Drawings
Build from these drawings—not from marketing photos. Scroll the set; each figure is the measuring source.
Materials
Gather these before you cut. Optional items use unit optional or qty 0 for notes.
| Qty | Unit | Item | Spec | Notes |
|---|---|---|---|---|
| 1 | each | Vessel | 55 gal (208 L) poly OR steel drum; food/beverage prior use preferred | No chemical or unknown prior contents; open-head preferred for stock-lid hinge |
| 1 | each | Head lid/plate | Stock open-head lid OR hinged plate in flat tight-head (~300×350 mm min) | Hinge on bottom edge of face; no hatch in curved barrel |
| 2 | each | Heavy hinges | 100 mm strap hinges with bolts | Bottom of lid face so it hangs open by gravity |
| 1 | optional | String | Cord for pull-handle / rare wind tie-down | No hasp/latch required |
| 6 | m | Leg frame | 38×38×3 mm angle iron OR 50×50 mm square tube | Weld; clearance under high end for bottle + hanging lid |
| 2 | each | Cradle saddles | Bent 50 mm flat bar lined with rubber hose | Spread load on poly drums |
| 1 | each | Drain valve (optional) | 19 mm (3/4 in) NPT ball valve at lowest point | Plus drilled weep cluster as primary drain |
| 1 | lot | Drain cluster | Many ~4–8 mm at geometric low point | No interior mesh; deburr |
| 1 | lot | Aeration holes | Sparse ~4–6 mm on sides + upper curve when tilted (mid shell) | Keep off ground-facing bottom curve—nothing should drain/fall out |
| 1 | lot | Adult entry ports | ~7–9 mm (under 10 mm) in open-end / top third on sides + upper curve | Adults fly in to oviposit; never on bottom curve when at 36° |
| 1 | each | Leachate catch | 20 L bucket or drain sump under low end | Route to treatment—not crop tea without testing |
| 1 | each | Harvest fitting | 50 mm (2 in) NPT bulkhead → 28-400 adapter OR welded boss on UNDERSIDE near head | Bottle hangs DOWN under high end |
| 1 | each | Collection vessel | 2–3 L PET bottle OR 5 L jar with matching threads | Bottom removed; empty when full |
| 1 | optional | Vent | Small drilled holes in lid/head or retained bung | Screen only if rodents force it |
| 1 | each | Gasket sheet (if cut plate) | EPDM or closed-cell strip for feed plate | Compress evenly |
| 16 | each | Fasteners | M8×40 mm bolts + nylock + washers | Frame; use stainless near wet zones |
| 1 | can | Exterior paint | Rust primer + topcoat if steel drum outdoors | Not on interior feed surfaces |
| 1 | set | Tools | Angle grinder; drill; hole saw; welder; inclinometer; deburr | File all shell edges |
Optional spreadsheet download: materials.csv
Design: BSF-55G-TILT-30
Version: 1.1.0
License: CERN-OHL-P-2.0
Family-compound / small-processor scale: upcycle a 55-gallon (208 L) drum (poly or steel), mount on a welded leg frame at 36° tilt, and use the inner floor/wall as the harvest ramp. Typical use: several related households sharing one unit (~0.5 kg/HH/day sorted scraps mid—UNEP-based planning), or a small food business (e.g. meat or bakery trim) with steady daily input. A full-service restaurant (~15–20 kg/day—claim) often needs a modular stack instead. Not a neighborhood-wide collection hub.
Same field simplifications as the 5-gallon design: stock/head lid hinged at the bottom (no latch), harvest bottle hanging under the high end, drilled drain cluster with no mesh.
Cross-cutting rules: /articles/tank-design/.
Concept
Same geometry as the 5-gallon design—scaled for higher throughput:
- Vessel on side, head end uphill.
- 36° shell tilt → interior climb angle in the published 28°–45° self-harvest band.
- Harvest port on the underside near the head, ~20–30 mm past the head chime/band; bottle hangs down.
- Drains: many small–medium drilled holes clustered at the low point (no mesh); optional 3/4 in ball valve at the lowest point.
- Leg height difference ≈ 523 mm (17.5 in) for a standard 35 in (889 mm) drum axis.
- Leave clearance under the high end for the hanging bottle and a lid that swings open downward.
