#indiasbesthiwinballscrewdealers#bestoffersindia#Qualityhiwinballscrew#trustedsellerhiwinballscrew#hiwinballscrewbestoffersindia#hiwinballscrewontimeservice#RoadSafetyFirst

#hiwinballscrewspecialoffers#savewater#planttreessavelife#DrugfreeNation#SaveEnergy#hiwinballscrewdealers#hiwinballscrewmanufacturer#Industrialhiwinballscrewdealers

#Industrialhiwinballscrewmanufacturer#industrialhiwinballscrewdistributer

Ball screws are used in aircraft and missiles to move control surfaces, especially for electric fly by wire, and in automobile power steering to translate rotary motion from an electric motor to axial motion of the steering rack. They are also used in machine tools, robots, and precision assembly equipment.

Ball Screw is a high-efficiency method of converting rotary motion to linear motion by using a recirculating ball mechanism between the screw shaft and the nut. Compared with a conventional sliding screw, the ball screw requires driving torque of one-third or less, making it ideal for saving drive motor power.

Ball screws are more efficient, requiring less torque. Ball screws have lower friction and run at cooler temperatures. Ball screws require grease or oil lubrication to achieve design life. Ball screws need to be replaced less frequently.

Ball screws excel in applications where efficiency, precision and high-speed, smooth motion are preferred. Lead screws can be a suitable solution for simple applications where smooth or quiet motion is of more value than rigidity, precision, accuracy, and speed

Ball screws are rolled out of alloy steel or stainless-steel grades that can be hardened by heat treating. The hardened ball screw material must hold up to the hardened balls loaded in the ball screw nut.

Ball screws date all the way back to the late 19th century, when an engineer placed ball bearings inside the nut threads to reduce friction. For centuries, the conventional lead screw (threaded shaft and nut) was the primary mechanism for converting rotary motion to linear motion.

Ball screws have more complex structures and components and appear to be bulkier than other types of screws. They are more expensive than other screw types, but their benefits and capability outweigh their cost.

Selection and Applications of Control Valves

July 3, 2017

P.Eng.

Meena Rezkallah

Definition of Control Valves

Unlike valves in a piping system that primarily serve to shut off, drain, fill, or divert, control valves are a part of an automated control system. They are considered the ‘‘final control element’’ in an automated and usually very sophisticated ‘‘control loop.’’ Aside from the control valve, the ‘‘loop’’ consists of a transmitter that measures the variable to be controlled (usually pressure, flow, level, or temperature) and a controller (nowadays a computer of sorts). Following an error in the variable to be controlled (such an error being sensed by the transmitter), the controller sends a signal change to the control valve which, in turn, responds by altering the flow rate through the valve sufficiently to restore the desired variable (such as pressure, for example).

Control valves have basically three interactive components: (1) a valve body sub assembly (either with a reciprocating or rotating stem), (2) an actuating device (usually a spring diaphragm type), (3) a valve positioner (an instrument that converts an electronic control signal from a controller, or computer, into an air signal to control the position of the control valve stem), and (4) an airset or regulator to supply air pressure to the positioner (see Figure A10.34).

How to Specify Control Valves

The first step in specifying a control valve is to define its function in the given application. In some, it will operate as an on-off valve that opens or closes following the commands of a programmable controller on, say, a batch process. In others, it will be used to remotely set a flow rate in a process—that is, it will be used as a manually controlled variable orifice in a pipe (an open-loop application). Finally, in more sophisticated applications, the control valve will serve as the final control element in a process control loop and respond to the sometimes infinitely small variations of a signal coming from a controller (typically a computer). The signal will be generated in response to a deviation in the desired temperature, pressure, or level of a process fluid as measured by a transmitter.

Application Classes

In the first type of application, any on-off valve with a pneumatic or electrical actuator (say, for example, a ball valve) may suffice. The requirements are to provide tight shutoff (perhaps with a Teflon® seat) to withstand the pressure, temperature, and corrosiveness of the fluid, and, finally, to have sufficient flow capacity. No valve positioner is required (see Figure A10.35).

Open-loop control requires a higher level of sophistication, such as a character- ized valve plug and good repeatability. The latter calls for a valve/actuator combina- tion with low dead band (low friction). A valve positioner, a device that is essentially a stem position controller with an accuracy between 0.5 and 1.0 percent of stem position, may be required. Controlling the stem position may not always assure that the valve plug or ball moves the required amount unless the stem or shaft is pinned or welded to the ball, vane, or plug (unless fluid pressure assures constant contact). See Figure A10.36.

The modulating control valve that is part of a control loop is the most sophisticated device. Typical features are plug or ball with either linear or equal percentage flow characteristic, low-friction packing and actuating devices, and, if required, low-noise or anticavitation features. These are in addition to the previously stated requirements.

Figure A10.37 shows an eccentric rotary plug valve with a low noise restrictor in the valve outlet port. Part of the pressure drop at moderate to high flow rates occurs across this slotted device. The smaller jets created by the slots produce about 10 to 15 dBA less noise than the valve itself.

Flow control is only possible if the control valve can reduce some of the fluid pressure. Such pressure reduction (also used for valve sizing) typically amounts to 5 to 10 percent of the maximum pump pressure. This makes a streamlined valve trim (highly desirable for on-off valves) actually less desirable for control purposes. It takes much higher velocities with a streamlined trim or valve (hence, more noise or cavitation) to achieve a certain pressure drop than with a nonstreamlined valve. Signals from controllers to control valves are 3 to 15 psi (0.2 to 1.0 bar) if pneumatic or 4 to 20 mA if electronic. Digital signals will be used in the future

once the question of fieldbus standardization has been resolved.

Control Valve Styles.

