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 first series of tests comparing different radiator tube designs for the Phantom II model.
| Identifier | ExFiles\Box 16\2\ Scan007 | |
| Date | 21th April 1931 | |
| x7250. To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to EG. Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} Ds. c. to Ey. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/KT. 21.4.31. x3678 P.II RADIATOR TESTS. We have now carried out the first series of tests comparing the latest square tube radiator, our existing standard tube, and two types of American tubes. The tests were not conducted under ideal weather conditions but we are satisfied that they are reasonably accurate, the figures for the standard tube being within .5 degree of those given last year in our Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/AD.14.10.30. Briefly the results show that the square tube without turbulence is not equal, area for area, with the round tube having dents at road speeds of 60 MPH. and over. We have yet to conduct the full throttle tests at 45 & 50 MPH. The figures show that if the Americans compare the P.II radiators they are receiving with a radiator built up with the type of tube they have been using i.e. the large hexagon tube, they will discover they are 2º - 3ºC hotter with the English tubes at high speeds. The figures for the small hexagon tubes are remarkably good and show an improvement of about 12% over our existing standard at 60 & 80 MPH. Since these tubes are produced in America more cheaply than those we are at present using, and Springfield have a wide experience of the type with, from their list of quarterly complaints, singularly few troubles, we think it is well worth while concluding our tests. We do not think there is any mystery about the American tubes, they gain 4 or 5% from having a tube that would give a 1/2mm. gap were it not dented. They get over the blocking up trouble, which drove us from this passage size, by putting large dents in the tube, these dents also having been carefully developed to give them max. turbulence. The hexagonal ends increase the free air area and surface slightly. We agree but we were most enthusiastic about the square tubes when they were at first suggested, we have since learnt that turbulence is of more importance than surface at any rate at high speeds. We shall shortly have the low speed value of turbulence carried to the limit by U.S.A. We might always be able to beat a turbulent round tube with a turbulent square tube but it would appear that | ||