Team 2822 Concept
Heron
Stacked Reach Arm · Four-bar lift + chain bar end-effector
// LINEAGE FROM V.1
From V.1
Spartan Hero Bot V1.0 chassis-class drivetrain and toggle architecture.
Changed
Lift → DR4B (double-reverse four-bar); Tube B intake variant.
Because
V2.0 exploration — taller reach for top-goal cycling; Tube B tested as alternative to Tube A.
Evidence
Tube B prototype data; reach math from the chassis-stacked-lift-geometry study.
📛 Why "Heron"
The compound mechanism's profile resembles a heron's posture — long-necked, hinged, capable of fast strike from stillness. The four-bar provides the gross lift (the bird's body height); the chain bar at the top provides reach extension and orientation control (the bird's hinged neck striking forward). Like Falcon, it's a predator with articulated reach — a coherent naming family for the Spartan fleet.
What it is
Architecture
Reach envelope
Motor budget
Torque
Manipulator analysis
Decision matrix
CAD starting point
Build sequence
Open questions
Port map
Build log
What this is
A compound (stacked) lift architecture: a standard four-bar parallel-linkage lift carrying a chain bar manipulator at its end. The four-bar handles bulk vertical motion while keeping the manipulator level; the chain bar adds reach extension and independent end-effector orientation, expanding the workspace beyond what either mechanism could achieve alone. More reach than a pure four-bar, simpler than a DR4B, more orientation control than either.
Why we're exploring it
Override scoring rewards both reaching tall goals (where height matters) and placing payloads at varied positions (where end-effector orientation matters). A four-bar alone gets the height; a chain bar alone gives the orientation; stacking them combines both at modest motor budget cost. The trade is build complexity — two mechanisms means two failure modes and double the tuning.
Architecture geometry
The four-bar's parallelogram lifts the chain-bar pivot platform straight up while keeping it level. The chain bar extends forward (or back) from that platform with a 1:1 chain holding the manipulator level through its arc. The result: an end-effector that translates in a 2D workspace bounded by the four-bar's vertical sweep and the chain bar's horizontal reach.
Side view — stacked architecture at three positions
Three positions: stowed (dashed gray, chain bar tucked back over chassis), mid-reach (orange, end-effector at short-goal height), full-extension (green, end-effector at tall-goal height plus reach over the SG2 boundary).
Approximate dimensions for prototyping
| Subsystem | Dimension | Value | Notes |
|---|---|---|---|
| Chassis | Width × depth × height | 18″ × 18″ × 4–5″ | Per R3; 4–5″ allows below-tower wiring/battery |
| Tower | Height (chassis top → 4-bar pivot) | 3–4″ | Lower the better; minimizes 4-bar arm length needed |
| Four-bar | Arm length | 14–16″ | Longer arm = more vertical sweep; sized for ~13″ vertical lift at the end platform |
| Four-bar | Parallelogram height | 3–4″ | Distance between upper and lower arm pivots; smaller = stiffer |
| Chain bar | Arm length | 10–12″ | Longer = more horizontal reach but more cantilever moment on 4-bar |
| End-effector platform | Mounting plate dim | 3″ × 4″ × 0.090″ Al | Holds chain bar pivot, sprocket, and chain bar's drive motor |
| Total vertical reach | Floor to manipulator center, max | 25–28″ | Tower (3″) + 4-bar lift (13″) + chain-bar height (8″) + manipulator (4″) |
| Total horizontal reach | Chassis center to manipulator center, max | ~12″ | Constrained by SG2 24×24 expansion zone |
The SG2 horizontal expansion limit is the hidden cost of stacked architecture. A 12″ chain bar arm extending from a four-bar that's already swept forward will hit the 24×24 envelope quickly. Heron has more vertical reach than Falcon, but its horizontal advantage is mostly capped by the rule. Plan to retract the chain bar before the four-bar reaches forward, or accept that "max horizontal extension" and "max vertical extension" are mutually exclusive states.
Reach envelope vs. Falcon vs. Osprey
Three architectures, three workspace shapes. Each has its strengths; the right pick depends on what scoring positions matter most for your driving strategy.
Reach envelope overlay — Heron / Falcon / Osprey
All three architectures shown to the same scale (1″ = 9 px). Goals positioned at ~25″ forward of chassis center. Heron's envelope is taller; Falcon's is more flexible (semicircle); Osprey's is smaller but well-matched to alliance and short-neutral goals.
