Jerry
230 lines
8.2 KiB
Markdown
230 lines
8.2 KiB
Markdown
# 10 — 9-cylinder radial aircraft engine
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> **Prompt**
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>
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> Design a 9-cylinder radial aircraft engine: a central round crankcase with nine finned cylinders arranged evenly in a star pattern around it, each cylinder with stacked cooling fins and a domed cylinder head, and a central propeller shaft hub at the front.
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Fully parametric OpenSCAD built from the prompt above — adjustable dimensions and colours, exported as `.SCAD` and rendered to the orbiting preview with [`render.sh`](render.sh).
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<p align="center"><img src="10-radial-aircraft-engine.gif" alt="9-cylinder radial aircraft engine — orbiting render" width="380"></p>
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**Parametric controls:** 15 dimensions · 6 colours
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**What it demonstrates**
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- Nine finned cylinders in a radial star, generated as a pattern around a crankcase
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- Stacked cooling fins, domed heads, and a central propeller hub
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- 15 parametric controls across 6 distinct part colours
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**Editable parameters**
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| Parameter | Default | Range / options | Description |
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| --- | --- | --- | --- |
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| `num_cylinders` | `9` | `[3:1:18]` | |
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| `crankcase_diameter` | `100` | `[50:5:150]` | |
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| `crankcase_thickness` | `40` | `[20:5:80]` | |
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| `hub_diameter` | `30` | `[10:2:60]` | |
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| `hub_length` | `35` | `[10:5:80]` | |
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| `shaft_diameter` | `12` | `[5:1:30]` | |
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| `shaft_length` | `40` | `[10:5:100]` | |
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| `cylinder_diameter` | `22` | `[10:2:50]` | |
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| `cylinder_length` | `60` | `[30:5:120]` | |
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| `fin_thickness` | `1.2` | `[0.5:0.1:3]` | |
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| `fin_spacing` | `3.5` | `[1.5:0.5:10]` | |
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| `fin_overhang` | `3` | `[1:0.5:10]` | |
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| `pushrod_diameter` | `3` | `[1:0.5:6]` | |
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| `intake_diameter` | `4` | `[1:0.5:8]` | |
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<details>
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<summary>OpenSCAD source — <code>10-radial-aircraft-engine.scad</code></summary>
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```scad
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/* [Engine Core] */
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num_cylinders = 9; // [3:1:18]
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crankcase_diameter = 100; // [50:5:150]
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crankcase_thickness = 40; // [20:5:80]
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hub_diameter = 30; // [10:2:60]
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hub_length = 35; // [10:5:80]
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shaft_diameter = 12; // [5:1:30]
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shaft_length = 40; // [10:5:100]
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/* [Cylinders] */
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cylinder_diameter = 22; // [10:2:50]
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cylinder_length = 60; // [30:5:120]
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fin_thickness = 1.2; // [0.5:0.1:3]
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fin_spacing = 3.5; // [1.5:0.5:10]
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fin_overhang = 3; // [1:0.5:10]
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/* [Details] */
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pushrod_diameter = 3; // [1:0.5:6]
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intake_diameter = 4; // [1:0.5:8]
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/* [Colors] */
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crankcase_color = "SlateGray";
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barrel_color = "Silver";
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head_color = "DimGray";
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pushrod_color = "LightGray";
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intake_color = "Gray";
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shaft_color = "Silver";
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$fn = 64;
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module engine() {
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// Crankcase
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color(crankcase_color) {
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// Main body
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cylinder(d=crankcase_diameter, h=crankcase_thickness, center=true);
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// Chamfer rings to soften the drum edges
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translate([0, 0, crankcase_thickness/2])
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rotate_extrude() translate([crankcase_diameter/2, 0, 0]) circle(d=4);
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translate([0, 0, -crankcase_thickness/2])
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rotate_extrude() translate([crankcase_diameter/2, 0, 0]) circle(d=4);
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// Front reduction gear housing
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translate([0, 0, crankcase_thickness/2])
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cylinder(d1=crankcase_diameter * 0.85, d2=hub_diameter * 1.5, h=12);
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translate([0, 0, crankcase_thickness/2 + 12])
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cylinder(d1=hub_diameter * 1.5, d2=hub_diameter * 1.2, h=hub_length - 12);
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// Bearing housing cap
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translate([0, 0, crankcase_thickness/2 + hub_length])
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cylinder(d=hub_diameter * 1.25, h=5);
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// Rear accessory section
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translate([0, 0, -crankcase_thickness/2]) rotate([180, 0, 0])
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cylinder(d1=crankcase_diameter * 0.85, d2=crankcase_diameter * 0.6, h=25);
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// Crankcase ribs/bolts details
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for(i=[0:num_cylinders-1]) {
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rotate([0, 0, i * 360/num_cylinders + 180/num_cylinders])
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translate([crankcase_diameter/2, 0, 0])
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cylinder(d=8, h=crankcase_thickness, center=true);
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}
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}
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// Prop Shaft
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color(shaft_color) {
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translate([0, 0, crankcase_thickness/2 + hub_length]) {
