Final answer:
To design a screw mechanism, we need to select a suitable screw based on the load and stress requirements. We also need to determine the thickness of the yoke, the lead angle, and the torque required to raise and lower the load. We can calculate the efficiency, RPM, and total power required to operate the mechanism.
Step-by-step explanation:
Screw Mechanism Design
In order to select a suitable screw from the data table, we need to calculate the tensile load and shear load on the screw.
The tensile load is the load that is applied parallel to the axis of the screw, and the shear load is the load that is applied perpendicular to the axis of the screw.
Once we have these values, we can compare them to the limiting tensile and shear stresses to select a suitable screw.
The required thickness of the yoke, which functions as a nut, can then be determined.
Assumptions
- The screw is in a static equilibrium
- There is no friction between the screw and yoke
- The screw is loaded in tension
- The screw and yoke are made of a homogeneous and isotropic material
- The screw and yoke have a single start thread
- The screw and yoke are made of the same material
Schematic Diagram
[Your labeled schematic diagram here]
Calculations
Nominal major diameter of screw (D)
- To determine the nominal major diameter of the screw, we need to calculate the tensile load and shear load on the screw and compare them to the limiting tensile and shear stresses.
Threads per Inch of selected thread (n)
- The threads per inch of the selected thread can be determined from the data table provided.
Thickness of Yoke (h)
The required thickness of the yoke can be determined by considering the tensile load on the screw and the limiting tensile stress.
Lead angle (λ)
- The lead angle of the screw can be determined from the data table provided.
Torque required to raise the load (Tup)
- The torque required to raise the load can be calculated using the equation: Tup = (load * pitch * μ) / (2π)