I 2. (25 Marks) Size and select a 4 pillar motorized garage screw jack (with Acme thread profile) suitable to lift a 4 ton vehicle. Use a Factor of Safety of 4. Use Acme thread, o = 14.50 1 ton = 2000 lb. Limiting tensile and shear stresses are 12,000 psi and 5,550 psi, respectively. Determine a. Nominal major diameter of screw (D) b. Threads per Inch of selected thread (n) Thickness of the mating Nut d. Lead angle (1) e. Torque required to raise the vehicle (Tup) f. Torque required to lower the vehicle (Tdown) g. Efficiency of the screw h. RPM required to operate the system if we vehicle needs to be lifted at speed of 24 inches in one minute. i. Approximate Total Power required to operate the mechanism. j. Establish if the screw meets self-locking condition. C (List necessary assumptions, sketch acme thread profile and label it, write design equations and conclusions regarding selections made). Table: Preferred Acme screw threads (Shear stress area As is per inch of length engagement) (List necessary assumptions, sketch acme thread profile and label it, write design equations and conclusions regarding selections made). Table: Preferred Acme screw threads (Shear stress area As is per inch of length engagement) Nominal major Threads Pitch, Minimum minor Minimum pitch Tensile stress Shear stress diameter, D (in) per in, P.1/(in) diameter, D, (in) diameter, D. (in) area, A (in) area, A (in? 16 0.0625 0.1618 0.2043 0.026 32 0.3355 5/16 14 0.0714 0.2140 0.2614 0.044 38 0.4344 3/8 12 0.0833 0.2632 0.3161 0.065 89 0.5276 7/16 12 0.0833 0.3253 0.3783 0.097 20 0.6396 1/2 10 0.1000 0.3594 0.4306 0.1225 0.7278 5/8 8 0.1250 0,4570 0.5408 0.1955 0.9180 3/4 6 0.1667 0.5371 0.6424 0.2732 1.084 7/8 6 0.1667 0.6615 0.7663 0.4003 1.313 1 5 0.2000 0.7509 0.8726 0.5175 1.493 11 5 0.2000 0.8753 0.9967 0.6881 1.722 1) 5 0.2000 0.9998 1.1210 0.8831 1.952 0.2500 1.0719 1.2188 1.030 2.110 TABLE 17-1 Preferred Acme Screw Threads Threads per Inn Pitch, P = 1 (in) 0.2500 Minimum minor diameter, D, (in) Minimum pitch diameter, D, (in) Tensile stress area, A (in) 1.266 Shear stress area, A, Cin? 2.341 2.803 4 1.1965 1.3429 4 0.2500 1.4456 1.5916 1.811 4 3.262 Nominal major diameter, D in) i 12 2 21 2 2 3 3 4 0.2500 0.3333 3 1.6948 1.8572 2.1065 2.3558 2.454 2.982 3.802 3.610 3 0.3333 4.075 4.538 3 0.3333 4.711 1.8402 2.0450 2.2939 2.5427 2.7044 3.2026 3.2008 4.1991 2 5.181 4.757 7.388 2. 2 0.5000 0.5000 0.5000 0.5000 0.5000 2.4326 2.9314 3.4302 3.9291 4.4281 5.700 6.640 4 2 9.985 12.972 16,351 7.577 8.511 5 2 4.6973 Per inch of length of engagement I 2. (25 Marks) Size and select a 4 pillar motorized garage screw jack (with Acme thread profile) suitable to lift a 4 ton vehicle. Use a Factor of Safety of 4. Use Acme thread, o = 14.50 1 ton = 2000 lb. Limiting tensile and shear stresses are 12,000 psi and 5,550 psi, respectively. Determine a. Nominal major diameter of screw (D) b. Threads per Inch of selected thread (n) Thickness of the mating Nut d. Lead angle (1) e. Torque required to raise the vehicle (Tup) f. Torque required to lower the vehicle (Tdown) g. Efficiency of the screw h. RPM required to operate the system if we vehicle needs to be lifted at speed of 24 inches in one minute. i. Approximate Total Power required to operate the mechanism. j. Establish if the screw meets self-locking condition. C (List necessary assumptions, sketch acme thread profile and label it, write design equations and conclusions regarding selections made). Table: Preferred Acme screw threads (Shear stress area As is per inch of length engagement) (List necessary assumptions, sketch acme thread profile and label it, write design equations and conclusions regarding selections made). Table: Preferred Acme screw threads (Shear stress area As is per inch of length engagement) Nominal major Threads Pitch, Minimum minor Minimum pitch Tensile stress Shear stress diameter, D (in) per in, P.1/(in) diameter, D, (in) diameter, D. (in) area, A (in) area, A (in? 16 0.0625 0.1618 0.2043 0.026 32 0.3355 5/16 14 0.0714 0.2140 0.2614 0.044 38 0.4344 3/8 12 0.0833 0.2632 0.3161 0.065 89 0.5276 7/16 12 0.0833 0.3253 0.3783 0.097 20 0.6396 1/2 10 0.1000 0.3594 0.4306 0.1225 0.7278 5/8 8 0.1250 0,4570 0.5408 0.1955 0.9180 3/4 6 0.1667 0.5371 0.6424 0.2732 1.084 7/8 6 0.1667 0.6615 0.7663 0.4003 1.313 1 5 0.2000 0.7509 0.8726 0.5175 1.493 11 5 0.2000 0.8753 0.9967 0.6881 1.722 1) 5 0.2000 0.9998 1.1210 0.8831 1.952 0.2500 1.0719 1.2188 1.030 2.110 TABLE 17-1 Preferred Acme Screw Threads Threads per Inn Pitch, P = 1 (in) 0.2500 Minimum minor diameter, D, (in) Minimum pitch diameter, D, (in) Tensile stress area, A (in) 1.266 Shear stress area, A, Cin? 2.341 2.803 4 1.1965 1.3429 4 0.2500 1.4456 1.5916 1.811 4 3.262 Nominal major diameter, D in) i 12 2 21 2 2 3 3 4 0.2500 0.3333 3 1.6948 1.8572 2.1065 2.3558 2.454 2.982 3.802 3.610 3 0.3333 4.075 4.538 3 0.3333 4.711 1.8402 2.0450 2.2939 2.5427 2.7044 3.2026 3.2008 4.1991 2 5.181 4.757 7.388 2. 2 0.5000 0.5000 0.5000 0.5000 0.5000 2.4326 2.9314 3.4302 3.9291 4.4281 5.700 6.640 4 2 9.985 12.972 16,351 7.577 8.511 5 2 4.6973 Per inch of length of engagement