Osprey

Architecture at a glance

Match cycle — loader → arc → goal

Osprey's defining feature: every scoring cycle is the same six steps in the same order. The chain bar has only two rest positions (back and front), and the only motion between them is one 180° arc with the manipulator held level by the static-sprocket. There is no “mid-arc deposit” option, no “score this cup at the short goal then turn around for the next pin” flexibility. Commit to the cycle, get repeatability for free.

1. Position back-cavity at loader. Robot drives back-end-first so the chassis-back cavity is under the alliance-color loader. Chain bar at 0° rest (manipulator at 13″ pivot height, pointed back).
2. Receive match load. Drive Team raises the loader (per SG11) and drops a cup, pin, or pin-on-cup combo into the manipulator at back-rest. Manipulator closes (pincer pneumatic, or tube cinch).
3. Drive to goal. Robot translates to the target goal. Arm stays at 0° (back-rest) during transit — low CoG, defensive contact tolerated.
4. Position front-cavity at goal. Robot drives so the goal sits inside the front-cavity notch in the chassis. Driver feels the chassis “hug” the goal as it nests.
5. Sweep + release. Chain bar arcs 0° → 90° → 180° (~1.5 s with rubber band assist). At 180° the manipulator is over the front cavity, directly above the goal. Release: pincer opens or tube cinch deflates. Cup/pin drops onto goal lip.
6. Reset. Arm sweeps 180° → 0° during the drive back to the next loader. Travel time and arm reset overlap.

Center tower — why and how tall

For a strictly-chain-bar lift with rest cavities at both ends of the chassis, the tower's X position is forced: it must sit at the geometric center of the 18″ chassis, halfway between front-cavity and back-cavity, so the arm at 0° rest reaches the back cavity and the arm at 180° rest reaches the front cavity with the same arm length. Symmetry is mandatory; the only free parameter is tower height.

Tower-height-vs-goal-height math

The team picks one tower height as the build commitment. 2822E's commitment is the tall-goal config (13″ pivot, ~9″ tower above the 4″ chassis top). Reasoning: tall-goal scoring is the highest point value per element in Override; loader-to-tall-goal cycling is what Osprey is geometrically optimized for. Short-goal and alliance-goal scoring become possible-but-unreliable secondary modes (the manipulator drops the cup from too high; bounces and roll-offs become likely).

This is the architectural commitment that makes Osprey distinct from Pelican. Pelican's four-bar can deposit at any goal height by stopping the lift mid-arc; Osprey can't. If the team strategy needs flexible-goal-coverage, Osprey is the wrong robot. If the team strategy needs fast, repeatable tall-goal scoring, Osprey is the right robot.

Side view — tower, two rests, the 180° sweep

Top view — tower at center, cavities, dual-side toggle

Toggle mechanism — dual-side mirrored

Override field toggles sit on top of the perimeter wall (wall is 11.54″ tall × 2.00″ thick; toggle assembly center is at ~12.5″ off field tile). The toggle is a 25.99″ long triangular bar (cross-section 2.03″ × 1.19″) that rotates around its long axis — three faces, three stable positions. The actuating mechanism is a flex wheel pressed against the toggle bar, spinning to roll the bar to the next face.

Why dual-side, not single-side

Toggles can appear on either field-perimeter side relative to the robot's heading. With single-side toggle (one wheel on one chassis flank), the driver has to either reorient the chassis 180° to engage a toggle on the wrong side, or skip the toggle this cycle. For Osprey specifically, where every cycle is a committed loader-to-goal arc, reorienting mid-cycle is an expensive interruption. Dual-side toggle costs one motor port and ~3 build hours; it eliminates reorientation cost across every match for the season.

Strategy A from the planning matrix wins on ports vs flexibility: two independent 5.5W motors (2 × 5.5W = 11W total), one flex wheel each side, mirrored 1×2×9 C-channel brackets, independent driver button bindings. Each side's toggle is mechanically and electrically independent — failure of one doesn't take down the other.

Bracket geometry

Driver controls

• L-trigger (or D-pad left): spins left flex wheel for 0.5–1.0 s, rolling the perimeter toggle to the next face on the robot's left side.
• R-trigger (or D-pad right): spins right flex wheel, same behavior on the robot's right side.
• Both triggers: spins both wheels simultaneously for symmetric engagement when a toggle is reachable from either side (the driver doesn't need to commit before approaching).

