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).
Conclusions from tests on overdrive gear, cooling system performance, and matrix blockages.
| Identifier | ExFiles\Box 131\1\ scan0351 | |
| Date | 19th October 1937 | |
| -2- Rm{William Robotham - Chief Engineer}/Std.3/AP.19110.37. On the same sheet is shown also similar test figures which have been obtained on the track. Conclusions. (1) The standard top gear figures do not provide reliable grounds for comparison. (2) The overdrive figures indicate that the matrix at the end of its mileage had dropped 3°C. in critical air temperature over its new condition, this being due to blockage of the air passages by innumerable insects, feathers, dirt etc. The matrix was flow tested and examined and there was no trace whatever of silting up or blocking of waterways. This drop in critical air temperature represents a 4½% drop in specific heat dissipation. (3) The overdrive figures indicate that the cooling system during its mileage while the blocked filter was in the water circuit, had dropped 6°C. in critical air temp. i.e. a drop in specific heat dissipation of 8.5%, which is made up of 4.5% due to matrix blockage as described above, and 4% due to blocked filter (this was found to be blocked by aluminium turnings from the engine, mixed with a small amount of linseed dope which had peeled off the cyl. heads or blocks. Note. A reduction of water flow of approx. 25% would account for 3°C. drop in critical air temp. (4) The larger belt fan drive with the 1.0/1 ratio is fairly satisfactory for the overdrive gear, but is not satisfactory for prolonged high speed work with the standard top gear. (5) It is not possible to rule from these tests whether we can dispense with an oil cooler or not, since the big end bearing failure which occurred was probably due to the journal of the crankshaft having been damaged by a previous big end failure. Summary We cannot consider the adoption of the lightened (and cheapened) construction for Mk.VI. matrices on Ph.III. since it reduces our already very slight margin of cooling. Reduction of this margin by blockage of the airways of the matrix can become serious over a long period of service under exceptional methods. continued | ||