ReCoil · WORKBENCH
PRIVATE
ReCoil · WORKBENCH
PRIVATE
Working doc, not final spec. Every number gets verified per-door by measurement + the Convert Designer tool.
SECTIONAL: drum radius constant. Weight transfers to horizontal track
as it opens. Torque demand falls ~linearly. Spring torque
falls linearly per unwound turn. Matched.
COILING: the curtain IS the load AND the drum.
Hanging weight falls as it coils: W(x) = w · (H - x)
Coil radius GROWS per wrap: R(n) = R_pipe + n · t
Torque demand at barrel: T(x) = W(x) · R(x)
KEY FACT: max weight at MIN radius (closed), min weight at MAX radius
(open). Geometry self-compensates — torque curve is FLATTER
than the weight curve → friendly to linear-rate torsion springs.
TURNS: commercial coils turn FEW times (~2-4) → factory springs are
short/fat/huge-IPPT. RESI springs are the opposite: long,
skinny, many-turn, modest IPPT (~55-70 in-lb/turn each).
k = (barrel-side drive radius) / (resi-shaft drive radius)
Spring shaft turns = k × barrel turns (more turns — resi home field)
Spring torque needed = barrel torque / k (less torque — ditto)
A — DIRECT COUPLE (CNC hub, 1:1) ← wins the VOLUME MID market B — CHAIN TORQUE COUPLE ← HEAVY doors; exact ratio, bidirectional C — CABLE TORQUE COUPLE ← tight clearance; cables only PULL D — BOTTOM-BAR CABLE LIFT — AVOID (doesn't coil the curtain). Helper only.
MID 12x12, 1.6 psf, 6" pipe ← THE VOLUME MARKET
Winner: YOUR springs (.325 × 3.75"ID × 46" pair), DIRECT 1:1
Match 89% · wind 7.8 turns · barrel 5.2 turns · peak 796 in-lb
Wire 118 ksi → >50k cycles. UNDERSTRESSED. NO drums, NO cables.
LIGHT 10x10: soft pair 1.8× too stiff at 1:1 → run ONE soft spring.
HEAVY 14x14, 2 psf: 1,311 in-lb → k≈1.5-2 chain couple + softer springs.
1/k² LAW: required stiffness falls with the SQUARE of ratio k.
Shaft rotation = barrel rotation (1:1, no reversal). Springs store torque in the barrel's COIL-UP direction: one LEFT + one RIGHT wound, one each side, cones anchored to wall brackets, winding cones inboard. SITE CHECK: hand-rotate barrel OPEN, confirm each spring TIGHTENS.
RELEASE CORD: extended cord, screw-eye guides down the jamb. FIRST eye placed so the initial pull stays in the 8500 lever's throw plane; zigzag freely after. Slack so routing never pre-loads the lever. Test at closed AND half-travel. SPIN DIRECTIONS: direct couple = one shaft, one rotation, no conflict. Chain / open-cable = same direction both shafts; CROSSED cable = reversed. Reversal is a ROUTING CHOICE, never a blocker. PULLEY KIT (heavy variant): resi low-headroom / rear-mount redirect tricks apply — sheaves zigzag the couple cable around obstructions. Each redirect adds friction to the balance calc; RATED pulleys only at commercial tension.
RESEARCH: rolling-door inner shafts run 1" / 1-1/4" (resi sizes). Head plates already carry barrel + hood. Inner-spring replacement is the trade's worst job. → ReCoil's statement: NEVER DROP A BARREL AGAIN. NUMBERS (verified): 1" solid shaft @ 1,311 in-lb → 6,700 psi shear (30k+ capacity) Collar bolts (6 @ 2.6" R) → 51-84 lb each (5/16 Gr5 rated >3,000) BEARINGS: curtain weight stays on stock head plates — barrel untouched. ReCoil shaft bearings carry only shaft+spring static (+chain radial). Resi 2" end bearings (2" race, 1" bore): comfortably rated. Confirmed. STOCK-SHAFT REUSE: existing 1"/1-1/4" solid, straight, ends protrude → REUSE natively. Bent/undersized/captive → replace with 1" solid CRS. Either way inner springs de-tensioned at the stock wheel + retired in place.
