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).
Knocking noise from a Bentley chassis axle shaft, explaining its cause and the manufacturing process.
| Identifier | ExFiles\Box 102\4\ scan0129 | |
| Date | 15th July 1938 | |
| GWH.{George W. Hancock - Head Chateauroux} (K). C. K.{Mr Kilner} (crossed out) C. Rm.{William Robotham - Chief Engineer} (crossed out) BY.6/G.15.7.38. BENTLEY CHASSIS. B.15-HM.{Capt. W. Hallam - Head Repairs} VANDERVELL. RE: AXLE SHAFTS. Referring to Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux}8/N.12.7.38. and the fact therein pointed out that a knock had developed in Mr. Vandervell's rear axle, and that it was traced to a 'bow' in the length of the axle shaft, which brought up a knock when the car was turning corners at a slow speed, the bow in question is not the result of anything to which the car has been submitted during its running life, it is undoubtedly the result of insufficient stretch of the axle shaft in the first place. In order to produce the best condition in the material to enable the shaft to resist the high stresses to which it is submitted by some customers, we have been forced to aim at a brinell hardness of 369. This entails machining the shaft in the normalised condition up to a certain point, hardening and tempering at this point and then finally grinding. The hardening operation as carried out even under careful conditions on a production basis, results in slight distortion in the form of 'bowing'. This has to be over-come by stretching the shaft back. The shaft should under these circumstances be pushed across its axis to a slight bend in the opposite direction, approximately a 20% bend in the opposite phase, as invariably a stretched shaft tends to return to the bowed condition under stress, as a result of the stresses imposed upon it during running. This is the first complaint we have had. It did not constitute in any sense a danger, nor had it any effect upon the gear teeth, the knock is due to the fact that the bearing behind the bevel wheel, formed on the end of the shaft, has a wide clearance to enable the gears to centre themselves in the differential, but about 3" away from this the shaft is centred by the fact that an oil seal has to be used. Under load the shaft truely centres itself. When turning a corner without load the shaft tends to turn in the oil retainer as a bearing which gives, under these conditions of eccentricity to the gear, and it is this temporary eccentricity under light load which causes the knock. BY.{R.W. Bailey - Chief Engineer} RH{R. Hollingworth} | ||