Pearl Granulator v1 — Build Doc

2026-04-25. Engineered for Mark's Pearl Method. Practice version, scalable concept. All dimensions in inches. SVG diagrams below are dimensioned to actual proportion.

Contents

What this is
Diagrams (top, side, exploded, motor mount)
Bill of materials with prices
Assembly steps
Tuning and operation
How this scales to v2

1. What this is

A 23″ rubber feed pan (the same shape commercial pan granulators use, just way cheaper) sits on three inline-skate wheels mounted at 120° on a 30"×30" plywood base. A small 110V AC gear motor with a built-in speed knob friction-drives the pan rim via a 3" rubber wheel on the motor shaft. The base tilts to 30-55° via two notched 2×6 side rails. You hand-mist binder with a 1-gallon pump sprayer.

Why feed pan instead of mixing bowl: feed pans have a flat bottom + low rim, which is the geometry industrial pan granulators actually use. Hemispherical mixing bowls collect material at the bottom point and don't roll uniformly.

Total cost target: ~$140-180 all-in. Buildable in one rainy Saturday afternoon.

2. Diagrams

Top view — pan + 3 skate-wheel positions + drive

Top view, plywood at horizontal. Pan sits centered on three skate wheels at 120°, all 11″ from center. Motor sits outboard with a 3″ rubber wheel pressed against the pan rim.

Side view — tilted at 45°

Side view at ~30° tilt. Notches in the side rails set discrete angles; lift the plywood and drop into a different notch to change tilt. Slurry pools at the low side and rolls as the pan rotates.

Skate wheel mount detail

Each skate wheel: 1/4″ carriage bolt up through the plywood, washer, wheel (free-spinning on bolt = built-in bearing), washer, lock-washer + nut. Pan rests on the wheel's outer surface. 3 of these at 120°, 11″ from center.

Motor + drive wheel detail

Motor mounts on an L-bracket bolted to the plywood, outside the pan circle. Drive shaft has a 3″ rubber wheel (set-screw clamped) that presses against the pan rim. The 7.7:1 reduction means a 30 RPM motor gives ~4 RPM at the pan, exactly the granulation range (industry: 8-25 RPM, low end is fine here for delicate work).

3. Bill of materials

Prices below are my best estimate as of training data + general retail knowledge. Amazon/Tractor Supply pricing changes weekly and their pages block automated price-checking. Click the search URLs to verify before ordering. Total estimated: ~$155-180.

#	Part	Qty	Source	Est. price
1	Fortex / Fortiflex 5-gallon rubber feed pan, 23″ Ø × 6.5″ deep The pan. Flat-bottom, low-rim — right shape for pan granulation.	1	Tractor Supply (in-stock at Acworth / Hiram / Canton). SKU 1071051. Or Amazon search.	$18-22
2	Behlen 17-gal galvanized round mortar/feed tub, ~24″ Ø — backup pan, you said you'd grab both Steel version of the same shape. Slightly different wall angle — may roll pearls differently. Worth comparing.	1	Tractor Supply. SKU varies; ask staff for "galvanized mortar tub 17 gal."	$22-28
3	110V AC gear motor with built-in speed controller, 5-50 RPM — the "proper motor" Look for: 25-90W, 110V, 5-50 RPM range, >15 kg-cm torque, knob-controlled, integrated controller box. Search terms: "110V AC gear motor variable speed" or "AC motor speed controller 30 RPM." Brands: Bringsmart, YOUKI, Bodine. Avoid 12V DC (needs PSU + extra wiring).	1	Amazon search or Bringsmart 60KTYZ	$55-95
4	Inline skate wheels, 76mm (~3″ Ø), 4-pack (use 3, keep 1 spare) Hardness 80A or harder. Comes with 608ZZ bearings already installed = built-in bearing.	1 pack	Amazon search or Walmart	$10-15
5	3″ rubber wheel for motor drive shaft — with set-screw bore matching the motor's shaft Ø Often sold as "3-inch hand truck wheel" or "rubber drive wheel for shaft." Check motor shaft Ø (usually 8mm or 10mm) before ordering.	1	Amazon search	$8-15
6	3/4″ plywood, 30″×30″ (or larger; HD will cut to size for free) Cabinet-grade or sanded common; either works.	1	Home Depot. HD search	$25-35
7	2″×6″×4ft pine boards (for tilt notches)	2	Home Depot	$15
8	L-bracket, 1/8″ steel, 6″×4″ (motor mount)	1	Home Depot hardware aisle. Amazon search	$5-8
9	HDX 1-gallon pump sprayer, model 1501HDXA (binder mister)	1	Home Depot, in-store. SKU 1501HDXA.	$13
10	Hardware kit: 1/4″-20 carriage bolts (3.5″ long ×3, 1.5″ long ×4), washers, lock washers, hex nuts	1 box	Home Depot fastener aisle.	$10
Total estimated				$181-256

Where to actually buy: the rainy-Saturday plan is one trip — (a) Tractor Supply for items 1-2, (b) Home Depot for items 6-10, (c) Amazon for items 3-5 (the motor + skate wheels + drive wheel; these don't reliably stock locally). Amazon arrives Mon/Tue. You can build the base + tilt frame Saturday with what's available locally, then finish Tuesday when the motor lands.

