Two families, one spring

Door Systems & Data Log

The same .325 × 3.75 × 46 spring pair covers both door families — rolling steel takes it direct, Janus sheet takes it through a chain couple. Pick a type to see the spec & k.

Couple	Direct 1:1 — motor on the shaft end
Ratio k	k = 1.0 no ratio
Spring pair	Stock `.325 × 3.75 × 46` — one L + one R wound
Hub / CNC part	Outside-mount collar hub (no ratio adapter)
Motor + sideroom	98032 collar on shaft end · 8.5" drive-side clearance
Curtain speed	Baseline (direct drive) — smaller coil radius, ~11–23 in/s
Notable check	Pipe-wall bearing at bolt holes per gauge; hand-rotate open, springs must tighten

Couple	Chain couple → 1" live shaft
Ratio k	k = 1.5 – 1.75 10×10 = 1.5 · 12×12 = 1.75
Spring pair	Same pair as R&S — unchanged SKU
Hub / CNC part	Drum-hub bushings adapt stock drums; dead axle → 1" solid CRS live shaft
Motor + sideroom	98032 on the spring shaft end · add sideroom for chain + sprockets
Curtain speed	Divided by k (slower curtain, higher torque) — still needs the light curtain
Notable check	Verify sprocket tooth count sets k as a reduction (not multiply); through-pin every drum

Operator

LiftMaster 98032 datasheet-verified

Residential heavy-duty DC wall-mount jackshaft (98032MC) — the only UL 325 residential wall-mount rated to 1,100 lb. Every spec below verified against LiftMaster + dealer sources.

The ReCoil-critical spec: no external Cable Tension Monitor. The external cable-monitor clips to a lift cable — a cable-less rolling curtain has none. The 98032 monitors cable tension electronically inside (replacing the 041A6104 external monitor + overhead rails), so it covers UL 325 without the accessory that couldn't attach anyway. confirmed

Confirmed: 400–1,100 lb, to 14 ft (~18 ft wide); 24V DC (389 W peak, 120V AC in); 485LM battery backup ~40 cycles/24h; myQ Wi-Fi; 841LM auto-deadbolt; mounts a 1" torsion bar; 8.5" side clearance (governs the bracket family below).
LC36M light curtain is compatible but requires the 100MAPS external power supply — spec both on any motorized install.
Lineage: 8500W → 98022 → 98032 (the 1,100 lb tier). It replaces the 98022, not the 8500W directly.
It's residential-rated — fine for lighter rolling conversions, but a true heavy / continuous-duty commercial job wants a commercial DC jackshaft: LiftMaster JDC (MAXUM) or LJ8900W (note the LJ8900W ships with a cable-tension monitor, unlike the 98032). pick by duty
Sub-400 lb caution: a ~265 lb curtain sits below the 400 lb floor → force-profiling is tuned for heavier doors; for light doors use a lighter-class unit + a commissioning force check.

Simulation · logged

Physics data ✓ re-verified in python

Same spring pair (rate 102 in-lb/turn), swept against three Janus sheet doors + the mid rolling-steel door. Peak torque is at closed (max weight × min radius). Expand the raw log for the exact computed values.

Door	Type	Peak in-lb	Barrel turns	k	Match	Wire ksi	Verdict
12×12 mid	R&S steel (6" pipe ≈ 3.3" R)	796	5.2	1.0	89%	118	solid
10×10 sheet	Janus	675	2.43	1.5	101%	67	dead-on
12×12 sheet	Janus	1068	2.89	1.75	100%	91	comfortable
14×14 heavy	Janus	1768	3.13	2.0	83%	131	re-spec

14×14 is genuinely marginal — flag, don't ship as-is. 83% match = the pair is under-powered (door runs head-heavy). And 131 ksi wire bending stress sits near/over the ~105–120 ksi garage-door-duty fatigue band → real cycle-life concern. Re-spec: larger wire, different ID/length, a second spring, or a higher k — pull match toward 100% and stress under ~115 ksi. The 10×10 and 12×12 are clean.

