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).
High-speed cooling tests, comparing bonnet ventilation and radiator temperatures under different conditions.
| Identifier | ExFiles\Box 15\1\ Scan109 | |
| Date | 12th June 1927 | |
| contd :- -2- for hill climbing than any 40/50 HP. car we have previously had. We know that the specific complaint was that the car over-heated at high speeds. We have repeatedly proved that high speed cooling is a matter of bonnet ventilation. In our last test on Brooklands (Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG12.6.27) we shewed that a car fitted with a louvred bonnet and driven at max. speeds would have a radiator temp. 20°C below that of the car driven in a similar manner with a plain bonnet. In view of this enormous difference we do not anticipate that we shall ever be able to build a car which can be driven at Max. speeds in hot weather without over-heating if a plain bonnet is fitted. On the other hand it is a fact that the present std. Phantom has given reasonable satisfaction without louvred bonnets. We therefore carried out a high speed test comparing a std. chassis on test fitted with a covered body with SS.{S. Smith} car 19-EX which was the car of which PN.{Mr Northey} specifically complained. Both cars were fitted with the equivalent of 14 tooth axles. The cars were driven as hard as possible over a 15 miles stretch of road averaging about 50 m.p.h. Both cars had unventilated bonnets. The ats. temp. was 23°C which is of course a summer temperature. (We have frequently had days with a temp of 30°C on our 10,000 miles tests). There was a light wind which made a considerable difference in the two directions. Against the wind the max. temperatures attained were: SS.{S. Smith} car 19-EX............ 75°C. Phantom car 73-OR....... 85°C. With the wind: SS.{S. Smith} car 19-EX............ 90°C ( Would be boiling Phantom car 73-OR....... 95°C ( at ats.temp. of ( 30°C. contd :- | ||