Pelican

Architecture at a glance

Split tower — three C-channels, two bays

The tower stands vertically from the rear of the chassis with three 1×5×1 aluminum C-channels arranged side-by-side along the lateral axis. The middle C-channel sits on the chassis centerline; the left and right C-channels are mounted near the chassis side rails. This creates two structural bays:

• Right bay — spans from the centerline to the right rail. Houses the four-bar lift and V5 claw. The right and middle C-channels carry the lift's pivot bearings.
• Left bay — spans from the left rail to the centerline. Houses the flex-wheel toggle mechanism. The left and middle C-channels carry the flex-wheel mounting and toggle motor.

The middle C-channel does double duty: it’s a structural member and a mounting point shared by both bays. This means it carries asymmetric loads (lift torque on the right face, toggle reaction force on the left face) and is the most stressed structural element in the tower. Bracing matters here — the middle channel needs a top cap or cross-brace tying it to the left and right channels so it doesn’t flex laterally under lift load.

Side view — tower, four-bar lift, V5 claw

Top view — bay layout, COG balance

Drivetrain — preseason 4-motor blue config

The drivetrain is the team's preseason configuration: four 11W V5 Smart Motors with Blue (600 RPM) cartridges, one per wheel on a tank-drive layout. This carries over unchanged from preseason testing and is shared with the Osprey baseline.

Right bay — four-bar lift + V5 claw

Left bay — flex-wheel toggle

Motor budget

If V5 claw is upgraded to 11W instead of 5.5W: total is 88W exactly, 0W spare. The team should keep 5.5W as the V5 claw default unless physical testing shows the half-motor can't open/close the claw fast enough under load.

Center of gravity analysis

The four-bar lift + V5 claw + 2 lift motors is a heavy assembly that lives on the right side of the rear tower. Without compensation, this would pull the COG significantly to the right, making the robot unstable under tight turns and likely to tip when the lift extends (extending lift → mass moves further right and up → right-side tipping moment grows).

Mass estimates (rough)

Vertical COG and tipping under lift extension

The harder problem is vertical COG when the lift is extended. With claw + cup at ~25″ above floor, that ~2 lb of mass is now 25″ up — raising the COG significantly. The robot becomes more tippy in any direction, especially if the lift swings through the side as it extends. The four-bar's parallel motion helps here (the claw doesn't swing around an arc the way a single-arm lift would; the end-bar translates without rotating). Even so, the robot should always extend the lift only when stationary or moving slowly, and the driver should be trained to retract before initiating any tight turns.

Inspection compliance — R3, SG2, SG12

This section walks through how the build holds up against the three V5RC rules that govern physical size. Verdict: passes SG2 easily, requires deliberate choices to pass R3, requires driver discipline to comply with SG12.

R3 — 18″ × 18″ × 18″ starting volume

The robot must fit inside an 18″ cube at the start of the match. Two stack-ups to verify: vertical (chassis + tower) and horizontal (chassis + lift forward extent).

SG2 — 24″ × 24″ horizontal expansion during match

SG12 — 18″ vertical limit in endgame zone

The lift at extended +60° puts the claw at ~26.6″ above floor (with a 12.5″ tower) or ~28″ (with a 13.5″ tower). This violates SG12 if the robot is in the endgame zone with the lift up. SG12 only applies in the endgame zone, not during regular play, so this is a driver-discipline issue, not a hardware issue.

Inspection summary

Two committed decisions get the robot through inspection: (1) tower length 12.5″ (1×5×1×25) and (2) match-start lift position +30° or higher. Both are within the build team’s control.

Game-ready analysis

How Pelican performs in a 2-minute match: which goals it covers, how long each scoring cycle takes, what the driver does, and the realistic cycle count per match. Used together with the decision matrix below, this is the “will it actually score points?” check before locking the build.

Goal coverage

Pelican’s four-bar puts the end-bar (and therefore the claw) at 14.5″ above field tile when arms are horizontal forward (the REST position) — that’s higher than even the tall goal at 8.77″. Goal deposits happen with the lift tilted below horizontal, dropping the claw to just-above-goal-lip height and opening to release. Maximum reach is reserved for endgame or special handoffs (extended +60° puts claw at ~26″).

All three field goals plus the loader-receive position are within reach. The four-bar’s parallel motion keeps the claw orientation level through the lift cycle, so cups don’t tilt or spill on the way to the goal.

Cycle time math

Two cycle types: floor pickup (drive to an element, claw it, lift to score) and loader catch (drive to loader, receive a placed element, lift to score). Floor pickups are the bread-and-butter; loader cycles are higher-value but longer.

