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).
Comparative table of radiator tube types and their critical air temperature performance under different ventilation conditions.
| Identifier | ExFiles\Box 182\M19\ img161 | |
| Date | 27th March 1930 guessed | |
| TYPE OF RADIATOR TUBE CRITICAL AIR TEMP. The difference between the top water temp. and Ats (t) subtracted from 100°. This temp. represents that at which the car will eventually boil in still air if driven sufficiently long full throttle. Table Columns: 1. TYPE OF RADIATOR TUBE 2. 60 MPH. No bonnet ventilation. 3. All cut bonnet vent. 4. All cut Vertical bonnet louvres Table Rows: Row 1: - Small Hexagonal Ended American Tube. Hexagon .30" across flats. Centre .255" dia. round. No. of Dents. 18 - 46. - 38. - 46. Row 2: - Large Hexagonal Ended American Tube. Hexagon .30" across flats. Centre .309" dia. round. No. of Dents. 20 - 41.5 - 38 ? This reading requires confirmation. - 42.5 Row 3: - Present standard tube. 6/7½ mm. Round tube E.73448. 4 dents/tube - 39.5 - 31. - 38.5 Row 4: - Square tube E.81389. 6 mm. square centre 8 mm expanded to 7½ mm. horizontally only. i.e. 1½ mm. vertical waterways. No horizontal waterways. - 38. - 38.5 - 39.0 Footer: Tests on 1-ex. Brooklands. Car weight 48 cwt. All radiator dimensions 25.9 X 23.7. | ||