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 endurance testing, detailing big end seizure failures and the effects of lubrication modifications.
| Identifier | ExFiles\Box 115\1\ scan0191 | |
| Date | 15th December 1930 | |
| 139 Rm{William Robotham - Chief Engineer}/wdl.12/AR.15.12.30. In order to try and reproduce these failures it was decided to run endurance under the previous speed conditions but at 1/4 load, to represent the throttle being closed after running at full throttle at high engine speeds on the road. This gave the desired results and the average time before big end seizure came out at approximately 2 hours with the normal Bentley lubrication. (2) Effect of lubrication. In order to demonstrate the effect of improved lubrication, the following is the history of one particular test bed engine B.17. Following a 10 hours successful full throttle run, No.3. big end seized after 3 hours at 1/4 load; after replacement No.4. big end seized in 5 minutes at 1/4 load and after replacement Nos. 2 & 5 big ends seized in 2 hours at 1/4 load. When these were replaced by new bearings in similar material the lubrication system was modified as follows - (1) An extra hole opposite to the existing drilled in each crankpin and crank journal. (2) The grooves in the intermediate main bearings modified to Rm.{William Robotham - Chief Engineer}244. bringing the effective sectional area of the grooves to that of the oil jet feed hole. The result of the above is shewn in the attached photograph (No.4), all the big end bearings being in good condition after 15 hrs. running at 1/4 load. With the freed lubrication it was necessary to increase the relief valve spring pressure in order to maintain a standard of 30 lbs. sq. in. pressure and consequently the increased oil flow from the big ends raised the oil consumption from 1.625 pints/hr. to 2 pints/hr. As we are not so happy with oil consumption, these lubrication modifications are now carried out with the exception of the extra hole in the crankpin and in this form there is no oil consumption increase over standard. Nos. 1, 2, & 3 photographs are records of the 1/4 load failures with standard lubrication. continued | ||