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).
Two graphs illustrating spring rating tests, comparing shackle angles and different spring systems.
| Identifier | ExFiles\Box 67a\1\ scan0214 | |
| Date | 27th May 1925 guessed | |
| (1) SPRING RATING TESTS (β) AND (α) EFFECT OF SHACKLE ANGLE. WIDE PADS. RATING LBS/IN. TOTAL LOAD LBS. α = 21° FORWARD SHACKLE β = VERTICAL SHACKLE WORKING RANGE 1100 LBS (δ) SPRING RATING TESTS. (δ) AND (β) COMPARISON OF SPRING SYSTEMS. RATING LBS/IN. TOTAL LOAD LBS. δ - NARROW PAD, 21° SHACKLE β - WIDE PAD, VERTICAL SHACKLE WORKING RANGE 1100 LBS | ||