1. An open belt drive connects a 450 mm driving pulley to another driven pulley 1000 mm in diameter. The belt is 300 mm wide and 10 mm thick. The coefficient of friction of the belt is 0.30 and the mass of the belt is 2.8 kg per meter belt length. Other data are as follows:
Center distance between shafts = 4 meters
Maximum allowable tensile stress of the belt = 1500 kpa Speed of driving pulley = 900 rpm
Determine:
1. The belt density in lb/in3 Answer: C A. 0.014
B. 0.024 C. 0.034 D. 0.044
2. The belt speed in ft/sec Answer: D
A. 63.34 B. 65.03 C. 67.37 D. 69.57
3. The angle of contact, rad Answer: A
A. 3 rad B. 4 rad C. 5 rad D. 6 rad
4. The power transmitted, kw Answer: B
A. 37.45 B. 40.80 C. 43.24 D. 48.34
5. The load at tight side Answer: A
A. 1011.47 lbs B. 1111.47 lbs C. 1211.47 lbs D. 1311.47 lbs 6. The load at slack side Answer: C
A. 559 lbs B. 569 lbs C. 579 lbs D. 589 lbs
2. A solid transmission shaft is 3.5 inches in diameter. It is desired to replace it with a hollow shaft of the same material and same torsional strength but its weight should only be half as much as the solid shaft. Find:
1. The outside diameter of the shaft Answer: A
A. 4.23 in B. 5.34 in C. 7.38 in D. 9.30 in
2. The inside diameter of the shaft Answer: C
A. 1.92 in B. 2.56 in C. 3.42 in D. 4.03 in
3. The volume of the hollow shaft per foot length Answer: B
A. 53.23 in3 B. 57.74 in3 C. 60.30 in3 D. 63.48 in3
4. The shearing stress of hollow shaft if it used to transmit 150 kw at 6000 rpm, Mpa
Answer: D
A. 12.84 B. 14.56 C. 16.23 D. 17.63
3. A double threaded right handed worm gear transmits 15 hp at 1150 rpm. The pitch of the worm is 0.75 inches and pitch diameter of 3 inches. The pressure angle is 14 ½° and the coefficient of friction is 0.12. Find:
1. The lead angle Answer: D
A. 1.63° B. 3.83° C. 7.23° D. 9.043°
2. The normal pressure angle Answer: C
A. 10.327° B. 12.327° C. 14.327° D. 16.327°
3. The worm gear efficiency Answer: A
A. 55.13% B. 50.23% C. 58.34% D. 60.34%
4. The power transmitted to gear (output) Answer: B
A. 6.39 hp B. 8.27 hp C. 10.27 hp D. 13.47 hp
5. The tangential force on gear Answer: B
A. 1,798 lbs B. 1,898 lbs C. 1,998 lbs D. 2,398 lbs
6. The tangential load on the worm Answer: A
A. 548 lbs B. 558 lbs
C. 568 lbs D. 578 lbs
7. The separating force Answer: C
A. 403 lbs B. 453 lbs C. 501 lbs D. 567 lbs
4. A band brake is installed on a drum rotating at 250 rpm, and a diameter of 900 mm. The angle of contact is 1.5π radians and one end of the brake band is fastened to a fixed pin while the other end to the brake arm 150 mm from fixed end pin. The coefficient of friction is 0.25 and the straight brake arm is 1000 mm long and is placed perpendicular to the diameter bisecting the angle of contact. Determine:
1. The torque transmitted Answer: D
A. 2.73 KN-m B. 3.92 KN-m C. 4.16 KN-m D. 1.91 KN-m
2. The tension at the slack side of the brake drum Answer: A
A. 1.89 KN B. 2.63 KN C. 3.28 KN D. 4.93 KN
3. The tension at the tight side of the brake drum Answer: B
A. 5.33 KN B. 6.14 KN C. 7.83 KN D. 8.28 KN
4. The minimum force in Newtons applied at the end of the brake arm necessary to stop the drum if 50 kw is being absorbed Answer: D
A. 125 N B. 150 N C. 175 N D. 200 N
