Furnace V1 Waste-Oil Foundry Plans (Rev C)

No. Furnace V1 is a Rev C design package, not yet built or fire-tested. It was designed, calculated and drawn, then checked by two automated (AI-run) design reviews: one on the numbers (33 findings) and one on the drawings and guide (28 findings). Every finding has been dealt with on paper, but 27 of the fixes can only be confirmed by a physical test on a real build. Four findings on the control wiring are on hold until the actual relay parts are chosen and reviewed. The fix register lists 8 open risks (see below). The first real build is next. Founder buyers get a free update to the first field-built revision, which will include what that build teaches.

Rev C is a paper revision of Rev B. Its main change is a stronger flame-safety chain:

• a UV flame detector replaces Rev B's cad cell, which could mistake a glowing furnace for a flame;
• a safety relay that needs a manual START after every trip;
• a separate 15 s light-up timer;
• two oil valves in series;
• an air switch that proves real air flow.

It also has:

• a screw-together pipe-fitting burner with a MIG-tip nozzle;
• no welding on the thin drum;
• a lighter lining and a swing-arm lid with no chains or counterweight;
• oil feed down to 5 °C;
• the tank moved to 3 m in a spill tray.

Rev C costs more to build than Rev B. The flame-safety chain is a design feature, not a safety guarantee: it has not been wired or tested, and no certified safety rating is claimed.

Only if you want a detailed, documented starting point and are comfortable building from an unproven design. Founder pricing (code FOUNDER25: 25% off Plans or Pro, first 25 orders) reflects the risk. If it is not what you expected, you get your money back within 14 days, no questions.

Nothing has been melted in it yet. It is designed for a 5 kg aluminium charge of recovered metal (dry, crushed cans, added in small batches) or a 7 kg brass/bronze charge.

• Brass needs high fire (38 kW), and the chamber must be kept at or below 1200 °C (measured with a thermocouple) to keep the lining's temperature margin. The full crucible weighs 11.8 kg against a 12 kg lift limit, so it is a two-person lift.
• Cast iron and steel are out of scope.

The fix register lists 8:

1. No wiring/firing release yet. The exact compatible relays, safety-relay inputs, air-switch contacts and UV-control terminals are not yet chosen or reviewed. The custom 120 V control panel needs a competent, component-specific electrical review and fuel-isolated bench fault tests before it is wired or fired.

2. Flame, air and oil safety depend on tests on the real build:

   • the UV eye must not see the ignition spark;
   • the flame signal must be steady at LOW;
   • detector temperature;
   • early and in-run flame loss;
   • welded-relay faults;
   • measured response time;
   • a separate leak test of each oil valve.

   The ≈ 17 mL of oil released on a flame failure is a model figure.

3. The lining's temperature margin is conditional, and the castable datasheets govern. You need a non-oil heat source for dry-out. The chamber must stay ≤ 1200 °C, the hot spots ≤ 250 °C and the lid-tab skirt ≤ 450 °C. Inspect after heating cycles. There is no measured efficiency.

4. The lifting tools are unproven and the lid motion is conditional:

   • crucible fit and mass;
   • a 25 kg proof test of the home-made tongs and shank;
   • a dry transfer rehearsal;
   • lid clearance, droop, latch and push tests;
   • two people for brass, ≤ 12 kg lift.

5. Adding cans needs a full stop, purge and relight, which depends on working controls. Drying cans never proves hidden cavities are dry. Stop after a second unplanned lockout.

6. Several things must be measured on site:

   • real compressor and blower performance;
   • cold-oil flow at the lowest tank level;
   • fitting availability and leaks;
   • atomizing air flow;
   • spill-tray volume;
   • site clearances.

7. Welding on the thin drum is avoided by design, but the structural welds, bolts and added brackets and tools still need inspection.

8. Costs are estimates ($1,556 scavenged / $2,840 bought) and above Rev B. The real controls, a dry-out heat source, local materials, shipping and tax may raise them.

