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 memorandum detailing spring stresses, ratings, and deflection specifications for various frames.
| Identifier | ExFiles\Box 100\1\ scan0092 | |
| Date | 25th February 1938 | |
| The following items of information answer questions put verbally to Ev.{Ivan Evernden - coachwork} or the writer. (1) (a) Maximum stresses in Packard spring in full bump position are: 103,000 lbs sq.in. uncorrected. 122,000 lbs sq.in. corrected. (b) Rating at wheel is 73 lbs/in. due to spring. (c) Initial deflection at wheel, assuming that upper triangle is horizontal in normal position, i.e. for sprung weight of 780 lb/wheel or total weight of 900 lbs/wheel (empty weight given by Sales is 880 lbs/wheel) is 10.7" (d) Bump movement is approx. 4 7/8" from above position, so that total deflection will be 15.575 approx. Free movement of wheel is of course considerably less than this as rebound is restricted. Prints of Packard layout received from By/Ald.{F. Allwood - Experimental Design} show Packard movement as approx. 7.6". (2) 6.5" Initial deflection springs have been done for both frames on B.III - for new frame on PD.86. 8.5" initial deflection springs for B.50 for 900 lbs normal sprung load can be obtained with a maximum corrected stress equal to that of the Packard provided that there is no allowance for packing for height adjustment. This allows for 3.500" bump movement. (3) (a) Front springs done for B.III are: 5", 6.5", and 8.5" for original frame. 6.5" for revised frame.(Max. corrected stress 106,600 lbs.sq.in.) (b) Front spring for B.50, for revised frame, has 6.500" static deflection. | ||