Let’s take a look at the characteristics of some of the most commonly used control valve types:

Globe valve. The globe valve (see Figure A10.34), which is the most widely used type of control valve, has a screwed-on, integrally attached, or cage-supported seat ring, and typically a lathe-turned, single-seated valve plug. Larger valves or high-pressure valves may have designs such that the valve plug is cage-guided and pressure-balanced to reduce actuator force requirements. Globe valves are cost effective in sizes NPS 2 (DN 50) and below and are available in sizes as small as NPS ¹⁄₄ (DN 6) for research applications. End connections are flanged or threaded. High-pressure or high-temperature valves can be welded to the piping. NPS 2 (DN 50) and smaller can be provided with socket-welding or threaded ends. NPS 2¹⁄₂ (DN 65) and larger are generally butt-welded or flanged.

Angle valves. Angle valves are a special variety of globe valves typically having an inlet port at a right angle to the valve stem and a discharge port in line with the valve orifice. Typical applications include flashing and erosive fluids.

Three-way valves. As the name implies, three-way valves are globe valves (or some rotary valves) that have three access ports and two plugs and orifices opposed to each other. Depending on the flow direction, three-way valves may serve as either mixing valves (where two different fluids enter the valve through two of the ports, and discharge as a mixture through the third), or diverting valves around heat exchangers (for example, where a fluid enters at one port and discharges through either the second or the third port).

Eccentric rotary plug valves. Eccentric rotary plug valves are designed especially for modulating control (i.e., they have solid stem connections, low or constant operating torque, a good flow characteristic, and tight shutoff). They feature a lower weight than globe valves and, therefore, have a cost advantage in sizes NPS 3 (DN 80) and above. They are either flanged or wafer-style for installation between flanges (Figure A10.37).

Characterized semispherical ball valves. The characterized semispherical ball valve is another form of ‘‘designed for modulation’’ rotary control valve with a backlash-free stem connection. Here, the seal is a thin metal or plastic ring that engages a segmented rotating ball. A V-notch in the ball surface gives a good repeatable flow characteristic. This valve type is popular in the paper industry and is available in either flanged or wafer-style (Figure A10.36).

Ball valves. Ball valves have a good shutoff characteristic and high flow capacity. As a result, they are a good choice for on-off or sequencing control. End connec- tions are flanged or wafer-style. Metal-seated ball valves are designed for high temperature applications and can be provided with welded connections. Soft- seated ball valves are used for normal liquid or gaseous fluids up to 482°F (250°C) and where tight shutoff is required (Figure A10.35).

Butterfly valves. Except for some special designs with low-torque and low-noise features, butterfly valves for modulating control have to be selected with care. This is because their high-torque (both seating and dynamic) and high-pressure recovery tend to encourage noise and cavitation. A lower-cost valve choice in sizes NPS 6 (DN 150) and above, butterfly valves are typically wafer-style due to their narrow profile.

Actuators. More than 90 percent of all control valves use pneumatic actuating devices—either spring-opposed diaphragm types or piston actuated. The spring/diaphragm actuator is by far the most popular due to its simplicity and ability to fail-safe (that is, the spring force will drive the valve either to close [fail- close] or in the open position [fail-open], depending on process safety requirements, should the air pressure be lost). Piston actuators provide more dynamic stiffness. In addition, because they use higher air pressures, they are more compact than spring-opposed diaphragm actua- tors. Other forms of actuation are electric or hydraulic. They are used more for special applications and their use is limited due to higher cost and limited reliability.

Materials of Construction. For noncorrosive use, the material of choice is carbon steel (ASTM A216 Grade WCB, if cast; and A105 when forged). Valve plugs and seat rings are typically ASTM A 351, CF8M (316 stainless steel). For mild, corrosive applications, valve housings are made from type CF8M (316 stainless steel). However, Teflon®-lined housings and exotic alloys, such as Hastelloy®, monel, or titanium are available for highly corrosive fluids. For additional information, refer to: Hans D. Baumann, Control Valve Primer, A User’s Guide, ISA, Research Triangle Park, 1998.

How to Size Control Valves

The flow capacity of control valves is expressed by the coefficient Cv. This is a combination of valve flow area and the valve’s headloss coefficient K. It is ex- pressed as

where A is the ‘‘vena contracta’’ area of the valve’s orifice, typically 70 percent of the orifice area. Cv is expressed in the flow of U.S. gallons per minute of water when the pressure drop is one psi. N1 is a numerical constant = 0.059 if A is in

mm2, or 38.1 if A is in inch2. For example, if K = 1 and A = 25 mm2, then the

Cv = 25 × 0.059/C1 = 1.475.

While Cv was initially a liquid flow coefficient, this term can also be used for gases or steam with the proper conversion coefficients as shown below.

We have to distinguish two modes of flow in a control valve which, in turn, governs the use of the correct equation.

Normal Flow. This occurs when the pressure drop across the valve lies below the following limits

where Aplim is the limited pressure drop across the valve (see equations), p1 is the valve’s inlet pressure, and pv is the vapor pressure of the respective fluid and at the flowing temperature (all pressures absolute).

Choked Flow. This occurs if the actual pressure drop exceeds Aplim. CAUTION: Such conditions could cause cavitation in valves handling liquids, or high sound levels with gas or steam. Consult your control valve supplier.

