Pulley mechanics

Drive system machinery, pulley mechanisms and control panels ... 

Different designs for converting rotary motion of a motor to the linear motion of the neutron absorber are in existence. These include rope and pulley mechanisms, rack and pinion drives and screw and nut mechanisms with split nuts for scramming. Use of linear induction motor or a linear synchronous motor eliminates use of a rotary prime mover thereby providing more reliability. However, these mechanisms are larger in size for the same load capacity and are not very popular for reactor applications. Rope and pulley mechanisms permit flexible layout of drive mechanisms with respect to the neutron absorber and can be accommodated within a very small >ace. While using rope and pulley mechanisms, proper tools ate necessary for retrieval of neutron absorber assembly subsequent to incidental rope snapping. 

Backstops. A backstop is a device that permits rotation of the pulley in the forward direction but automatically prevents rotation in the opposite direction. A backstop should be installed at the headshaft of an inclined belt to prevent the belt from moving in reverse if the power to the motor is intermpted or if there is a failure in the mechanical drive system. 

FIG. 29-75 Conil.ined irialile-speed and motor drive. CRueres Pulley Co. from Kenl, Mechanical Engineers Handliook. 12th ed, Wiley, ew York, 1961. ... 

The mechanical seal on the radiator water pump of your car has to work under severe conditions. This seal must resist the pressures and temperatures, corresponding to the velocities of the motor, and the variable operating times. This seal is not a precision seal (it has stamped parts rather than machined components) and the pump is a portable pump. The pump doesn t use a direct coupling but a v-belt pulley with radial loading. The seal must resist many vibrations commencing with the v-belt slapping and whipping. 

Pulley systems with varying mechanical advantages. 

A fixed pulley is a device for changing the direction of an applied force. A common form is a mounted wheel with a rim around which a rope passes. In a vei y primitive form it could he a vine looped over a tree branch. A pull downward on the rope (vine) results in lifting a load on the other end. Neglecting friction, the mechanical advantage of the single fixed pulley is 1 the load moves the same distance as the applied force. 

Some questions will require the identification of various mechanical tools or devices. Some of the types of mechanical devices that may appear on the exam— and covered in this chapter—include hand tools, gears, pulleys, levers, fasteners, springs, valves, gauges, and pumps. In addition to individual mechanical devices, the exam may test your knowledge of various systems, or combinations of mechanical devices. A common example of a mechanical system is the internal combustion engine of an automobile. 

Mechanical devices cover a wide range of types of tools. In general, they are tools that relate to physical work and are governed by mechanical forces and movements. You can usually see what they do and how they work—as opposed to, say, a light switch or a battery, which are electrical devices. Some tools are used to directly accomplish a specific task, as when you use a hand saw to cut a piece of wood. Others, such as pulleys and gears, may be used indirectly to accomplish certain tasks that would be possible without the device but are easier with it. Still others, such as gauges, only provide feedback information on the operation of other mechanical devices. You see and use mechanical devices many times each day, so there is no reason to be intimidated by a mechanical aptitude section on the exam. 

A pulley consists of a wheel with a grooved rim in which a pulled rope or cable is run. Pulleys are commonly used with ropes or steel cable to change the direction of a pulling force or to add mechanical advantage. 

Another common use for a pulley is to connect an electric motor to a mechanical device such as a pump. One pulley is placed on the shaft of the motor, and a second pulley is placed on the shaft of the pump. A belt is used to connect the two pulleys. When the motor is turned on, the first pulley rotates and causes the belt to rotate, which in turn causes the second pulley to rotate and turn the pump. This arrangement is... 

Rings are held by a pair of pulleys mounted on roller bearings, a mechanism being provided to rotate one or both pulleys automatically during the test. It is not satisfactory to use pegs or fixed pulleys because the rubber does not readily slip over the surfaces and is therefore not uniformly stretched. However, lubricated spindles are specified in ASTM D412 to try and overcome the problem. 

A work reservoir is similarly defined as any body or combination of bodies, used as part of the surroundings, whose only interaction with the system is one that may be described in terms of work. We may have a different type of reservoir for each mode of interaction other than thermal interaction. A work reservoir then is used to perform work across the boundary separating the reservoir and the thermodynamic system and to measure these quantities of work. In the following we are, in order to simplify the discussion, primarily concerned with mechanical work, but this limitation does not alter or limit the basic concepts. A reservoir for mechanical work may be a set of weights and pulleys in a gravitational field, an idealized spring, or a compressible fluid in a piston-and-cylinder arrangement. In any case the reservoir must... 

Out-of-limit temperatures for rotating mechanical components and systems are usually based on values established by the manufacturers. Pump and compressor equipment that could benefit from an infrared thermography inspection program include motor gears, bearings, shafts, couplings, V—belts, pulleys, compressors, vacuum pumps, and clutches. 

The finish of an uncoloured plastic film or moulding is said in the industry to be natural such finishes can be serviceable and perfectly adequate in some uses (as in pulley wheels or other unseen parts in mechanical assemblies). 

Pascal 3. The hydraulic lever. The hydraulic jack is a problem in fluid equilibrium, just as a pulley system is a problem in mechanical equilibrium (no accelerations involved). It s the static situation in which a small force on a small piston balances a large force on a large piston. No change of pressure need be involved here. A constant force on one piston slowly lifts a different piston with a constant force on it. At all times during this process the fluid is in near-equilibrium. This principle is no more than an application of the definition of pressure as F/A, the quotient of... 

Fig. 7 Examples of mechanical bonds in society (a) decorative mechanical bonds of a Mursi woman, (b) portrait of a Khayan Lahwi woman, (c) shower curtain, (d) wristwatch makes a rotaxane with the hand and body as stoppers, (e) chain link, (f) abacus, (g) children s bead maze, (h) keychain, (i) lock, (j) pulley on a sailship, (k) chainmail, (1) seatbelt buckle, (m) doorknob has the essence of the dumbbell portion of a rotaxane (the door is the ring), (n) the mechanical bond of a carabiner helps climbers cling to rock faces, and (o) hundreds of mechanical bonds exist in the chain, crank, and wheels of a bicycle...

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