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).
Analysis of engine heat flow, piston friction, and performance improvements from component changes.
| Identifier | ExFiles\Box 144\3\ scan0029 | |
| Date | 13th February 1934 | |
| -4- by the crankcase, the less would have to be dissipated by the cooler so that the accuracy of our results may have been affected. The temperature of the Test House throughout the test was 24°C. or 75°F.{Mr Friese} and in order to keep our results as accurate as possible these conditions will be adhered to as closely as possible in the event of us having further tests to do. As mentioned earlier in the report, we also tried the effect of Crankshaft Balance on the heat given to the oil. We found that by completely removing the balance weights there was an increase in the heat to the oil of 90.45 B.T.U's/minute. The total heat given to the oil with the large Balance Weights fitted was 210.2 B.T.U's/minute, but this figure was increased to 300.65 B.T.U's/minute by removing the Balance Weights completely. From this it would appear that we may expect a greater amount of heat to be given to the oil when the standard arrangement of Balance Weights and Connecting Rods are used as compared with the arrangement that was used for our tests. The heat to oil figure may approach the figure we arrived at by not using any balance weights since we may also expect a rise in heat due to the use of white metal big end bearings. The reason for assuming that we may expect a rise in the heat given to the oil by the use of white metal big end bearings, is that the clearance at high temperatures may not be so large as when using Duralumin rods, in which case there may be an increase in the heat to the oil due to increased friction. Since carrying out these experiments we have, made a direct comparison between R.E.1299 Pistons and Aerolite Pistons in order to confirm our opinion that we should expect a reasonable increase in power by reducing the piston friction. From our Heat Flow figures, we found that Aerolite Pistons showed a reduction when compared with R.E.1299 Pistons of 420 B.T.U's/minute, or approximately 10.0 H.P., by actual comparison from power curves taken with these Pistons in the same engine we find we get an increase of 7.0 B.H.P. at 4000 r.p.m. and 7.8 B.H.P. at 4250 r.p.m. By far the most remarkable feature is the increase in B.M.E.P. over the whole of the lower and middle speeds. This increase amounts to 6.0 to 7.0 B.M.E.P. The mechanical efficiency increases correspondingly, and as a check on the reliability of the figures we also determined the I.H.P. and this we found to be identical in each case, so that we can now definitely say that there is an improvement by fitting Aerolite Pistons. | ||