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).
Summary of features affecting gearbox silence, comparing American (Cadillac) and R.R. designs.
| Identifier | ExFiles\Box 125\1\ scan0220 | |
| Date | 15th March 1935 | |
| -3- As is usual American practice, the teeth are of coarser pitch than we use. This automatically necessitates a greater helix angle to obtain a reasonable amount of overlap of the helical teeth. We cannot see any reason why a coarse pitch gear should be quieter except that it may enable greater accuracy to be obtained in the grinding operation. A further interesting feature of the gear wheels is that they are not hollowed out for lightness as is done on R.R. gears. This results in a more rigid support for the gear teeth and eliminates the possibility of vibrations in the thin web of the gear. This is a point which should be settled by experiment. A summary of the features of the Cadillac gearbox is as follows :- A.{Mr Adams} Features which are against the silence of the Box. (1) Ball bearings in bad condition. (2) Use of taper roller bearings for 1st and 2nd speed wheels. (3) Reverse pinion and idler always in mesh. (4) Large flat sides of box. (5) Most heavily loaded gears, i.e., 1st and 2nd speeds, situated mid way between bearings 12" apart. B. Features which should make the Box silent. (1) Outer races of bearings a slack fit in housing. (2) Cast Iron Box. (3) Rigid support of gear teeth and no thin web to gear wheels. (4) Very accurate grinding of teeth. (6) Coarse pitch may be of assistance. The features A, 1, 2, 3, and B.1 refer mainly to idling conditions. The silence of the box under load we attribute to B.3, 4, 5 and possibly 6. | ||