5. A steel band with maximum tensile stress of 55 Mpa and 3.0 mm thick will be used. What should be its width in millimeters? Answer: A
A. 37 mm B. 39 mm C. 41 mm
D. 43 mm
5. A helical compression spring has scale of 400 lbs/inch, an inside diameter of 2.5 inches, a free length of 8 inches and with squared and ground ends. Material is to be chrome vanadium steel with working stress of 63,000 psi and G = 10,800,000 psi. For a load of 825 lbs, and for an average service, Whall factor, k = 1.25. Determine:
1. The standard size wire diameter Answer: B
A. ¼ in B. ½ in C. ¾ in D. 1 ¼ in 2. The spring index Answer: A
A. 6 B. 7 C. 8 D. 9
3. Number of active coils Answer: D
A. 8.23 B. 11.23 C. 5.34 D. 7.81
4. The solid height Answer: C
A. 2.83 in B. 3.26 in C. 4.91 in D. 6.34 in
5. The stress at solid height Answer: A
A. 94,546 psi B. 95,735 psi C. 96,735 psi D. 97,735 psi
6. A 2 ½ inches double square thread with two threads/inch is to be used. The frictional radius of the collar is 2 inches and the coefficient of friction are 0.10 for the threads and 0.15 for the collar. The velocity of the nut is 10 ft/min. For a lifting load of 4000 lbs, find:
1. The lead angle Answer: D
A. 5.23° B. 6.27° C. 7.94° D. 8.05°
2. The torque required to turn the screw Answer: A
A. 1102.35 in-lbs B. 1293.65 in-lbs C. 1493.65 in-lbs D. 1693.65 in-lbs
3. The torque required to overcome collar friction Answer: B
A. 1000 in-lbs B. 1200 in-lbs C. 1400 in-lbs D. 1600 in-lbs
4. The efficiency of the screw Answer: C
A. 25.58% B. 26.58% C. 27.65% D. 28.58%
5. The power input of the screw Answer: B
A. 1.37 hp B. 4.38 hp C. 7.37 hp D. 9.37 hp
7. A 16 mm plate is lapped over and secured by fillet weld on the inside and outside to form a penstock 1.5 m diameter. An allowable stress of 140 Mpa on the plate and an allowable shearing stress of 90 Mpa on the throat side of the 14 mm fillet weld. Determine:
1. The internal pressure that can be carried by the plate Answer: A
A. 3 Mpa B. 5 Mpa C. 7 Mpa D. 9 Mpa
2. The internal pressure that can be carried by the welded joint Answer: B
A. 1.38 Mpa B. 2.38 Mpa C. 3.38 Mpa D. 4.38 Mpa
3. The thickness of the plate if the internal pressure is 2 Mpa (neglecting welded joint)
Answer: A
A. 16.67 mm B. 18.67 mm C. 14.67 mm D. 12.67 mm
4. The thickness of the plate if the internal pressure is 20 Mpa (neglecting welded joint)
Answer: D
A. 130.17 mm B. 160.17 mm C. 170.17 mm D. 190.17 mm
5. Factor of safety of the plate if ultimate stress is 450 Mpa Answer: C
A. 3 B. 4 C. 5 D. 6
8. A safety valve spring having 9-1/2 coils has the ends squared and ground. The outside diameter is 115 mm and wire diameter is 13 mm. It has a free length of 203 mm. The spring must be initially compressed to hold the boiler pressure of 1.38 Mpa on the valve seat of 32 mm diameter. Modulus of rigidity is taken as G = 80 Gpa. Determine:
1. The force acting on the spring Answer: B
A. 0.811 KN B. 1.11 KN C. 1.45 KN D. 1.87 KN 2. The spring index Answer: B
A. 6.85 B. 7.85 C. 8.85 D. 9.85
3. The coil deflection Answer: A
A. 31 mm B. 33 mm C. 35 mm D. 45 mm
4. The compressed length of the spring Answer: D
A. 142 mm B. 152 mm C. 162 mm D. 172 mm
5. The spring stress if it is compressed to its solid length Answer: C
