RiverBrick Classifier Stack — Engineering Blueprint

System Overview

Purpose

4-level stackable classifier system that seats directly on top of the RiverBrick InletBrick V3.2. Separates raw streambed material into four size classes before entering the sluice, dramatically improving gold recovery by preventing riffle overload and ensuring optimal particle-to-riffle sizing.

Operating Principle

Material is loaded onto the top (Grizzly) screen. Water flow or manual agitation drives undersized particles through each progressively finer screen. Each level captures a specific size class. The finest material (flour gold bearing) passes directly into the sluice channel.

Key Features

Male/female interlocking stacking lips with 0.3mm tolerance. Integrated side handles for shake classification. Corner drain notches for continuous water flow. Bottom frame includes seat overhang lip to lock onto InletBrick edges.

Gold Recovery Impact

Classification is the single highest-impact upgrade for sluice recovery. Pre-sized material allows riffles to work at optimal capacity. Studies show classification can improve fine gold recovery by 40–80% vs. unclassified feed, particularly for particles below 30 mesh.

Frame Dimensions

Parameter	Value (mm)	Value (in)	Notes
Outer Width	160.0	6.30"	brick_channel_w + 2 × wall_t
Outer Length	208.0	8.19"	brick_channel_l + 2 × wall_t
Frame Height	45.0	1.77"	Per level, excluding lip
Wall Thickness	4.0	0.16"	All four sides
Screen Floor	2.5	0.10"	Mesh support layer
Stacking Lip	8.0 tall × 2.0 inset	—	Male protrusion on top; female socket on bottom
Stack Tolerance	0.3	—	Gap between male lip and female socket
Handle Extension	5.0 deep × 40.0 wide × 15.0 tall	—	Both sides; centered vertically at 30% frame height
Seat Overhang	10.0	0.39"	Bottom frame only — rests on InletBrick edges
Full Stack Height	~206	~8.1"	4 frames + lips, assembled

Exploded Stack View

L1 — GRIZZLY ½"

L2 — COARSE ¼"

L3 — FINE ⅛"

L4 — ULTRAFINE 1/20"

INLETBRICK V3.2

Mesh Screen Detail — All 4 Levels

Level 1 — Grizzly

½"

Aperture: 12.70mm
Bar width: 4.45mm
Grid: ~8 × 11 holes
Rejects: cobbles, gravel

Level 2 — Coarse

¼"

Aperture: 6.35mm
Bar width: 2.50mm
Grid: ~16 × 22 holes
Rejects: coarse gravel

Level 3 — Fine

⅛"

Aperture: 3.175mm
Bar width: 2.50mm
Grid: ~26 × 35 holes
Rejects: coarse sand, pickers

Level 4 — Ultrafine

1/20"

Aperture: 1.27mm
Bar width: 2.50mm
⚠ USE STEEL MESH CLOTH
Passes: flour gold, black sand

Why classify? Gold settles according to Stokes Law — terminal velocity scales with particle diameter squared. A 1mm gold particle settles ~100× faster than a 0.1mm particle. Unclassified material means fine gold gets swept past riffles designed for coarser material. Each RiverBrick riffle zone has an optimal Rouse number (Ro = ws / κu*) window — classification ensures every particle lands in the zone where Ro ≈ 1.2–2.5 for maximum capture probability.

Screen Specifications

Level	Name	Aperture	Mesh Equiv.	Bar Width	Open Area %	Target Capture	Print Method
L1	Grizzly	12.70mm (½")	~2 mesh	4.45mm	~55%	Nuggets, coarse pickers	FDM direct print
L2	Coarse	6.35mm (¼")	~4 mesh	2.50mm	~52%	Small pickers, heavy flakes	FDM direct print
L3	Fine	3.175mm (⅛")	~8 mesh	2.50mm	~39%	Fine flakes, small gold	FDM (0.2mm layer)
L4	Ultrafine	1.27mm (1/20")	~20 mesh	N/A	~45%	Flour gold, black sand cons	Frame only + SS mesh cloth

Stacking Interlock — Cross Section

Bill of Materials — Full Stack

#	Component	Qty	Material	Est. Print Time	Est. Filament	Notes
1	L1 Grizzly Frame (½")	1	PETG / ASA	~4 hrs	~85g	Print upside-down
2	L2 Coarse Frame (¼")	1	PETG / ASA	~5 hrs	~95g	Print upside-down
3	L3 Fine Frame (⅛")	1	PETG / ASA	~6 hrs	~110g	0.2mm layer mandatory
4	L4 Ultrafine Frame (no mesh)	1	PETG / ASA	~3 hrs	~70g	Solid floor with recess
5	SS Mesh Cloth — 20 mesh	1 pc	304 Stainless	—	—	Cut 150×198mm, epoxy into L4 recess
6	Marine Epoxy (mesh bond)	~5ml	—	—	—	JB Weld WaterWeld or equivalent

Total filament estimate: ~360g (~$9 in PETG). Total print time: ~18 hours across 4 prints. The 20-mesh stainless cloth for L4 runs about $5–8 for a 12"×12" sheet — one sheet yields 3+ screens.

Print & Assembly Notes

PRINT ORIENTATION: Print each frame upside-down (mesh floor facing up on build plate) for best hole quality on FDM. The mesh openings print as top surfaces this way, giving clean edges.
LAYER HEIGHT: Use 0.2mm for L1–L3. The fine screen (L3, ⅛" aperture = 3.175mm) needs this resolution. L1 can tolerate 0.3mm if speed is preferred.
MATERIAL: PETG is the minimum — good water resistance, decent UV tolerance. ASA is ideal for long-term field use (excellent UV + chemical resistance). PLA will degrade in water/sun within weeks.
INFILL: 40–60% recommended. These take abuse in the field. Concentric infill on floors gives the best mesh support.
STACKING FIT: Print a test lip section first. The 0.3mm tolerance should give a snug slip-fit. Sand lightly if too tight. Add 0.1mm tolerance if your printer runs tight.
L4 ULTRAFINE: Do NOT attempt to print 1.27mm holes on FDM — they will clog. Print L4 as a frame with a solid 2.5mm floor, then cut/drill a center opening and epoxy in the stainless mesh cloth.
FIELD TIP: Run the stack under flowing water. Agitate by lifting and dropping each level 1–2 inches repeatedly. The ½" grizzly clears fast — pull it first and check for nuggets.
GOLD RECOVERY: After running material through all 4 levels, the finest material passes directly into the RiverBrick sluice channel. Each retained fraction can be panned separately — the L3 retained fraction (⅛"–¼") is prime picker territory.