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).
Radiator tests conducted at Brooklands, comparing the efficiency and hydraulic resistance of hexagonal and square tube designs.
| Identifier | ExFiles\Box 29\3\ Scan309 | |
| Date | 19th May 1931 | |
| K788 To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} c. to Sg.{Arthur F. Sidgreaves - MD} Nor. c. to Da.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} RADIATOR TESTS. BROOKLANDS. We have now completed our tests on the two hexagonal tube radiators and the square tube radiator having vertical waterways only. EFFICIENCY? 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 5ºC. 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 5ºC. 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 30ºC. to 35ºC. On the continent an air temp. of 30ºC. is frequently obtained but 35ºC. is very exceptional. The total gain in efficiency of these tubes over our 1930 standard is 15º to 17º, 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 mn. 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. | ||