The whole appliance, and a metal shop to build it

At the start of these four weeks the design was a 48-line sketch of a box that receives refrigerated carbonated water from another appliance and injects flavoring into it. That document was deleted on 7 April.

What replaced it describes a complete machine: a custom stainless pressure vessel it carbonates in, its own refrigeration loop, a five-layer insulated cold core with the flavor bladders nested in the thermal gradient, and a front-hot, back-cold under-sink layout. The hardware directory went from five entries to eleven, gaining a bill of materials, a purchase ledger, a regulatory position, plumbing diagrams and wiring diagrams.

The shop

A $3,899 handheld fiber laser welder was ordered on 6 April and arrived on the 13th. Around it came a 12-ton hydraulic press, a 24-inch slip roll, a welding cart, an argon cylinder and regulator, three spools of stainless MIG wire, magnets, practice coupons, a pipe tap, and a copper chill bar. Three heavy workbenches arrived to hold it.

A complete soldering bench landed on 22 April in one order, and a full refrigeration bench between the 21st and 23rd: vacuum pump, manifold gauges, leak detector, isobutane, torch kit, silver braze rod, flaring tool, tube cutter and bender, filter-driers, and a gram scale.

No weld, press or roll is recorded by 25 April. The filler wire matching the chosen alloy was ordered on the 24th and arrives after these four weeks close.

The pressure vessel

The vessel changed shape through the period: a welded round cylinder, briefly an off-the-shelf air tank, a racetrack body rolled from flat sheet, a 3D-printed plastic sphere, then two press-formed steel half-shells.

On 24 April it settled on a commodity 5-inch stainless tube capped with two quarter-inch laser-cut discs, with the four ports tapped straight into the thick discs so no fitting needs welding in. Ten tubes and twenty end plates were ordered the same day, about $1,358 of stock. Every other geometry moved into a folder named plan-b.

Two other things closed with it. The spray nozzle became a bubbler stone, which produces bubbles at the available pressure where the nozzle produced no spray. Level sensing became a magnet floating on a rod, read by sensors glued to the outside, so nothing pierces the wall.

Refrigeration by teardown

The 1 April plan was a $420 pre-charged refrigeration module that never gets opened. By the 15th, two countertop ice makers had been bought as donors. On the 17th one was disassembled and its refrigerant circuit traced by hand — the compressor model read off the can, the capillary tube found bonded to the suction line, the ice-harvest bypass valve identified for deletion.

The refrigerant is isobutane, which is exempt from the federal venting rules, so the loop can be cut, brazed, evacuated and recharged without certification.

Paperwork

A per-unit bill of materials came to about $1,287 after an audit caught five double-counting errors and fixed pack amortization; it had read about $1,505 a week earlier. Alongside it: a capital ledger, and a written regulatory posture covering refrigerant handling, end-use approval, the hydrocarbon-appliance safety standard, and the required flame markings and charge limits.

Marketing became a directory: a target-market definition, five competitor write-ups, an open-questions list, and a sixteen-concept video plan. The price moved from a flat $6,000 to two tiers — the first fifty units hand-built, numbered, signed and sold with a personal install call at $7,500, and everything after at $5,500.

What churned

Two-thirds of the period's commits touched printed parts. What they left behind is one two-piece snap-together pump case, a shared snap-fit library holding a single empirically chosen tolerance, a mock tube, and two README stubs. The insulating shell took 59 commits and ends the period as a README and an empty placeholder.

Also gone: the multi-stage design pipeline documents, the 55-step cartridge build sequence, the bag frame, and a printed plastic pressure vessel whose threaded ports leaked under pressure.