Build a drone: around, bolts and standoffs

Four arms, four legs and four standoffs stand evenly around the drone. One function places a shape that many times, and every part that repeats uses it from here on; it does for the TypeScript drone what the Around module does for the Rete one.

1. Arms, motors, propellers, legs and standoffs all stand evenly around the drone, so one function repeats a shape count times around the upright axis, half a step off the axes: at 45, 135, 225 and 315 degrees for four. Its first use is the plate's leg openings, a hole 6 millimetres across, 52 from the centre, repeated for every leg and cut away with the vents.

   • Make parts/around.ts:

   export function around(shape: Bit.Inputs.OCCT.TopoDSShapePointer, count: number) {
       const angles = Array.from({ length: count }, (_, i) => (i + 0.5) * 360 / count);
       return bitbybit.occt.transforms.rotateShapes({
           shapes: angles.map(() => shape),
           axes: angles.map((): Bit.Inputs.Base.Vector3 => [0, 1, 0]),
           angles,
       });
   }

   • Import at the top of parts/frame.ts:

   import { around } from "./around";

   • In parts/frame.ts, change export async function framePlate() { to export async function framePlate(legs: number) {.
   • In parts/frame.ts, change const cuts = await vents(); to const cuts = [...await vents(), await legOpenings(legs)];.
   • Add at the end of parts/frame.ts:

   async function legOpenings(legs: number) {
       const opening = await bitbybit.occt.shapes.solid.createCylinder({ radius: 6, height: 3, center: [52, 0, 0], direction: [0, 1, 0] });
       return bitbybit.occt.shapes.compound.makeCompound({ shapes: await around(opening, legs) });
   }

   • In main.ts, change const plate = await framePlate(); to const plate = await framePlate(sizes.legs);.
   • Run it with Run The Code.
   

2. An M3 bolt is a profile revolved into its body, with a hexagon socket cut into its head; the standoffs, the arms and the legs all use it. A standoff is a post 10 millimetres tall between the plates, with a bolt from below and a flipped bolt from above. Turned back half a step, the standoffs stand between the arms, as many as there are arms.

   • Make parts/bolt.ts:

   export async function m3Bolt(length: number) {
       const profile: Bit.Inputs.Base.Point3[] = [
           [0, -3, 0], [2.35, -3, 0], [2.75, -2.6, 0], [2.75, 0, 0],
           [1.5, 0, 0], [1.5, length - 0.4, 0], [1.1, length, 0], [0, length, 0],
       ];
       const outline = await bitbybit.occt.shapes.wire.createPolygonWire({ points: profile });
       const face = await bitbybit.occt.shapes.face.createFaceFromWire({ shape: outline, planar: true });
       const body = await bitbybit.occt.operations.revolve({ shape: face, angle: 360, direction: [0, 1, 0], copy: false });
       const hexagon = await bitbybit.occt.shapes.wire.createNGonWire({ nrCorners: 6, radius: 1.45, center: [0, -3.5, 0], direction: [0, 1, 0] });
       const socketFace = await bitbybit.occt.shapes.face.createFaceFromWire({ shape: hexagon, planar: true });
       const socket = await bitbybit.occt.operations.extrude({ shape: socketFace, direction: [0, 2.5, 0] });
       return bitbybit.occt.booleans.difference({ shape: body, shapes: [socket], keepEdges: false });
   }

   • Make parts/standoffs.ts:

   import { around } from "./around";
   import { m3Bolt } from "./bolt";
   
   export async function standoffs(arms: number) {
       const post = await bitbybit.occt.shapes.solid.createCylinder({ radius: 3.2, height: 10, center: [40, 3, 0], direction: [0, 1, 0] });
       const bolt = await m3Bolt(8);
       const lower = await bitbybit.occt.transforms.translate({ shape: bolt, translation: [40, 0, 0] });
       const flipped = await bitbybit.occt.transforms.rotate({ shape: bolt, axis: [1, 0, 0], angle: 180 });
       const upper = await bitbybit.occt.transforms.translate({ shape: flipped, translation: [40, 16, 0] });
       const pair = await bitbybit.occt.shapes.compound.makeCompound({ shapes: [lower, upper] });
       const halfBack = -180 / arms;
       const postBetween = await bitbybit.occt.transforms.rotate({ shape: post, axis: [0, 1, 0], angle: halfBack });
       const pairBetween = await bitbybit.occt.transforms.rotate({ shape: pair, axis: [0, 1, 0], angle: halfBack });
       return { posts: await around(postBetween, arms), bolts: await around(pairBetween, arms) };
   }

   • Import at the top of main.ts:

   import { standoffs } from "./parts/standoffs";

   • Add at the end of main.ts:

   const posts = await standoffs(sizes.arms);
   await draw(looks.accent, posts.posts);
   await draw(looks.steel, posts.bolts);

   • Run it with Run The Code.
   

Next: one arm.