A. 360 Mpa B. 380 Mpa C. 400 Mpa D. 420 Mpa
9. The large diameter and face of the disk of a multiple disk clutch are 255 mm and 25 mm respectively. The helical compression spring used to engaged the clutch has 9-1/2 efeective coils of 10 mm steel wire. The outer coil diameter is 80 mm. the free length of the spring is 185 mm. When in place with clutch engaged, its length is 130 mm. Assuming that there are 10 pairs of friction surface in contact, that the motor runs at 1200 rpm, with coefficient of friction on contatct surface f = 0.15, ( G = 80 Gpa), determine:
1. The axial force available for the clutch Answer: A
A. 1.69 KN B. 2.69 KN C. 3.69 KN D. 4.69 KN
2. The mean frictional radius Answer: C
A. 125.45 mm B. 145.45 mm C. 115.45 mm D. 155.45 mm 3. The torque transmitted Answer: B
A. 0.192 KN-m B. 0.292 KN-m C. 0.392 KN-m D. 0.492 KN-m
4. The power that the clutch can transmit Answer: D
A. 30.69 Kw B. 32.69 Kw C. 34.69 Kw D. 36.69 Kw
10. An electric motor running at 1200 rpm drives a punch press shaft at 200 rpm by means of a 130 mm wide and 8 mm thick belt. When the clutch is engaged the belt slips. To correct this condition, an idler pulley was installed to increase the angle of contact but the same belt and pulley were used. The original contact angle on the 200 mm motor pulley is 160 degrees. The original tension ratio is 2.4 and the net tension is 12 N/mm of the belt width. If an increase in transmission capacity of 20% will prevent slippage, determine:
1. The coefficient of friction Answer: A
A. 0.313 B. 0.413 C. 0.513 D. 0.613
2. The tension at the tight side in the original installation Answer: B
A. 2.37 KN B. 2.67 KN C. 2.97 KN D. 3.67 KN
3. The tension at the slack side in the original installation Answer: D
A. 2.22 KN B. 3.33 KN C. 4.44 KN D. 1.11 KN
4. The tension at the slack side when the idler was installed Answer: C
A. 0.452 KN B. 0.653 KN C. 0.802 KN D. 1.290 KN
5. The new angle of contact Answer: B
A. 210° B. 220° C. 230° D. 240°
11. A four wheel vehicle must developed a draw bar pull of 17,500 lbs. The engine, which develops 500 hp and drives through a gear transmission a 34-tooth spiral bevel pinion gear which meshes with a spiral bevel gear having 51 teeth. Determine:
1. The speed of the wheels Answer: B
A. 55 rpm B. 60 rpm C. 65 rpm D. 70 rpm 2. The speed of shaft Answer: C
A. 80 rpm B. 85 rpm C. 90 rpm D. 95 rpm
3. The transmission gear ratio should be used if the engine develops maximum torque at 1500 rpm Answer: D
A. 12.67 : 1 B. 13.67 : 1 C. 14.67 : 1 D. 16.67 : 1
4. The torque required per wheel, in-lbs Answer: A
A. 210,000 B. 220,000 C. 230,000 D. 240,000
5. The axial diameter for an allowable torsional stress at 12,000 psi, the efficiency of the bevel gear differential is 80% Answer: A
A. 4 ½ in B. 1 ½ in C. 2 ½ in D. 3 ½ in
12. The smaller of two concentric helical springs is made of 22 mm diameter steel spring and has an outside diameter of 100 mm with 10 active coils. The outer spring is made of 32 mm steel spring and has an outer diameter of 250 mm with 8 active coils. Before the load is applied, the outer spring is 25 mm longer than the inner spring. If the load of 90 KN is applied to the nest of the springs. (G = 80 Gpa).
