Cost Savings Analysis Report¶
1. Purpose & Scope¶
A companion to the Weight Distribution Report: where the weight study asks where is the mass and where can it be cut, this asks where is the cost and where can it be saved. It breaks the build down by system, separates one-time capital from recurring/consumable spend, and ranks the realistic savings levers.
All figures are the mid-column estimates from the Cost Breakdown (the itemized source of truth); the build mid-total is ~$27,539.
2. Method — Capital vs Recurring¶
Just as the weight study set aside the fixed container shell to find the addressable design, a cost study has to separate the one-time capital build from spend that recurs or is consumed — savings strategy is different for each.
| Bucket | Mid | What it is |
|---|---|---|
| Capital build (one-time hardware) | $24,349 | The systems you build once — this is where build-savings live |
| Consumable (per 50-print batch) | $1,650 | Cyanotype chemistry + substrate (Standard ½-Ware) — recurs every batch |
| Recurring (per deployment) | $750 | Commercial-hire transport |
| Soft / regulatory | $790 | Licenses & permits |
Build-savings work on the $24,349 capital. The $1,650 consumable is attacked separately (bulk chemistry, cheaper substrate) because it repeats every batch and quickly dominates lifetime cost.
3. Where the Cost Is¶
Capital systems ranked by mid cost:
| System | Mid | % of capital | Notes |
|---|---|---|---|
| Processing water system | $5,804 | 24% | Tray (304 SS) + IBC frame dominate |
| Film-plane mechanism | $3,684 | 15% | Carriages, Option-A cross-slides, cam-lever clamps, wall-seat saddles |
| Container + delivery | $3,300 | 14% | Grade-dependent (CW vs WWT) |
| Perimeter walkway | $2,488 | 10% | GRP grating + steel cantilevers |
| Power & electrical | $2,384 | 10% | Battery + solar + distribution + protection |
| Light lock | $1,728 | 7% | Plastic-skin custom fabrication |
| Hinged panel structure | $1,408 | 6% | Stepped frame + PP skins + Al core + EPDM + latches + B2 bay |
| Swing pivot | $1,143 | 5% | Pivot post + bearings + cage + fixed RHS door frame |
| Interior conversion | $1,138 | 5% | Insulation, sealing, safelight |
| Ventilation & cooling | $884 | 4% | Fans + cooler + inverter + baffle-duct fab + canopy |
| Chemistry prep shelf | $203 | 0.8% | Fold-down phenolic board + frame + hinge/stays + tap extension |
| Optics — pinhole | $185 | 0.8% | Trivial (it is a pinhole) |
The water system is 24% of the capital build and the 304 SS processing tray is its single biggest line ($1,300–$2,015) — the same item that topped the weight study.
4. Savings Opportunities¶
Ranked by dollar potential and ease. Status is updated as levers are actioned.
| # | Lever | System | Saves | Ease / risk | Status |
|---|---|---|---|---|---|
| 1 | Container grade CW → WWT (wind-water-tight used vs cargo-worthy — fine for a stationary darkroom) | Container | ~$1,350 | Easy, low risk | Available |
| 2 | Drop film-plane electric actuation → manual (the mechanism already supports manual tilt/swing) | Film plane | ~$827 | Easy, if manual is acceptable | Actioned 2026-06-13 (banked) — manual is the standard build, so this is already realized, not a still-available saving; electric is a documented upgrade only (Cost Breakdown §4.4) |
| 3 | Processing tray: 304 SS → poly (poly needs a support frame over the 4.5 m span + poly-weld fab) | Water | ~$600–$1,000 | Medium | Decided 2026-07-05 — keep 304 SS (self-supporting + durable; not revisiting) |
| 4 | Battery — already 1×100 Ah (the lean config; Water System Report: 1×100 Ah ≈ 25+ prints/charge). A 2nd pack is a +$375 optional upgrade, not a saving. | Power | +$375 (add) | — | Not a saving — 100 Ah is the standard |
| 5 | Solar 3 → 2 panels (if the power budget allows) | Power | ~$133 | Easy | Available — computed (drop 1× 200W panel) |
| 6 | Valves / fittings value-engineering | Water | ~$100–$200 | Medium | Available |
After the material decisions, the only still-available build-savings levers are 1 (container grade) + 5 (solar) — together ~$1,500 off the $24,349 capital build (~6%), plus ~$100–200 of valve value-engineering (#6). Everything else is settled: lever 2 banked (manual is the standard build), lever 3 kept 304 SS (decision), lever 4 already 1×100 Ah.
Derivation note. Lever 1 (container grade), lever 5 (solar), and the roll-up total + percentage are computed in
costing.py— container is a true CW − WWT subtraction off the scenario layer, solar is a real 1-panel subtraction (drop 1×solar-panel-200w), and the roll-up is the summed still-available levers over the capital build, so all cascade on any cost change. Bucket-B finding (2026-07-05): modeling each option against the as-built BOM showed lever 2 (film) is already banked — manual is the standard build — and lever 4 (battery) is moot — the standard is already 1×100 Ah, and its 2nd pack is a +$375 upgrade, not a saving — so both were dropped from the roll-up. Lever 3 (tray) is now decided too — 304 SS kept (over the 4.5 m span a poly tray needs a support frame that erodes the saving, plus poly-weld fab) — so it also leaves the roll-up.
5. The Cost–Weight Tension¶
Cost and weight do not always move together — some weight savings cost money, and vice versa. Worth keeping in view when prioritizing:
- The GRP walkway grating (corrosion immunity in the chemistry zone) added ~$720–890 to save 62 kg. Decided 2026-07-05 — keep molded GRP: the 62 kg weight saving + corrosion immunity are worth the premium; the ~$800 galvanized-steel alternative is not being taken.
- The processing tray (lever #3): SS → poly would cut both cost and weight, but decided 2026-07-05 to keep 304 SS — over the 4.5 m span a poly tray needs a support frame (eroding the saving) plus poly-weld fabrication; 304 SS is self-supporting and durable.
6. What Is Effectively Fixed¶
- Container shell — already the cheapest large steel box; only the grade is a lever (#1).
- Light lock — already the cheap custom option ($1,728 mid vs $2,500–4,500 for a commercial darkroom door).
- Swing pivot, ventilation, optics — small absolute spend; diminishing returns.
- IBC frame, pumps, filters — load-bearing or commodity; little to cut safely.
7. Source References¶
- Cost Breakdown — itemized build cost, three scenarios, all sources cited (the figures this report summarizes).
- Weight Distribution Report — the companion mass study; the tray is the shared top lever.
- Film Plane Mechanism Report — manual vs electric actuation (lever #2).
- Water System Report — processing tray (304 SS) and battery/pump sizing (levers #3, #4).
- Electrical Report — power-system sizing (levers #4, #5).