The floor-pickup cycle is fundamentally limited by the V5 claw close time and the absence of an active intake: every element requires the robot to stop or slow, position over the cavity, and execute the claw-close sequence. This is the trade-off of using a claw-based intake instead of a roller — reliability and grip-strength are higher, but cycle pace is slower than continuous-roller architectures like Skimmer.

Auton routine (15 s)

Pelican’s auton plays to its strength: the V5 claw is reliable enough to pre-load and score quickly without complex sensing. A representative routine:

1. 0.0–0.5 s: Pre-loaded element in claw at match start. Lift starts at +45° (R3 inspection-compliant), drops to REST horizontal as the round goes live.
2. 0.5–2.5 s: Drive forward to alliance goal.
3. 2.5–4.5 s: Lift to alliance deposit angle (-40°), open claw, drop pre-load.
4. 4.5–7.5 s: Drive forward over a floor pin in the alliance zone (cavity engagement), close claw.
5. 7.5–9.5 s: Lift to alliance angle, drop second element on alliance goal.
6. 9.5–12.5 s: Drive to second alliance pin, repeat pickup.
7. 12.5–15.0 s: Score third element on alliance goal.

Realistic auton output: 2–3 alliance scores plus auton bonus. Stretch goal: 4 scores if pin-pickup-and-score sequences run cleanly without drift correction time.

Driver-control routine (1:45)

The 105-second driver-control phase is where Pelican’s cycle count compounds. A representative driver pattern:

• 0:00–0:30 (alliance run, ~30 s): Cycle 1–5 on alliance pins lying in the alliance zone. Lift stays in the -40° to REST range. Quick cavity-grab-lift-drop pattern. Target 4–5 cycles.
• 0:30–1:00 (loader trip, ~30 s): One trip to the alliance loader for a tall-goal cup. Drive back-end-first, lift to +45°, human places cup, claw close, drive to tall goal, lift to -15° deposit, drop. Costs ~9 s for one high-value score; net 2–3 alliance scores worth of points in one cycle. Target 1 loader cycle and 2–3 floor cycles in this window.
• 1:00–1:30 (toggle + cleanup, ~30 s): Toggle activation when path crosses a field toggle (flex wheel takes 0.5–1 s of contact time). Floor cycles for any remaining accessible elements. Target 3–4 cycles plus 1 toggle.
• 1:30–1:45 (endgame, ~15 s): Retract lift to REST (under 18″ for SG12), drive to endgame zone, hold position. No scoring.

Realistic driver-control output: 11–14 cycles + 1 toggle. Combined with auton: 13–17 elements scored per match, plus toggle bonus.

Strengths

• V5 claw reliability. The claw is a manufactured VEX kit with predictable open/close behavior. No R24 plastic risk, no custom-fab failure modes.
• Parallel-motion lift. Four-bar keeps the claw level through the lift arc — cups don’t tilt, no orientation correction needed.
• Independent toggle. The toggle motor is mechanically separated from the lift, so toggle activation doesn’t share duty cycle or thermal load with scoring.
• All-three-goal coverage. Lift angle adjusts to deposit at any goal height. No goal is out of reach.
• Loader-friendly geometry. Tower at chassis back means the robot drives back-end-first under the loader chute — the same direction the chassis is shaped to retract from after a successful catch.

Limitations

• No active intake. Every floor element requires drive-stop-grip; no roller-while-driving like Skimmer. Cycle floor is ~5.5 s, hard to push below.
• Cavity dependency. Element must enter the cavity in a known position before claw close. If the cavity geometry doesn’t funnel reliably in physical testing, the claw can miss-grip and the cycle fails.
• Tipping under extended lift. Lift at +60° raises COG — aggressive turns under load can tip. Driver must retract before tight maneuvers.
• Inspection start-position dance. Lift held at +45° for R3, drops to REST as auton step. One additional auton action.
• No multi-element capacity. One element at a time. Can’t pre-stage multiple cups for batch scoring.

Match scenarios

Decision matrix — Pelican vs. fleet

How Pelican compares to the four other named architectures across six dimensions, scored 1–5 (5 = best), out of 30 total.