Dimensions (typical US 55-gal drum)
| Parameter | Value |
|---|---|
| Shell diameter | ~572 mm (22.5 in) |
| Axis length (drum on side) | ~889 mm (35 in) |
| Leg height difference (36°) | ~523 mm (17.5 in) |
| Harvest port from head ring | 90 mm ± 15 mm (underside) |
| Feed opening (min) | 300 × 350 mm in head / lid |
Tools
Welder, angle grinder, drill, 2 in hole saw, 4–8 mm bits, deburr tools, level, inclinometer, silicone (harvest fitting), optional NPT taps, strap hinges, string optional.
Build sequence
1. Source and inspect drum
- Prefer food-grade poly or clean steel (beverage, food syrup, soap—not industrial chemicals).
- Confirm tight-head (fixed top with bungs) or open-head (removable lid).
- Pressure-wash; air dry.
2. Welded leg frame
- See
drawings/side-elevation.svg.
- Four legs or two A-frames; high cradle at head, low cradle at tail.
- Vertical distance between shell centerlines at cradles = axis × sin(36°) ≈ 523 mm.
- Saddles: bent flat bar + rubber hose liner; do not point-load poly shells.
- Add cross-bracing—a full drum weighs 150–200 kg loaded.
- Clearance under high end for bottle + hanging lid.
- Verify 36° ± 2° (band 35–38°) before mounting drum.
3. Drainage (drilled holes only)
- Mark the geometric low point on the tail half underside.
- Drill many ~4–8 mm holes, densest at the low point (same idea as 5-gal; larger shell may use a few 8 mm holes in the densest zone).
- Deburr; no interior mesh.
- Optional: weld or bulkhead-mount 19 mm (3/4 in) NPT ball valve at the geometric low point—easier flushing (Cheng bin study notes side/low routing helps).
- Place 20 L+ leachate catch under drains.
4. Head access
Open-head drums (preferred when available):
- Adapt the stock clamp-ring lid.
- Hinge on the bottom edge of the lid face (nearest ground) so it opens and hangs down with gravity.
- No hasps—tilt + lid weight usually enough; optional string handle or wind tie.
Tight-head drums:
- Cut feed window in the flat head (not the curved barrel).
- Hinge the plate on its bottom edge; no latch required.
- Keep a bung or drill small vent holes in the head (screen optional at this scale if rodents are a problem).
5. Harvest bottle port
- See
drawings/harvest-port.svg.
- Underside (ground-facing), ~90 mm below head chime.
- Poly: 2 in NPT bulkhead → reducer → 28-400 adapter → PET collection bottle hanging down.
- Steel: weld 50 mm boss, tap or fit threaded ring for bottle neck; file smooth inside.
- Prepupae crawl up the incline and drop into the bottle.
- For heavy harvest, use 3 L bottle or screw-on wide-mouth jar.
6. Mount drum
- Lower drum into cradles; strap with two metal bands (poly) or tack-weld saddles (steel).
- Confirm drum cannot roll; check tilt after strapping; confirm lid and bottle clear the frame.
7. Leak and load test
- Add 20 L water; exercise valve (if fitted) and inspect weeps.
- Fix leaks before biological startup.
8. Operation notes
- Shade or roof mandatory—large drums overheat in sun (larval shade claim).
- Batch feed through the open hanging lid; stir crust weekly with a paddle.
- Expect higher throughput than 5-gal; plan 2–4 collection bottles per week at steady state for a compound or small shop (site-dependent).
- Rodent exclusion: elevate frame; string-tie the lid in windy pest-heavy sites if needed (facility hygiene).
Plastic vs steel drums
| Poly tight-head | Steel | |
|---|---|---|
| Weight | Lighter; strap cradles | Heavier; weld saddles |
| Fittings | NPT bulkheads | Weld bosses; watch interior burrs |
| UV | Chalks outdoors—paint or shade | Rust—prime and paint exterior |
| Heat | Insulates slightly | Can hot-spot in sun—shade |
Maintenance
- Clear clogged weeps with a stick or re-drill nearby; flush valve if fitted.
- Inspect bottle threads monthly.
- Re-torque straps after first loaded week.
Files
| File | Purpose |
|---|---|
bom/materials.csv |
Bill of materials |
drawings/side-elevation.svg |
Side view, frame |
drawings/harvest-port.svg |
Underside harvest fitting |
drawings/drain-pattern.svg |
Low-point drill cluster |
geometry/stand.scad |
Leg height calculator |
References
/articles/tank-design/ · 5-gallon sibling design