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).
Table of critical air temperature figures for a Phantom II car under different speed conditions.
| Identifier | ExFiles\Box 155\1\ scan0233 | |
| Date | 19th May 1931 | |
| Critical Air Temperature Figures for Ph.II Car with last standard radiator: i.e., large, hexagon-ended American tubes (taken from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}8/KT.19.5.31). Condition Critical Air Temperature. (1) 30 M.P.H., full throttle (three ventilating shutters per side of bonnet - open). 29.5°C. (2) -ditto- but 45 M.P.H. 30.0°C. (3) -ditto- but maximum speed. 35.0°C. (approx. - estimated). | ||