MECH1230 - Part I: Dynamics Lab 2 Kinematics of Plane Mechanisms Lab Handout MECH1230 Solid Mechanics 2023/24 Dr Ida Shafagh UNIVERSITY OF LEEDS Lab Guidance Background This laboratory exercise centres on the kinematic analysis of several plane mechanisms. Each of the mechanisms used as part of this assessment are driven by a rotary input. During the course of the laboratory, you will determine experim ally the relationship between the crank angle input and the kinematic behaviour of the output slider. You will also use a software package, that contains a mathematical model of each mechanism, to predict the behaviour of the mechanism. Equipment A mechanism (slider crank, scotch yoke, slotted link quick return and Whitworth quick return), a PC and printer. Objectives 1. To analyse the behaviour of a chosen mechanism using computational methods and comment on the realities of the analysis. 2. To conduct a simple parametric analysis based on a mathematical model of the mechanism. 3. To gain experience of teamwork and delegation of responsibility within the team. Organisation 1. This assignment requires that you work in groups of at least 4 (maximum 5). 2. Each group must complete a single report for the laboratory. Use the instructions to guide you in preparing the report. You will each conduct a peer assessment to document your views as to the contributions made by each team member. You are required to submit your assessment on "Minerva → MECH1230 Semester1: Dynamics → Practical Activity 2 Buddycheck Pilot". The link will be made available after all lab sessions are completed. You may find a guide for this in the Practical Activity 2 folder. 3. Deadline for submitting the lab report is Thursday 1st February 2024 at 12noon. You are required to submit your report on "Minerva → MECH1230→ Semester1: Dynamics → Practical Activity 2 → Lab Report Submission Link". The submission link will be made available after all lab sessions are completed. Guidance notes 1. Sections 3, 4 and 5 explain the detail of the laboratory. It is up to you to decide how to delegate responsibility for the completion of each section. If you have any queries concerning this, then consult with one of the lab demonstrators at the time of the laboratory. 2. You will be given one mechanism, use this particular mechanism during each stage of the lab. 3. Analysis of the mechanism motion using kinematics software a. With the aid of Figure 1, write down the displacement loop equations for the chosen mechanism and include these in the report together with the 'stick diagrams' which describe the mechanism. 2 MECH1230 Dr. I Shafagh b. Use the kinematics software to analyse the motion of the mechanism. To do this you will need to input certain dimensions. You will be given these dimensions during the lab demonstration session. For all mechanisms you should assume the crank is rotating with a constant angular velocity of 10rad/s. The output quantities are the displacement, velocity and acceleration of the output slider. 4. Experimental determination of the mechanism motion a. By taking measurements from the mechanism, plot a displacement graph of the output p of the slider, against the input angle q for a complete revolution of the input shaft. b. Find the velocity of p (i.e. dp/dt) assuming a constant angular input velocity which will be the same as that used in the computer simulation and plot this against the input angle q. Angular velocity of input w = 10rad/s, where w = dq/dt. c. Determine the acceleration of p (i.e. d²p/dt²) at the same value of w and plot this against the input angle q. d. Include the results from 4a-c inclusive in the report. These results should take the form of correctly annotated graphs. 5. Parametric study Use the computer model of the mechanism to conduct a simple parametric study to investigate the effect that a change in one parameter has on the magnitude of the acceleration of the output slider. Select one of the parameters ₁ to an used to define the geometry of your mechanism. You should choose a suitable resolution of 0. Assume: a. The input crank is rotating with the same angular velocity as used in section 4. b. The parameter can vary between the following limits about its original value: Minimum value = 0.5 x Original. Maximum value = 2 × Original. What effects have these changes made to the displacement and velocity of the output slider? 6. Analysis and Discussion a. Discuss the results obtained in sections 3 and 4 which are expected to be in reasonable agreement. Discuss the differences and similarities. b. Comment on the results of the parametric study by comparing the results obtained in section 5 to those obtained for the original mechanism model. Describe what this tells you about the kinematics of the mechanism with respect to the chosen parameter. MECH1230 Dr. I Shafagh 3 Da Axiz system positive directions P₁ vectors a scalars P₁↑ 4 X a₁ 34 P₂ 2₂ B+ Scotch yoke mechanism az P4 Whitworth quick retum mechanism 212 a5 P₂ 2₁ MECH1230 P₁ P₁ B P2 Slotted link quick retum mechanism B P4 Dr. I Shafagh Slider crank mechanism 24 a3 Figure 1: Position diagrams for the planar mechanisms. a₁ B E Preparation of the report 1. Add a standard coursework submission sheet as the front page. Include the following sections within the main body of the report: 2. a. The mechanism i. A description of the mechanism used and its relevance in engineering. ii. A list of the numerical values of the mechanism parameters. b. Computer based results for the original mechanism. i. Loop equations (displacement, velocity, acceleration). ii. Graph of displacement of output slider against input angle (using the available software). iii. Graph of velocity of output slider against input angle (using the available software). iv. Graph of acceleration of output slider against input angle (using the available software). c. Experimental results for the original mechanism i. Tabulated calculation of velocity and acceleration at different angles. ii. Graph of displacement against input angle. iii. Graph of velocity of output slider against input angle. iv. Graph of acceleration of output slider against input angle. d. Parametric study i. State which parameter you have chosen to vary and why. ii. Graph of acceleration of output slider against input angle (original model parameter). iii. Graph of acceleration of output slider against input angle (0.5 × original parameter). iv. Graph of acceleration of output slider against input angle (2× original parameter). v. Comment on the results of this analysis. Did the results show the form that you anticipated? e. Discussion i. Discuss the results in b,c and d. What differences and similarities are there between the experimental and the computational model results? Can you explain the differences and quantify whether the magnitude of the differences is consistent with your explanations? ii. Discuss the values from b and d. f. Conclusions i. Summarise your main findings. It is often useful to use bullet points, to create such a summary using the minimum number of words. This approach is recommended for this exercise. 3. Complete the peer assessment (as described in the organisation section). Make sure the above sections (apart from 3) are assembled properly into a single report and is professionally presented. On the module page on Minerva you will find additional documents that will support you in structuring your report. MECH1230 Dr. I Shafagh LO 5

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MECH1230 - Part I: Dynamics Lab 2 Kinematics of Plane Mechanisms Lab Handout MECH1230 Solid Mechanics 2023/24 Dr Ida Shafagh UNIVERSITY OF LEEDS Lab Guidance Background This laboratory exercise centres on the kinematic analysis of several plane mechanisms. Each of the mechanisms used as part of this assessment are dri