Spin direction matters: the toggle has three faces, so each press should advance one face (~120° rotation). The motor pulse duration is calibrated to 120° of toggle rotation given the flex wheel's surface speed and friction. Open question: does the driver want both wheels spinning the same direction, or opposite? Same-direction means a left and right press both rotate the toggle the same way; opposite-direction means left and right press rotate opposite ways. Test in driver practice; pick whichever is more intuitive.

Motor budget — 77 W with 11 W spare

The 11 W spare is real headroom — recovers what Hero Bot four-bar lost by going to two mirrored arm motors. Possible uses for the spare:

• Sensor port reservation. Spare 5.5 W half-motor port can become an additional encoder, IMU, or limit switch port without crowding the brain.
• Manipulator upgrade. If the team starts with pincer (5.5 W) and wants to swap to tube (11 W) later, the 5.5 W spare absorbs the increase without needing to rebalance.
• Toggle motor upgrade. Per-side toggle motor can be upgraded from 5.5 W to 11 W if bench-testing shows the 5.5 W is marginal against the actual toggle bar resistance.
• Hold as buffer. Keep the spare unallocated; gives the team flexibility to react to in-season testing data without re-engineering the whole budget.

Recommendation: hold the spare as buffer through Phase A. Allocate after first scrimmages reveal what's actually marginal in match conditions. Spare-as-buffer is more useful than spare-allocated-to-something-uncertain.

Inspection compliance — R3, SG2, SG12

Three rules dominate Osprey's chassis-and-lift compliance: R3 (start configuration), SG2 (in-match horizontal envelope), SG12 (endgame vertical envelope). The chain-bar geometry simplifies all three because the lift has only two rest positions, both inside the chassis envelope.

R3 — 18×18×18″ start cube

The chain bar tip at 0° rest is exactly at chassis-back edge — mechanical commitment, not safety margin. If the build comes in slightly off-spec (arm 9.1″ instead of 9.0″), the tip extends past the envelope. Mitigation: build the arm to 8.8″ nominal, accept 0.2″ shortfall on cavity reach (cavity can be cut 0.2″ deeper to compensate). Safer to be under-envelope than to argue with the inspector.

SG2 — 24×24″ horizontal during match

During match play (post-start), horizontal expansion is limited to 24″ × 24″. The chain bar's two rest positions both put the manipulator AT the chassis edge (not extending past it). Only at mid-arc (90°) does the arm point vertical — horizontal extent at 90° equals chassis footprint (18″), which is well under 24″. SG2: PASS with 6″ horizontal margin — comfortable.

SG12 — 18″ vertical in midfield endgame

During the last 10 seconds, midfield expansion drops to 18″ vertical. Issue: at 90° mid-arc, the chain bar arm tip is at 22″ off tile — that's over the SG12 cap. Mitigation: chain bar must be at 0° or 180° rest before entering midfield zone in endgame. Both rest positions put the manipulator at 13″ (under 18″ cap).

Programming requirement: auton routine ends with chain bar commanded to 0° or 180° rest, and the driver-control endgame trigger (or a button-bound “arm stow”) commands rest. Don't rely on the driver remembering — bind it as a habit. SG12: PASS conditionally on programming discipline.

Game-ready analysis

How Osprey performs in a 2-minute match: which goals it covers, how long each cycle takes, what the driver does, and the realistic cycle count per match. Osprey's defining trade-off is committed cycle for repeatability — every cycle is the same six steps in the same order, which is slower per-cycle than Skimmer's passive intake but more predictable than Pelican's variable-deposit four-bar.

Goal coverage (at 13″ tower, tall-goal config)

Osprey is tall-goal-optimized. This is the deliberate architectural commitment. Pelican (sister-bot Hero Bot four-bar) covers all three goal heights via lift-angle adjustment; Osprey trades that flexibility for cycle reliability and mechanical simplicity. If team strategy needs all-three-goal coverage, the team plays Pelican. If team strategy is “tall goals win matches,” the team plays Osprey.

Cycle time math

One cycle type only: loader → goal. No floor pickup option (no roller intake; manipulator can't reach tile). Every element scored comes through the loader.

Compare to Pelican's loader cycle (~8–11 s) and Skimmer's loader cycle (~5.5–8 s). Osprey is faster than Pelican because the chain bar's committed sweep is faster than the four-bar's variable-deposit sequence, but slower than Skimmer because Skimmer's vertical-tube-at-rest geometry catches loader drops without arm motion. The middle of the fleet on loader cycle pace.