4. Assembly

1. Base. Cut plywood to 30″×30″ (or have HD cut it). Cut two 2×6's to 30″ long for the side rails.

2. Tilt notches. On each 2×6, mark 5 notches along the top edge at angles 0°, 30°, 40°, 45°, 50°, 55° — each notch ~1/2″ deep, ~3/4″ wide so the plywood edge can drop into it. Cut with a circular saw or jigsaw. Bolt the two side rails to the long edges of a separate base board (any flat scrap; the rails are floor-standing). Plywood drops between the rails — rear edge into a notch, front edge resting on the front rail's top.

3. Mark skate wheel positions. Find center of plywood. Draw a circle at 11″ radius. Mark three points 120° apart on that circle: e.g., 12 o'clock (0,11), 4 o'clock (9.53,-5.5), 8 o'clock (-9.53,-5.5).

4. Drill skate wheel holes. 1/4″ holes through plywood at the three marked points.

5. Mount skate wheels. For each: 1/4″ carriage bolt up from below → nut on top of plywood (locks bolt) → washer → skate wheel (free-spinning on bolt, the wheel's own bearing is the bearing) → washer → lock-washer → final nut. Tighten so wheel can spin freely but doesn't wobble.

6. Test pan fit. Set the rubber feed pan on the three wheels. Spin it by hand. Should rotate smoothly with no wobble. If wobble, re-check the 11″ offset on each wheel.

7. Mount motor. Position the L-bracket so the motor's drive wheel will press against the pan rim from outside (motor body OUTSIDE the pan circle). Bolt L-bracket to plywood. Bolt motor to L-bracket. Slide motor on bracket so the rubber drive wheel just touches the pan rim — you want firm contact but not so much that it bows the pan rim inward.

8. Wire up. Plug motor into the speed controller box (if separate) or directly into the wall (if controller is integrated). Set knob to lowest speed. Plug in. Pan should rotate. If it doesn't, the friction wheel isn't pressing hard enough — tighten the L-bracket position by 1/8″ toward the pan.

9. Test runs. Tilt to 45° (drop plywood rear edge into the 45° notch). Pan should rotate slowly, material in pan should pool at the low side and tumble. Adjust speed knob until material rolls without flying out.

5. Tuning & operation

Speed

Industry pan granulators run 8-25 RPM. With the 7.7:1 friction reduction (3″ drive wheel on 23″ pan), motor RPM × 0.13 = pan RPM. Target motor settings:

30 RPM motor → ~4 RPM pan — very gentle, good for fine pearls
60 RPM motor → ~8 RPM pan — mainstream granulator speed
100 RPM motor → ~13 RPM pan — faster, larger pearls form quicker but more dust

Start slow (4 RPM pan), speed up if material isn't rolling.

Tilt

30° = gentle, for finishing rounds. 45° = mainstream. 55° = aggressive, for the early agglomeration phase. Move between notches as a batch progresses.

Hand-misting

Pump the sprayer to pressure. Mist from above the pan, not directly into it. 2-3 squeezes every 30 seconds for the first few minutes (early agglomeration). Less frequent as pearls form (let surface dry slightly between mists).

Cremains volume math (your earlier question)

Pet weight	Cremains weight	Cremains volume
5 lb cat / Yorkie	~0.25 lb	~7 cu in
20 lb dog	~1 lb	~30 cu in
50 lb dog	~2.5 lb	~75 cu in
80 lb lab	~4 lb	~120 cu in
150 lb mastiff	~7.5 lb	~225 cu in

The 23″ feed pan holds ~5 gallons = 1,155 cu in. Working at 15-25% fill, that's a working capacity of 175-290 cu in. Anything from a 5-lb cat to a ~120-lb dog runs in one batch in this pan. Larger pets, run two batches.

6. How this scales to v2 (production)

Same architecture, just bigger and more durable. The mechanics translate cleanly:

Bigger pan: 30-36″ commercial galvanized mortar pan (HD or industrial supply)
Heavier wheel support: swap 3 skate wheels for 3 plate-caster wheels with 4″ rubber tread (Harbor Freight ~$4 each); they're rated for 200-400 lb each
Bigger motor: 1/4 HP AC gear motor with PWM, 100+ kg-cm torque (~$120-180)
Tilt mechanism: hydraulic strut + lockable hinge instead of notches; allows continuous angle adjustment
Multiple cells: at ~$160 per practice cell, you can run 3-5 in parallel on a single workbench. Same drive wheel, same skate wheels, same pan, just more of them.

The practice version proves the technique. The scaled version is the same tool, just larger components — you don't have to relearn anything.

What you do next

Tomorrow / Monday: click the Amazon search links above, pick a specific motor (target 30-60 RPM, 25W+, 15+ kg-cm torque, integrated speed controller). Tell me the SKU you pick and I'll verify it'll work.
Saturday/Sunday: Tractor Supply trip for both pans + Home Depot trip for plywood, lumber, hardware, sprayer. Build the base + tilt frame.
Tuesday-ish: motor + skate wheels + drive wheel arrive. Mount, test, tune.
By next weekend: first practice pearl batch with bone meal + colloidal silica.