Calculations confirming spring and shackle performance, including stiffness and load under different camber settings.
| Identifier | ExFiles\Box 43\2\ Scan124 | |
| Date | 5th April 1928 | |
| OyS-E-4526 -4- April 5th, 1928 (8) Confirmation of result 5 above by calculation. (30º and 21º shackles.) a. {Mr Adams} For 1" camber (assuming circular curve of spring) spring shortens by .060". b. For change from 1" to 2" camber spring shortens by .178". c. For first 1" of deflection from flat front shackle pin drops .060 x .578 = .0346 (for 21° shackle .0232) Centre of spring drops .0175 (for 21° shackle .0116). Increase in stiffness for 30° shackle 1.7% (for 21° shackle 1.16%) d. {John DeLooze - Company Secretary} For second 1" of deflection from flat, front shackle pin drops .178 x .578 = .103 (for 21° shackle .069) Centre of spring drops - .0515 (for 21° shackle .0345) Increase in stiffness 5% (for 21° shackle 3.5%). e. {Mr Elliott - Chief Engineer} Effect of horizontal tension due to inclined shackle Let P = load at centre of axle P1 = actual load obtained with spring free at ends l = working half-length. Taken as 19.75". A = angle of shackle to vertical d = camber of spring. P = P1 / (1 + d tan A) Taking a spring of rating 310 lbs./in. 3-1/2" free camber, 30° angle of shackle, loads will be as follows: | Camber | P1 | P (neglecting drop of shackle pin) | Stiffness | P (with drop of shackle pin) Items c and d above | Stiffness | |--------|------|--------------------------------------|-----------|----------------------------------------------------|-----------| | 2" | 465 | 439 | 314 | 460 | 298 | | 1" | 775 | 753 | 332 | 758 | 327 | | 0 | 1085 | 1085 | 353 | 1085 | 359 | | -1" | 1395 | 1438 | 374 | 1444 | 393 | | -2" | 1705 | 1812 | | 1837 | | | ||
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).