C.I.C.D. — Nerdy Layers 3D

Build log

C.I.C.D. — Built & Competed

Continuous Impact, Continuous Destruction. A beetleweight (≤1500 g) vertical spinner — a “meta” weapon choice. Separate robot from the Lucille MK2 line, but reuses the MK2 brushless drive motors + gearboxes and the ELRS control stack; the weapon, chassis, and drive layout are new. (Competition results in the log below.)

C.I.C.D. follows the abandonment of the MK2 drum (judged not efficient enough). The thesis shifts from horizontal brute-force drum to a vertical spinner for vertical bite and self-righting potential, while keeping the reliable 4WD brushless drive that MK2 proved out. The real bot is a hybrid chassis: carbon-fibre top and bottom plates (waterjet/laser CF, the cf_cuts tab) sandwiching a 3D-printed TPU body structure and weapon uprights, carrying the 8 mm Hardox weapon — not an all-printed robot.

Photos & real build

Album: Google Photos. The physical build (see photo below) confirms: CF-twill chassis plates, steel/Hardox toothed blade + front forks, single toothed-belt weapon drive, 4× knobby wheels, socket-head bolt assembly, “CICD” engraved in the lower CF plate.

CAD is the source of truth

The Onshape assembly (link) has three front-end configurations — Clean (bare chassis), Forks, and Wedge. The competition build is the single-blade Snaggletooth weapon. An earlier concept twinned two co-axial discs; that was dropped — there’s no weight budget for two blades in the 1500 g cap.

The real build

Assembled C.I.C.D. — carbon-fibre twill chassis plates; the machined Hardox Snaggletooth blade on its belt pulley (toothed synchronous belt visible); the two Hardox front forks with ground edges; 4× knobby wheels; socket-head bolt assembly. More in the photo album.

Weapon — Vertical Spinner (single Snaggletooth blade)

Final design is a single blade, not the earlier twin-disc — the 1500 g budget doesn’t allow two. In the Onshape Weapon part studio the weapon is built from parts blade + bar on a hub (19 features; Revolve + circular-pattern teeth), selected in the assembly via the Forks configuration.

Form factor: single Snaggletooth toothed blade/bar on the central hub/pulley.
Blade design: the open-source Just’Cuz Robotics “Snaggletooth” (reference; CAD on their GrabCAD). Stock is 6″ / 0.25″ AR500 — we used the design but had it machined locally in 8 mm Hardox (not purchased from the store).
Material: 8 mm Hardox (abrasion-resistant steel) — for both the blade and the front forks. Density ≈ 7.85 g/cm³ (matches the measured mass/volume).
Blade mass: 277 g (0.277 kg — from Onshape mass properties, part blade; volume 35,270 mm³, density ≈ 7.85 g/cm³ confirms Hardox).
Spin-axis inertia: Lxx = 374.4 kg·mm² → I ≈ 3.744×10⁻⁴ kg·m² (largest principal MoI = spin axis for a flat bar; Lyy 104.6, Lzz 272.8). Verify axis against the motor-shaft mate connector.
Hub/pulley radius: 30 mm. Tooth-tip radius: TBD (measure tip-to-center).
Drive: D2830 1000 kv, single belt 1:1 → weapon RPM = motor RPM. Weapon 50A ESC.

Computed performance (4S, 1:1)

Weapon RPM: ~11,800 (1000 kv × 14.8 V × ~0.8 load) → ω ≈ 1236 rad/s
Stored energy: ~286 J (E = ½·I·ω² with I = 3.744×10⁻⁴, ω = 1236).
Tip speed: ~43–56 m/s (v = ω·r; firm up once tooth-tip radius is measured)

~286 J at 1:1 — now in-band

With the Hardox blade (277 g, I = 3.744×10⁻⁴), 1:1 already gives ~286 J, inside the competitive beetleweight window (~300–700 J). A 2:1 step-up would push ω to ~2470 rad/s → ~1140 J, likely more than the chassis/belt/mounts can survive. Recommendation flips: keep ~1:1 and firm up tip speed, rather than chase a step-up. Confirm the spin axis (Lxx assumed) before treating 286 J as final.

Weapon bearings (needle-roller, sizing analysis)

Moving the weapon to needle-roller bearings on the existing dead M8 axle (8 mm fixed shaft through the mounts; the blade + belt-pulley hub rotates around it).

Selected: 2× HK0808 drawn-cup needle bearings, straddle-mounted (one at each end of the rotating hub → splits impact load, resists cocking).
Dimensions: bore 8 mm (fits the M8 dead axle) · OD 12 mm · width 8 mm → the hub bore must be Ø12 mm, ≥16 mm deep for the two cups.
Load rating: dynamic Cr ≈ 2.55–2.75 kN, static Cor ≈ 2.4–2.6 kN per bearing. High radial capacity for the size — the reason needles beat the tiny 8 mm-bore ball bearings here for impact.
Speed rating: ~14,000 rpm (grease) / ~19,000 rpm (oil). Standards DIN 618-1 / ISO 3245.