#Little_PEng

Engineering Consultant Services

TAGS:

Control Valves

valves

Selection and Applications of Control Valves

300+ TOP THEORY of MACHINES - Mechanical Engineering Multiple choice Questions and Answers

THEORY of MACHINES Questions with Answers  :-

1. Which of the following disciplines provides study of inertia forces arising from the combined effect of the mass and the motion of the parts (a) theory of machines (b) applied mechanics (c) mechanisms (d) kinetics (e) kinematics. Ans: d 2. Which of the following disciplines provides study of relative motion between the parts of a machine (a) theory of machines (b) applied mechanics (c) mechanisms (d) kinetics (e) kinematics. Ans: e 3. Which of the following disciplines provides study of the relative motion between the parts of a machine and the forces acting on the parts (a) theory of machines (b) applied mechanics (c) mechanisms (d) kinetics (e) kinematics. Ans: a 4. The type of pair formed by two elements which are so connected that one is constrained to turn or revolve about a fixed axis of another element is known as (a) turning pair (b) rolling pair (c) sliding pair (d) spherical pair (e) lower pair, Ans: a 5. Which of the following is a lower pair (a) ball and socket i (b) piston and cylinder (c) cam and follower (d) (a) and (b) above (e) belt drive. Ans: d 6. If two moving elements have surface contact in motion, such pair is known as (a) sliding pair (b) rolling pair (c) surface pair (d) lower pair (e) higher pair. Ans: e 7. The example of lower pair is (a) shaft revolving in a bearing (b) straight line motion mechanisms (c) automobile steering gear (d) all of the above (e) none of the above. Ans: d 8. Pulley in a belt drive acts as (a) cylindrical pair (b) turning pair (c) rolling pair (d) sliding pair (e) surface pair. Ans: c 9. The example of rolling pair is (a) bolt and nut (b) lead screw of a lathe (c) ball and socket joint (d) ball bearing and roller bearing (e) all of the above. Ans: d 10. Any point on a link connecting double slider crank chain will trace a (a) straight line (b) circle (c) ellipse (d) parabola (e) hyperbola. Ans: c 11. The purpose of a link is to (a) transmit motion (b) guide other links (c) act as a support (d) all of the above (e) none of the above. Ans: d 12. A universal joint is an example of (a) higher pair (b) lower pair (c) rolling pair (d) sliding pair (e) turning pair. Ans: b 13. Rectilinear motion of piston is converted into rotary by (a) cross head (b) slider crank (c) connecting rod (d) gudgeon pin (e) four bar chain mechanism. Ans: b 14. Pitch point on a cam is (a) any point on pitch curve (b) the point on cam pitch curve having the maximum pressure angle (c) any point on pitch circle (d) the point on cam pitch curve having the minimum pressure angle (e) none of the above. Ans: b 15. The values of velocity and acceleration of piston at near dead center for a slider-crank mechanism will be (a) 0, and more than co2r (b) 0, and less than coV (c) 0, 0 (d) cor, 0 (e) none of the above. Ans: a 16. The example of spherical pair is (a) bolt and nut (b) lead screw of a lathe (c) ball and socket joint (d) ball bearing and roller bearing (e) none of the above. Ans: c 17. Cross head and guides form a (a) lower pair (b) higher pair (c) turning pair (d) rolling pair (e) sliding pair. Ans: e 19. A circular bar moving in a round hole is an example of (a) incompletely constrained motion (b) partially constrained motion (c) completely constrained motion (d) successfully constrained motion (e) none of the above Ans: a 20. If some links are connected such that motion between them can take place in more than one direction, it is called (a) incompletely constrained motion (b) partially constrained motion (c) completely constrained motion (d) successfully constrained motion (e) none of the above. Ans: a 21. If there are L number of links in a mechanism then number of possible inversions is equal to (a) L + 1 (b) L - 1 (c) L (d) L + 2 (e) L - 2. Ans: c 22. Kinematic pairs are those which have two elements that (a) have line contact (b) have surface contact (c) permit relative motion (d) are held together (e) have dynamic forces. Ans: c 24. The lower pair is a (a) open pair (b) closed pair (c) sliding pair (d) point contact pair (e) does not exist. Ans: b 25. Automobile steering gear is an example of (a) higher pair (b) sliding pair (c) turning pair (d) rotary pair (e) lower pair. Ans: e 26. In higher pair, the relative motion is (a) purely turning (b) purely sliding (c) purely rotary (d) purely surface contact (e) combination of sliding and turning. Ans: e 27. Which of the following has sliding motion (a) crank (b) connecting rod (c) crank pin (d) cross-head (e) cross head guide. Ans: d 28. The example of higher pair is (a) belt, rope and chain drives (b) gears, cams (c) ball and roller bearings (d) all of the above (e) none of the above. Ans: d 29. Which of the following mechanism is obtained from lower pair (a) gyroscope (b) pantograph (c) valve and valve gears (d) generated straight line motions (e) all of the above. Ans: e 30. Which of the following would constitute a link (a) piston, piston rings and gudgeon pin (b) piston, and piston rod (c) piston rod and cross head (d) piston, crank pin and crank shaft (e) piston, piston-rod and cross head. Ans: e 31. The Scott-Russell mechanism consists of (a) sliding and turning pairs (b) sliding and rotary pairs (c) turning and rotary pairs (d) sliding pairs only (e) turning pairs only. Ans: a 32. Davis steering gear consists of (a) sliding pairs (b) turning pairs (c) rolling pairs (d) higher pairs (e) lower pairs. Ans: a 33. Ackermann steering gear consists of (a) sliding pairs (b) turning pairs (c) rolling pairs (d) higher pairs (e) lower pairs. Ans: b 34. A completely constrained motion can be transmitted with . (a) 1 link with pin joints (b) 2 links with pin joints (c) 3 links with pin joints (d) 4 links with pin joints (e) all of the above. Ans: d 36. Oldham's coupling is the (a) second inversion of double slider crank chain (b) third inversion of double slider crank chain (c) second inversion of single slider crank chain (d) third inversion of slider crank chain (e) fourth inversion of double slider crank chain. Ans: b 37. Sense of tangential acceleration of a link (a) is same as that of velocity (b) is opposite to that of velocity (c) could be either same or opposite to velocity (d) is perpendicular to that of velocity (e) none of the above. Ans: c 38. A mechanism is an assemblage of (a) two links (b) three links (c) four links or more than four links (d) all of the above (e) none of the above. Ans: c 39. The number of links in pantograph mechanism is equal to (a) 2 (b) 3 (c) 4 (d) 5 (e) 6. Ans: c 40. Elements of pairs held together mechanically is known as (a) closed pair (b) open pair (c) mechanical pair (d) rolling pair (e) none of the above. Ans: a 41. Shaft revolving in a bearing is the following type of pair (a) lower pair (b) higher pair (c) spherical pair, (d) cylindrical pair (e) bearing pair. Ans: a 42. Rectangular bar in a rectangular hole is the following type of pair (a) completely constrained motion (b) partially