Auton routine (15 s)

1. 0.0–0.5 s: Pre-loaded element in manipulator at 0° back-rest. Chain bar starts at 0° (R3-compliant, no inspection start-position dance needed).
2. 0.5–3.0 s: Drive forward to alliance partner's tall goal (2.5 s if path is clean).
3. 3.0–3.5 s: Position front-cavity at goal.
4. 3.5–5.0 s: 180° sweep + release + first score.
5. 5.0–7.5 s: Drive back-end-first to loader.
6. 7.5–9.5 s: SG11 raise + drop into back-rest.
7. 9.5–12.0 s: Drive forward to goal again.
8. 12.0–13.5 s: Sweep + release + second score.
9. 13.5–15.0 s: Drive back-end-first to loader, position for driver-control handoff.

Realistic auton output: 2–3 alliance/tall scores plus auton bonus. Stretch goal: 4 scores if loader timing is tight and field traffic is light.

Driver-control routine (1:45)

• 0:00–1:30 (relentless cycling, ~90 s): Loader-to-tall-goal cycles. Target 9–13 cycles depending on field traffic and defense. Each cycle ~7–10 s; the variance comes from defensive contact and loader timing.
• 0:30 and 1:00 (toggle activations as opportunistic, ~2 × 1 s): When driver path crosses a perimeter toggle, fire L-trigger or R-trigger as path approaches the wall. Independent dual-side means no chassis reorientation required — toggle activates without disrupting loader-goal cycle pace. Net cost: 1 s per toggle, no cycle interruption.
• 1:30–1:45 (endgame, ~15 s): Chain bar to 0° rest (under 18″ for SG12), drive to endgame zone, hold position. No scoring after 1:30.

Realistic driver-control output: 9–13 cycles + 2–3 toggle activations. Combined with auton: 11–16 elements scored per match plus toggle bonus.

Strengths

• Mechanically committed cycle. Same six steps every time. Driver doesn't choose deposit angle. Programming is simpler. Auton is more reliable. Practice-time investment compounds because every cycle is the same.
• Static-sprocket geometry. 1:1 chain bar holds manipulator level through the entire arc. No mid-air orientation correction. No cup tilt or pin spin during transit.
• Cavity-on-goal alignment. Front cavity physically nests on the goal — alignment is mechanical, not sensor-dependent. Driver feels the chassis “hug” the goal.
• 11 W spare in motor budget. Recovers headroom that Hero Bot four-bar lost. Buffer for in-season tuning decisions.
• Single lift motor. One chain bar motor instead of two mirrored four-bar motors — fewer parts, fewer failure modes, easier alignment.
• Dual-side toggle. Any toggle reachable without chassis reorientation. Toggle activation overlaps with loader-goal travel; net cost is ~1 s of motor pulse.
• Defensive durability. Manipulator gripping (pincer or tube cinch) is harder to dislodge than open-claw approaches; cup stays in manipulator under contact.

Limitations

• No floor pickup. Every element comes from the loader. Pins lying on field can't be ingested directly — alliance partner or human player must load them. Strategic dependency.
• Tower height locks goal target. 13″ tower optimizes tall goal. Short and alliance scoring are unreliable. Team must commit to tall-goal strategy.
• Cavity precision needed. Front-cavity-on-goal requires accurate driving. Misalignment by 1″ can put manipulator off-center over goal — cup deposit may miss.
• Chain bar slack risk. Long chain run from motor sprocket up the tower to the arm sprocket (~9″). Slack accumulates over a season. Tensioner required; pre-match chain check is mandatory.
• SG11 dependency. Back-cavity loading depends on SG11 loader-raise being in effect. If a tournament rules variant disables SG11, Osprey's primary input degrades.
• SG12 endgame discipline. Mid-arc position is over 18″ vertical cap. Driver/program must stow arm at rest before midfield in endgame.
• Build complexity from dual-side toggle. Two mirrored brackets, two motors, four motor-port wires, two button bindings. Modest but real complexity vs single-side.

Match scenarios

Decision matrix — Osprey vs. fleet

How Osprey compares across six dimensions, scored 1–5 (5 = best), out of 30 total. The fleet entries are the named team-builds (Skimmer = 2822A, Pelican = 2822C, Osprey = 2822E) and the active concept architectures (Falcon, Heron).

