Concept Build Readiness | Spartan Design VRC

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Why This Page Exists

Phase A locks in Skimmer, Pelican, Spoonbill, and Osprey. The four concept architectures (Heron, Crane, Stork, Falcon) are documented for engineering notebook coverage but not yet committed to build. If Phase B opens with capacity for a fifth bot, this page surfaces the readiness data needed to choose which concept to commit to.

Headline Findings

Crane is the most regulation-friendly concept. No SG2 lockout needed; six-bar motion stays vertical. R3, SG3, SG12 all pass with margin.
Stork has the strongest endgame story. 5-6″ stowed clears SG12 (18″ midfield limit) with the widest margin in the fleet. If endgame midfield dominance is the Phase B priority, Stork is the answer.
Heron has the highest reach but the most operating-angle restrictions. Stacked 4-bar + chain bar reaches 28″+ but the horizontal-forward pose violates SG2 by ~2″. Requires a software-stop floor like Pelican.
Falcon is the most ambitious and least committed. 4-DOF arm requires kinematic exclusion zones in the controller plus 5+ axis driver control. Documented for notebook depth; building it requires programming skill the team hasn't yet demonstrated.

📊

Important constraint: the team has 6 active competition slots (2822A through 2822F). Phase A fills A, C, D, E. Slots B and F are open. Phase B is an opportunity, not a requirement — the team can choose to deepen Phase A bots instead of building new ones. Don't commit to a concept just because the slot exists.

How This Compares to Phase A Commit Decisions

Phase A commits had similar gates:

Gate	Phase A passed by	Concepts must pass
R3 18″ cube at start	All 4 bots ✓	Yes — must demonstrate stowed config fits
SG2 24″ horizontal envelope	3 bots ✓; Pelican needs lockout	Yes — must identify lockout requirement
R10 88W motor cap	All ≤ 88W (Spoonbill at 88W exactly)	Yes — must fit motor budget
SG12 endgame < 18″ midfield	All 4 bots ✓ (stowed heights 6–10″)	Yes — must fold compactly
Programming complexity	2–3 motors driver-controlled per bot	Variable — up to 5 axes for Falcon
Build time available	~6 weeks per Phase A bot	Phase B has less time; complexity must drop

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Regulatory Compliance Status

Game-manual rule compliance per concept. Green is pass-as-designed; yellow needs documented mitigation; red requires architecture change.

Rule	Heron	Crane	Stork	Falcon
R3 18″ cube at start	PASS (7″ stowed)	PASS (9″ stowed)	PASS (5-6″ stowed ★)	PASS (4″ stowed)
SG2 24″ horizontal envelope	NEEDS LOCKOUT	PASS (vertical-dominant)	NEEDS LOCKOUT	NEEDS EXCLUSION ZONE
SG3 50″ vertical mid-match	PASS (~28″ max)	PASS (~28″ max)	PASS (~26″ max)	PASS (~22″ max from shoulder)
SG12 18″ midfield endgame	PASS (7″ stowed)	PASS (9″ stowed)	PASS (5-6″ stowed ★)	PASS (4″ stowed)
R10 88W total motors	PASS (~77W est.)	PASS (~66W est.)	PASS (~66W est.)	EXACTLY 88W (no headroom)
R11 55W drivetrain cap	PASS (44W drive typical)	PASS (44W drive typical)	PASS (44W drive typical)	55W drive (at cap; no PTO)
R25 Pneumatics (if used)	Optional; no constraint	Optional; no constraint	Optional; no constraint	Optional; no constraint
TOTAL	4 pass, 1 lockout	5 pass, 0 mitigations	4 pass, 1 lockout	3 pass, 1 lockout, 1 cap

What "Lockout" vs "Exclusion Zone" Means

Three different mitigation strategies map to three different programming patterns:

Lockout (single-axis floor): the lift can't drive below a specific angle. Implementation: in the driver loop, ignore lower-direction commands when the rotation sensor reads below the floor. One conditional in opcontrol(). Used by Pelican (Phase A) and would be used by Heron + Stork.
Exclusion zone (multi-axis): the arm's end-effector cannot enter a defined 2D region in arm-space (typically "anything past chassis-front + 6″"). Implementation: forward-kinematics solver computes end-effector position from joint angles each cycle; if the computed position would enter the zone, the controller ignores that joint command. Much more complex code. Required by Falcon's 4-DOF arm.
No mitigation needed: the architecture physically can't exceed the envelope. Crane is the only concept in this category.