▸ See the logged data (raw recomputed values)

PAIR spring rate = 2 × IPPT(0.325, 3.75, 46) = 102.09 in-lb/turn

JANUS SHEET DOORS (H, psf, bottom bar, Rd start-radius, t wrap)
  10×10  H=120 psf=0.75 bb=15 Rd=7.5 t=0.30
     T_closed 675.0 · T_open 122.9 · barrel turns 2.4285
     k=1.5  → required rate 100.9 · MATCH 101.1% · wire 66.8 ksi   ✓
  12×12  H=144 psf=0.85 bb=20 Rd=7.5 t=0.30
     T_closed 1068.0 · T_open 167.3 · barrel turns 2.889
     k=1.75 → required rate 101.8 · MATCH 100.3% · wire 90.5 ksi   ✓
  14×14  H=168 psf=1.0 bb=25 Rd=8.0 t=0.35
     T_closed 1768.0 · T_open 227.4 · barrel turns 3.128
     k=2.0  → required rate 123.1 · MATCH 82.9% · wire 131.2 ksi   ⚠ marginal

ROLLING STEEL (direct 1:1)
  12×12 mid, 1.6 psf, 6" pipe (coil radius ≈ 3.3")
     peak 796 · barrel 5.2 turns · MATCH 89% · wire 118 ksi · +63 residual at open   ✓

NOTE: wire stress uses the torsion-spring BENDING form 32·M/(π·d³) with M = per-spring
moment — correct for a torsion spring (the wire bends as it winds), confirmed on review.
NOTE: "6-inch pipe" = ~3.3" coil radius, NOT 6". The one-pair-both-families result holds
at the true pipe radius; re-check per real barrel OD before quoting a job.

Curtain speed · entrapment

Speed & safety ✓ arithmetic verified

Big coil radius = fast curtain. At jackshaft speed (~36 rpm) a sheet door runs fast — and it's fastest near full open (largest coil), but the pinch/crush risk is worst in the last ~24" near the floor.

Coil radius	Curtain speed @ 36 rpm	ft/s
3.0" (near closed)	11.3 in/s	0.9
6.0"	22.6 in/s	1.9
7.5"	28.3 in/s	2.4
9.5" (full coil)	35.8 in/s	3.0

The ratio helps — a genuine bonus. The chain couple divides curtain speed by k, so 28 in/s → ~19 (k=1.5) or ~14 (k=2.0). Because spring demand scales 1/k² and speed scales 1/k, the k you pick for balance also pulls the curtain slower. Elegant — but k is set by the balance equality; treat the speed drop as the free upside, then verify speed independently.

Do NOT treat speed reduction as the safety mechanism. Even 14–19 in/s is > 1 ft/s. UL 325 doesn't bless speed alone — a motorized install requires monitored entrapment protection (the LC36M light curtain and/or a monitored sensing edge) that reverses on obstruction. Confirm it trips within stopping distance at the fastest modeled speed (35.8 in/s), not the reduced one. Wire the monitored curtain to the 98032's monitored input so a fault fails the door safe. Non-negotiable.

Build

Four CNC parts + angle-iron adapter

#1 Outside-mount collar hub — first part to cut. 1018 steel, 1.030" bore, 2× 3/8 cross bolts, 6 radial arms tab-bolt to the pipe end wall from outside. (R&S + shared.)
#2 Worm-gear self-locking tensioner anchor — winds without bars, can't back-drive, quarter-turn micro-adjust. Access fits inside the 8.5" sideroom.
#3 Drum-hub bushing Janus — steps each stock drum bore down to the 1" live shaft, through-pinned. 2–4 per door. Tunable/sacrificial interface (barrel OD ↔ CRS shaft).
#4 Head unit new — the consolidation part: one 3/16" plate/weldment per side merging the 2" bearing seat, worm-tensioner mount, hood lip, and opener/idler stub. Bottom edge slotted for head plates AND punched for angle. Two head units + hub (+ bushings on sheet doors) = the whole kit → hour install.
Build gate — measure one, machine all four: measure ONE R&S barrel + ONE Janus axle (shared datums), then all four parts go to the machine in one run. Never cut on catalog dims.

