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).
Design and materials of engine timing gears from Buick and Cadillac.
| Identifier | ExFiles\Box 136\1\ scan0042 | |
| Date | 3rd June 1933 | |
| X-11 To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}3/KT.3.6.33. ENGINE TIMING GEARS. In view of the fact that the Buick car which we tried the other day was exceptionally quiet, we have looked up some of the information we obtained from America on the way in which they make their timing gears. They have only three timing gears, the centre one being the cam wheel made in Textolite, and the others made in steel. Exceptionally little backlash is allowed in these gears, and they recommend replacement when the back-lash becomes appreciably greater than .0015". The diametral pitch and helix angle can be obtained from the gear that we hand you herewith which we have just obtained from Buicks. The timing gear case is interesting because it has a double wall which Buicks state is very effective in reducing timing gear noise. They also state that the smooth finish of the inside of the timing gear case prevents any currents of air which might cause a whistle. Strangely enough the timing gear cover is a steel pressing. We must admit to a certain extent that our own experience bears out the fact that the lighter metals transmit sound rather easily because we found that our valve noise increases considerably when we made a tappet cover in magnesium. We attach a picture of the Buick timing gear case showing the double walls. Cadillacs, who are a part of General Motors organisation, have proved that a high helix angle facilitates the manufacture of quiet gears, and state they have found that the greatest benefit is derived when the angle is between 45 and 50°. Cadillacs were also emphatic that up to 40° the helix angle is not nearly as effective as above this point. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} | ||