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).
Five-stage process undertaken to diagnose and cure a 'thud' noise in a Bentley B.24-GA engine.
| Identifier | ExFiles\Box 90\4\ scan0068 | |
| Date | 11th November 1936 guessed | |
| REPORT ON WORK DONE TO CURE THUD IN RAYMOND MAYS' BENTLEY NO. B.24-GA. ------------------------------------------------- The work was carried out in five stages:- 1. Instructions were issued to dismantle the engine and open up for inspection. Before doing this we tested No. 1 main bearing for slack and found it to be .004". We then dismantled Nos. 2, 3,5 and 6 main bearing caps and all connecting rod bearings for inspection. 2. We were instructed to fit new Hall's metal liners to the big ends, these being supplied by the Experimental Department, and to re-assemble all bearings on crankshaft and rig up for oil test. This was done and as the flow from No. 7 was greater than the others we were instructed to reduce the liners of this bearing by .002". We also reduced those of No. 6 by .001" to make the flow more even. We were also instructed to fit a new large capacity oil pump. 3. The engine was then re-assembled and tested. On test, the thud was worse. In fact, so bad as to cause suspicion that the flywheel might be loose. 4. We dismantled the gearbox, clutch and lower half, but the flywheel was found to be perfectly tight. Also clutch and ball races on the first motion shaft in the gearbox all O.K. We then decided to examine the main bearings again and first took down Nos. 1, 4 and 7. We found No. 7 had been hammering in the cap. This bearing was clocked up and we found that the joint face of No. 7 bearing lower half was .007" lower than the joint face of the bearing cap. No. 4 was not so bad and No. 1 was O.K. We then bedded the back of No. 7 bearing into the cap and re-topped bearing and cap. This was also done on Nos. 3, 4, 5 and 6. Nos. 1 and 2 were O.K. 5. Engine was re-assembled and tested and the thud was found to have been cured. (sgd) THOS. E.{Mr Elliott - Chief Engineer} HURST. | ||