Learn amatrol linkages, cams, and turnbuckles – Flashcards
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Friction
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resistance caused by two surfaces rubbing together
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High friction
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keeps nails and screws in place
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Low friction
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allows for things to move such as bike wheels on an axis
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Static friction aka starting friction
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resistance that exists when an object is at rest, must be overcome to move object
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Kinetic friction aka sliding friction
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exists when two objects are already moving against one another, less than static friction and why an object stops
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Coefficient of friction
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describes the amount of friction between two objects
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Coefficient of friction depends on
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types of surfaces, amount of force between them, wether the friction is static or kinetic
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Force of friction formula (normal force)
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coefficient of friction and normal force
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force of friction is greater when
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object is at rest
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coefficients of friction are
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us and uk
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Wheels
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reduce the amount of friction between a load and a surface
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Rolling friction
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when a wheel rolls, it makes a slight depression in the surface and is trying to climb out which reduces efficiency
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Rolling friction comparison to other frictions
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less than static
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Incline plane
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any flat surface set at an angle with respect to the horizontal, allows load to be lifted by a force less than the loaded weight (mechanical advantage)
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As the angle of an inclined plane decreases
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mechanical advantage increases
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Mechanical advantage formula for incline planes
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weight/forceneededtomovelead or lengthofplane/heightofplane
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Linkage
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mechanism that is defined as a bar or system of bars attached together to transmit energy from one point to another
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Linkages can transmit energy
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in a straight line or change the direction of energy transmission
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Examples of linkages
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chain, rope, string, or almost anything can connects objects together, may convert rotary motion of motor to a linear motion
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Slider crank linkage
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used to change rotary motion to back and forth motion, example is a hedge cutter, can also convert reciprocating motion to rotary motion, example is a steam piston
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Double rocker linkage
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aka four-bar linkage, rod connects driver to a follower which makes motion, driver and follower move back in forth to make two partial circle, example is windshield wipers.
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Crank rocker linkage
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also a four-bar linkage, has a drive that moves with a rotary motion while follower moves in a line, examples are shallow oil well pumps and valve lifters in automotive engines
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Slider crank linkage construction
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connecting rod is attached to drive arm and slider and base forms third arm of system
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Operation of slider crank linkage
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when crank has rotary motion, it's transferred to the connecting rod that pulls the slider
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dead spot
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aka toggle position is 8 degrees above or below the base and can stop the system of the slider is the driver
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Double rocker linkage
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driver arm, connecting rod, and a follower, movement of follower is same as driver
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Linkage differences
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four-bar linkages differ from three-bar linkages because the connecting rod which connects the driver to a follower moves in an arc, not the same motion as the driver
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Double rocker linkage construction
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consists of driver, connecting rod, and follower
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Double rocker operation
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when turning force is applied to driver it turns in rotary motion to cause connecting rod to move linear
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Cam
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wheel mounted on axis with a key, translates rotary to linear, cam follower follows contour of cam surface
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Cylindrical cam and follower
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cam has a curved line like a barber shop that follower is pushed through
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Radial cams and followers
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follower is pushed up and down by cam as it spins, the kind in our class
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Template cam and follower
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follower goes through carved in shape that moves lever connected to pivot point
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Cam example
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sewing machine
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Constant velocity
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rate cam is turning
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Rise
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when follower moves away from center of cam
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Fall
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when follower moves towards center of cam
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Dwell
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when follower doesn't change distance from cam
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Base circle
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reference point of cam
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Dwell time
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determined by basic circle
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Center of rise and fall
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180 degrees
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Turnbuckle
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device used for adjusting rods, ropes, or cables
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Turnbuckle example
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wire cables are tightened after stretching over time
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Turnbuckle construction
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barrel and two bolts, one bolt has right-hand threads and the other has left-hand threads
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Thread types
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hook, eye, or jaw
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Turnbuckle operation
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rope or cable is attached to both ends, turning the barrel causes both to go in or out
