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).
Required recalibration of Wraith III speedometers due to a change in tyre radius.
| Identifier | ExFiles\Box 165\2\ img097 | |
| Date | 25th June 1937 | |
| To: [REDACTED] from HPS{Horace Percy Smith - Experimental Factory Mgr}/WSC.{W. S. Cassel} RMWst 6065, HPS{Horace Percy Smith - Experimental Factory Mgr}/WSC.{W. S. Cassel}27/BA.25.6.37. 0/54127 Wraith III Speedometers. Owing to the alteration in the static effective radius of the tyres on the Wraith car, it has become necessary to revise the calibration of Wraith speedometers. The new calibration of value revs. per mile is 776, as compared with the present value of 772 revs per mile. We hand you herewith, Speedometer No.S.807, will you please have this returned to the makers to be made right for 776 revs. per mile. At the same time we would point out that this instrument was found to be 5.5% fast at 30 m.p.h. 7% fast at 60 m.p.h and nearly 9% fast at 90 m.p.h whereas we expect them to be accurate at 30.m.p.h. HPS{Horace Percy Smith - Experimental Factory Mgr}/WSC.{W. S. Cassel} | ||