1. Find the spring rate of the inner spring Answer: A
A. 493.80 KN/m B. 593.80 KN/m C. 693.80 KN/m D. 793.80 KN/m
2. Find the spring rate of outer spring Answer: A
A. 126.50 KN/m B. 136.50 KN/m C. 146.50 KN/m D. 156.50 KN/m
3. Find the load carried by the inner spring Answer: C
A. 49.13 KN B. 59.13 KN C. 69.13 KN D. 79.13 KN
4. Find the load carried by the outer spring Answer: B
A. 10.87 KN B. 20.87 KN C. 30.87 KN D. 40.87 KN
5. Find the percentage load carried by the inner spring Answer: D
A. 70.81% B. 72.81% C. 74.81% D. 76.81%
13. A flange coupling connects two 2” diameter shafts. The flanges are fitted with 6 bolts of SAE 1040 steel on a 7” bolt circle. The shafts runs at 300 rpm and transmits 45 hp. Assume a factor of safety of 5, ultimate tension of 70,000 psi, and ultimate shear of 55,000 psi. Determine:
1. The torque transmitted Answer: B
A. 8,453.80 in-lbs B. 9,453.80 in-lbs C. 10,453.80 in-lbs D. 11,453.80 in-lbs 2. The force applied per bolt Answer: C
A. 451.17 lbs B. 430.17 lbs C. 450.17 lbs D. 470.17 lbs
3. The diameter of the bolt required Answer: A
A. 0.228 in B. 0.328 in C. 0.428 in D. 0.528 in
4. The thickness of flanged to be used Answer: A
A. 0.141 in B. 0.241 in C. 0.341 in D. 0.541 in
14. A simple band brake has a 76 cm drum and fitted with steel band 2/5 cm thick lined with a brake lining having a coefficient of friction of 0.25. The arc of contact is 245°. The drum is attached to a 60 cm hoisting drum that sustains a rope load of 820 kg. The operating force has a moment arm of 1.50 m and the band is attached 12 cm from the pivot point. Find:
1. The torque just required to support the load (clockwise) Answer: C
A. 2,013.26 N-m B. 2,213.26 N-m
C. 2,413.26 N-m D. 2,613.26 N-m
2. The tension at the slack side of the brake Answer: A
A. 3321.50 N B. 3421.50 N C. 3521.50 N D. 3621.50 N
3. The operating force at the end of brake arm Answer: A
A. 773.80 N B. 775.80 N C. 777.80 N D. 779.80 N
4. The width of a steel band for a tensile stress of 50 Mpa Answer: D
A. 40.40 mm B. 44.40 mm C. 46.40 mm D. 48.40 mm
15. A mechanical press is used to punch 6 holes per minute on a 25 mm thick plate. The hole is 25 mm in diameter and the plate and has an ultimate strength in shear of 420 Mpa. The normal operating speed is 200 rpm and it slows down to 180 rpm during the process of punching. The flywheel has a mean diameter of one meter and the rim width is 3 times the thickness. Assume that the hub and arm account for 5% of the rim weight concentrated at the mean diameter and density of cast iron is 7,200 kg per cubic meter. Find:
1. The maximum force required to punched a hole Answer: B
A. 804.67 KN B. 824.67 KN C. 844.67 KN D. 864.67 KN
2. The power required to drive the press Answer: B
A. 0.833 kw B. 1.031 kw C. 1.56 kw D. 2.13 kw
3. The flywheel weight Answer: D
A. 3.23 KN B. 5.39 KN C. 7.38 KN D. 9.71 KN
4. The thickness of the rim Answer: A
A. 118 mm B. 130 mm C. 162 mm D. 184 mm
5. The width of the rim Answer: D
A. 324 mm B. 334 mm C. 344 mm D. 354 mm
16. A flange coupling is to connect two 57 mm shafts. The hubs of the coupling are each 111 mm in diameter and 92 mm thick and the flange web are 19 mm thick. Six 16 mm bolts in a 165 mm diameter circle connect the flanges. The keyway is 6 mm shorter than the hub’s thickness and the key is 14 mm x 14 mm. Coupling is to transmit 45 kw at 160 rpm. For all parts, yield point value in shear is one-half the yield value which is 448 Mpa. Find the following:
1. The force on the shaft Answer: A
A. 94.25 KN B. 90.23 KN C. 86.34 KN D. 80.34 KN
2. The factor of safety in the shear key Answer: B
A. 1.83 B. 2.86 C. 3.48 D. 5.34
3. The factor of safety in bearing key Answer: D
A. 5.34 B. 4.23 C. 3.20 D. 2.86
4. The force applied per bolt coupling Answer: A
A. 5.43 KN B. 6.94 KN C. 7.39 KN D. 8.39 KN
5. The factor of safety in shear of bolts Answer: C
A. 6.39 B. 7.39 C. 8.30 D. 9.30
17. A hydraulic control for a straight motion utilizes a spherical pressure tank “A” that is connected to a work cylinder “B”. “A” maintains pressure in the tank at 4000 psi.
1. The tank is 32 inches in diameter, welded with 100% joint efficiency and made of steel plates with an allowable tensile strength of 7,500 psi. Calculate the required thickness of the tank. Answer: B
A. 0.23 in B. 0.43 in C. 0.54 in D. 0.65 in
2. The pressure drop between tank and the cylinder is 30 psi. Assume allowance for friction in the cylinder and packing to be 10 percent of F, the operating force. Calculate the diameter of the piston if value of F is 5000 lbs. Answer: D
A. 1.27 in B. 2.39 in C. 3.29 in D. 4.35 in
3. Determine the wall thickness of work cylinder B if it is made of cast iron having an allowable tensile stress of 2,000 psi. Answer: A
A. 0.488 in B. 0.560 in C. 0.653 in D. 0.837 in
4. The piston stroke of the work cylinder is 18 inches; the time of a work stroke is 5 seconds. Calculate the horsepower output of the cylinder. Answer: C
A. 1.29 hp B. 4.23 hp C. 2.73 hp D. 5.34 hp
5. Assume that the work cycle of the piston rod occurs every 30 seconds, that the overall efficiency of the hydraulic control is 80 percent, and the pump efficiency is 60 percent, determine the horsepower of the motor continuously operating the slump. Answer: C
A. 0.25 hp B. 5.34 hp C. 0.95 hp D. 1.27 hp
18. Consider a 304.8 mm section of a single-riveted lap joint made up with plates of 6.35 mm thickness and 6 rivets, 15.87 mm in diameter. Assume that the rivet holes are 1.58 mm larger in diameter than the rivets. In this joint, the entire load is transmitted from one plate to the other by means of rivets. Each plate and the six rivets carries the entire load. Design stress for shear is 598 kg/cm2, for bearing, 1406 kg/cm2, and for tension, 703 kg/cm2. Assume that the rivets will not tear or shear through the plate to the edge of the joints. Find:
1. The force that can be carried by unpunched plate Answer: A
A. 13,606.40 kg B. 16,606.40 kg C. 17,606.40 kg D. 19,606.40 kg
2. The force to cause tensile stress on plate between rivets Answer: C
A. 6,394.56 kg B. 7,083.09 kg C. 8,932.6 kg D. 9,099.45 kg
3. The force to cause shearing stress on rivets Answer: B
A. 7,580.90 kg B. 8,580.90 kg C. 9,580.90 kg D. 10,580.90 kg
4. The force to cause bearing stress on rivets Answer: A
A. 9,347.70 kg B. 10,347.70 kg C. 11,347.70 kg D. 12,347.70 kg 5. The efficiency Answer: B
B. 63.06% C. 60.45% D. 76.34%
19. A 76 mm solid shaft is to be replaced with a hollow shaft of equal torsional strength. The outside diameter of the hollow shaft is 100 mm.