Reach summary
| Robot | Max vertical reach | Max horizontal reach | Best at |
|---|---|---|---|
| Osprey | ~22″ | ~9″ | Alliance + short neutral. Tall is reachable but tight. |
| Falcon | ~25″ | ~17″ (any angle) | All three goals + load station + endgame zone. Most flexible. |
| Heron | ~28″ | ~12″ (capped by SG2) | Tall center goal + reaching over alliance partners. Loses flexibility to Falcon. |
Reading the comparison: Heron beats Falcon on vertical (~3″ extra) but loses on horizontal flexibility (Falcon can reach any angle within its semicircle; Heron's chain bar is forward-back only). The right architecture depends on whether your scoring strategy needs height (Heron wins) or orientation/angle flexibility (Falcon wins).
Motor budget — can it fit in 88 W?
Override caps total motor power at 88 W per R10a. Heron's stacked architecture spends motors on three subsystems: drivetrain, four-bar lift, and chain bar. The remaining headroom is what's available for the manipulator.
Motor budget arithmetic (Heron baseline):
Drive : 5 × 11 W Blue (600 RPM) ........ 55.0 W
Four-bar : 1 × 11 W Red (100 RPM) ......... 11.0 W
Chain bar: 1 × 11 W Red (100 RPM) ......... 11.0 W
Toggle : 1 × 5.5 W half-motor ........... 5.5 W
Subtotal (no manipulator) ............... 82.5 W
Headroom for manipulator ................ 5.5 W
Cap (R10a) .............................. 88.0 W
5.5 W is enough for one 5.5 W half-motor manipulator (V5 claw or polycarb tube rotation) or zero (pneumatic pincers, which use no electric motor). The toggle is allocated 5.5 W for a flex-wheel interaction motor following the Skimmer pattern.
Manipulator-specific budget impact (with toggle allocated)
| Manipulator choice | Motor cost | Air cost | Total power | Spare ports / headroom |
|---|---|---|---|---|
| V5 claw | 1 × 5.5 W | 0 | 88.0 W | At cap; 0 spare |
| Pneumatic pincers | 0 | 1 cylinder + solenoid + air supply | 82.5 W | 5.5 W spare; 1 spare motor port |
| Polycarb tube + cinch | 1 × 5.5 W (rotation) | 1 cylinder + solenoid + air supply | 88.0 W | At cap; 0 spare |
Pneumatic pincers' hidden advantage on Heron: by trading the manipulator's electric motor for pneumatics, you free 5.5 W and a motor port. That port can become a 6th drive motor (Blue 11 W → 66 W total drive, +20% top speed) without breaking the 88 W cap. None of the other manipulators give you that drivetrain upgrade option.
Torque analysis — can both motors handle the load?
Heron's stacked architecture has two motors carrying loads through their own ranges. The four-bar carries the chain bar + manipulator + payload through vertical sweep. The chain bar carries just the manipulator + payload through a horizontal-arc sweep. Both need their own torque analysis — the four-bar's is significantly worse because it carries everything below it.
Worst-case load — four-bar at horizontal, chain bar fully forward
Worst case: four-bar horizontal forward, chain bar fully extended forward, cup at chain bar tip. Total moment arm to cup = 25″ (15″ four-bar + 10″ chain bar). The four-bar motor sees the entire stacked load; the chain bar motor only sees the load past its own pivot.
The math — four-bar (worst case)
Four-bar torque demand (horizontal extension):
Cup payload .................. 0.5 lb at 25" ......... 12.5 lb-in
Manipulator + chain bar ...... 1.0 lb at 20" ......... 20.0 lb-in
End platform ................. 0.3 lb at 15" .......... 4.5 lb-in
Four-bar arm self-weight ..... 0.6 lb at 7.5" ......... 4.5 lb-in
Total τ_demand_4bar ........................................ 41.5 lb-in
11W Red 100 RPM motor with 1:7 sprocket reduction:
Stall torque (motor-side) ............................... 14 lb-in
Stall torque (output-side, after 7:1) ................... 98 lb-in
τ_demand / τ_stall = 41.5 / 98 = 42% → near thermal limit, will overheat in match
─────────────────────────────────────
With rubber band assist (8 × #64 @ ~10 lbf, 6" perpendicular):
τ_assist (peak, arm horizontal) = 10 × 6 = 60 lb-in counter-torque
τ_assist (effective at horizontal, geometry-derived) ~ 30 lb-in
Net motor torque required:
τ_net = 41.5 - 30 = 11.5 lb-in (12% utilization, well under thermal limit)
The math — chain bar (separate motor)
Chain bar torque demand:
Cup + manipulator ............ 1.0 lb at 10" ......... 10.0 lb-in
Chain bar arm self-weight .... 0.4 lb at 5" ........... 2.0 lb-in
Total τ_demand_chainbar .................................... 12.0 lb-in
11W Red 100 RPM with 1:5 sprocket reduction:
Stall torque (output-side) ............................. 70 lb-in
τ_demand / τ_stall = 12 / 70 = 17% → comfortable, no assist needed
Chain bar can be sized without rubber band assist; the 1:5 reduction is sufficient.
