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).
Faults and modifications related to grinding, pinion alignment, and supercharger failures.
| Identifier | ExFiles\Box 143\2\ scan0190 | |
| Date | 24th June 1941 | |
| - 5 - Continued : side of the grinding wheel has been made clear. It has also been stated that the rim of the wheel should be "point ground" and not "line ground" so that the whole surface can be flooded with coolant. The problem of mal-alignment of the wheel and pinion is purely a question of an accumulation of drawing limits and an alteration has been put through which moves the moderate pinion .025" in the opposite direction to the general tendency of the limits and it is thus hoped to improve the linability of the job. The web of the pinion is also being increased in section by .050" to add strength and compensate for any turning marks which may be apparent as owing to the high mechanical strength of the material used, it is difficult to obtain a smooth turned finish and the design of the pinion makes it impossible as a grinding operation. These troubles were followed by complaints of excessive oil consumption and oil dripping from the air intakes. Immediately an engine was obtained and on stripping it was found that the supercharger tail bearing had failed. Some four or five engines were then taken and a general examination carried out which revealed the following faults:- 1. Lack of concentricity of the bore of the fixed bronze bush with the spigot, both on the elbow and the mating diameter of the rear half supercharger. This varied up to .012" clock reading. 2. Distortion of the joint face of the elbow as much as .006" clock reading. 3. It was found that the diameter of the fixed bronze bush was as much as .001" under size and it was clear that the steel bush had not been rotating thus all the rotational effects were carried on the inner floating bronze bush, entirely defeating the design principles of the bearing. This error probably occurred due to the fixed bronze bush being fitted with an incorrect interference. 4. A check on supercharger rotor balance was carried out and it was calculated that the out of balance experienced on the supercharger rotor could produce loads on the tail bearing due to out of balance effects as high as 300 lbs. This was due to the rotor being balanced between wide limits in its unit stage so that lack of dynamic balance was experienced. This feature has now been dealt with. These questions have been fully discussed with Crewe, Glasgow and Derby and it is thought that these failures will now be overcome. An instruction sheet has also been issued on the extent of permissible limits on the essential dimensions. We are also fitting six ground taper dowel bolts in the perimeter ring of bolts in the supercharger casing to ensure that it cannot move and a method of manufacture is being considered to enable the supercharger elbow to be made as an interchangeable part. - continued - | ||