RPM margin is tight — reinforces the 1:1 belt decision

Weapon runs ~11,800 rpm at 1:1 — that’s ~84% of the HK0808 grease limit (14k). Fine as-is with standard grease, but there’s little headroom. A 2:1 step-up (~23,600 rpm) would destroy these bearings (well past even the oil limit) — so the needle-bearing choice is another reason to stay at 1:1. Drawn-cup needles also want a hardened shaft as the inner race; the M8 axle should be a hardened dowel/bolt, not a soft cap screw.

Self-righting: vertical spinners often need it — TBD

To finalize (CAD)

Confirm the spin axis (assumed Lxx = 374.4) against the motor-shaft mate connector → locks stored energy.
Measure tooth-tip-to-center radius → locks exact tip speed.
Belt ratio: ~1:1 (~286 J) now looks right; only revisit a step-up if impacts are weak.
Rework hub bore to Ø12 mm for the 2× HK0808; confirm hardened M8 axle (needle bearings run directly on the shaft as the inner race).

Drive

4WD, 2× 2322 brushless + 25:1 planetary gearbox (one per side)
Each motor mounts on the rear wheel and drives the front wheel via a single belt, 1:1 (no reduction) — changed from the MK2-style mid-mounted / dual-belt layout.
Wheel pulley 22 mm; 56×28 RZ Lego tyres

Electronics & Power (per CAD)

Drive ESCs: 2× 40A (one per side).
Weapon ESC: 50A.
Power distribution: XT30 distribution board (XT30_DIST_BOARD_LC).
Battery: 4S 650mAh Tattu is the primary in the assembly; a 3S 850mAh MiniStar (carried from Lucille) also appears in the model — confirm which is the flight pack vs a leftover instance.

Control (inherited from Lucille MK2 / MK1)

RadioMaster ER6 ExpressLRS 2.4 GHz PWM receiver
EdgeTX radio — new model slot: CICD

Onshape Reference

Document: C.I.C.D. (Main workspace) on Onshape

CAD axis orientation — Front plane is the robot’s BACK

As with Lucille MK2, Onshape’s Front plane looks at the rear of the robot — the CAD +Y points away from the weapon, but in combat the weapon/fork side is the front (the business end). When reading views or the mass-properties axes, mentally flip: Onshape “Front” = robot rear.

Configurations (front-end variants): Clean (bare chassis), Forks (single-blade spinner — the competition build), Wedge.

Assembly instances (Forks config, 17): Body · drive motors · 4s650-tattu (battery) · 50A (weapon ESC) · 2× 40A (drive ESCs) · 3s850-MiniStar (battery) · 2× 56x28rz assembly (wheels: tire_56_x_28 + 56x28rz_sprocket + 625-zz bearing) · WeaponMountAssembly + Mirror 1 · XT30_DIST_BOARD_LC · Jackei-fork (weapon) · Assembly 1 · armor · M5×0.8×35 hex socket cap screw + M5 prevailing-torque thin nut (weapon shaft). 10 fastened mates.

Tabs: Assembly · Body · WeaponMountAssembly · WeaponMount · Weapon (parts: blade, bar, +2) · armor · old · cf_cuts (+ Sketch 1.dxf) · drive motors.

Renders (from Onshape, Forks config)

Captured 2026-07-14. Per the warning above, Onshape “Front” = robot rear — the fork/weapon side is the true combat front.

Isometric — full robot: 4WD chassis with “CICD” embossed, blue weapon-mount towers, drive belts, electronics tray, fork weapon at the front.

Front three-quarter — the two Hardox front forks extending forward, weapon blade behind them; drivetrain, PCB and weapon-mount exposed.

Weapon part studio — Hardox blade/fork plate (grey) + belt pulley & toothed hub (blue). Parts: blade, bar, +2.

Onshape Back = robot FRONT — the Snaggletooth blade + pulley centered, flanked by the blue weapon towers and drive wheels. The money shot.

Onshape Front = robot rear — “CICD” barrel, wheels, weapon towers behind.

Onshape Right = robot’s LEFT side — fork prongs, raised weapon arm, wheelbase.

Remaining views

Still to capture (drop into _resources/, cicd- prefixed to avoid filename collisions across robots): cicd-assembly-left-cad.png (Onshape Left = robot RIGHT, weapon-motor side), cicd-assembly-top.png, cicd-assembly-bottom.png, plus onshape-cicd-weaponmount.png and onshape-cicd-body.png sub-studios.

Open design questions

Tip-speed target, weapon belt ratio (1:1 vs 2:1 step-up), armor spec, self-righting scheme, which battery is the flight pack, first event target. (Resolved from CAD: single-blade weapon, drive/weapon ESCs, power board, CAD document link.)

Competition log

Jogália
🏆 Winner

event2026-07-11 location_onInstituto Superior Técnico, Tagus Park (Oeiras)
First event C.I.C.D. entered — won the tournament (11–12 July 2026).

What went wrong
- Wheels were the weak point. The rims were too brittle and took damage over the fights.
- Hub screws didn’t tighten properly — wheels worked loose; needs a better hub/fastener scheme.
Risks to fix before the next event
- Weapon belt keeps slipping into the weapon’s spin path — a belt jump/derail near the spinning blade is a reliability and safety hazard. Needs a guard or a re-route/tensioner so the belt can’t reach the blade arc.
To do
- Redesign wheels — stronger rims (less brittle material/geometry) + proper hub clamping so screws hold.
- Contain the weapon belt path — tensioner and/or guard to keep it clear of the blade.