The four-bar's rubber band assist is non-negotiable on Heron. Without it, the four-bar motor runs at 42% of stall torque continuously when the chain bar is forward — which is well above the 25% threshold where V5 motors begin tripping internal thermal protection during a 2-minute match. The 8 × #64 band sizing comes from solving for τ_net ≈ 12 lb-in at horizontal. Document this math in the engineering notebook with the resulting band count; judges score the explicit torque-analysis-with-band-sizing artifact higher than just "we used rubber bands."
Manipulator analysis — three choices
The chain bar's level-preserving property means Heron's end-effector arrives at the goal in a known horizontal orientation. The manipulator's job is just to grip and release. Three reasonable options — each with a different trade profile.
Option A — V5 Claw (motor-actuated grip)
What it is: the standard VEX 276-2270 claw assembly driven by a single 5.5 W motor at the chain bar's tip. Open/close via motor speed; hold via PID position-hold or simple stall current.
Build interface: claw mounts to chain-bar end via 1×1×3 C-channel + screw plate. Motor mounts inboard of claw to keep weight close to chain-bar pivot. Rough envelope: 5″ × 4″ × 3″.
Element handling: grips a pin (1.6″ dia) cleanly. Grips a cup waist (2.32″) with a wider claw spread. Combo (pin-in-cup) requires the claw's grip width to span the full cup OD — tight fit, prone to slipping. Cycle time: ~600 ms per pickup-release cycle (claw motor speed limited).
Option B — Pneumatic Pincers (cylinder-actuated grip)
What it is: two pivoting jaws actuated by a single short-stroke pneumatic cylinder (e.g., VEX 276-2470 single-acting cylinder). Cylinder retracted = jaws open; cylinder extended = jaws closed.
Build interface: custom jaw plates (could be R24 polycarbonate or aluminum), cylinder mount block, two pivot pins. Jaws ~4″ long, opening to ~4″ spread. Air line runs from chassis tank up the four-bar arm to the cylinder. Rough envelope: 5″ × 5″ × 2.5″.
Element handling: grips pin and cup equally well (jaw travel covers 1.5–4″). Combo handling depends on jaw geometry — with curved pin-conforming jaw faces, the combo grip is excellent. Cycle time: ~150 ms per cycle (pneumatic actuation is essentially instant).
Option C — Polycarbonate Tube + String Cinch
What it is: heat-bent polycarbonate tube with a pneumatic-pulled string cinching around the held element, plus a 5.5 W motor rotating the tube around its axial axis for fine orientation control. See the design study and OnShape guide for full mechanism documentation.
Build interface: end caps on both sides of tube via #4-40 mechanical fastening; rotation drive via 1:5 sprocket reduction; cylinder + air line as for pincers. Rough envelope: 6″ × 3″ × 5″.
Element handling: tube ID 2.55″ accepts cup waist (2.32″) with margin; pin (1.6″) sits loosely until cinched. Combo handled at the cup's waist, with the pin retained inside the cup. Cycle time: ~300 ms per cycle (cinch is fast; rotation is the throttle).