CAD starting point — numbers for OnShape

Subassembly dimensions to feed straight into OnShape. Lengths use VEX 1×N C-channel hole spacing convention (N holes at 0.5″ spacing → channel length in inches ≈ N/2).

• CHASSIS18″ × 18″ × 4″ aluminum 1×2 box rail (same as V1.5 baseline; preseason carryover)
• CENTER TOWER1×5×1×18 aluminum C-channel (length = N/2 = 9″), vertical, mounted at chassis geometric center on top of chassis frame. Pivot at top → 4″ chassis + 9″ tower = 13″ off field tile.
• CHAIN BAR ARM1×2×18 aluminum C-channel (9″ length). Two arms in parallel-bar configuration (the chain bar is a 4-bar linkage variant with 1:1 chain coupling). Sprockets at pivot end and arm-tip end, 1:1 ratio, #25 chain.
• SPROCKETS18T sprockets at pivot and at arm tip. 1:1 ratio → manipulator stays level through arc (this is the static-sprocket geometry). #25 chain sized to arm length (~9″ pitch path).
• MOTOR MOUNT (lift)1×11W Red 100 RPM, mounted at base of tower (next to pivot bearing). Direct drive to pivot sprocket. Rubber band assist sized to net out gravity at horizontal rest (count TBD; bench-test 4–6 #64 bands, adjust based on stall current).
• MANIPULATOR PLATE2.0″ × 3.0″ × 0.090″ aluminum face plate at arm tip. 4× #4-40 holes (⌀0.116″) at corners of 1.5″×2.5″ rectangle. 0.50″ center hole. (Same universal manipulator-mount spec as Pelican.)
• BACK CAVITY2″ × 2″ × 2″ cutout in chassis-back midline. Sized to clear loader-dropped element + cavity walls. Final cavity dims TBD per loader chute physical mock-up.
• FRONT CAVITY3″ × 3″ × 4″ cutout in chassis-front midline. Sized to nest tall goal (3″ ⌀ at base) + 0.5″ clearance per side. Final cavity dims TBD per goal physical fitment.
• TOGGLE BRACKET (×2)1×2×18 aluminum C-channel (9″ length), vertical, one each on left and right chassis flanks. Bolted to chassis frame with 4× #8-32 hardware per bracket. Diagonal cross-brace from bracket top to chassis frame at 6″ height (additional 1×2×6 piece).
• TOGGLE FLEX WHEEL (×2)4″ ⌀ × ~1″ thick flex wheel, 45A durometer (start point; downgrade to 30A if grip marginal). Mounted on 0.25″ stub axle at top of bracket, axis horizontal pointing toward chassis center. Wheel center at 12.5″ off field tile.
• TOGGLE MOTOR (×2)5.5W half-motor (one per side), mounted to bracket at ~6″ height. 12T → 24T = 2:1 chain reduction (#25 chain) to flex wheel sprocket.

