From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical data sheet defining the variables and formulas for spiral springs.
| Identifier | ExFiles\Box 52\1\ Scan180 | |
| Date | 31th January 1929 | |
| X4490. 31.1.29. SPIRAL SPRINGS. Diameter of wire = d (") " " coil = D (") Number of effective turns = n Length " " " = l (") Whole length of spring = L (") Fully compressed length of spring = L' (") Modulus of shear = C (lbw/sq.") Maximum { Load on spring = W (lbw) { Deflection of spring = δ (inches) { Stress on material = f (lbs/sq.") Then l∅ = (d {John DeLooze - Company Secretary} /2) θ where ∅ = f {Mr Friese} /C and θ = δ / (D {John DeLooze - Company Secretary} /2) so that since l = π D n (π D n f) / C = (d δ) / D i.e. δ = (π D² n f) / (d C) or f = (C d δ) / (π D² n) | ||