Workingmodel

Working Model Tutorial #1

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INTRODUCTION
Setting Up the Workspace
Working Model provides several tools to make it easier to create and position simulations. These tools are located on the Workspace submenu of the View menu. X, Y Axes, Grid Lines, and Rules are aids that intersect at (0,0), the origin of the axes. Grid Lines are dotted lines that are spaced at equal intervals on thescreen. Rules appear at the left edge and bottom of the workspace.

Defining workspace settings
Turn the drawing axes, grid, and rules on now. • Select View menu, Workspace, a box will appear. • Check the boxes for: o X, Y Axes. o Grid Lines. o Rulers. Then close the box. Note: These instructions assume that you have just installed Working Model. If you have changed your workspace settings before,or if someone else may have used your Working Model, refer to Figure 1., which shows all the settings that should be on (have a check mark to the left of them) under View menu, Workspace box.

Figure 1. Workspace window. The ruler is numbered at every meter. The smaller hash marks represent 0.1-meter intervals. The grid line appears at 1-meter intervals.

Grid snap
Accurate placement ofobjects in Working Model is difficult without the use of special drawing aids. The Grid Snap feature allows you to accurately align objects to the grid. Grid Snap is located on the View menu; a check mark to its left indicates that it is activated. If it is not already on, turn Grid Snap on now.

Object snap
Object snap allows the user to accurately place points, motors, actuators and etc to specificpoints on the workspace rectangles, circles, and polygons. The object snap will appear as an “x” on by the cursor. When the “x” appears then the object will be accurately placed at that point.

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Objectives
• In this tutorial you will learn to: • Reshape polygons • Use the Smart Editor. • Use the Slot tools. • Rotate objects Kinematic analysis of the four-bar linkage. Coupler points andcurves Kinematic analysis of the slider-crank linkage

Design principles related to this tutorial
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Problem Statement
A vast number of machines are created from only three basic kinematic linkages: the four-bar, the slider-crank, and the double-slider crank. Steering mechanisms in vehicles, windshield wiper systems, and lawn sprinklers are only a few examples of mechanisms that can becreated from four-bar linkages. Slider-crank linkages are used in the design of internal combustion engines and air compressors. Figure 2. shows schematics of the four-bar and the slider-crank linkages, and the dimensions to be used for this tutorial. You will create Working Model simulations for both types using the dimensions shown in the figure as follows: Create the four-bar linkage using aninput angular velocity of ωAB = 2 rps counterclockwise. Show the path of point C as this mechanism moves, and output a graph of the coordinates of this path. Also, show a graph of the ratio of output angular velocity to input angular velocity (ωDE /ωAB). Create a slider-crank linkage using the same input angular velocity, ωAB. Show graphs of the position, Velocity, and acceleration of slider D asfunctions of time. Rotate the path of the slider 45° clockwise, and show the resulting position, velocity, and acceleration of the slider. All sliders are 0.4 m x 0.6 m

Figure 2. Example description.

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Creating the Components
Open a new, untitled Working Model window, with the default workspace you have used in each tutorial. The unit system and the accuracy mode should be the Working Modeldefaults, SI (degrees) and Accurate. You will start by creating the four-bar linkage. • Create two rectangles with the following dimensions: 1. 2. • • • height = 0.1 m; height = 0.1 m; width = 1 m width = 2 m

These rectangles represent bars AB and DE. Use the Polygon tool to create an isosceles triangle with base = 2 m and height = 1 m. Its lower-left vertex should be located at (-1, -2)....