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cylinder(d=shaft_diameter, h=shaft_length);
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// Propeller mounting flange
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translate([0, 0, shaft_length * 0.3]) {
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difference() {
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cylinder(d=shaft_diameter * 2.5, h=4);
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// Bolt holes
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for(b=[0:5]) {
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rotate([0, 0, b * 360/6])
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translate([shaft_diameter * 0.9, 0, -1])
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cylinder(d=2, h=6);
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}
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}
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}
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translate([0, 0, shaft_length * 0.3 + 4])
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cylinder(d=shaft_diameter * 1.5, h=shaft_length * 0.1);
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}
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}
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// Cylinders and Rods
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for(i=[0:num_cylinders-1]) {
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angle = i * 360 / num_cylinders;
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rotate([0, 0, angle]) {
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// Cylinder
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translate([crankcase_diameter/2 - 5, 0, 0])
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rotate([0, 90, 0])
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radial_cylinder();
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// Pushrods (Front)
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pushrod_base_x = crankcase_diameter * 0.31;
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pushrod_base_z = crankcase_thickness/2 + 6;
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pushrod_top_x = crankcase_diameter/2 - 5 + cylinder_length * 0.9;
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pushrod_top_y = cylinder_diameter * 0.25;
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pushrod_top_z = 0;
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draw_rod([pushrod_base_x, -pushrod_top_y, pushrod_base_z],
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[pushrod_top_x, -pushrod_top_y, pushrod_top_z],
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pushrod_diameter, pushrod_color);
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draw_rod([pushrod_base_x, pushrod_top_y, pushrod_base_z],
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[pushrod_top_x, pushrod_top_y, pushrod_top_z],
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pushrod_diameter, pushrod_color);
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// Intake pipe (Back)
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intake_base_x = crankcase_diameter * 0.37;
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intake_base_z = -crankcase_thickness/2 - 8;
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intake_top_x = crankcase_diameter/2 - 5 + cylinder_length * 0.85;
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intake_top_y = 0;
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intake_top_z = -cylinder_diameter * 0.4;
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draw_rod([intake_base_x, 0, intake_base_z],
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[intake_top_x, 0, intake_top_z],
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intake_diameter, intake_color);
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}
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}
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}
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module radial_cylinder() {
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// Barrel
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color(barrel_color) {
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// Core
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cylinder(d=cylinder_diameter, h=cylinder_length * 0.7);
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// Fins
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num_fins = floor((cylinder_length * 0.65) / fin_spacing);
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for(f=[1:num_fins]) {
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translate([0, 0, f * fin_spacing + 2])
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cylinder(d=cylinder_diameter + 2 * fin_overhang, h=fin_thickness, center=true);
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}
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}
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// Head
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color(head_color) {
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translate([0, 0, cylinder_length * 0.7]) {
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// Lower head block
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cylinder(d=cylinder_diameter + 2, h=cylinder_length * 0.2);
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// Domed top
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translate([0, 0, cylinder_length * 0.2])
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scale([1, 1, 0.7]) sphere(d=cylinder_diameter + 2);
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// Rocker boxes
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translate([0, cylinder_diameter * 0.25, cylinder_length * 0.2])
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rotate([90, 0, 0])
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cylinder(d=cylinder_diameter * 0.5, h=cylinder_diameter * 0.5, center=true);
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translate([0, -cylinder_diameter * 0.25, cylinder_length * 0.2])
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rotate([90, 0, 0])
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cylinder(d=cylinder_diameter * 0.5, h=cylinder_diameter * 0.5, center=true);
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// Head fins
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head_fins = 3;
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for(f=[1:head_fins]) {
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translate([0, 0, f * fin_spacing - 1])
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cylinder(d=cylinder_diameter + 4, h=fin_thickness, center=true);
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}
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}
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}
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}
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module draw_rod(p1, p2, dia, rod_color) {
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color(rod_color) {
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dist = norm(p2 - p1);
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dir = (p2 - p1) / dist;
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axis = cross([0,0,1], dir);
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angle = acos(max(-1, min(1, dir[2])));
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translate(p1)
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if (norm(axis) > 0.001) {
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rotate(a=angle, v=axis)
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cylinder(d=dia, h=dist);
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} else {
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cylinder(d=dia, h=dist);
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}
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}
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}
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engine();
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```
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</details>
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