Open questions for the build team

• C-channel length (R3-constrained). Choose 1×5×1×25 (12.5″) or 1×5×1×27 (13.5″). Both pass R3’s 18″ vertical cube limit when stacked on the 4″ chassis. Recommendation: 1×5×1×25 (12.5″) for the 1.5″ margin against hardware and chassis-height variance. Lift reach at +60° from a 12.5″ tower still puts the claw at ~26.6″ above floor — trivially above the tall goal at 8.77″, so no capability lost.
• Lift arm length. 14″ baseline assumed in side view. Final value depends on (a) goal-clearance margin, (b) chassis-front to claw-rest distance (the cavity-clearance constraint), and (c) torque load on lift motors at extended position. Compute torque at extended position before locking.
• Lift pivot height on tower. 11″ baseline for the lower pivot. Tradeoff: higher pivot → more reach but more tipping moment. Verify the cavity clearance check (~5.7″) at whatever pivot height is chosen.
• V5 claw motor power. 5.5W half-motor or full 11W? Recommend 5.5W to preserve the 11W spare. Bench-test the half-motor closing speed against a loaded claw (cup + pin combo) to confirm.
• Alignment cavity geometry. Where exactly is the cavity floor, walls, and entry mouth? Side view shows it at chassis-front low, ~5.7″ below claw-rest; CAD or physical mockup needed for actual dimensions. Pin/cup geometry must funnel into a known position before claw closes.
• Flex wheel diameter and contact height. 4″ baseline assumed. Verify against actual game-toggle height/geometry. The flex wheel needs to spin against the toggle’s active surface, which has a specific field-mounted height per the manual.
• Battery / brain exact placement on the left. The COG analysis assumes ~5″ lateral offset from centerline. To improve balance further, push battery toward the left rail (offset 6-7″) and put brain just behind it. CAD this in once the lift is in place.
• Anti-tip strategy. Driver discipline only? Or add anti-tip wheels? Decide after first drive-and-extend test.
• Intake? The current build doesn’t include a separate intake mechanism — the V5 claw is the intake. Acknowledge: this means the robot can’t pick up pins from the floor without driving up to them and lowering the claw. If field testing shows this is too slow, an intake roller becomes a future addition (within the 5.5W spare).
• Middle C-channel bracing. The middle C-channel takes asymmetric load from both bays. Add a top cap or X-brace tying it to the left and right C-channels. Specify in CAD.

Relationship to Osprey (chain-bar baseline)

Osprey is the chain-bar variant of Pelican (V1.0 baseline architecture) architecture — the original baseline the team explored for V1.5. This build (the four-bar variant with V5 claw and split tower) descends from that line of thinking but has converged on different mechanism choices:

The decision to diverge was driven by (a) the V5 claw kit being a known, manufactured part with predictable behavior versus a custom chain-bar end-effector, (b) the four-bar's parallel motion preserving claw orientation through the lift cycle (chain bars require additional linkage to keep the claw level), and (c) the team's interest in a clearly separated toggle mechanism that doesn't share hardware with the lift.

Port map (template — fill in as built)

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

Open architectural question — dual-side toggle?

Pelican currently specs a single 11 W flex wheel toggle in the left bay of the split rear tower. The new Osprey (2822E) dual-side architecture (2 × 5.5 W mirrored, independent L/R driver controls) raises the question whether Pelican should reconsider — with one architectural complication that doesn’t apply to Skimmer or Osprey: the split tower already allocates the left bay to toggle and the right bay to the four-bar lift. There’s no symmetric “right-side bay” for a second toggle.

See also

• Spartan Hero Bot V1.5 — the four-bar architectural baseline Pelican commits to. Read this for the V1.5 platform reference and the manipulator-architecture menu (A/B/D/E).
• Kite — Pelican’s direct architectural sibling (Team 2822F). Same four-bar lift + V5 claw + V1.0 baseline; diverges on power transmission only. Kite shares the two 11W lift motors with the toggle via a single driven shaft using different sprocket ratios (arm geared for torque, toggle geared for speed). The clearest A/B comparison in the fleet for “dedicated motor per mechanism” (Pelican) vs “shared motor across mechanisms” (Kite). 16.5W spare on Kite vs 11W spare on Pelican.
• Spoonbill — sister-bot (Team 2822D) using a center tower with rotating V5 claw and dual-wheel rear toggle. Same four-bar lift mechanism as Pelican, different tower placement and toggle architecture. The orientation-control counterpart to Pelican’s static-claw cycle-reliability.
• Osprey — sister-bot (Team 2822E) using the chain-bar variant of the same baseline. Same chassis, same drivetrain, same toggle architecture; different lift mechanism. The committed-cycle counterpart to Pelican's variable-deposit four-bar.
• Owl — sister-bot (Team 2822O) using a pneumatic-pivot flex-wheel manipulator instead of Pelican’s V5 claw. Inherits Spoonbill’s chassis (center tower, dual rear toggle); the manipulator is Owl’s defining divergence. Useful comparison for “commercial claw vs custom active intake” trade-offs across the V1.0 family.
• Skimmer — Team 2822A’s simultaneous build (different architecture: 2-bar swing arm + polycarb tube intake). Compare motor budgets and complexity.
• Heron — the team’s alternative four-bar concept, paired with a chain bar instead of a claw. Useful reference for four-bar mechanics.
• Falcon — the 4-DOF articulated arm concept. The V1.5 Hero Bot is the simpler counterpoint — less articulation, fewer motors, more reliable cycles.
• Fleet overview — all named robots and concepts.