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).
The results of radiator tests at Brooklands, comparing hexagonal and square tube designs.
| Identifier | ExFiles\Box 182\M19\ img070 | |
| Date | 19th May 1931 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to Da.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer} c. to Ey. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}8/KT.19.5.31. X7250. Y5250. X766. X788. RADIATOR TESTS. BROOKLANDS. EFFICIENCY. We have now completed our tests on the two hexagonal tube radiators and the square tube radiator having vertical waterways only. The results confirm the fact that the smaller hexagon tube is exceedingly efficient both at low and high speeds. As an approximation it is fair to say that the top water temp. would be 5°C. lower with this type of tube under conditions when over-heating is likely to take place, than the best of the other english tubes that we have tested. This 5°C. is of great value because it puts the atmospheric temp. at which the car could be made to over-heat under exceptional conditions of driving from 30°C. to 35°C. On the continent an air temp. of 30°C. is frequently obtained but 35°C. is very exceptional. The total gain in efficiency of these tubes over our 1930 standard is 15° to 17°C. or over 20%. HYDRAULIC RESISTANCE OF RADIATOR. The gap between the small hexagon tubes is .047 approx + increase in area due to indentations. Our standard gap on the 40/50 is .060 and on the 20 HP. .040 We attach a curve of the hydraulic resistance which shows that the hexagon tube is the same as the standard 40/50. On the 25 HP. we should expect to have less hydraulic resistance than with the standard tube. As a safety first measure we might recommend a 1½ mm. gap if these tubes were used for the 40/50 standard. at the same time we could run some cars with the reduced gap. Our existing preventatives, oxidised water passages in the block appear to have reduced the chance of deposit in the top row of tubes very considerably. COST OF RADIATOR. You already have the figures showing the relative cost of U.S.A. tubes and square tubes. | ||