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).
Gearbox engagement issues, specifically 'clicking' and 'klonking', and proposed modifications.
| Identifier | ExFiles\Box 182\M19\ img126 | |
| Date | 26th February 1931 | |
| - 3 - Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey}3/RT.26.2.31.Cont. From the first tests on this car it is evident that we have a long way to go to achieve a reliable fool proof change. The two chief troubles are clicking, and engaging when speeds are not synchronous. The first can be certainly reduced by a reduction in the dog face angle. (the spring strength is already as weak as we can do with, third gear occasionally comes out on the overrun). The 10º face angle gives a very large engagement face, one would think that half this would be sufficient. We will try 5º face angle and also 2º (as sugges-ted by Da{Bernard Day - Chassis Design}/Hdy.{William Hardy}) A reduced face angle should help in (2), where engagements of top gear is now impossible when the car is stationary. Rounded engagement corners in addition would also help in this respect, this we will try after reducing the face angle. If these fail we shall have to try an increased number of teeth as suggested by Da{Bernard Day - Chassis Design}/Hdy.{William Hardy} in para-graph (3) of Da{Bernard Day - Chassis Design}/Hdy.{William Hardy}r/20.2.31. With regard to paragraph (4) of the same memo. we are not optimistic as regards easily preventing the "klonk". From the fact that it is not possible to engage top gear with the car stationary we deduce that dog engage-ment does not actually occur at exactly synchronous speeds but when the driving dog speed is slightly less than the driven dog in the case of top speed and the reverse in the case of third speed and that the "klonk" heard is due not to the dogs shooting home but to the engagement faces making contact, i.e. a small jar takes place each time. In addition to the modifications to the actual dogs we shall have to modify the preselector mechanism (in this case the ordinary gear change). At present the selector plunger springs are weaker than the dog engaging springs so that in making a preselected change the gear lever has to be held in position whilst the change is being made, otherwise the gear lever is shot back into the neutral position by the dog engaging springs. Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey} | ||