You task is to design the shaft of a double pulley system and select suitable bearings and the dimensions of all relevant mechanical elements. You are required to choose relevant design parameters appropriately, using relevant formula. A schematic image is provided below for a single pulley system. You are to submit, as ONE pdf through Canvas containing the following three parts: – Your calculations, by hand on paper, no computer-generated calculations will be accepted (scans are preferred, photos will be acceptable – make sure the pictures are all clear and readable, as we cannot mark what we cannot read). Indicate the numbers of all tables, figures, etc. from the textbook you used to acquire values wherever applicable. – An engineering drawing of your final shaft design following AS1100 – by hand on paper, no computer-generated drawings will be accepted; choose a suitable scaling factor so that the shaft fits on an A4 or A3 sheet (depending on your preference); you must use a ruler, all measures need to be clearly readable; the thicknesses of lines as thick or thin need to be clearly discernible. No title block is required for the drawing. – A brief textual description of your engineering design rational (about half a page) – this must be typed with word or similar software tools. Here, you should concisely describe your design progress. You may use the following questions as guidelines: How did you start? What approach did you take? What decisions did you make and how did you select relevant parameters? What changes (if applicable) were necessary to these later? Please provide justifications and explain your reasoning.
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Swinburne University of Technology MEE30003 Faculty of Science, Engineering and Technology Machine Design Final Assessment Individual Submission, 30% of final mark Outline: You task is to design the shaft of a double pulley system and select suitable bearings and the dimensions of all relevant mechanical elements. You are required to choose relevant design parameters appropriately, using relevant formula. A schematic image is provided below for a single pulley system. You are to submit, as ONE pdf through Canvas containing the following three parts: – Your calculations, by hand on paper, no computer-generated calculations will be accepted (scans are preferred, photos will be acceptable – make sure the pictures are all clear and readable, as we cannot mark what we cannot read). Indicate the numbers of all tables, figures, etc. from the textbook you used to acquire values wherever applicable. – An engineering drawing of your final shaft design following AS1100 – by hand on paper, no computer-generated drawings will be accepted; choose a suitable scaling factor so that the shaft fits on an A4 or A3 sheet (depending on your preference); you must use a ruler, all measures need to be clearly readable; the thicknesses of lines as thick or thin need to be clearly discernible. No title block is required for the drawing. – A brief textual description of your engineering design rational (about half a page) – this must be typed with word or similar software tools. Here, you should concisely describe your design progress. You may use the following questions as guidelines: How did you start? What approach did you take? What decisions did you make and how did you select relevant parameters? What changes (if applicable) were necessary to these later? Please provide justifications and explain your reasoning. Task description and points distribution: You are to design the shaft and select suitable…
The Correct Answer and Explanation is :
To design the shaft of a double pulley system, we must focus on the key parameters that determine the shaft’s dimensions, material, and supporting elements like bearings. Here’s how to approach the task step by step:
1. Define the Loading Conditions:
- Load on the Pulley: Identify the forces acting on the pulley system, such as the load being lifted, frictional forces, and centrifugal forces due to rotation.
- Torque on the Shaft: Based on the pulley’s radius and the applied load, the torque (T) on the shaft can be calculated using the formula: [
T = F \times r
] where: - (F) is the force acting on the pulley (which can be calculated from the weight of the load),
- (r) is the radius of the pulley. For a double pulley system, consider the individual torques and their combined effect on the shaft.
2. Calculate Shaft Diameter:
- The shaft must be designed to withstand bending and torsional stresses. Using the following formula for torsional stress: [
\tau = \frac{T \cdot r}{J}
] where: - (T) is the torque,
- (r) is the radius of the shaft,
- (J) is the polar moment of inertia for the shaft ((J = \frac{\pi d^4}{32}) for a solid shaft, where (d) is the diameter of the shaft). You can solve for (d) once the torsional stress is determined. The allowable stress for the material will guide this calculation.
3. Select Suitable Bearings:
- Bearings must be selected based on the radial and axial loads they will experience. Common bearing types for shaft applications are ball bearings or roller bearings.
- Calculate the bearing load and consider the material properties and the lifespan of the bearings.
- Use the bearing manufacturer’s catalog or standard tables (like those in the textbook) to choose the right bearing size.
4. Material Selection:
- The shaft material should have sufficient strength to withstand the torsional and bending stresses. Steel alloys, such as SAE 1045 or 4140, are commonly used for shaft applications because of their good mechanical properties and availability.
5. Design the Shaft:
- Once you have calculated the required diameter and material, you can proceed with drafting the engineering drawing. Follow the AS1100 standards for dimensioning and scaling to ensure clarity in your drawing.
6. Engineering Rational:
In your report, describe your thought process, starting from identifying the loads and constraints to selecting materials and bearings. You should explain the reasoning behind the size of the shaft, bearing choice, and how you ensured that the system would operate safely under expected loads.
Example of Design Process:
- Start with load analysis to determine the forces acting on the pulley.
- Calculate the torque on the shaft from the applied load and pulley radius.
- Use torsional stress and deflection formulas to determine the shaft diameter and material.
- Select bearings based on the load and speed, using standard tables.
- Draw the shaft dimensions and components accurately on paper following AS1100.
In your textual explanation, justify all the decisions based on safety, material properties, and design principles. For instance, the shaft diameter ensures minimal torsional stress, while the bearing selection balances load capacity and cost.
Let me know if you need further details or help with calculations!