1. The inside diameter of hollow shaft Answer: A
A. 86.55 mm B. 88.34 mm C. 90.28 mm D. 92.34 mm
2. The percentage of weight saved Answer: C
A. 50.34% B. 53.34% C. 56.56% D. 65.34%
20. The engine of a motor vehicle with a wheel diameter of 712 mm develops 50 kw at 2,000 rpm. The combined efficiency of the differential and transmission is 75% with an overall speed reduction of 25 is to 1. Determine:
1. Torque to be delivered by the clutch in N-m Answer: B
A. 224 N-m B. 239 N-m C. 245 N-m D. 265 N-m
2. Axial force on the clutch in KN. Outside and inside diameter of the clutch are 300 mm and 240 mm respectively. There are two pairs of mating surface with a coefficient of friction of 0.30. ( Use uniform wear method). Answer: B
A. 2.34 KN B. 2.95 KN C. 3.25 KN D. 4.39 KN 3. Torque on wheels Answer: D
A. 1.234 KN B. 2.56 KN C. 3.56 KN D. 4.476 KN
4. Draw bar pull developed in KN Answer: A
A. 12.57 KN B. 15.23 KN C. 17.30 KN D. 19.39 KN
5. Speed of travel of the vehicle in km/hr Answer: C
A. 5.34 km/hr B. 7.49 km/hr
C. 10.74 km/hr D. 12.03 km/hr
21. A single threaded trapezoidal metric thread has a pitch of 4 mm and a mean diameter of 18 mm. It is used as a translation screw in conjunction with a collar having an outside diameter of 37 mm and an inside diameter of 27 mm. The load is 400 kg and coefficient of friction is 0.3 for both threads and collar. Find:
1. The collar torque Answer: A
A. 1920 kg-mm B. 1763 kg-mm C. 1890 kg-mm D. 2003 kg-mm
2. The torque required for thread Answer: D
A. 1293 kg-mm B. 1192 kg-mm C. 1598 kg-mm D. 1401 kg-mm 3. The total torque Answer: C
A. 1083 kg-mm B. 2089 kg-mm C. 3321 kg-mm D. 4873 kg-mm
22. It is found that the shearing machine requires 205 joules of energy to shear a specific gauge of sheet metal. The mean diameter of the flywheel is to be 76.20 cm. The normal operating speed is 200 rpm, and slows down to 180 rpm during shearing process. The width is 30.48 cm, and the weight of cast iron is 7,196.60 kg/m3. The arms and hub account for 10% of the rim weight concentrated at mean diameter. Determine:
1. The rim weight Answer: A
A. 33.88 kg B. 35.23 kg C. 37.23 kg D. 39.45 kg
2. The thickness of the rim Answer: D
A. 0.145 cm B. 0.345 cm C. 0.764 cm D. 0.587 cm
23. A double reaction gear assembly is mounted on three parallel shafts located on the same horizontal plane. Shaft A is driven from a 2 kw source at 3,500 rpm. The pinion on shaft A has 24 teeth and meshes with a gear on shaft B. Another pinion on shaft B is in mesh with a gear on shaft C with 160 teeth. The centerline distance between shaft A and shaft C is 154 times the module. The overall gear train ratio is 14:1. Assume module for all gears are the same, determine:
1. The speed of shaft B Answer: A
A. 1000 rpm B. 1100 rpm C. 1200 rpm D. 1300 rpm
2. The number of teeth on gears at shaft B Answer: A
B. 84 & 50 teeth C. 84 & 60 teeth D. 84 & 70 teeth 3. The torque on shaft A Answer: C
A. 3.28 N-m B. 4.34 N-m C. 5.46 N-m D. 6.94 N-m
4. The torque on shaft B Answer: D
A. 10.23 N-m B. 13.45 N-m C. 16.39 N-m D. 18.14 N-m 5. The torque on shaft C Answer: B