Decision matrix — manipulator choice for Heron
Score 1–5 (5 = best). The reasoning column matters more than the score; if your team's strengths or weaknesses change the weighting, the totals change.
| Dimension | V5 Claw | Pneumatic Pincers | Polycarb Tube |
|---|---|---|---|
| Cycle time grip → release per element | 3 ~600 ms motor-limited | 5 ~150 ms instant pneumatic | 4 ~300 ms cinch + orient |
| Build difficulty hours, parts count, R-rule risk | 5 stock VEX, ~2 hrs | 3 custom jaws, plumbing, ~6 hrs | 1 R24 fab + plumbing + drive, ~12 hrs |
| Programming difficulty PID loops + state machine | 3 claw PID + 4-bar PID + chain bar PID | 4 digital out + 2 PIDs (4-bar, chain bar) | 2 cinch + rotation PID + 4-bar + chain bar (4 axes) |
| Driving ease cognitive load on driver | 3 3 buttons (4-bar, chain, claw) | 4 2 sticks + 1 trigger; binary grip | 2 2 sticks + cinch + rotation; 4 controls |
| Element flexibility cup / pin / combo | 3 pin OK, cup OK, combo iffy | 4 all three work with curved jaw faces | 5 all three; cinch holds combo at cup waist |
| Motor budget impact spare for drive upgrade | 3 5.5 W spare | 5 11 W spare → 6th drive motor possible | 3 5.5 W spare |
| Total (out of 30) | 20 | 25 | 17 |
Recommendation for Heron: pneumatic pincers. The combination of (1) fastest cycle time, (2) freed motor port enabling 6-motor drive, and (3) adequate element flexibility makes pincers the best fit for the stacked architecture. The chain bar already provides the level-orientation that the polycarb tube's rotation would otherwise add — on Heron, the tube's rotation feature is partially redundant, which is why it scores lower here than on the Osprey design study.
Decision matrix — Heron vs. Falcon vs. Osprey
With the recommended manipulator (pincers for Heron, claw for Falcon as built, claw for Osprey baseline), how does Heron compare overall?
| Dimension | Osprey (chain bar + claw) | Falcon (4-DOF arm + claw) | Heron (stacked + pincers) |
|---|---|---|---|
| Goal coverage | 3 alliance + short, tall is tight | 4 all three goals well | 5 all three + reach over partner |
| Cycle time (avg) | 3 ~3.0 s/cycle | 4 ~2.5 s/cycle (4-DOF efficient) | 3 ~3.5 s/cycle (sequencing 2 lifts) |
| Build complexity | 4 familiar parts | 3 articulating arm tuning | 2 two stacked mechanisms + pneumatics |
| Driving cognitive load | 4 2 controls (lift + claw) | 2 5 controls (shoulder, elbow, wrist, claw, drive) | 3 4 controls (4-bar, chain, pincers, drive) |
| Notebook story | 3 familiar architecture | 4 articulating arm = rich design choices | 5 stacked architecture rare; many decision matrices |
| Risk of failure (higher = lower risk) | 5 single-mechanism, well-understood | 3 arm tuning is a known headache | 2 2 mechanisms = 2× tuning, 2× failure modes |
| Total (out of 30) | 22 | 20 | 20 |
Heron and Falcon tie at 20 points; Osprey leads at 22. The matrix is telling us that for a team without specific reasons to commit to compound-mechanism complexity, Osprey hero is still the most robust starting point. Heron only earns its place if (a) the team has already mastered four-bar and chain bar separately, (b) the strategic value of the extra ~3″ vertical reach is high, and (c) the additional 8–10 hours of build/tuning time is available without sacrificing driver practice.
CAD starting point — numbers to put into OnShape today
If your team commits to prototyping Heron, here are the dimensions to start with. These are conservative estimates — expect to iterate during build.
Subassembly dimensions
- CHASSIS18″ × 18″ × 4″ aluminum 1×2 box rail frame
- DRIVE5 × 11 W Blue 600 RPM, 5:3 reduction, 4″ omni; or 6 × 11 W if pneumatic pincers used
- TOWER (4-BAR PIVOT)3.5″ tall, centered laterally, 4″ from chassis back edge
- FOUR-BAR ARM15″ between pivot centers; 3″ between upper and lower arm pivots (parallelogram height)
- FOUR-BAR DRIVE11 W Red 100 RPM, 1:7 sprocket reduction (12T → 84T) + rubber-band assist (8 × #64 bands)
- END PLATFORM3″ × 4″ × 0.090″ aluminum plate; mounts chain-bar pivot + chain-bar drive motor
- CHAIN-BAR ARM10″ from pivot to manipulator mount; 12T sprocket on tower-fixed side; 12T sprocket on manipulator side; #25 chain
- CHAIN-BAR DRIVE11 W Red 100 RPM, mounted on end platform, 1:5 reduction
- MANIPULATOR MOUNT2″ × 3″ aluminum plate at chain-bar tip with universal #4-40 hole pattern (see below)
Universal manipulator mounting plate
To keep the manipulator interchangeable across prototypes (claw / pincers / tube), design a single mounting plate at the chain-bar tip with a standardized bolt pattern. Each manipulator subassembly gets its own adapter that bolts to the same plate.