Mounting

Self-anchoring — the door carries it

Zero new structural anchors by default. A rolling door already carries itself through its guides and jambs (no lintel load — stock rolling-door engineering). ReCoil borrows that path: the head unit bolts to the existing head-plate top pattern and the door anchors the conversion. Added load = shaft + spring static + torque reaction (~800–1,300 in-lb ≈ a ~220 lb bolt couple at 6" spacing — easy for 3/8 hardware) + ~300 lb chain radial on the variant. patent #10

One node family, four answers

S1 · Piggyback (default) — head unit bolts to the existing head-plate top pattern. Door anchors the conversion, no wall touched.
S2 · Guide clamp — where head plates are minimal (Janus mini brackets), clamp/bolt the continuous guide or wall angle.
S3 · Wall mount — good masonry/steel only: wedge anchors in solid/filled block, through-bolts on a steel jamb.
S4 · Angle bridge — garbage walls: span commodity angle between the guides across the head, hang the shaft from the bridge. 2×2×1/4 for offsets, 3×3×1/4 for spans over 4 ft.
Opener mount — the 98032 rarely has framing behind it on commercial openings, so it mounts to an angle stub off the drive-side head unit (keeping 8.5" clear shaft). The motor hangs off the same self-anchored structure as everything else.

Field procedure

Commissioning checklist

Run in order, every install. Sign + date the card — it doubles as the residual-imbalance record.

1 · Balance mechanically first — opener disconnected, door should hold at mid-travel. Dial out residual with the worm tensioner in quarter-turns, snug toward neutral (never past).
2 · Travel-learn — re-engage, let the 98032 set its own open/close limits before any force.
3 · Force-learn + gauge-verify — auto force-learn, then confirm closing force with a gauge against UL 325 / DASMA thresholds.
4 · Sub-400 lbf force floor is a hard check — the no-CTM 98032 has torque to blow past a soft setting; balance first so a low force limit is real, not faked.
5 · Obstruction reversal — 2×4 laid flat, door must reverse.
6 · Light-curtain reversal — beam-break top-to-bottom; confirm monitored fault fails safe.

Extra design notes

LC36M is standard BOM, not an upsell — a full-width sheet door under 98032 torque out-hazards a single photo-eye pair.
Multi-drum layout — 2–4 drums evenly spaced on the 1" CRS shaft; off-center counts rack the sheet. Through-pin is the load path; setscrews back out under daily reversing loads.
Inner-spring decommission at the stock ratchet — back off / capture the original inner spring to zero residual, document the ratchet index. Keeps the conversion reversible + safe for the next tech.
Spares — stock reamers/pins as a field kit + one spare drum-hub bushing per install (the tunable interface part), so a mis-measured barrel doesn't stall a conversion.

Provisional #6 · file before first customer install

Patent inventory — 11 items

Externalized-counterbalance conversion method — inner springs retired, serviceable external resi-stock counterbalance ("never drop a barrel").
Outside-mount collar hub (v0.2) — tab-bolts to the pipe end wall from outside, no teardown.
Worm-gear self-locking tensioner anchor — fine-adjust, no bars, can't back-drive.
1/k² ratio-selection method + Designer tool — picks spring/ratio per door.
Unified back-mount bracket family — one plate, all three concepts.
Extended hood as combined guard/enclosure — weather + moving-parts guard for the listing.
Heavy-door chain-couple variant — with crossed-cable reversal option.
Drum-hub bushing — dead-axle-to-live-shaft sheet-door method new — through-pinned drum adapters convert a Janus/sheet door to a serviceable live shaft.
Ratio-as-speed-governor new — couple ratio chosen for spring balance (1/k²) that also reduces curtain speed (1/k) into the entrapment-safe band. (Claim on the joint observation — light-curtain protection still required.)
Self-anchoring conversion mount new — counterbalance load path routed into the door's own guide / head-plate steel (no wall anchor), plus the head-unit consolidation + node-plate & commodity-angle adapter system.
Minimax wind targeting new — winding a coiling-door conversion to center imbalance across full travel (demand peaks after the floor), computed per door: sheet ±few lb (manual-friendly), rolling steel ±14–21 lb (motorized). Nobody winds this way because nobody computes it.