A. 56.34 N-m B. 68.95 N-m C. 73.23 N-m D. 78.30 N-m
24. A key is to be desired for a 12.7 cm, shaft which will transmit power of 150 kw at 360 rpm. If allowable shear stress for the key is 920 kg/cm2 and the allowable compressive stress is 1200 kg/cm2, determine the following:
1. Cross-sectional dimensions of the flat key to be used Answer: B
A. 1.11 cm B. 2.22 cm C. 3.33 cm D. 4.44 cm
2. Force acting on a key Answer: A
A. 62.66 KN B. 64.34 KN C. 66.04 KN D. 68.34 KN
3. Length of key under shearing stress Answer: D
A. 7.34 cm B. 6.31 cm C. 4.23 cm D. 2.19 cm
4. Length of key under compressive stress Answer: C
A. 2.03 cm B. 3.49 cm C. 4.79 cm D. 5.34 cm
5. Safe length of key to be used Answer: B
A. 2.03 cm B. 4.79 cm C. 6.34 cm D. 8.03 cm
6. Axial force to remove the hub from the shaft if the coefficient of friction is 0.45 Answer: B A. 45.23 KN B. 56.40 KN C. 58.34 KN D. 65.45 KN
25. A pinion rotating at 1800 rpm and supported on each side by a ball bearing transmits 18 kw to a mating spur gear. If the pressure angle is 20 degrees and the pitch diameter is 102 mm, determine the following:
Note: Add 3 degrees to the pressure angle to compensate for the friction 1. Pitch line velocity Answer: B
A. 8.10 m/sec B. 9.61 m/sec C. 11.02 m/sec D. 13.03 m/sec
2. Torque transmitted by the pinion Answer: D
A. 65.34 N-m B. 75.23 N-m C. 87.23 N-m D. 95.49 N-m
3. Tangential load on gears Answer: C
A. 1,563 N B. 1,754 N C. 1,872 N D. 1,908 N
4. Separation load on gears Answer: A
A. 794.6 N B. 872.3 N C. 982.3 N D. 1,735.8 N 5. Total load on gears Answer: A
A. 2,034 N B. 3,034 N
C. 4,034 N D. 5,034 N
26. A dumb waiter designed to travel a height of 3 m when loaded will have a maximum gross weight of 100 kg. A coil spring is provided below to absorb shock in the event that the dumb waiter should fall freely because of sudden breakage of the wire rope carrying it. If the coil spring will be deflected to 30.48 cm, if the dumb waiter should accidentally fall and it hit the spring from its maximum height of travel, determine the following:
Note: Use spring index of 8 and assume maximum induce stress and shear modulus of elasticity to be 3868 kg/cm2 and 808,720 kg/cm2, respectively
1. Whaal factor Answer: D
A. 1.045 B. 1.863 C. 1.564 D. 1.184
2. Maximum force acting on spring Answer: B
A. 1872.34 kg B. 2168.50 kg C. 2235.40 kg D. 2634.66 kg 3. Wire diameter Answer: C
A. 1.20 cm B. 2.34 cm C. 3.68 cm D. 41.23 cm 4. Mean coil diameter Answer: A
A. 29.42 cm B. 34.23 cm C. 37.45 cm D. 41.23 cm
5. Number of active coils Answer: A
A. 10.20 B. 14.23 C. 16.34 D. 18.34
27. The maintenance shop of PAL has a motor operated hoisting which consists of the following mechanical parts: Motor shaft “A” is fitted with a double threaded left handed worm in mesh with 56 tooth worm wheel at shaft “B” directly below. Compounded on shaft “B” is a 20 tooth 5 module pinion in mesh with a spur gear keyed on shaft “C” with a horizontal center line distance of 150 mm. Mounted on the same shaft “C” is a 200 mm diameter hoisting drum. The cable wrap around the drum