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).
Investigation into an engine seizure on a 4 1/4 Litre Bentley, concluding the cause was outdated crank lubrication holes.
| Identifier | ExFiles\Box 114\3\ scan0102 | |
| Date | 3rd March 1938 | |
| By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. to Ms. c. Da.{Bernard Day - Chassis Design} c. Mx.{John H Maddocks - Chief Proving Officer} c. RHC.{R. H. Coverley - Production Engineer} c. OWH. c. Hd.{Mr Hayward/Mr Huddy} c. K.{Mr Kilner} Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}6/AP.3.3.38 B.149.JY. (DEVEREUX) 4 1/4 LITRE BENTLEY. We have examined the bearings of the engine unit out of the above car on which No.5. big end seized and shed a rod through the crankcase. The most noticeable thing is that the remaining big end bearings are in good condition with every sign of adequate lubrication. From this, therefore, it can be reasoned that although the unit has the small oil pump the latter cannot be entirely responsible for the seizure by its insufficient capacity, otherwise the big ends generally would show signs of being shy of oil. Evidence of the crankpin shows that seizure took place opposite to the single oil hole in the pin, and is reminiscent of the seizures we had when running light at high speeds during the development of the crank lubrication. This was cured by having an extra opposite hole making two in each crankpin and we consider that this is the most important factor in keeping clear of seizures. It may be said that the fact of the failure being on No.5. rod, is the old complaint of either No.2. or 5 to go first, but we would point out that this unit has the full section grooving of the intermediate main bearings and we have found in such circumstances that any one rod is as liable to seize as another. Some hammering of the main bearings, which is being checked for us, may have been contributory to the cause of seizure, likewise the small capacity pump, but the main reason we are convinced is the crank not having the up-to-date lubrication holes. It is not so much a question of having a large flow of oil at the big ends as a small quantity in the right places, and is therefore not so susceptible to loss of oil through main bearing hammer or incapacity of the small pump. As stated in the complaint form, the car was travelling at 90 m.p.h. when the seizure occurred and we would say that the throttle was closed just prior to the seizure. Although there are a great number of 4 1/4 litre Bentleys in service which are not up-to-date in their lubrication etc. (O.M.J. and up to the 175th chassis in K) we consider that this should be carried continued | ||