⚠

Exclusion zones are notebook-rich but build-risky. The team has not yet demonstrated multi-axis kinematic constraint programming. Building Falcon means committing to learn forward kinematics + numerical solver + safety-validated motion control over a season. Engineering judges score the iteration narrative; if the team can show pre-build code that prevents violations, that's strong. If the team can't, Falcon fails inspection during scrimmage.

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Build Cost — Time, Motors, Parts, Code

Effort estimates for each concept if committed to Phase B build. Time estimates are CAD-to-first-scrimmage; assumes weekly meetings and consistent attendance.

Metric	Heron	Crane	Stork	Falcon
Motor count (drive + mech)	4 + 3 = 7	4 + 1 = 5	4 + 1 = 5	5 + 4 = 9
Wattage allocated	~77W	~66W	~66W	88W (cap)
Sensors (typical)	2-3 (rotation sensors + IMU)	1-2 (rotation sensor + IMU)	2 (rotation sensors + IMU)	5+ (IMU + 4 joint sensors)
Pneumatic complexity	Optional (claw or pincer)	Optional (manipulator only)	Optional (manipulator only)	Optional (claw at arm tip)
Custom polycarb pieces	~3 (chain bar mount, claw shroud)	~2 (carriage, manipulator mount)	~4 (mid platform, carriage, mounts)	~6 (4 arm segments + cover plates)
Lift bars count	4 (4-bar) + 2 (chain bar)	8 (six-bar = 2× four-bar stacked)	8 (DR4B = 2× four-bar cascade)	2-3 (rigid arm segments)
Build hours estimate	30-40 hr	40-50 hr	50-60 hr	60-80 hr
Programming hours estimate	15-20 hr	10-15 hr	15-20 hr	40-60 hr
Driver axes	3 (drive + lift + chain bar)	2 (drive + lift)	2 (drive + lift)	5 (drive + 4 arm DOFs)
Total effort	~50 hr	~55-65 hr	~65-80 hr	~100-140 hr

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Time estimates assume the team has done the architecture before. A four-bar is familiar (Pelican, Spoonbill). A chain bar is familiar (Osprey). A six-bar isn't. A DR4B isn't. A 4-DOF arm definitely isn't. For first-time architectures, multiply build time by 1.5-2×.

Code Complexity Specifically

EZ-Template handles drivetrain PID for all four concepts identically — that part is no harder for one bot than another. The complexity scales with the manipulator:

Subsystem	Code patterns	EZ-Template support
Drivetrain (all 4 concepts)	`chassis.pid_drive_set()`, `chassis.pid_turn_set()`	✓ Full support
Single-axis lift (Crane, Stork)	Subsystem PID + position presets	✓ `ez::PID` class
Lift + chain bar (Heron)	Two coordinated PIDs + state machine	~ Two `ez::PID` instances, custom coordination
Pneumatic claw (any)	Binary `set(true/false)`	✓ `ez::Piston` class
Pneumatic pincer (Osprey-style)	Same as claw	✓ `ez::Piston` class
SG2 lockout (Heron, Stork)	One conditional in opcontrol loop	n/a — custom user code
4-DOF kinematic exclusion (Falcon)	Forward kinematics solver + zone check	n/a — entirely custom

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Per-Concept Detail Card

What each concept requires if the team commits to it. Includes the one-line "what's new for the team" and the readiness verdict.

Heron — Stacked 4-bar + Chain Bar

What's new for the team	Compound manipulator coordination (4-bar carrying a chain bar); two PIDs that must hold position simultaneously while driving
What's familiar	4-bar from Pelican/Spoonbill; chain bar from Osprey
Strategic role	Highest reach with horizontal extension — can score over partner bots; only concept that does this
Regulatory gotcha	SG2 violation at horizontal-forward extension (~2″ past envelope); needs software stop on the 4-bar at +30° min
Verdict	CONDITIONAL GO — build only if the team can demonstrate two-PID coordination in code first (in simulation or off-robot)

Crane — Six-Bar Parallelogram

What's new for the team	Six-bar mechanism design (essentially two stacked four-bars sharing middle arm); rubber-band assist tuning at two heights
What's familiar	Four-bar parallelogram math; single-PID lift control
Strategic role	Highest vertical reach in a compact horizontal envelope; tall-goal scoring with no SG2 risk
Regulatory gotcha	None — this is the cleanest concept
Verdict	GO — lowest-risk concept to commit to if Phase B opens for build

Stork — DR4B (Double-Reverse Four-Bar)