constrained motion (c) incompletely constrained motion (d) freely constrained motion (e) none of the above. Ans: a 43. A foot step bearing and rotor of a vertical turbine form examples of (a) incompletely constrained motion (b) partially constrained motion (c) completely constrained motion (d) successfully constrained motion (e) none of the above. Ans: b 44. A slider crank chain consists of following numbers of turning and sliding pairs (a) I, 3 (b) 2, 2 (c) 3, 1 (d) 4, 0 (e) 0, 4. Ans: c 46. Relationship between the number of links (L) and number of pairs (P) is (a) P = 2L-4 (b) P = 2L + 4 (c) P = 2L+2 (d) P = 2L-2 (e) P = L-4. Ans: c 2.49. In problem 47, the chain is unconstrained when (a) L.H.S. = R.H.S. (b) L.H.S. > R.H.S. (c) L.H.S. R.H.S. (d) there is no such criterion for checking above requirement (e) none of the above. Ans: a 51. The tendency of a body to resist change from rest or motion is known as (a) mass (b) friction (c) inertia (d) resisting force (e) resisting torque. Ans: c 53. The type of coupling used to join two shafts whose axes are neither in same straight line nor parallel, but intersect is (a) flexible coupling (b) universal coupling (c) chain coupling (d) Oldham's coupling (e) American coupling. Ans: b 54. The advantage of the piston valve over D-slide valve is that in the former case (a) wear is less (b) power absorbed is less (c) both wear and power absorbed are low (d) the pressure developed being high provides tight sealing (e) there is overall economy of initial cost, maintenance and operation. Ans: c 55. Flexible coupling is used because (a) it is easy to disassemble (b) it is easy to engage and disengage (c) it transmits shocks gradually (d) it prevents shock transmission and eliminates stress reversals (e) it increases shaft life. Ans: d 56. With single Hooke's joint it is possible to connect two shafts, the axes of which have an angular misalignment up to (a) 10° (b) 20° (c) 30° (d) 40° (e) 60°. Ans: d 57. The Hooke's joint consists of : (a) two forks (b) one fork (c) three forks (d) four forks (e) five forks. Ans: a 58. The Klein's method of construction for reciprocating engine mechanism (a) is based on acceleration diagram (b) is a simplified form of instantaneous center method (c) utilises a quadrilateral similar to the diagram of mechanism for reciprocating engine (d) enables determination of Corioli's component (e) none of the above. Ans: c 59. It is required to connect two parallel shafts, the distance between whose axes is small and variable. The shafts are coupled by (a) universal joint (b) knuckle joint (c) Oldham's coupling (d) flexible coupling (e) electromagnetic coupling. Ans: c 60. The e.g. of a link in any mechanism would experience (a) no acceleration (b) linear acceleration (c) angular acceleration (d) both angular and linear accelerations (e) none of the above. Ans: d 61. In elliptical trammels (a) all four pairs are turning (b) three pairs turning and one pair sliding (c) two pairs turning and two pairs sliding (d) one pair turning and three pairs sliding (e) all four pairs sliding. Ans: c 62. In automobiles the power is transmitted from gear box to differential through (a) bevel gear (b) universal joint (c) Hooke's joint (d) Knuckle joint (e) Oldham's coupling. Ans: c 63. The indicator using Watt mechanism is known as (a) Thompson indicator (b) Richard indicator (c) Simplex indicator (d) Thomson indicator (e) none of the above. Ans: b 64. The Ackermann steering mechanism is preferred to the Davis type in automobiles because (a) the former is mathematically accurate (b) the former is having turning pair (c) the former is most economical (d) the former is most rigid (e) none of thfr above. Ans: b 12-65. Transmission of power from the engine to the rear axle of an automobile is by means of (a) compound gears (b) worm and wheel method (c) Hooke's joint (d) crown gear (e) bevel gears. Ans: c 66. When a ship travels in a sea, which of the effect is more dangerous (a) steering (b) pitching (c) rolling (d) all of the above (e) none of the above. Ans: b 67. In an ideal machine, the output as compared to input is (a) less (b) more (c) equal (d) may be less or more depending on efficiency (e) always less. Ans: c 68. Governor is used in automobile to (a) decrease the variation of speed (b) to control (c) to control SN (d) all of the above (e) none of the above. Ans: c 69. In gramophones for adjusting the speed of the turntable, the following type of governor is commonly employed (a) Hartung governor (b) Wilson Hartnell governor (c) Pickering governor (d) Inertia governor (e) none of the above. Ans: c 70. For fluctuating loads, welsuited bearing is (a) ball bearing (b) roller bearing (c) needle roller bearing (d) thrust bearing (e) sleeve bearing. Ans: c 71. Crowning on pulleys helps (a) in increasing velocity ratio (b) in decreasing the slip of the belt (c) for automatic adjustment of belt posi-tion so that belt runs centrally (d) increase belt and pulley life (e) none of the above. Ans: c 72. Idler pulley is used (a) for changing the direction of motion of the belt (b) for applying tension (c) for increasing -velocity ratio (d) all of the above (e) none of the above. Ans: b 73. In multi-V-belt transmission, if one of the belt is broken, we have to change the (a) broken belt (b) broken belt and its adjacent belts (c) all the belts (d) there is no need of changing any one as remaining belts can take care of transmission of load (e) all the weak belts. Ans: c 74. The moment on the pulley which produces rotation is called (a) inertia (b) momentum (c) moment of momentum (d) work (e) torque. Ans: e 75. Creep in belt drive is due to (a) material of the pulley (b) material of the belt (c) larger size of the driver pulley (d) uneven extensions and contractions due to varying tension (e) expansion of belt. Ans: d 76. TJie horse power transmitted by a belt is dependent upon (a) tension on tight side of belt (b) tension on slack side of belt (c) radius of pulley (d) speed of pulley (e) all of the above. Ans: e 77. The locus of a point on a thread unwound from a cylinder will be (a) a straight line (b) a circle (c) involute (d) cycloidal (e) helix. Ans: c 78. To transmit power from one rotating shaft to another whose axes are neither parallel nor intersecting, use (a) spur gear (b) spiral gear (c) bevel gear (d) worm gear (e) crown gear. Ans: d 79. For S.H.M. cam, the acceleration of the follower at the ends of the stroke and aimidstroke respectively, is (a) maximum and zero (b) zero and maximum (c) minimum and maximum (d) zero and minimum (e) maximum and minimum. Ans: a 80. Throw of a cam is the maximum distance of the follower from (a) base circle (b) pitch circle (c) root circle (d) prime circle (e) inner circle. Ans: a 81. To obviate axial thrust, following gear drive is used (a) double helical gears having opposite teeth (b) double helical gears having identical teeth (c) single helical gear in which one of the teeth of helix angle a is more (d) mutter gears (e) none of the above. Ans: a 82. Which of the following is false statement in respect of differences between machine and structure (a) Machines transmit mechanical