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).
Spring failures due to wire defects and torsion fatigue, detailing the specifications for 'Aero quality wire' and a new double telescopic spring design.
| Identifier | ExFiles\Box 126\2\ scan0040 | |
| Date | 19th June 1935 guessed | |
| - 2 - (2) skin during the drawing and did not show up until the spring had been in work. This fault presumably existed on the rod from which the wire was drawn. Another surface defect has been a groove in the wire in most cases in the vertical plane, but in one or two in the horizontal plane. In broken springs incomplete cracks are shown starting from these grooves. These defects show up after etching. These springs are in Aero quality wire. A fair number of breakages in the middle of the spring have occurred and in our opinion these are not due to surge. They, are, however, torsion fatigue failures. Shortly after the start of this trouble a double telescopic spring P.53371/2 was designed and put into production. We had not then sufficient evidence to say that the bulk of our failures were due to faulty material, but this is now our opinion. This double spring P.53371/2 has given no trouble whatsoever. It will be seen that the stress on the double spring is lower than on the single spring. Aero Wire Specification. C. .7 - .8% Mn. .2 - .4% Tempered at 450°F.{Mr Friese} for 20 - 30 min. after coiling. Si. .1 - .18% Tensile strength 100 - 110 tons/sq.inch. S. .03% max: P. .03% max: The steel from which the wire is drawn is Swedish base. Blue prints of P.35762, P.39567, P.53371/2, SK.21822/3 and SK.21652 are enclosed. | ||