| Plate feature | Spec | Purpose |
|---|---|---|
| Plate dimensions | 2.0″ × 3.0″ × 0.090″ aluminum | Provides mating surface for all three manipulator types |
| Bolt pattern | 4 holes, 0.116″ dia (#4-40 clearance), at corners of a 1.5″ × 2.5″ rectangle | Centered on plate; symmetric so manipulator can rotate in 90° increments if needed |
| Center hole | 0.50″ dia, plate center | Wire pass-through for cylinder air line, rotation motor power, sensor cabling |
| Chain-bar attachment | 4 × 0.140″ dia holes for #6-32 bolts to chain-bar end | Attaches plate to the chain-bar arm tip; uses larger fasteners than the manipulator side because of higher cantilever loads |
Manipulator-specific adapter dimensions
| Manipulator | Adapter spec | Total assembly weight |
|---|---|---|
| V5 claw | 1×1×3 C-channel bracket bolted to mounting plate; claw motor mounted inboard | ~0.45 lb (claw + bracket + motor) |
| Pneumatic pincers | Custom aluminum base 3″ × 4″ with cylinder mount block + 2 jaw pivots + jaw plates | ~0.55 lb (assuming aluminum jaws) |
| Polycarb tube | End caps from VEX 1×1×3 C-channel + tube body + rotation drive subassembly | ~0.40 lb (lightest; polycarb is lighter than aluminum) |
OnShape document structure suggestion
Set up the OnShape document with three Part Studios, then assemble:
- Part Studio 1 — Chassis & Tower: chassis frame, drive motor mounts, tower, battery and brain locations.
- Part Studio 2 — Four-Bar Lift: upper arm, lower arm, parallelogram links, end platform, drive sprocket and chain.
- Part Studio 3 — Chain Bar: chain-bar arm, chain-bar drive sprockets, end-platform-side and manipulator-side bearings, manipulator mounting plate.
- Assembly — Heron: mate all three Part Studios + selected manipulator (use the polycarb tube model from /polycarb-tube-onshape-guide as one of the manipulator options).
Build sequence — if you commit to Heron
The right order matters. Building the four-bar and chain bar in parallel means double the partial-assembly debugging. Sequential is safer.
- Phase 1 — Chassis & drivetrain (week 1). Build the rolling chassis with motors, controller, drive code. Drive practice can begin immediately on a chassis-only robot. Stop point check: chassis drives forward, backward, turns; battery sits flat; brain is accessible.
- Phase 2 — Four-bar lift only (week 2). Add the tower, four-bar arm, end platform (no chain bar yet). Tune the four-bar PID to hold position at three setpoints (low, mid, high). Stop point check: four-bar lifts smoothly with rubber-band assist sized correctly; doesn't sag at full extension under platform-only load.
- Phase 3 — Chain bar on a fixed test stand (week 3, parallel). Build the chain-bar subassembly on a separate test fixture (a piece of 1×2 extrusion clamped to a workbench). Tune chain-bar PID to hold three setpoints. Don't bolt to the four-bar yet. Stop point check: chain bar arcs 0–180° smoothly; manipulator stays level via the chain.
- Phase 4 — Integration (week 4). Bolt the chain-bar subassembly to the four-bar's end platform. Re-tune both PIDs (the dynamic load on the four-bar changed). Test combined motion. Stop point check: all three goal heights reachable with chain bar both forward and back; no oscillation when stopping.
- Phase 5 — Manipulator integration (week 5). Mount the chosen manipulator (claw, pincers, or tube). Test pickup at loader and deposit at all three goals. Stop point check: 100 cycles at the loader → goal → loader without dropping a payload.
- Phase 6 — Driver practice + iteration (weeks 6–8). Driver practice begins. Expect at least one PID re-tune as the driver discovers edge cases the bench testing missed.
If Phase 4 integration fails (re-tuning the four-bar with chain-bar load proves intractable), abandon Heron and revert to Falcon or Osprey. Don't sink more than 6 hours into Phase 4 without success — that's the signal that the architecture is over your team's bandwidth this season. Document the failure for the engineering notebook (it's a strong "we tried, we learned, we pivoted" story).