work, whereas structures transmit forces (b) In machines, relative motion exists be-tween its members, whereas same does hot exist in case of structures (c) Machines modify movement and work, whereas structures modify forces (d) Efficiency of machines as well as structures is below 100% (e) Machines are run by electric motors, but structures are not. Ans: d 83. If D1 and D2 be the diameters of driver and driven pulleys, then belt speed is proportional to (a) D1/D2 (b) D2/D1 (C) D1-D2. (d) D1 (e) D1+D2. Ans: d 84. Typewriter constitutes (a) machine (b) structure (c) mechanism (d) inversion (e) none of the above. Ans: c 85. Lower pairs are those which have (a) point or line contact between the two elements when in motion (b) surface contact between the two elements when in motion (c) elements of pairs not -held together mechanically (d) two elements that permit relative motion (e) none of the above. Ans: b 86. A point on a link connecting double slider crank chain traces a (a) straight line (b) circle (c) parabola (d) hyperbola (e) ellipse. Ans: e 87. A pantograph is a mechanism with (a) lower pairs (b) higher pairs (c) rolling pairs (d) turning pairs (e) spherical pairs. Ans: a 88. Kinematic pairs are those which have (a) point or line contact between the two elements when in motion (b) surface contact between the two ele-ments when in motion (c) elements of pairs not held together mechanically (d) two elements that permit relative mo-tion (e) none of the above. Ans: d 89. If the opposite links of a four bar linkage are equal, the links will always form a (a) triangle (b) rectangle (c) parallelogram (d) pentagon (e) trapezoid. Ans: c 90. Higher pairs are those which have (a) point or line contact between the two elements when in motion (b) surface contact between the two ele-ments when in motion (c) elements of pairs not held together mechanically (d) two elements that permit relative motion (e) none of the above. Ans: a 91. A cam mechanism imparts following motion (a) rotating (b) oscillating (c) reciprocating (d) all of the above (e) none of the above. Ans: d 92. A cam with a roller follower would con stitute following type of pair (a) lower pair (b) higher pair (c) open pair (d) close pair (e) cam pair. Ans: b 93. The approximate straight line mechanism is a (a) four bar linkage (b) 6 bar linkage (c) 8 bar linkage (d) 3 bar linkage (e) 5 bar linkage. Ans: a 94. "Open pairs are those which have (a) point or line contact between the two elements when in motion (b) surface contact between the two ele-ments when in motion (c) elements of pairs not held together mechanically (d) two elements that permit relative motion (e) none of the above. Ans: c 95. Peaucellier mechanism has (a) eight links (b) six links (c) four links (d) twelve links (e) five links. Ans: a 96. Hart mechanism has (a) eight links (b) six links (c) four links (d) twelve links (e) five links. Ans: b 97. A chain comprises of 5 links having 5 joints. Is it kinematic chain ? (a) yes (b) no (c) it is a marginal case (d) data are insufficient to determine it (e) unpredictable. Ans: b 99. The main disadvantage of the sliding pair is that it is (a) bulky (b) wears rapidly (c) difficult to manufacture (d) (a) and (b) above (e) (a) and (c) above. Ans: d 100. For a kinematic chain to be considered as mechanism (a) two links should be fixed (b) one link should be fixed (c) none of the links should be fixed (d) there is no such criterion (e) none of the above. Ans: b 101. An eccentric sheave pivoted at one point rotates and transmits oscillatory motion to a link whose one end is pivoted and other end is connected to it. This mechanism has (a) 2 links (b) 3 links (c) 4 links (d) 5 links (e) none of the above. Ans: c 102. Whitworth quick return mechanism is obtained by inversion of (a) slider crank mechanism (b) kinematic chain (c) five link mechanism (d) roller cam mechanism (e) none of the above. Ans: a 103. In its simplest form, a cam mechanism consists of following number of links (a) 1 (b) 2 (c) 3 (d) 4 (e) none. Ans: c 104. Which of the following mechanisms produces mathematically an exact straight line motion (a) Grasshopper mechanism (b) Watt mechanism (c) Peaucellier's mechanism (d) Tchabichiff mechanism (e) Ackermann mechanism. Ans: c 105. In a mechanism, usually one link is fixed. If the fixed link is changed in a kinematic chain, then relative motion of other links (a) will remain same (b) will change (c) could change or remain unaltered depending oh which link is fixed (d) will not occur (e) none of the above. Ans: a 106. A kinematic chain requires at least (a) 2 links and 3 turning pairs (b) 3 links and 4 turning pairs (c) 4 links and 4 turning pairs (d) 5 links and 4 turning pairs (e) none of the above. Ans: c 107. In a darg link quick return mechanism, the shortest link is always fixed. The sum of the shortest and longest link is (a) equal to sum of other two (b) greater than sum of other two (c) less than sum of other two (d) there is no such relationship (e) none of the above. Ans: c 108. The following is the inversion of slider crank chain mechanism (a) Whitworth quick return mechanism (b) hand pump (c) oscillating cylinder engine (d) all of the above (e) none of the above. Ans: d 109. Kinematic pairs are those which have (a) two elements held together mechani-cally (b) two elements having relative motion (c) two elements having Coroili's com-ponent (d) minimum of two instantaneous centres (e) all of the above. Ans: b 110 A typewriter mechanism has 7 number of binary joints, six links and none of higher pairs. The mechanism is (a) kinematically sound (b) not sound (c) soundness would depend upon which link is kept fixed (d) data is not sufficient to determine same (e) none of the above. Ans: a 111. In a four-bar chain it is required to give an oscillatory motion to the follower for a continuous rotation of the crank. For the lengths of 50 mm of crank and 70 mm of the follower, determine theoretical maximum length of coupler. The distance between fixed pivots of crank and followers is (a) 95 mm (b) slightly less than 95 mm (c) slightly more than 95 mm (d) 45 mm (e) none of the above. Ans: b 112. In above example, the minimum length of the coupler will be (a) 45 mm (b) slightly less than 45 mm (c) slightly more than 45 mm (d) 95 mm (e) none of the above. Ans: c 113. In S.H.M., acceleration is proportional to (a) velocity (b) displacement (c) rate of change of velocity (d) all of the above (e) none of the above. Ans: b 114. For simple harmonic motion of the of follower, a cosine curve represents (a) displacement diagram (b) velocity diagram (c) acceleration diagram (d) all of the above (e) none of the above. Ans: c 115. In S.H.M., the velocity vector w.r.t. displacement vector (a) leads by 90° (b) lags by 90° (c) leads by 180° (d) are in phase (e) could be anywhere. Ans: a 116. A body having moment of inertia o:m2 is rotating at 210 RPM and r with another body at rest having I 40 kg m2. The resultant speed after ing will be (a) 90 RPM (b) 100 RPM (c) 80 RPM (d) data are insufficient (e) none of the above. Ans: a 117. Inertia force acts (a) perpendicular to the accelRead the full article