These are model estimates:

• Aluminium 5 kg from cold: about 76 minutes at normal fire, 49 minutes at high fire.
• Aluminium 5 kg, furnace already hot: 28 / 17 minutes.
• Brass 7 kg (high fire): about 69 minutes cold, 23 minutes hot.
• Adding cans: each addition costs a stop, purge and relight of about 3 minutes, so a hot aluminium melt with 4 or 6 can additions takes about 49 or 60 minutes.

These are first-order calculations (about ±30 % or worse), not measurements.

About 1.2 / 2.6 / 3.9 litres per hour at low / normal / high fire (12 / 25 / 38 kW), and about 3.2 L for one cold aluminium melt at normal fire (model estimate). The 20 L tank lasts about 5 hours at normal fire. Log your real fuel use; the savings over Rev B are model numbers.

The 85-line parts list estimates about $1,556 using salvage and scrap where sensible ($1,310 build + $246 of PPE), or about $2,840 by the cheapest buy route. The buy route still uses some tested used/surplus items, such as the UV parts and safety relay; buying those new retail brings it to about $3,150. The scavenged route also includes purchased parts:

• dense and insulating castable, ceramic blanket and firebricks;
• an air compressor with a rated receiver;
• the flame-safety controls (about $405 scavenged / $793 bought);
• the crucible and PPE.

Prices are estimates and were not quoted. The Pro spreadsheet lets you enter your local prices.

• Comfortable cutting and welding mild steel (none on the thin drum sheet).
• Threaded pipe and compression fittings.
• 120 V control wiring, plus a competent electrical review of the panel before it is wired.
• Mixing and casting refractory.
• Safe molten-metal practice.
• A purchased compressor with a rated receiver (≥ 25 L/min, 0.9 SCFM, free air at 30 psi).

If any of that is new to you, get an experienced person involved.

Filtered used engine oil from a known, traceable source. That means not "free oil" of unknown origin: the guide says to reject any oil you can't vouch for. A Babington burner atomizes it. The oil is settled for at least 7 days, then filtered through a 100-micron sock and a 100-mesh strainer. Burning used oil is regulated or banned in some places, so check your local rules first.

No furnace that burns oil and holds molten metal is "safe". The safety measures are:

• In the design: a UV flame detector and safety relay with manual restart, a separate light-up timer, two oil valves in series, air-flow proving, a sealed drain, a spill pan and a tank spill tray.
• In the guide: commissioning tests that are release conditions, a dry-out schedule and a full safety section.

It is not certified and not professional engineering advice, the flame-safety chain has not been wired or tested, and you build and use it at your own risk. Outdoors only. Read the Safety Disclaimer before buying.

Pro adds the 26 DXF CAD files (cover/index + 25 drawings) and the parts spreadsheet (.xlsx/.csv). Take Pro if you use CAD, have parts cut by a shop, or want to price the build.

The Plans are a PDF: 26 A3 sheets (cover/index + 25 drawings), plus the guide. It prints fine at A3 or tabloid and is readable on screen. Pro adds DXF R2010 in mm, XLSX and CSV.

Millimetres, kg and °C, with imperial in brackets where useful; pipe and fittings use the US sizes you buy them in.

Yes. Castings and items you make with a furnace built from these plans are yours to sell. What you can't do is resell or share the plans or files, or sell furnaces built from them as a product without a commercial license.

No. The license is for one buyer. Your friend can buy their own copy, or get the free sample first.

The cover, the full contents, one complete drawing sheet (WOF-C-D01 general arrangement), a parts-list excerpt and the pre-run safety checklist.

14 days, no questions: email us or reply to your receipt. Founder buyers can also get a refund if no field-built revision is issued within 12 months of their purchase.

After the first real build and commissioning. There's no fixed date, and progress will be posted in public.

Our merchant of record (Gumroad) processes payment, adds and remits sales tax/VAT where required, and delivers the files instantly by download link and email.

Please email [email protected]. Confirmed errors are fixed in free errata for Rev C for every buyer.