Spring Calculator

Torsion-spring counterbalance for any door — residential 1.75" springs through commercial. Set the spring + door, read the match, solve the length, and run the balance check. Real math, live.

✓ DDM-catalog validated (≤0.2%) · π/32 rate, E=30e6 · minimax wind

Inputs

Wire dia. d "

Spring ID "

Spring length L "

Dead coils

Couple ratio k

Door height ft

Door width ft

Curtain weight psf

Start coil radius R₀ "

Wrap per turn t "

Calibrate C to a rated spring (pair IPPT)

constant C = 10.19

Spring / demand match

—

Pair rate

— in·lb/t

Required rate

— in·lb/t

Peak demand (shaft)

— in·lb

Wind / barrel turns

—

Wire stress

— ksi

Solve → length

— in

⚙ Balance check — mid-travel imbalance

Wind at closed (naïve) turns → lb worst

Minimax wind (centered) turns → lb worst

COIL & CURTAIN — drag the travel scrubber

Door travel 0" closed

TORQUE ACROSS TRAVEL — demand vs supply (minimax wind)

demand spring supply travel

Spring Calculator

Inputs — minimize

⚙ Balance check — mid-travel imbalance

Inputs