How-to Convert a Mopar A-Body to Front Disc Brakes

We ditch drums for a front disc brake kit that’ll work with small-bolt pattern 14-inch Rallye wheels on your pre-’73 A-Body.

In our continuing saga to build a daily driver ’66 Slant Six Dart GT, it was time to ditch the drums for front disc brakes. The small 9-inch drums had to go. While they worked perfectly without pulling, they were barely adequate for 1966 traffic, let alone the insanity of 2019. Late-model vehicles have a big braking advantage over our outdated, drum brake–equipped classic Mopars.

Most of today’s vehicles brake so well, the drivers think nothing of pulling out in front of you, making sudden stops, or other inconsiderate moves. An old drum brake Mopar can’t safely stop in time with their abrupt braking habits and shorter braking distances. That’s why in previous episodes we’ve been modernizing the Dart — most recently with a Borgeson quick-ratio power steering system for more responsive, no-slop steering. Suspension mods from PST improved handling, road-holding ability. And engine bolt-ons (TTI 2 1/2-inch exhaust, Holley 2bbl) aided acceleration to safely merge onto the highway. In this installment, we’re focusing on deceleration.

For surer, safer braking with reduced stopping distances, a front disc brake upgrade will provide no-fade braking in back-to-back panic stops at highway speeds. Past testing has proven this. Using our ’67 Coronet R/T test mule with stock 11-inch drums versus 11-inch front disc brakes has produced these results in back-to-back 60-to-0-mph panic stops. The drums showed us a best 60-to-0 stop of 168 feet (cold), with backup stops (hot) fading to a frightening 230 feet achieved on our third stop test. The front discs showed us a repeatable 140 to 142 feet without any signs of brake fade in three back-to-back 60-to-0 panic stops. This was achieved after we adjusted the rear proportioning valve for no rear brake lockup. As on our ’67 R/T, we’ll opt for slotted/drilled rotors with an adjustable prop valve for the Dart’s front disc conversion. It’s a proven, safer combination than drum brakes.

