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 comparing the cooling performance of different radiator tube types under various bonnet ventilation conditions.
| Identifier | ExFiles\Box 149a\3\ scan0082 | |
| Date | 27th March 1930 guessed | |
| CRITICAL AIR TEMP °C. The difference between the top water temp. and Ats (At) subtracted from 100°C. This temp. represents that at which the car will eventually boil in still air if driven sufficiently long full throttle. | TYPE OF RADIATOR TUBE | 60 MPH. No bonnet ventilation. | All Out. No bonnet vent. | All Out. Vertical bonnet louvres. | |----------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------|------------------------------------|-----------------------------------| | Small Hexagonal Ended American Tube. Hexagon .305" Across Flats. Centre .255" Dia. round. No. of Dents. 18. | 46. | 38. | 46. | | Large Hexagonal Ended American Tube. Hexagon .360" Across Flats. Centre .309" Dia. round. No. of Dents. 20. | 41.5 | 38. This reading requires confirmation. | 42.5 | | Present standard tube. 6/7½ mm. Round E.79<48. 4 dents/tube | 39.5 | 31. | 38.5 | | Square tube E.81389. 6 mm. square centre. Ends expanded to 7½ mm. horizontally only. i.e. 1½ mm. vertical waterways. no horizontal waterways. | 38. | 29.5 | 39.0 | Tests on 13-EX. Brooklands. Car weight 48 cwt. Axle 11x41. All radiator dimensions 25.9 X 23.7. | ||