MECH3460 8460 9460
Assignment 3
Shaft Methodologies – Chain Drive Mixer
Introduction:
Assignment 3 focuses on the use of two analysis methods to arrive at a suitable design of a shaft to suit the chain drive to a mixer. The layout of the drive is shown pictorially in Figure 1.0 below and in the SALA catalogue (compare old and new), available on CANVAS. Note the use of a shaft mounted gearbox.
Operating Environment:
It is intended to use an available appropriate synchronous motor rated to operate at 1440 rpm. The motor which weighs 40 kg will be directly coupled to the input shaft of the gearbox, (not using a belt drive as shown in Figure 1.0.) The output of the gearbox is to run at 100 rpm within 5%. The pitch circle diameter of the chain sprocket is to be approximately 330 mm. The tension in the chain will vary with the volume and density of the material in the mixer drum used in a paper mill, but it has been determined that the highest tension will be 18.0 kN and that the high-tension leg of the chain will be within 15⁰ of vertical. The movement of the material within the mixing drum will produce essentially no shock loads. The SALA catalogue also specifies other factors to be considered. This installation will be operated for single shifts of 12 hours per day (i.e., 12 hours continuous service), with less than 8 starts per hour and all starts will be carried out with an empty drum. The assembly is expected to last 20 years of normal operation. The operating environment is quite dusty.
Figures 2.0 and 3.0 below, show views of SW models of the proposed drive assembly. They show the motor, gearbox, bearing blocks, chain sprocket and shaft.
Assignment Requirements:
Shaft Material:
The initial expectation is that the shaft will be made from cold drawn CS1030 steel with an UTS of at least 500 MPa and a Yield Point of at least 250 MPa. You will need to reference a suitable supplier that you have selected. The shaft is initially expected to be a parallel sided cylinder bar (no steps).
Core Assignment Requirements:
You are to prepare an EXCEL spreadsheet and accompanying short summary PDF report for an engineering manager, addressing the following points:
• Design a suitable shaft diameter using AS1403 and one other analysis methods covered within the course notes: Gerber, Goodman or ASME Ellipse. (Note FEA is not permitted).
• State the diameter and length of the stock material you are proposing to use to manufacture one off your shaft design and the material property.
• Select a gearbox from the SALA catalogue provided.
• Determine a suitable key between your shaft and the boss on which the chain sprocket is mounted.
• References are to be included in your spreadsheet for each key point.
• Use good logical reasoning to explain your design process, key steps, equations used etc.
The EXCEL spreadsheet is to be easily read and serve as a guide for new graduates that will learn from you and extend your design to other applications.
Additional Design Aspects to be Considered:
• Select bearings and bearing plummer blocks to suit this installation. To do this you must determine the angular misalignment of the shaft at the bearings, to allow bearings and or plummer blocks to be selected that can function with that misalignment.
• Suggest appropriate tolerances for the coplanar alignment of the mounting faces for the two plummer blocks, and their deviation from the horizontal.
• Determine the lateral deflection of the shaft at the sprocket and assess its effect in terms of the possibility of the chain not engaging correctly with the sprocket due to the shaft deflection.
• Include a detail drawing of a steel frame. you have designed (not an Assembly Drawing) to deal with the points above on an A3 or bigger size drawing sheet to AS1100. This drawing MUST be included in the PDF report as an appendix (separate upload will NOT be marked).