetary carrier locked, one turn of the sun gear results in − N s N r {\displaystyle \;-{\tfrac {\,N_{\text{s}}\,}{N_{\text{r}}}}\;} turns of

1320-461: The ratio is equal to − N s N p . {\displaystyle -{\tfrac {\,N_{\text{s}}\,}{N_{\text{p}}}}\;.} For instance, if the sun gear has 24 teeth, and each planet has 16 teeth, then the ratio is ⁠− + 24 / 16  ⁠ , or ⁠− + 3 / 2  ⁠ ; this means that one clockwise turn of the sun gear produces 1.5  counterclockwise turns of each of

1364-415: The relationship N r = N s + 2 N p , {\displaystyle \,N_{\text{r}}=N_{\text{s}}+2\,N_{\text{p}}\;,} the equation can be re-written as the following: where These relationships can be used to analyze any epicyclic system, including those, such as hybrid vehicle transmissions, where two of the components are used as inputs with

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1408-692: The ring gear is held stationary and the sun gear is used as the input, the planet carrier will be the output. The gear ratio in this case will be 1 / ( 1 + N r N s ) = N s N s + N r , {\displaystyle \,1/\left(1+{\tfrac {\,N_{\text{r}}\,}{N_{\text{s}}}}\right)={\tfrac {N_{\text{s}}}{\,N_{\text{s}}+N_{\text{r}}\,}}\;,} which may also be written as N s : N s + N r   . {\displaystyle \;N_{\text{s}}:N_{\text{s}}+N_{\text{r}}~.} This

1452-539: The ring gear. The ring gear may also be held fixed, with input provided to the planetary gear carrier; output rotation is then produced from the sun gear. This configuration will produce an increase in gear ratio, equal to 1 + N r N s = N s + N r N s   . {\displaystyle \;1+{\tfrac {\,N_{\text{r}}\,}{N_{\text{s}}}}={\tfrac {\,N_{\text{s}}+N_{\text{r}}\,}{N_{\text{s}}}}~.} If

1496-507: The sky assumed that each followed a trajectory traced by a point on the planet gear of an epicyclic gear train. This curve is called an epitrochoid . Epicyclic gearing was used in the Antikythera Mechanism , circa 80 BCE, to adjust the displayed position of the Moon for the ellipticity of its orbit , and even for its orbital apsidal precession . Two facing gears were rotated around slightly different centers; one drove

1540-476: The speed ratios for the simple planetary gear train under different conditions: 1. The carrier is held fixed, ω c =0, 2. The ring gear is held fixed, ω r =0, 3. The sun gear is held fixed, ω s =0, Each of the speed ratios available to a simple planetary gear train can be obtained by using band brakes to hold and release the carrier, sun or ring gears as needed. This provides the basic structure for an automatic transmission . A spur gear differential

1584-698: The stationary. The fundamental equation becomes: Western Bloc The Western Bloc , also known as the Capitalist Bloc , is an informal, collective term for countries that were officially allied with the United States during the Cold War of 1947–1991. While the NATO member states , in Western Europe and Northern America , were pivotal to the bloc, it included many other countries, in

1628-410: The sun and ring gears. In discussing the spur gear differential, the use of the term ring gear is a convenient way to distinguish the sun gears of the two epicyclic gear trains. Ring gears are normally fixed in most applications as this arrangement will have a good reduction capacity. The second sun gear serves the same purpose as the ring gear of a simple planetary gear train but clearly does not have

1672-400: The sun gear. The planet and sun gears mesh so that their pitch circles roll without slip. If the sun gear is held fixed, then a point on the pitch circle of the planet gear traces an epicycloid curve. An epicyclic gear train can be assembled so the planet gear rolls on the inside of the pitch circle of an outer gear ring, or ring gear, sometimes called an annulus gear . Such an assembly of

1716-471: The sun, planet carrier and ring axes are usually coaxial . Epicyclic gearing is also available which consists of a sun, a carrier, and two planets which mesh with each other. One planet meshes with the sun gear, while the second planet meshes with the ring gear. For this case, when the carrier is fixed, the ring gear rotates in the same direction as the sun gear, thus providing a reversal in direction compared to standard epicyclic gearing. Around 500 BCE,

1760-554: The third providing output relative to the two inputs. In one arrangement, the planetary carrier (green in the diagram above) is held stationary, and the sun gear (yellow) is used as input. In that case, the planetary gears simply rotate about their own axes (i.e., spin) at a rate determined by the number of teeth in each gear. If the sun gear has N s {\displaystyle \,N_{\text{s}}\,} teeth, and each planet gear has N p {\displaystyle \,N_{\text{p}}\,} teeth, then

1804-425: The torques applied to the mechanism (input torques). Output torques have the reverse sign of input torques. These torque ratios can be derived using the law of conservation of energy. Applied to a single stage this equation is expressed as: In the cases where gears are accelerating, or to account for friction, these equations must be modified. A convenient approach to determine the various speed ratios available in

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1848-746: Was first headquartered on Sunset Blvd in Los Angeles, then building a new factory in West Hollywood and moving there in 1930, and finally moving operations to its factory location in Glendale, California in the 1940s. Its final location was in Sun Valley California where it moved in the 1970's. The Mitchell Camera Movement was utilized for animation in George Lucas Star Wars films. Mitchell Camera Corporation

1892-467: Was known as Technichrome. The resulting film used sequences filmed in three-strip Technicolor, Technichrome, and Technicolor Monopack, the latter also filmed with a Newall NC. Certain models were copied in whole or in part by the U.S.S.R. , mostly models which were intended for filming animation or special effects process plates, or for high-speed filming. In a few cases, the U.S.S.R. added spinning mirror-shutter reflex focusing and viewing, thereby deleting

1936-562: Was privately and quietly purchased in mid 1929 by William Fox of Fox Film Studios , just before the Great Depression began, though George Mitchell continued working with the company until he retired in the 1950s. Although William Fox had lost control and possession of his own Fox Film Studios and theaters empire in March of 1930, he apparently quietly retained possession of the Mitchell Camera Company, as his two daughters still owned

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