Open questions for the build team

1. Tower-height commitment: 13″ (tall) vs 10″ (short). 2822E's working assumption is 13″ (tall-goal optimized), but the team has not formally committed. The deep-dive analysis is in /spartan-hero-chainbar-lift. Switching to 10″ later in Phase A is straightforward (replace tower C-channel with shorter piece; sweep math doesn't change). Lock this decision before machining the tower.
2. Manipulator choice: pincer vs tube. Both bolt to the same universal mount plate. Pincer is faster (pneumatic open/close ~30–50 ms vs tube cinch ~150–300 ms) and grips harder; tube handles cup-on-pin combos cleaner via its enclosed catch geometry. Bench-test both with actual game elements before committing. Manipulator decision can be reversed mid-season (4-bolt swap, ~30 min).
3. Toggle flex wheel durometer: 45A vs 30A. Harder durometer (45A) gives more positive engagement with the toggle bar; softer (30A) is more forgiving on alignment but may slip under the 1.19″-tall toggle's resistance. Start with 45A; downgrade to 30A only if bench-testing shows slip. Same approach as Skimmer's compression-wheel sizing: bench-test with the actual toggle, measure stall current, decide based on data.
4. Toggle spin direction: same or opposite L vs R. Three-face toggle has three stable positions; each motor pulse advances 120°. If left and right wheels spin the same direction, both pulses rotate the toggle the same way. If opposite, they rotate opposite ways. Test in driver practice; pick whichever is more intuitive. Wire-the-other-way is a 30-second swap.
5. Front cavity goal-clearance fitment. 3″×3″×4″ cavity is the working dimension, but the actual tall-goal base diameter and the chassis frame structural minimum near the cavity opening need physical mock-up before committing the cavity cut. Don't cut the chassis until the goal physically nests in a cardboard mock-up.
6. Back cavity SG11 timing calibration. Loader-raise (SG11) puts the chute mouth at ~12″ off tile, dropping into the back-rest manipulator at 13″ height. The 1″ vertical clearance is tight; verify with the actual loader prop before locking the back-rest manipulator orientation. May need a small angle on the back-rest (5°–10° below horizontal) to widen the catch zone. Test with Drive Team timing.
7. Rubber band assist sizing for chain bar. Chain bar mass + manipulator + element load creates a torque demand at horizontal rest (worst case). 4–6 #64 bands is the working starting point. Bench-test: drive the arm to horizontal at full power, hold; measure motor temperature after 30 s. If temperature climbs faster than ambient, add bands. Document final count in EN4.
8. Chain tensioner for the tower-spanning chain. The chain runs from the lift motor sprocket up the tower to the pivot sprocket (~9″). Slack accumulates over a season; chain skip is the main failure mode. Idler sprocket on a slotted bracket at the tower mid-height is the standard mitigation. Pre-match checklist item: inspect chain tension. Optional encoder feedback to detect skip programmatically (extra sensor port, but worth it for elim-round reliability).
9. SG12 endgame stow-arm automation. Mid-arc puts the manipulator at 22″ off tile — over the 18″ SG12 cap when robot is in midfield during last 10 s. Solution: bind a button OR a time-based auto-stow that retracts the chain bar to 0° rest at endgame trigger. Don't rely on the driver remembering. Document the button binding in EN4.

Relationship to Pelican & the V1.5 baseline

Osprey and Pelican are sister-bots — both descend from the four-bar baseline at Spartan Hero Bot V1.5. They share chassis, drivetrain, toggle architecture, and manipulator mount. The architectural divergence is the lift mechanism, and that single divergence cascades into different cycle profiles, goal coverage, and strategic roles.

Together, the two team-builds give Spartan 2822 architectural diversity within a shared platform. The engineering notebook can frame this as “same Hero Bot chassis, same drivetrain, same toggle architecture — two intentionally different lift mechanisms exploring different strategic profiles.” That's a strong design-tradeoff narrative for judges.

Port map (template — fill in as built)

Planned port assignments. Update as actual build is wired. Mirror these in robot-config.cpp so software and hardware match.

Build log (template)

Each build session adds an entry: date, team members, what was attempted, what worked, what didn't, decisions made.

Engineering notebook references

See also

• Spartan Hero Bot V1.5 — the four-bar baseline that Osprey diverges from. Same chassis, drivetrain, toggle architecture; different lift mechanism.
• V1.5 Alt Lift — Strictly Chain Bar — the deep architectural analysis that Osprey is the team-build instance of. Tower-height-vs-goal math, full R3/SG3/SG11/SG12 reasoning, three-scenario tower configs, trade-offs vs four-bar and stacked.
• Spoonbill — sister-bot (Team 2822D), four-bar with center tower + rotating V5 claw + dual-wheel rear toggle. Different lift mechanism from Osprey but shares the center-tower placement. The orientation-precision counterpart to Osprey’s tall-goal pace.
• Pelican — sister-bot (Team 2822C), four-bar variant. The flexibility-and-durability counterpart to Osprey's repeatability-and-pace.
• Kite — sister-bot (Team 2822F), four-bar variant with shared-shaft power transmission. The motor-budget-conscious build in the V1.0 family — 71.5W total with 16.5W spare vs Osprey's 77W with 11W spare. Different design philosophy: Osprey trades motor count for pneumatic plumbing; Kite trades dedicated mechanisms for sprocket-ratio specialization.
• Owl — sister-bot (Team 2822O), the V1.0 family’s other pneumatics user. Where Osprey uses pneumatics for the pincer manipulator (binary grip), Owl uses them for the pivot of an active flex-wheel intake. Both pages cover similar plumbing concerns (tank placement, R26 gauge visibility, hose routing through the arm) — useful cross-reference for Phase A pneumatic implementation.
• Skimmer — Team 2822A build, different lineage (355Z 2-bar). The fleet's floor-pickup + cycle-pace specialist; complements Osprey's loader-only role.
• Fleet page — full architectural overview of all six named robots.