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 testing, detailing issues and performance of tappets, springs, pistons, and water leaks from cylinder head gaskets.
| Identifier | ExFiles\Box 4\1\ 01-page233 | |
| Date | 28th January 1935 | |
| -2- The tappets on this engine operated very satisfactorily, the cast iron eccentrics on the coppered shafts overcoming the wedging trouble we experienced with whitemetal on steel. As developed on the Phantom, poppet valves are used in the plungers and the casings with oil metering plugs. The plungers have .0015 diametrical clearance and there is little or no bobbing of the plungers with hot oil and idling, this being the worst condition. Spacing springs between the eccentrics were not successful as when running at high speeds two retaining washers came off the dowels, this happening on staggered rockers. For the present we have decided to return to using the solid distance pieces. With cold oil the plunger return springs E.85904 were not strong enough to return the plungers and eccentrics, these being replaced by the original plunger springs E.86321, which are stronger and are just up to the job, although the return is sluggish. Using E.85316 valve springs which have a seat loading of 52 lbs., valve bounce occurred between 4000 r.p.m. and 4250 r.p.m. and we have instructed that Hs.{Lord Ernest Hives - Chair}1607 springs be fitted, having a seat loading of 65 lbs. These latter springs when tried on No. 2 unit which had the Hs.{Lord Ernest Hives - Chair}1536 camshaft in conjunction with the same diametrical plunger clearance of .0015, overcame valve bounce up to 4500 r.p.m. The semi-split pistons used in No. 3 unit are for some reason very quiet under hot or cold conditions on this engine, but A side overoils badly at high speeds, B side being O.K. Very bad water leaks were experienced from both A & B cylinder head gaskets and worst at the rear end when running at high speeds. As this gets worse as the speed increases we suspect that the restrictions to the outlet builds up excessive pressure. Another indication of this is that even at high speeds the temperature rise from the pump inlet to the rear end of the cylinder block was from 50°C. to 80° - 90°. We cannot say whether the new crankcase to LsC.4074 with modified water passages in both the case and cylinder head will help us in this respect but it will be on test almost immediately. The actual outlet from the head at the rear end and the top water rails considerably restricts the flow as shewn by the results of water flow tests previously carried out. | ||