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).
Performance table comparing various bonnet ventilation configurations at different speeds.
| Identifier | ExFiles\Box 22\1\ Scan219 | |
| Date | 25th November 1924 guessed | |
| SHEET 2. VALUE OF VARIOUS TYPES OF VENTILATION 20A MATRIX. | | δt | % difference from 'A' | Critical atmospheric temperature. | |---|---|---|---| | 30 M.P.H. BONNET DETAILS. | | | | | Standard - shutters closed. | 77°C | 'A' | 18°C | | Open - small shutters. | 71.2°C | 7.5% Improvement. | 23.8°C | | Open - louvres. | 70.5°C | 8.5% Improvement. | 24.5°C | | Open - larger shutters. | 69.0°C | 11.5% Improvement. | 26°C | | Top panels off. | 65.2°C | 15.3% Improvement. | 29.8°C | | Side panels off. | 62.4°C | 19% Improvement. | 32.6°C | | 40 M.P.H. | | | | | Standard - all closed. | 71.6°C | 'A' | 23.4°C | | Front large shutters open. | 63.0°C | 12% Improvement. | 32.0°C | | Rear " " | 64.4°C | 10% Improvement. | 30.6°C | | All " " | 60.8°C | 15% Improvement. | 34.2°C | Small shutter - dimension - 4" X 10.5". Large " " - 8" X 14.5". | ||