Pain2HuStle · Field Engineering Instrument

Counterbalance Sizer / rolling steel door

First-order sizing for a serviceable, standard-spring counterbalance. Answers one question: can stocked torsion springs — ganged and/or ratio-coupled — carry this door, and what does that demand of the anchor?

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Concept-grade, not a stamped design. Outputs are first-order estimates for exploration. Stored spring energy is lethal. Nothing here gets built onto a live opening without a licensed mechanical PE, a bench test rig, and an independent drop-safety. Curtain weight is the input that drives everything — get it from real slat spec, not a guess.

Door & barrel01

Opening width ft

Opening height ft

Curtain weight lb / ft² — the critical number

Single-skin ≈ 2.0–2.8 · insulated ≈ 3.0–4.5. Verify from slat datasheet.

Barrel outer dia in

Anchor bolt-circle radius in

Spring package02

Spring rate source

IPPT / spring in-lb per turn

Max usable turns

# springs ganged

Coupling ratio N shaft:barrel

N = 1 → outboard/on-axis (Arch B). N > 1 → chain-coupled faster shaft (Arch A), multiplies torque, lets smaller stocked springs win.

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Enter valuesLive readout updates as you type.

Curtain weight

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Peak counterbalance torque

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at closed · W × barrel radius (first-order)

Travel turns (barrel)

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Required wind on shaft

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turns to hit balance torque

Balance window03

Required wind must land between travel turns (or the door won't stay up) and spring max turns (or it's over-stressed). Needle inside the green = feasible.

0turns

Practical checks04

Torque coverage

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Winding room

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Anchor fastener

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Available winding-bar clearance around cone in — radius

Standard winding bars sweep ≈ 18–24″. Below that, no one can wind or release the spring in place — the whole serviceability goal dies here.