Open questions for the team
- Manipulator choice. Pincers is the matrix recommendation, but does your team have pneumatic experience? If not, the claw's lower programming load may matter more than pincers' speed advantage.
- Chain-bar drive location. Mount the chain bar drive motor on the four-bar's end platform (cantilever load, but simple chain run) or at the four-bar's pivot via a long routed chain (added complexity, but reduces moving mass)?
- Rubber-band assist on chain bar. Sized for what payload weight? Run the math for cup + pin combo at full chain-bar extension.
- Reach math. Run the kinematic analysis: at chain-bar fully extended forward, where is the manipulator in (X, Y) coordinates? Does it actually reach the tall goal AND clear the alliance partner's robot?
- Comparison vs. Falcon. Is the extra 3″ of vertical reach worth the loss of horizontal flexibility? Driver practice will tell you.
- Build sequence. Build four-bar and chain bar separately first (Phases 2–3) or design them together from CAD?
📐 Architecture references (public site):
Four-bar fundamentals — spartandesignrobotics.org/mechanism-lifts. Chain bar deep dive (sprocket math, build sequence, AURA origin) — spartandesignrobotics.org/mechanism-chain-bar. The compound four-bar + chain bar architecture itself isn't a public-site page yet; if Heron progresses past concept, that page becomes worth writing.
Concept sketches
To be added during prototyping. iPad + Apple Pencil sketches and napkin geometry as the team explores the architecture. Photograph each iteration with a date in the corner.
CAD exploration
To be added once CAD prototyping begins. OnShape document link and screenshot once a starting concept is locked in.
Decision log
To be filled in as the team decides. Each significant design decision and the reasoning behind it. This is the "show your work" record for both EN4 and future seasons.
Port map (template — fill in if Heron progresses to build)
Pre-allocated port assignments for Heron's planned motor layout. If the team commits to building Heron, copy this table into robot-config.cpp and update as wired.
| Port | Subsystem | Motor / sensor | Notes |
|---|---|---|---|
| 1 | Drive front-left | 11W Blue 600 RPM | 5:3 reduction · 4″ omni |
| 2 | Drive front-right | 11W Blue 600 RPM | reversed |
| 3 | Drive mid-left | 11W Blue 600 RPM | — |
| 4 | Drive mid-right | 11W Blue 600 RPM | reversed |
| 5 | Drive back-center | 11W Blue 600 RPM | OR 6th drive if pneumatic pincers manipulator |
| 6 | Four-bar lift | 11W Red 100 RPM | 1:7 sprocket reduction · rubber band assist (8 × #64) |
| 7 | Chain bar | 11W Red 100 RPM | 1:5 sprocket reduction · mounted on four-bar end platform |
| 8 | Manipulator | 5.5W half-motor (claw or tube rotation) OR pneumatic out (pincers) | Pincers frees this port |
| 9 | Toggle (if added) | 5.5W half-motor | Optional — Heron's headroom allows; not in baseline budget |
| 10–21 | Spare | — | Reserved for sensors and post-swap expansion |
| ADI A | Limit switch | — | Four-bar zero-position reference |
| ADI B | Pot V2 | — | Chain bar position feedback |
Build log (template — if Heron progresses)
Each build session adds an entry: date, team members, what was attempted, what worked, what didn't, decisions made.
Template entry:
2026-MM-DD · Team members: ___ · Phase: ___
What we attempted: ___
What worked: ___
What didn't: ___
Decision made: ___
Next session focus: ___
2026-MM-DD · Team members: ___ · Phase: ___
What we attempted: ___
What worked: ___
What didn't: ___
Decision made: ___
Next session focus: ___
See also
- Skimmer — Team 2822A's active build. Different architectural philosophy (single-DOF + dual-feed) but the manipulator decisions inform how Heron should think about its tube option.
- Falcon — the 4-DOF arm concept (formerly Mantis). Heron's most direct comparison for "more reach than Osprey."
- Crane — six-bar vertical lift concept; same parallelogram family as Heron's four-bar.
- Stork — reverse four-bar (DR4B) concept; the compact-folding cousin in the long-necked-bird family.
- Osprey — the chain-bar baseline. Heron extends this architecture by adding a four-bar lift underneath.
- Polycarb tube design study — the manipulator option C deep dive.
- Polycarb tube fabrication guide — if option C, the bench reference.