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).
Engine performance tests, modifications to the cylinder block and gears, and analysis of piston friction, gear rattle, and whine.
| Identifier | ExFiles\Box 82\2\ scan0198 | |
| Date | 27th September 1934 guessed | |
| -2- The maximum power developed was 116.9 BHP. and maximum M.E.P. was 118.3 at 2000-2500 r.p.m., the low speed M.E.P. was reduced somewhat due to the later timing as this amounted to 3.9% at 750 r.p.m. In order to find what B.H.P. we should be likely to lose due to Piston friction by adopting the latest piston grinding, we fitted a cylinder block with bores .002 over standard dimensions and in this condition and with the late valve timing the unit developed 121.2 B.H.P. maximum and a maximum M.E.P. of 123 at 2000-2500 r.p.m. This means that we lose approximately 3.5% of power due to piston friction, this figure will no doubt fall as the pistons are run longer and may only be about 2% after the unit has run two or three thousand miles. In order to overcome the gear rattle a new cam wheel was fitted at the end of this last test having a backlash with the crank pinion of .001, the rest of the gears were adjusted to have .002 backlash and at this setting the gears whined very badly. At the same time that the new cam wheel was fitted a new cylinder block having standard bores was also fitted. With this new cylinder block and new cam wheel which of course altered the valve timing to timing "C" a maximum B.H.P. of 118.6 was recorded with a maximum M.E.P. of 121.5 at 2000-2500 r.p.m. From these figures it would appear that the power had increased somewhat from the power developed by the original standard diameter bore cylinder block due to the settling down of the pistons. The gears were much better as far as rattle was concerned but a considerable amount of whine persisted from the idler wheel; upon investigation the idler wheel spindle was found to be too long and fouling the wheelcase badly. When the spindle was shortened and made clear of the wheelcase the whine was considerably reduced and there persisted only a slight whine at about 500 r.p.m. In this condition the gears were "passed off" as from our experience of the previous set of Textolite gears on this unit we found that the whine has a tendency to improve the longer the gears are run. | ||