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).
Examination report on a big-end failure in a Bentley unit after 800 miles, caused by foreign matter in the oil system.
| Identifier | ExFiles\Box 89\4\ scan0024 | |
| Date | 5th January 1937 | |
| To Rm.{William Robotham - Chief Engineer} from HPS{Horace Percy Smith - Experimental Factory Mgr}/RH.{R. Hollingworth} c.to RHC.{R. H. Coverley - Production Engineer} c.to HPS.{Horace Percy Smith - Experimental Factory Mgr} # 261 This may have been mainly a regulator trouble FILE BENTLEY UNIT - No. R.6.B.R. The above unit (removed from a customer's car) has been stripped for examination following a big-end failure after 800 miles on the road. The bearing which failed was that in No. 5 connecting rod, the top half of the bearing being chiefly affected. In that half, the metal had completely broken away all round the flange of the bush on both sides, and in the cap-half there appeared 5 radial cracks, 3 on one side and two on the other (See drawing Ex.I.119) There is distinct evidence that the bearing had been running hot and the cause of the failure was insufficient lubrication, with the possibility that this bearing had smaller initial clearance than did the others. On further investigation, a large piece of foreign matter was found under the relief-valve of the oil pump, composed of some fabric such as that used for cleaning-rag etc, and this, in our experience, would be sufficient to cause a very serious drop in the main oil-pressure. There was, also, a lot of foreign matter at the bottom of the sump, other than bearing-metal from the damaged bearing. It is, however, difficult to form an accurate opinion as to the exact cause of failure without a full knowledge of the circumstances under which it took place. Herewith drawing No. Ex.I.119 showing roughly the state of the bearing concerned. Flywheel gear ring teeth are damaged due to foreign matter having got between the teeth and crankcase. These should receive attention before assembly. R.{Sir Henry Royce} Hollingworth. | ||