<< Click to Display Table of Contents >> Navigation: Getting Started Tutorials - MechDesigner > Tutorial 2A: Four-bar Kinematic-Chains > Step 2.5: Reconfigure to a 4-bar Slider-Crank |
In this Tutorial:
Video 1:
1.We delete a Pin-Joint (the middle of the two Joints in the R-R-P dyad), and add a new Pin-Joint
2.We change the Dyad Closure of the R-R-R Dyad
Video 2:
3.Move the Motion-Dimension FB to the Slide-Joint. The input becomes a Slider.
Typically, the name of the new mechanism is a Slider-Crank.
4.We will look at the Kinematics Tree again.
Delete Pin-Joint Add Pin-Joint Change Dyad Closure |
Delete •Motion-Dimension Rocker Add •Motion-Dimension ... ...to a Slide-Joint ... ...to make a Slider |
We want to move the Pin-Joint to the different end of the sliding-Part. We delete the Pin-Joint, and add a new Pin-Joint. There are many ways to delete an element. In this step we will practice using the contextual-menu with 'Hover-above-element + Right-Click' , and then click Delete Element |
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STEP 1: Delete the Pin-Joint with the Sliding-Part We can delete an element with a contextual menu - IF we can right-click the element and only that element. You may need to edit your Symbol Selection Size. I reduced mine to be one less than the Symbol Size. See Edit menu > Application-Settings > Accessibility tab > Graphics > Symbol Selection Size The image shows ONLY the Pin-Joint is Red
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1.Hover + Right-Click' above ONLY the Pin-Joint If more than one element becomes red, a different contextual-menu will show. 2.Click Delete element at the top of the contextual-menu (the menu may not be easy to see!) |
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STEP 1: Move the Sliding-Part and add a new Pin-Joint 1.Hover + Drag the Part Outline of the Sliding-Part. When the start-Point of the sliding-Part is near to the end-Point of the other Part. 2.Click Kinematic elements toolbar > Add Pin-Joint 3.Click the two Points |
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STEP 3: Edit the Closure - again. If the R-R-P Dyad Closure is the same as this image to the left, then we can change its closure. There is a right-click short-cut... |
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1.Click Kinematic elements toolbar > Change Closure The short-cut to complete the command: 2.Right-Click a Part in the R-R-P Dyad. The right-click short-cut selects the element and also closes the Command-Manager. Do step 1 - 2 again and again until the Dyad is the same as the image. Note: You can do the right-click short-cut when the Command-Manager has one selection-box or only one more element to select for the selection-box. |
When the Motion-Dimension FB is at a Pin-Joint, we call the Motion-Part a Rocker. When the Motion-Dimension FB is at a Slide-Joint, we call the Motion-Part as Slider. |
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Before we can add a new Motion-Dimension FB to the Slide-Joint we must delete the Motion-Dimension FB at the Pin-Joint
STEP 1: Delete the Motion-Dimension FB 1.Click the Motion-Dimension FB, or the Motion-Dimension arrowhead, in the graphic-area |
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The Motion-Dimension FB element will be in the Selection-Window 2.Right-click the Motion-Dimension FB in the Selection-Window In the contextual menu 3.Click Delete in the contextual-menu Note: Alternatively, you can click an element so that it becomes red, then use your delete key on your keyboard. |
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All of the Part-Outlines in the kinematic-chain should be Blue. The kinematic-chain has one degree-of-freedom again. Remember: Blue Part-Outlines are NOT kinematically-defined. |
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2.Drag the rotating Part Drag the Part-Outline of the Part that was the 'Rocker'. Move the Parts to a position that is similar to that shown in the image to the left. NOTE: Some users can make a Part-Outline Red by hovering over the Part-Outline at the arcs, near the start-Point of the Part Now, we will add a new Motion-Dimension FB. |
STEP 2: Add the Motion-Dimension to the Sliding Part. 1.Click Kinematic FB toolbar > Add Motion-Dimension FB |
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When we want to add a Motion-Dimension FB to a Sliding PartJoint The Command-Manager shows you must select three elements from the graphic-area. Notes on the Command-Manager •Do not click inside a selection-box. If you do click in a selection-box, you clear all elements. •Each time you select an element, the Command-Manager automatically advances to the next selection-box. |
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Select the three elements for Add Motion-Dimension FB 1.Click First Element: the Slide-Joint The Slide-Joint symbol is two(2) rectangles that are along the length of each Line that specify the Slide-Joint. Please look at the image carefully to see the symbol of the Slide-Joint.
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When the Slide-Joint is the first element, the second and third elements you must select are Points. 2.Click Second Element: Click a Point I find it best to select the Point that is the start-Point of the Line.
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The second Point is at one end of the Line in the Free-Part. A Free-Part has a Blue Part-Outline. 3.Click Third Element: Click a Point at one end of the Line in Added-Part Again, I find it best to select the Point that is the start-Point of the Line. |
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4.Click You can also Right-click in the graphic-area to complete the command. The kinematic-chain is now kinematically-defined again. The Part-Outlines are Green. The Part that was a Free-Part is now a kinematically-defined Part. Because the Part is a child to a Slide-Joint, it is a Slider. |
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STEP 3: Add a Motion FB - if needed. 1.Click Kinematic-FB toolbar > Add Motion FB 2.Click the graphic-area. 3.Connect a wire from the output-connector of the Linear-Motion FB to the new Motion FB 4.Connect a wire from the output-connector of the Motion FB to the Motion-Dimension FB
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If the Closure is not correct STEP 4: Change the Dyad Closure if it is not correct. 1.Do Kinematic element toolbar > Change Dyad Closure 2.Click
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Slide-Joint BEFORE we add a Motion-Dimension FB A Free-Part The symbols that represent a Slide-Joint are:
The small arrowhead is the Positive Direction of the Slide-Joint. |
Slide-Joint AFTER we add a Motion-Dimension FB The Free-Part is now a Solved-Part The small arrowhead, and the Wide and Narrow rectangles are Green. The symbols for the Motion-Dimension include:
Increasing motion-values move the Slider in positive direction, as indicated by the small arrowhead. |
The Kinematics-Tree has changed in Tutorial 2. It has changed from a: •Rocker and R-R-R Dyad (Step 2.1) to a: •Rocker and R-R-P Dyad (Step 2.3) to a: •Slider and R-R-R Dyad (This Step) |
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This Kinematic-Chain is a Slider and an R-R-R Dyad. The Slider is a Motion-Part. It has three elements: a.Slide-Joint b.Part c.Mot-Dim Slider – a Motion-Dimension FB for a Slider The R-R-R Dyad is one of the five Planar Dyads. The R-R-R Dyad has these five elements: d.Pin-Joint e.Part f.Pin-Joint g.Part h.Pin-Joint |