What's new for the team	Cascading two-stage lift with chain-coupling; chain routing under tension; stage synchronization (both stages move together via the chain, but a single drive motor sees combined torque)
What's familiar	Four-bar mechanism (Pelican); rubber-band assist (Heron concept)
Strategic role	Most compact stowed profile (5-6″) — dominant endgame midfield position; mid-match still reaches tall goal
Regulatory gotcha	"Both stages horizontal" pose sits AT SG2 limit with no margin; needs software stop preventing both stages from going fully horizontal simultaneously
Verdict	CONDITIONAL GO — build if endgame midfield dominance is the Phase B strategic priority; otherwise Crane is simpler

Falcon — 4-DOF Articulating Arm

What's new for the team	4-DOF arm kinematics; forward-kinematics solver (compute end-effector position from joint angles); inverse-kinematics solver (compute joint angles to reach a target position); kinematic exclusion zone enforcement; 5-axis driver control
What's familiar	Drivetrain only
Strategic role	Maximum reach flexibility; can address all goal heights from one position; engineering notebook depth (judges score multi-DOF systems highly)
Regulatory gotcha	17″ arm extends ~8″ past SG2 at full forward; requires arm-space exclusion zone implementation. 88W cap = zero motor headroom. 5-axis driver control = significant practice time required
Verdict	NO-GO for Phase B — documented for notebook depth but not buildable in Phase B time frame. Re-evaluate as a Phase C project after team has built kinematic experience on simpler concepts.

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Phase B Concept Decision

Putting all four sections together into a recommendation. The team makes the actual call; this is the analyst's read.

Recommendation

🏆

If the team builds a fifth bot in Phase B, build Crane. Lowest regulatory risk (no lockout needed), familiar 4-bar mechanics doubled into a 6-bar, highest vertical reach in the fleet, fits the team's existing programming skill (single-axis PID). 55-65 hour total effort estimate is consistent with the Phase A bots' build budgets.

Why Not the Others

Heron: Compound manipulator with two coordinated PIDs is one complexity layer above where the team is. The reach advantage is real but doesn't compensate for the build risk. Revisit in season 2.
Stork: The 5-6″ stowed advantage is genuinely the best in the fleet, but DR4B chain routing is unforgiving — misaligned chain coupling means the two stages desync and the carriage tilts. Build risk too high for a Phase B bot without a dedicated mentor on chain routing. Strong notebook story even unbuilt.
Falcon: 4-DOF arm + kinematic exclusion zone is two complexity layers above where the team is. The 17″ reach is impressive but the SG2 violation requires arm-space exclusion-zone code the team can't yet write. Definitely keep documented for notebook depth; don't build.

Alternative: Don't Build a Fifth Bot

The Phase A fleet (Skimmer, Pelican, Spoonbill, Osprey) covers floor pickup + tall-goal stacking + quadrant toggling. Capacity exists, but capacity isn't a reason to build. Consider:

Deepen Phase A V2: use Phase B time to add pneumatic pincer to Osprey (replacing V5 claw), iterate Skimmer's Path B mechanism based on bench-test data, improve Pelican's lift PID tuning
Driver practice: running scrimmage drives across all 4 Phase A bots will produce more wins than a fifth bot at 60% reliability
Notebook depth on the concept architectures: all four concept pages can be expanded with prototype-stage iteration narratives (build a paper-mockup, test a sub-mechanism on a Phase A chassis) without committing to a full bot. Judges score this kind of iterative documentation.

💡

The conservative call is "Don't build a fifth bot." The aggressive call is "Build Crane." Both are defensible. The right answer depends on team capacity, attendance through the back half of the season, and whether competition results in scrimmage 1 suggest a strategic gap (e.g., "we couldn't reach the tall goal under endgame pressure") that a fifth bot would close.

Decision Framework for the Coach

Use this three-question filter before committing to Phase B build:

What strategic gap does the fifth bot close? If "none specifically" or "general capability" → don't build. If "we need tall-goal scoring from compact endgame stance" → Crane closes it.
Does the team have 50+ hours of build capacity remaining after Phase A finishes? Add up remaining meetings × productive hours per meeting. If under 50, don't commit.
Is there a programmer who can write the new patterns? Crane is one new PID subsystem. Heron is two coordinated PIDs. Stork is chain-coupled motion. Falcon is kinematics. Pick a concept where the answer to "who's writing this" is a specific student name, not "we'll figure it out".

If all three answers point GO, build Crane. If any answer is uncertain, deepen Phase A instead.