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).
Suspension component testing, including life expectancy calculations and specific failure analysis of springs.
| Identifier | ExFiles\Box 154a\2\ scan0357 | |
| Date | 1st July 1941 | |
| -2- I have marked this in attached chart together with some other salient points e.g. Chevrolet Dubonnet unit expectancy, 1,000,000 cycles at 5½" stroke, and approximate figures for 'H' type rear springs. I have also put down 100 hours on the bump rig, approx. 1,300,000 cycles. This is on the continuation of our leaf spring expectancy line and is also in line with Rolls Royce experience. The bump rig is not accurately chartable because of resonance bouncing of the tyres between cams, etc. The chart does not aim to be extremely accurate. For this we should have to plot against max. stress and stress range. What I have aimed to show is that we should reasonably expect, for complaint-free service on any suspension system. 1. A life of 100,000 cycles at least on 7½" stroke. 2. 300,000 cycles on 5½" stroke. 3. 100 hours on bump rig. 2" cams. The figures for G type torsion rods at 5½" stroke are now all out of date. Later results indicate average figures over a million cycles. M.OLLEY" The Myth Spring broke after only 14,887 cycles at the centre bolt hole in the top plate thus indicating that there was too much flexing of the spring within the rubber insulator pads. The failure started at the tension surface. The test results were as follows :- Toledo Woodhead grooved section spring as described in Rm{William Robotham - Chief Engineer}/GB.8/ET.13.1.41 and Rm{William Robotham - Chief Engineer}/GB.12/ET.24.4.41, No.3 in latter memo. Measured rate = 157lb/inch. Opening at start at 827lb = + .425" Settling after 12,000 cycles = .06" Friction at start = 40 lb. " after 12000 cycles = 62 lb. As a result of the experience gained in this test, | ||