When we began searching, we noticed there’s many different front disc brake conversion kits available for the pre-’73 A-Body, but most require you move up to the bigger 4.5-inch bolt pattern that the B-, C-, and E-Body cars utilize. We see so many A-Bodies (like ours) sporting the popular small-bolt pattern (4.0-inch) Rallye wheels, so we wanted to find a front disc brake kit that didn’t require changing the spindles, ball joints, and upper control arms, while allowing you to keep the 4.0-inch bolt pattern wheels. We didn’t want or need to change all those aforementioned components. Recently, we rebuilt and beefed up the front end with select PST components and didn’t care to do it all over again.

Since our ’66 Dart is equipped with 9-inch drum brake spindles, it made the search even harder than if we had 10-inch drum brake spindles, like many later A-Bodies. After a lot of looking, we found Classic Industries offered just the front disc upgrade kit we needed. And yes, we could retain our small-bolt pattern 14-inch Rallye wheels and not need to change out the spindles, ball joints, and upper control arms.

OK, smart A-Body folks know we could’ve found a used 1965-1972 Kelsey Hayes four-piston disc setup, complete with its disc brake spindles. But that used parts setup would’ve required new or rebuilt calipers, rotors, hoses, and other related parts. This complete front disc kit includes everything needed with all-new parts and hardware. It features new single-piston calipers for less pedal effort. Available with a power brake option, we elected to go the manual disc/drum master cylinder route. We felt the bracket that holds the power booster and master cylinder setup would take up too much room. It appears the bracket would move the booster and master too close to the Slant’s carb and air cleaner and not look right in our early A-Body’s tight engine compartment, though we didn’t measure fitment to know for sure.

On a pre-’67 Mopar like ours, the single-line master cylinder has to be replaced with a dual-line disc/drum-type master cylinder. Also required for the dual-line master conversion is brake lines, a distribution block, and an adjustable proportioning valve to eliminate rear brake lockup. For safety’s sake, it would also be a good idea to replace the 50-something-year-old brake lines. Don’t forget, if you have a ’67-up dual-line four-wheel drum master, replace it with a disc/drum type master cylinder. For our front disc conversion, we looked to Inline Tube for the disc/drum master, dual master conversion and front brake lines, adjustable prop valve and distribution block.

Safety is of the utmost importance by having all-new braking components. Detailing the area surrounding those new parts will add more eye appeal and protection for your classic Mopar. We used Eastwood restoration paints for that long-lasting, cool clean look. Personally, I needed to coat-over the gaudy, gold-colored calipers with Eastwood’s Hi-Temp Black Caliper and the bare-steel caliper brackets with the tough 2K Chassis Black paint. The firewall area near the master cylinder, front framerails, and wheelwells also received the Eastwood treatment. Hey, the parts and background of the pictures in this article need to look good too.

In future installments, we plan to add even more go to the sluggish Slant Six. These engines need to live up to their nickname, “The Leaning Tower of Power.” A cam swap and porting the head could give the slanted engine another 50 hp to the wheels. A testdrive and break-in of our new front disc brakes wasn’t possible due to the ice, snow, and salt covering the streets here in the Northeast, but after that goes away, we’ll have no fear of driving our old Mopar into the back of a new car that jams on the brakes.

Safer braking with shorter stopping distances without fade is achieved from disc brakes. This front disc brake kit (PB40011, $999.99) from Classic Industries will allow us to retain our small-bolt pattern 14-inch Rallye wheels, 9-inch drum spindles, ball joints, and upper control arms. We opted for cross-drilled/slotted rotors to reduce heat buildup on the pads and rotors, lessening the possibility of brake fade.

Even though these 9-inch drum brakes had quality semimetallic shoes, newer wheel cylinders and hoses, plus they functioned well without pulling, they’re still no match for disc brakes. Drum brakes exhibit fade when hot and aren’t safe and sufficient in today’s world of repetitive, stop-and-go traffic, along with those sudden last-second stoppers.

We found the instructions included in the kit to be somewhat incomplete. There are unmentioned details and tasks that’ll need to be done. Follow along with us, as we took many pictures to make the job easier to do. Seen here, from the right front (R/F), passenger side, the complete drum brake assembly is removed. The spindle and its shaft was cleaned up and readied for the kit installation and aesthetics.

We elected to coat the bare metal caliper brackets with Eastwood’s 2K Chassis Black (14146Z, $24.99). This tough, durable ceramic paint has been holding up for years on other projects we’ve used it on. We’re confident these caliper brackets will look good and be rust-free in our upcoming retirement years.

The stock spindle bolts cannot be reused. Here’s the included spindle-to-caliper bracket bolts and washers needed to mount the caliper bracket.

Notice the bracket position is to front-mount the caliper. First, put the caliper bracket in position with the two 7/16-inch bolts and place the two 7/16-inch spacers on the top mounting holes between the bracket and the spindle. Next, install the two 1/2-inch bolts for the bottom mounting holes. Place the two 1/2-inch spacers between the mounting bracket and the spindle for the bottom 1/2-inch holes. All four spindle-to-caliper bracket nuts and bolts received 70 lb-ft of torque. Here, the important spindle to inner bearing spacer is put in its place. The bearing spacer placement isn’t mentioned in the instructions!

The wheel bearings need to be packed with a high-temp, high-quality bearing grease. We use to “hand pack,” but this time we used the “bearing packer” seen here. Either way, be sure the grease goes through from the bottom and coming out of the top of the bearing.

After installing the inner bearing and grease seal, mount the rotor onto the spindle. Install the outer bearing until it seats on the spindle shaft and bearing race. We put the spindle/bearing washer in place followed by the castle nut to hand-tight. Next, the hub/rotor assembly was rotated forward and reverse a bunch of times before and after applying roughly 15 to 20 lb-ft of torque. We backed off the nut until hand-tight and again rotated the rotor a few more times. Finally, we torqued the castle nut to only 7 to 10 lb-ft, installed the cotter pin, and tapped on the dust cap with a rubber mallet.

