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).
Oil consumption on Bentley engines, specifically concerning an extra oil hole in the connecting rods.
| Identifier | ExFiles\Box 159\6\ scan0090 | |
| Date | 19th October 1937 | |
| -3- bed running, in spite of making every effort to do so. We have had no success with the anodic treatment of the pistons. We are therefore left with the extra piston lubrication when starting up, which successfully completed 10,000 miles on 21-G-IV. In view of the recurring trouble we are proposing to standardise this". This was done so, commencing on chassis B-189-DK. Oil Consumption on Bentley. Test bed report Rm{William Robotham - Chief Engineer}/MTHS.{Reg Matthews}8/MR.19.10.37 curve, fig.iii. shows the effect of blanking up the extra oil hole in the connecting rod. "It should be mentioned that these curves are taken on the test bed under full throttle conditions. The curve shows however, that with good bedding rings, not fluttering, the use of the extra oil hole does not upset consumption. Service reports by G.W.H. show that blanking up the hole does definitely improve consumption under certain conditions. But against this, since adopting the extra oil supply, we have had no complaints of seized pistons. It therefore appears that for future engines, we should retain the extra oil and use correctly designed rings to control the extra oil supplied". Memo to W/P - SR/VA - Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}8/KW.15.10.36 states :- "On all 4 1/4 litre Bentley cars we have the extra oil hole drilled in the connecting rods. When the piston rings are in good condition, this makes but little difference to the oil consumption. When wear takes place, however, blanking up the hole in the rod may improve the consumption by as much as 300 m.p.g. In the case of a badly worn cylinder block, the risk of seizure seems exceedingly remote and we therefore recommend that you cut off the additional oil supply from the connecting rod in cases where you do not wish to rebore. If at any time the engine is rebored and new pistons fitted, this hole should be opened out". Rm{William Robotham - Chief Engineer}/Hm.{Capt. W. Hallam - Head Repairs} | ||