Comprehensive Sheet Metal Parrilla Design and Fabrication Package

We are seeking an experienced engineer or designer to develop a complete sheet metal parrilla (wood-fired grill) from a detailed requirements brief. The successful freelancer will be responsible for producing the full design and a fabrication package ready for direct use by a laser cutter.

Project Overview:
Design a freestanding parrilla on castors, featuring a crank wheel mechanism to raise and lower the cooking deck over hardwood embers. A side brasero will be included for burning logs into coals. The design must accommodate a novel spit mounting system on the lifting carriage, allowing the crank to also adjust the spit-to-ember distance. No gas components or lid are required.

Key Requirements:

Cooking Deck:
- Dimensions: 900x500 mm.
- Three interchangeable 300 mm modules (V-grate, round-bar, plancha).
- Each module must weigh a maximum of 8 kg and be hot-swappable with one hand.
- The deck must fall 15 mm forward to a removable 304 stainless steel drip trough.

Lift Mechanism:
- 400 mm travel (deck height adjustable from 700 mm to 1100 mm).
- Left-hand crank operation.
- Maximum 10 kg rim effort when fully loaded.
- Must include a positive lock to prevent carriage free-fall.
- Designed to handle a load of 40 kg (carriage) + 25 kg (spit), with the lock holding twice this load.
- Utilizes a shaft/drum/chain system; no counterweights.

Spit System:
- Ø16 mm 304 stainless steel spit, mounted in bronze bushes 180 mm above the deck.
- Removable 12 V motor with a quick-release mechanism.

Brasero:
- Pivot-out V-basket, typical Argentine style.

Firebox:
- Sized to accommodate whole 230x115x25 mm refractory tiles for the floor and back, without requiring any tile cutting.
- Internal dimensions approximately 1290x590 mm.
- Tile top at 650 mm height.
- Tiles to be loose on a 5 mm pan with a ventilated cavity below.
- Back courses secured in angle rails.

Materials:
- 5 mm thick steel for sides, cheeks, and floor pan.
- 4 mm thick steel for shell walls.
- 6 mm thick plancha (as/nzs 3678-250).
- SHS 65/50/40 for the frame.
- 30x30x3 angle for V-bars.
- Ø10 mm 304 stainless steel rods.
- 1.5 mm thick 304 stainless steel for the drip trough.
- No coatings on food contact surfaces; no zinc near the firebox.

Fabrication Considerations:
- Design must be optimized for a fabricator with only MIG welding and drilling capabilities.
- Plate parts should feature tab-and-slot design for self-jigging assemblies.
- Hot clearances (for deck cycling between 300–450 °C) must be specified.
- Wear parts must be hand-tool replaceable.
- Purchased parts must be Australian catalogue items, specified by part number.

Deliverables:
- Initial sketch for approval before full manufacturing documents commenced.
- Full cad models and step files.
- 1:1 DXF files in mm per thickness, with cut and engrave layers separated.
- Detailed drawings for every welded assembly, including a weld map.
- Comprehensive parts list.
- Engineering note specifically addressing the lift mechanism design.
- CAD dry-fit analysis with cold and hot interference checks.
- Design issues requiring written approval before fabrication begins.