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Flash-LGS is an easy-to-use vector drawings editor with extensive parameterization capabilities. It is based on the following underlying idea - you draw an approximate sketch, apply a set of constraints to the sketch elements and Flash-LGS beatifies this sketch automatically according to those constraints. The user interface is traditional for drawing programs. On the left of the drawing window you see a set of tools and controls, separated into the following sections, from top to bottom:
- File operations that allow creating new drawing, loading and saving your own designs, and loading predefined samples.
- Recalculate the model button - performs geometry calculation using the LGS engine.
- Management tools: Object properties, Delete object and Drawing description.
- Drawing tools.
- Quick constraint tools: most frequently used constraint types, which are set to quick access buttons; the whole list of provided constraints is available through the More constraints button.
- Drawing browser consists of two sections: a list of geometry objects and a list of constraints.
You can quickly remember any tool purpose by moving a cursor to an appropriate button - the tool-tip appears automatically.
In this tutorial you will learn the basics of Flash-LGS interface and usage, by creating step-by-step a simplest parameterized model of a stroke-engine mechanism. We recommend keeping Tutorial window on the screen simultaneously with Flash-LGS application and performing tutorial by following these instructions.
This sketch shows kinematics of a common stroke engine mechanism. Changing the crankshaft angle forces LGS-engine to calculate the piston (marked as a circle) position and the angle between a connecting rod and a crankshaft. For reference you can load such model from the Predefined samples list.
So, let's begin.
First of all - draw the shown sketch using Line and Circle tools. At this stage you do not need to make precise elements drawing, just draw them in a shape similar to the picture.
You can remove incorrectly drawn objects by selecting them either in the drawing or in the list (object gets highlighted in the drawing too) and pressing the Delete object button (marked by the red square on the picture blow).
As a result, you will have three lines and one circle in the Object List.
Now - let's set the constraints, which will convert this simple sketch into an accurate mechanism model. So, step by step:
Choose the Select object tool, point out the "horizontal line" by a cursor and click with the left mouse button - orange color marks the selected line. When the line is selected, click on the More constraints button (marked by the red square on the picture blow). From the menu of available constraints choose "Horizontality" - the first constraint will be added to list - you can check it out by switching to the "Constraints" tab. Also an appropriate constraint icon is displayed near the line.
Note that the constraints menu highlights those options depending on type of selected objects.
With the first constraint set you already can perform model calculation - just click on the Recalculate the model button. If you have set a constraint properly - the line becomes precisely horizontal. Further on we will use this line as the base axis.
Next - let's set the fixed position constraint for endpoint of the "crankshaft" line.
To select a point rather than the whole object - move a cursor to a cross-mark and click it. The marked point becomes orange.
Select the left endpoint of the crankshaft line (on the picture marked by the green circle) and press the Fixation button (marked on the picture by the red square).
Now let's set a more complicated constraint for two objects.
To select two or more objects simultaneously - press and hold the "Shift" key while using the Selection tool.
At this stage we'll set a constraint that will fix endpoint of the short line (crank) on axis. Select endpoint of the line and horizontal line. In the Constraints menu choose Distance constraints. Since Distance is a quite frequently used option - it is also invoked by pressing the Distance button (marked on the picture below by the red square).
Distance constraint appears in the list. Select it there and press the Object properties button (marked on the picture below by the red square) - a dialogue of constraint properties appears. Set the value of the distance to 0.
Press the Recalculate the model button - an endpoint of the line shall sticks to the horizontal axis.
You can move objects apart at any time, however when you press Calculate - Flash-LGS will bring them together according to constraints set.
You also can use Coincidence constraint on order to set zero distance between point and line.
To finalize mechanism creation, you should also set the following constraints:
Connecting rod and crankshaft endpoints Coincidence (marked on the picture below by the red square).
Length of crankshaft. To do that - select crankshaft endpoints (not the line!) and set Distance constraint. After the distance constraint is created - change its value by the Object properties tool. Set this length, for instance, for to 120.
When you select some constraint in the list, it is also highlighted in the drawing by the red color.
In the same manner set the length of connection rod to 240.
Select the circle center and connection rod free endpoint and set the Coincidence constraint (on the picture marked by the green circle) - so the "piston" is connected to the connection rod.
Set the Distance constraint for the circle ("piston") center and horizontal axis. Of course, the value of this constraint is 0.
Finally, set the Angle constraint between the crankshaft and horizontal axis.
That's it - just press the Recalculate the model button to bring all parts together. Now you can change the value of the Angle constraint and Flash-LGS will calculate positions of all elements according to the angle.