CORE every job · CNC machined part · v0.2 latest design. All resi/truck stock except the CNC pieces.
| Part | Spec / note |
|---|---|
| CORE — every conversion | |
| Shaft CORE | REUSE stock 1"/1-1/4" solid if straight & protruding; else 1" solid CRS. Resi bearings, springs, 8500 all fit it natively. |
| Resi torsion springs CORE | Sized by the sizer. Mid ≈ .325 × 3.75" ID × 46" pair, one L + one R wound. Light = one soft spring. Heavy = softer long pair at k≈1.5-2.5. |
| Outside-mount collar hub CNC v0.2 | The first CNC part to cut. Split collar, 1.030" bore, clamped by 2× 3/8 cross bolts, 6 radial arms tab-bolt to the PIPE END WALL from outside — no barrel teardown, installs at the head plate. 1018 steel. (Supersedes v0.1 insert hub.) |
| Worm-gear tensioner anchor CNC v0.2 | Component #2. Self-locking worm; drill/ratchet input; can't back-drive → replaces winding bars. Micro-adjust by quarter-turns. Output ≥ 1.5× peak shaft torque; turn counter/index ring. |
| Resi 2" end bearings CORE | 2" race, 1" bore. Carry only shaft + spring static weight — barrel stays on stock head plates. |
| Back-mount bracket family v0.2 | 3/16" min steel plate, bolts to guide angle / jamb steel (never wood). Carries end bearing, worm anchor, hood lip, and (variant) chain-idler post. Slotted holes. One plate family, holes for all three concepts. |
| Extended hood v0.2 | 24 ga galvanized (stock hood practice), lengthened past the brackets to cover external springs/tensioner/chain. Weather + finger guard; doubles as the moving-parts guard the safety listing wants. |
| Safety bearing v0.2 | Rolling-door inertia brake (stops free-fall on spring/drive failure). Stock component — SPEC ONE drive-side on every motorized conversion. Non-negotiable. |
| LiftMaster 98032 CORE | Residential HD DC jackshaft (replaces the 98022) — monitors cable tension internally so no external monitor, 400–1,100 lb, mounts a 1" bar, 8.5" sideroom. Heavy/continuous commercial → JDC or LJ8900W instead. Datasheet-verified; full write-up on Door Systems. |
| Release cord + screw-eye guides CORE | Extended cord to the door side; first eye in the 8500 lever's throw plane, zigzag after. Redirect pulley if the pull angle is tight. |
| CHAIN COUPLE — heavy doors (Concept B) | |
| Barrel-ring drive sprocket CNC | Ring-clamp sprocket — the chain-couple invention piece. |
| Shaft sprocket + idler | Tooth count sets ratio k. Idler tensions and can flip rotation sense for safe wind handedness. |
| #41 / #48 roller chain | Truck stock. Bidirectional — powers the door down as well as up. |
| CABLE COUPLE — tight-clearance variant (Concept C) | |
| Resi cable drums | On the spring shaft — truck stock. |
| Barrel-end drum flanges CNC | Larger radius = ratio k. CNC or welded band on the barrel ends. |
| Aircraft cable + clamps | 2 sets min (both ends), 3rd center on wide doors. Crossed run = reversed rotation. Cables only PULL. |
| RATED redirect pulleys | Rated for commercial tension — NOT resi extension-spring sheaves. Route around clearance problems. |
CHAIN (open loop) → both sprockets SAME direction
CHAIN (+ back idler) → FLIPS shaft to OPPOSITE (and tensions the chain)
CABLE (open run) → drums SAME direction
CABLE (crossed /
redirect pulley)→ drums OPPOSITE
You're never forced into a bad wind handedness — reversal is a routing choice. And the low-headroom / rear-mount pulley trick you pictured is real: sheaves can zigzag the couple cable around obstructions. Cautions: those resi tricks redirect lift cables to the bottom bar (here it's the shorter drum-to-drum loop, keep wraps clean, small fleet angles), and cable only pulls — need the motor to drive the door down through the couple? That's the chain's job, not cable.
v0.2 OUTSIDE-MOUNT COLLAR (cut this one): Split shaft collar, 1.030 bore, 2× 3/8 cross bolts, 6 radial arms → tabs bolt to the PIPE END WALL from OUTSIDE. Installs at the head plate, no barrel teardown. Positive bolt engagement (never friction- only). Two per door, or one drive-side + stock idler at the other end. Material: 1018 steel. v0.1 insert hub (DXF, offline) = earlier concept, superseded. MEASURE FIRST on a real barrel: pipe end-wall thickness/gauge, shaft size + straightness, ring positions, guide bolt pattern, run-out.
Public use without filing risks foreign rights. Eleven items (full detail on the Door Systems page):