OpenSCAD

Discussing the blimp design with Andrew, he came to me with so far unknown tool – OpenSCAD. I’ll quote Wikipedia to introduce it a bit:

OpenSCAD is a free software application for creating solid 3D CAD (computer-aided design) objects. It is a script-only based modeller that uses its own description language; parts can be previewed, but cannot be interactively selected or modified by mouse in the 3D view. An OpenSCAD script specifies geometric primitives (such as spheres, boxes, cylinders, etc.) and defines how they are modified and combined (for instance by intersection, difference, envelope combination and Minkowski sums) to render a 3D model. As such, the program does constructive solid geometry (CSG). OpenSCAD is available for Windows, Linux and OS X.

And you know what? It instantly made my brain spinning. I started playing with that on the same day and all my basics from AutoCad + Blender came finally to some use here.

Same late evening … an EDF unit came up.

While the above may look like some super-sophisticated mechanical part rendering – achieving this with the OpenSCAD is pretty simple. Actually 40-liner.

use <ShortCuts.scad>
use <Naca4.scad>

module TubeSimple(h, r1, r2, t) {
    difference(){
        cylinder(h, r1, r2, center = false);
        cylinder(h, r1 = r1 - t, r2 = r2 - t, center = false);
    }
}

module edf(){
    Ry(90){
        //back ege
        Tz(4)
        TubeSimple(0.2, 4, 3.9, 0.2);
        
        //main body
        Tz(-1)
        TubeSimple(5, 4, 4, 0.2);

        //front inlet
        Tz(-3)
        TubeSimple(2, 5, 4, 0.2);
     
        //rotor
        Tz(-2) {
            sphere(1);
            cylinder(h = 6, r1 = 1, r2 = 1, center = false);
        }
        Tz(4)
        cylinder(h = 2, r1 = 1, r2 = 0, center = false);
    }
    
    //Propeller
    n=12;
    for(w=[0:360/n:359])
    Rx(w)
    proprep(tip_scale=1, L = 2, r = 3.6, twist=-30, rot=-20, naca = 1408);
}

Now, how difficult it would be putting together our Blimp?! So couple more nights later …

This time is code bit longer, so adding just the main part for its illustration.

use <ShortCuts.scad>
use <Naca4.scad>
use <blimp_parts.scad>

$fn=30;

Rx(90) {
    // Main body
    %body(5);

    //EDFs
    color("DimGray") {
        edf_custom(-7,0,-16, 270);
        edf_custom( 7,0,-16, 270);
    }

    //Inner support
    color("SandyBrown")
    inner_support();

    //Tube Left + nozzle
    tube(-7,0,-16, 50, 1, 1, 0.01);
    tube(-7,0, 34, 3, 1, 0.6, 0.01);

    //Tube Right + nozzle
    tube(7,0,-16, 50, 1, 1, 0.01);
    tube(7,0, 34, 3, 1, 0.6, 0.01);

    //Controls
    color("Silver"){
        rudder(14,0,15,180);
        rudder(-14,0,15,0);
        rudder(-7,7,15,270);
        rudder(7,7,15,270);
    }

    //gondola
    gondola_skelet(0,-9.2, 0);
}

Let’s move on! OpenSCAD can export its models in STL format, making things even more interesting.

STL (an abbreviation of “stereolithography“) is a file format native to the stereolithographyCAD software created by 3D Systems. STL has several backronyms such as “Standard Triangle Language” and “Standard Tessellation Language”. This file format is supported by many other software packages; it is widely used for rapid prototyping, 3D printing and computer-aided manufacturing. STL files describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes. The STL format specifies both ASCII and binary representations. Binary files are more common, since they are more compact.

At this stage I’ve exported our current Blimp model as the STL file and apparently there are some clever WordPress plugins to view it in “3D”, however my licence doesn’t allow me to install those and I don’t want to upgrade yet. So if you are interested, here is DYI:

• Download the model through this link
• Go to ViewStl website
• … and use instructions there to get it going 🙂

… now I just need some VERY BIG 3D printer! 🙂