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MP1 — Modular Breathing Apparatus (BA) Stowage

A universal, modular stowage system for SCBA/BA kits designed with Emergency One (E1).
The MP1 replaces bespoke, one-off fixtures with a configurable assembly that fits single cylinders and twin-pack systems while meeting ergonomics and crash-load requirements.

Design Envelope & Constraints

• Cab integration envelope: 256 mm (W) × 735 mm (H) × 275 mm (D), derived from E1 cab CAD (“green zone”) so installation is drop-in compatible. Targeting the cab envelope allows easy adaptation for rear lockers as well. See the cab “green zone” CAD in Figure 1.

• Use context: tight cab clearances; operation in full PPE (low dexterity/visibility); rapid egress; valve access while docked. Shallow depth is the controlling constraint; width/height are more forgiving.:contentReference[oaicite:2]{index=2}

• Crash requirement: withstand 10 g with a ~20 kg cylinder (≈1962 N equivalent load in tests).

System Architecture (what’s in the design)

• Back plate & sliding front panels — structural spine that bolts to E1’s seat frame; two sliding panels set the clamping width for single or twin-pack kits.

• Side-clamping, hands-free mechanism — user pushes the BA into the dock; the push plate retracts and pair of curved clamping arms wrap the cylinder(s); a Southco rotary latch locks the arms. Torsion springs reset the mechanism open.

• Vertical restraints — spigot at the base carries static weight; top stopper (L-bracket + bumper) prevents upward “bounce” over rough terrain.

• Release & override — seat-integrated pull handle connected by cable for quick release; manual access to the latch for emergency override is preserved. Controls are colour-coded red for visibility in the cab.

Locking & Release

• Locking: Southco R4 rotary latch + matching catch — automotive-grade, stress-tested component; the hook mounts to rear of the push plate.
• Release: seat pull-handle (cable) for fast, gross-motor actuation in PPE; manual override access retained per client safety requirement.

Bottle Restraints (Vertical Control)

• Bottom spigot: carries static weight; bracketed to the back plate.
• Top stopper: L-bracket + elastomer bumper; captures the crown of the cylinder to stop upward movement.

Materials & Finish

• Structure: 3 mm mild steel sheet (E1 standard stock) — balances strength, cost, and manufacturability on E1’s laser + brake-press lines.
• Fasteners & springs: stainless fasteners; torsion springs sized for repeatability and reset force margins.
• Bumpers: nylon/rubber stoppers at contact points to control impact/wear.
• Finish: powder coat; red for user-actuated parts (handle, moving arms) to increase discoverability in dark cabs.

Structural Performance (FEA highlights)

Global requirement: survive 10 g crash events and daily operational shocks.

• Back plate (V4.0):
  Max stress ≈ 398.8 MPa (< UTS 724 MPa); peak deflection ~0.26 mm. V4 bends cut peak stress by ≈29.7% vs flat plate.

• Main body assembly:
  Max stress ≈ 1.533×10⁸ N/m² at slide-to-back-plate interface; deflection ~0.075 mm; welds at pivot/latch brackets remain elastic.

• Top stopper & spigot:
  Stopper max stress ≈ 3.94×10⁷ N/m², deflection ~0.5 mm under bump; spigot max stress ≈ 1.98×10⁶ N/m², deflection ~0.0087 mm under static weight — ample margin.

• Clamping arms:
  Max stress ≈ 1.46×10⁸ N/m² at inner curve; tip deflection ~0.93 mm under half-side load (981 N), acceptable with latch engagement and dual link bars.

Fatigue Life (S-N based)

• Main body: with operational stress ≈ 1.533×10⁸ N/m² and daily cyclic events (top/bottom hits, braking pulls), life exceeds 15 years; stresses stay below ~327.5 MPa endurance limit (assumed for alloy steel).
• Clamping mechanism: ~21,915 cycles (4 open/close per day × 15 yrs) → > life target, only sub-millimetre tip deformation expected; no critical fatigue hot-spots.

Manufacturing & Assembly (DfMA)

1. Laser cut all steel parts from 4 mm sheet; nests yield efficient material use.
2. Brake-press bends on back plate, push plate, and stopper bracket (controlled radii to avoid cracking).
3. MIG weld pivot mounts, latch brackets, and link connectors (QA for penetration/position).
4. Powder coat for corrosion/wear resistance and part identification.
5. Final assembly: build main body + clamping module on the back plate; fit springs, latch, cable; set sliding panels to kit width; pin via pilot holes to prevent drift.

Human Factors

• Gross-motor release (seat handle) avoids fine motor actions in PPE.
• Valve access preserved for in-vehicle checks.
• Vertical orientation avoids “submarining” under crash loads.
• Shallow depth prioritised for cab comfort; red touch-points improve discoverability.

Integration & Naming

The product integrates with E1’s existing seat mounts and naming convention: MP1 (Modular Pack 1), complementing SP1/SP2. Sliding panels + spigot allow single or twin-pack kits without bespoke re-engineering, improving standardisation across fleets.