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).
Gear tooth pressure angles for the Spectre Gearbox.
| Identifier | ExFiles\Box 94\1\ scan0012 | |
| Date | 6th June 1934 | |
| <4049> 3.28 To BY.{R.W. Bailey - Chief Engineer} From HDY.{William Hardy} c.c. Mr. H.B. Hs.{Lord Ernest Hives - Chair} Mr. HHG. HDY.{William Hardy}3/HP.6.6.34. [Signature] SpectreCodename for Phantom III Gearbox. ---------- With regard to the obliquity of the teeth for the constant mesh, 3rd and 2nd speed gears, we ask for 20° on N. Sch.4049 but on further consideration we think that 14½° should be tried first as the evidence appears to be in favour of the latter angle for silence and it seems doubtful whether the 20° tooth is less stressed when allowance is made for the diminished number of teeth in contact. The increase of the Lewis factor for a 30 tooth gear from 14½° and 20° is 12%, and the reduction of the length tooth contact is 23%, so there is a margin in favour of 14½° to allow for some of the increased tooth contact not being realised. We do not expect to be troubled by picking up of the tooth surface on these gears so shall not need the larger radius of surface given by 20°. In the case of the first speed gears the increase of strength with the higher pressure angle is more marked owing to the small number of teeth in the pinion. There is also the greater need for a large radius of curvature of the surface with these gears and consequently there is here no question of the superiority of the higher pressure angle. HDY.{William Hardy} | ||