We tried to mount the caliper onto the caliper bracket with the supplied caliper bolts to no avail. The caliper needed to be clearance grinded in the pointed-out area to clear the spindle. This might be an early A-Body issue due to spindle design. Roughly an 1/8 inch was grinded from the caliper for enough caliper-to-spindle clearance fitment and function.

The shiny spot on the spindle near the upper-caliper bracket bolt is where we clearance-grinded roughly .100 inch for extra insurance. We checked to be sure the caliper could float side to side on its slider pins with sufficient clearance. Here you can see where the spacers should be installed between the caliper bracket and spindle.

Look closely, after grinding and fitment checks, there’s roughly an 1/8 inch of clearance for the floating caliper to function properly. Notice the R in the caliper for the right side. Be sure the bleeder screw is pointing upward.

The left image is before, and the right is after clearance-grinding the two raised bosses on the calipers for sufficient clearance (1/8 inch) of the rotor hat/hub area.

After all the caliper grinding, we needed to add another coat of Eastwood’s High Temp Ceramic Caliper Paint (11839ZA, $18.97). It’s a super-durable paint that has proven itself to last and look good for years. This can of paint has already coated three pairs of calipers with enough left for another pair.

Once we got passed the clearance grinding, we feel this is a well-designed front disc brake conversion kit. We prefer the look of black calipers over the gold color they were painted.

From Inline Tube, we ordered these pre-bent OEM-type reproduction front brake lines (MFG73490A, R/F: MFG73490B L/F: call for price). The 50-something-year-old, rusty originals were in dire need of replacement. Now we’ll have no-fear of a blown brake line.

We routed the included brake line hose so it couldn’t rub against anything during suspension travel or full steering to the left and right. The Inline Tube, R/F steel brake line features OEM looks and bends, plus it’s a nice fit without leaks. We coated the framerail and fenderwell with leftover Eastwood Chassis Black for improved looks and protection.

A single line master cylinder doesn’t produce enough brake fluid pressure for disc brake calipers to function properly. The Dart’s original, leaky master cylinder contaminated and crinkled the paint around and below the master cylinder. The master seen here replaced the leaky original a few years ago.

The brake fluid contaminated area was taken down to bare metal. We wiped the area clean with Eastwood’s Pre about five times to ensure there wasn’t any residual brake fluid. Compressed air was used to blow dry the area. With a foam brush, we first spotted-in Eastwood Rust Encapsulator followed up with the leftover Gloss Black Caliper Paint

We ordered this four-bolt 1971- to 1974-style disc/drum brake master (MMC500, $75) from Inline Tube. It will bolt right in place of the stock single-line, drum brake master cylinder. The larger reservoir is for the disc brake calipers that require more fluid volume and pressure (over 1,000 psi) than drum brake wheel cylinders (400 psi).

Also necessary for the dual master to front disc conversion is this slew of parts also sourced from Inline Tube. Distribution block (BLK243, $35), adjustable proportioning valve (ADJP 01, $39) and dual master conversion lines (MFG70143A, MFG70143B, call for price)

The new master was coated with Eastwood’s Brake Gray (11756Z, $19.97) to protect the bare cast iron from rusting quickly. We haven’t used it before, but Eastwood says it’s a durable, heavy-duty coating that resists brake fluid and up to 400 degrees F temperatures. It looks great too.

An adjustable proportioning valve is an absolute necessity to prevent rear brake lockup on panic stops. By adjusting the prop valve, we’ve seen 60-to-0-mph stops reduced 10feet by eliminating rear brake lockup. By turning the knob, you’re simply adjusting brake line pressure to the wheel cylinders and brake shoes to stop the lockup tire skidding.

First, compressed air was blown through all the access holes in the L/F framerail numerous times to rid it of loose rust. After no loose rust was coming out of the access holes, we sprayed Eastwood Internal Frame Coating (15275Z, $21.99) inside the framerail. Notice the position of the prop valve adjusting knob for easy access adjustments.

The new Inline Tube brake lines to distribution block were finger-tightened into position before installing the master cylinder. We think our spot-in job at the firewall looks good enough for our future frequent driver in our upcoming retirement years. The gasket for the master was in stock at our home garage.

The original brake pedal rod was swapped over to the new master. We coated the rod’s eyelet and the bolt with bearing grease for long-term, smooth brake pedal action.

To lengthen the brake line going from the master to the prop valve, we removed the loop. After tightening the lines, we added fluid and bled the brakes manually with help from my wife. We checked for leaks and tested the system at each wheel. The pedal feels OK for now, but the snow-covered streets prevented us from a testdrive.

The nice thing about this kit is there’s plenty of clearance to run the small-bolt pattern 14×5.5 Rallye wheels. Peeking through the slots, you can notice the drilled and slotted rotors rather than the humdrums.

The new braking system is another welcome addition to our ’66 Slant Six Dart GT. We’re another step closer to making it a more enjoyable and safer driver in today’s stop-and-go traffic. For our next adventure, we’ll add more go to “The Leaning Tower of Power” with a cam swap and porting the head.

Here’s a few of the previous adventures updating our outdated ’66 Slant 6 Dart GT:

Borgeson Quick Ratio Power Steering 1-Barrel To A 2-Barrel Holley On A Slant 6 TTI Exhaust And Performance Distributors Electronic Ignition For A Slant 6

The post How-to Convert a Mopar A-Body to Front Disc Brakes appeared first on Hot Rod Network.

from Hot Rod Network https://www.hotrod.com/articles/convert-mopar-body-front-disc-brakes/ via IFTTT