Mechanics of Machines Assignment-Report Guideline and Marking Format
Mechanics of Machines
Assignment-Report Guideline and Marking Format
Guideline
The logical steps to analyse the mechanism using Abhary’s Method is as follows:
1. Before you start, you must speculate on the operation of your mechanism and fully
understand how it works (otherwise you will go wrong).
2. Identify the input and output links and their corresponding loads.
3. Draw a proper scaled CAD figure of your mechanism, sufficiently large to ease the
analysis. Keep the original assignment sheet for future references.
4. If the labelling of links and joints are not consistent with Abhary’s Method conventions
change them: number links consecutively, starting from the input Link 2; label stationary
joints by Oi the point where the Link i is pivoted.
5. Convert the geometry of the mechanism to the Vectorial Illustration of the mechanism.
To achieve this denote link centrelines as vectors, show the position of centre of gravities
by vectors, and ensure all other fixed dimensions are converted to vectors.
6. Identify loops with smaller number of vectors and develop the loop vectorial equations.
Get my verification of your loop equations before you continue. Otherwise, most
probably you get stuck, waste a lot of time and cannot continue with the analysis.
7. Ensure that in each loop only TWO unknowns are left to be determined otherwise this
indicates that your loop is useless and you must revise the vectorial illustration of the
mechanism.
8. Identify the CASE of each vectorial equation and solve it by using corresponding
Equations 5 to 11 for Position Analysis in the lecture slides. Cross check the numerical
results with those of the scaled figure of the mechanism illustrated in Step 3. DO NOT
proceed further until you realise the analytical and graphical results of position analysis
are consistent.
9. Perform. Velocity Analysis by using corresponding Equations 13 to 16 and Acceleration
Analysis by using corresponding Equations18 to 21 in your lecture slides.
10. To perform. Force Analysis you should start from the output link and move towards the
Input link. If the output load of your mechanism is unknown, determine it using Eqn 6.1
on page 5-11 of the Reader then begin the Force analysis.
A detailed sample of the work you should do on your assignment is illustrated for Quick-Return
Mechanism in your Reader, Page 4-11 to 4-13 (Kinematic Analysis) and Page 5-17 to 5-18
(Force Analysis; to understand this you should refer to FBD of the links in the lecture slides,
Page 5-1 to 5-18). The APPROACH was thoroughly explained in the lecture using the same
Quick-Return Mechanism. Also included in your Reader is another fully illustrated example on
Page 4-16 to 4-21.
Mechanics of Machines Assignment-Report Guideline and Marking Format
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Report Format
The following format explains what quantities must be calculated and how your analysis should
be presented.
Prepare the report strictly according to the following format; otherwise the report will be poorly
marked. Submit one hard copy (per group) for marking and upload the electronic copy (one per
group) on the course website for my records. The electronic copy MUST be strictly ONE file,
otherwise will be rejected. Use Abhary’s method for the kinematic and kinetic analysis of the
mechanism. Each of the following steps must start on a new page.
1. Cover page, including the title (Mechanics of Machines), Assignment Number, your name,
the lecturer’s name and date of submission. Use the school standard assignment cover page.
2. Signed disclaimer.
3. A proper scaled CAD drawing of the mechanism, positioned at the specified input angle (if
no input angle is specified seek my advice). Relabel your mechanism (joints, centres of
gravity and links) as per conventions you learnt in the topic if it is not already done for you.
4. Copy the figure constructed in Step 2, convert it into a proper CAD vectorial illustration of
the mechanism and specify the xy coordinate system. List of the vectors must appear on the
same page alongside the vectorial illustration. Set up the table below and place it under the
figure along with other geometrical, dynamics and input information, if any, as per the
assignment sheet.
Link
(including the
virtual links)
1 2 3 ... n
Link
segments
indicating the
position of
their C.G.
(mm)
m (kg)
J (kg m2)
Scale of the figure:
5. Position analysis of the mechanism; equations and results structured as per Table 1.
6. Velocity analysis of the mechanism; equations and results structured as per Table 2.
7. Acceleration analysis of the mechanism; equations and results structured as per Table 3.
8. Force (kinetic) analysis of the mechanism. Draw the necessary free body diagrams of all
links (neat sketches using drawing equipments. Drawing FBDs using CAD is optional). Then
structure the results as per Table 4.
9. Check the correctness of your calculations. For this purpose, draw the FBD of the whole
mechanism and, using the numerical value of forces at the special position of the mechanism,
ensure that the Force- and Moment-Equilibrium Equations of the whole mechanism hold
true.
10. Attach your draft of manual calculations of Part 4–7 as appendices. Neat handwritten
calculations and sketches will do.
Mechanics of Machines Assignment-Report Guideline and Marking Format
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NOTE 1: The report must be typed (except the draft), use Equation Editor to type equations in
the following tables; figures to be drawn with the aid of a CAD software (FBDs
optional).
NOTE 2: Calculate Lengths in round mm, Angles in round degrees, Velocities in m/s (three
decimals), Accelerations in m/s2 (three decimals), Forces in round N (two decimals),
Torques/Moments in round Nm (three decimals), and Power in kw (three decimals)
NOTE 3: The equations in Table 1 to Table 4 must appear in the logical order of
calculations. What you see in these tables below are just hypothetical examples. You
may copy the tables and customise them to suit your needs.