School of Computing, Engineering and Mathematics
300600 Mechatronic System Design
TUTORIAL ASSIGNMENT 1 (10/10)
Softcopy due at 17:00pm, Wednesday, Week 4, 22nd August, 2018
Instructions:
This tutorial assignment 1 is concerned with Shaft Design and your answers must be given in a step-by-step manner.
Tutorial Assignment 1 is due at 17:00pm, Wednesday, Week 4, 22nd August, 2018 and only an electronic version is accepted for submission via the vUWS site.
Note that q is the last three digits of your student identification number in all the following questions.
Question 1 (1.5/10):
A solid rectangular bar has a cross section of (3 + q/1000 mm) × (5 + q/1000 mm) and a length of 250 + q/100 mm. It is made from nylon 66 plastic and subjected to a steady tensile load of 200 + q/100 N. The properties of nylon are shown in Table 1-1 and Figure 1-1. As a mechanical engineer, you are required to: a) Compute the elongations of the bar under the following conditions
1) immediately after the load is applied;
2) after 1 hour; 3) after 100 hours; and 4) after 5000 hours.
b) Compare the elongations using a table, plot the results in a graph with the x- axis standing for the time and the y-axis is for the elongation. Explain why the elongations have such a phenomenon when considering the time effect.
Question 2 (1.5/10):
The following figure shows a rotating shaft carrying a steady downward loads F1 and F2 at C and D, respectively, which is supported by two bearings at A and B, respectively. The detailed graph near the location B shows the sizes of the shaft at its different portions AB and BC as well as the radius of the fillet in the shoulder.
For this direct design problem, you are only required to specify a suitable material to the shaft via a design analysis, considering the value of external loads, and a design factor of 2.0 + q/1000.
Figure 1-2 A rotating shaft carries two steady loads
Question 3 (3/10):
Figure 1-3 A shaft as a part of a drive for an automated transfer system in a metal stamping plant
The shaft in Figure 1-3 is a part of a drive for an automated transfer system in a metal stamping plant. The shaft rotating at 550 + q/100 rpm carries a spur gear B having 96 teeth with a diametral pitch of 6. The teeth are of the 20°, full-depth, involute form. Gear Q delivers 20 + q/100 (kW) to gear B. Sheave D delivers the power to its mating sheave as shown.
You are required to:
a) Determine the magnitude of the torque in the shaft at all points
b) Compute the forces acting on the shaft at all power transmitting elements
c) Compute the reactions at the bearings
d) Draw the complete load, shear, and bending moment diagrams
e) Select an appropriate steel material for this shaft
f) Give a suggested geometry at point C of the shaft and specify the minimum acceptable diameter for the shaft at this point with implementing a design factor of 2.5 + q/1000.
Neglect the weight of the elements on the shafts, unless otherwise noted.
Question 4 (4/10):
A drive is shown in the above figure which is designed for a system to crush coal and deliver it by conveyor to a railroad car. Gear A delivers 15 + q/100 (kW) to the crusher, and gear E delivers 7.5 + q/100 (kW) to the conveyor. All power enters the shaft through gear C. The shaft carrying gears A, C, and E rotates at 480 + q/100 rpm. The distance from the middle of each bearing to the middle of the face of the nearest gear is 100 + q/1000 mm.
As a design engineer, you are required to design that shaft with neglecting the weight of the elements on the shafts.