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).
Technical report detailing various mechanical, gear, and component noises on a vehicle.
| Identifier | ExFiles\Box 22\3\ Scan085 | |
| Date | 14th February 1932 | |
| -2- Mechanical and Gear Noises. The only engine noises apparent are from tappets and a whine which apparently emanates from the camshaft driving chain. A special type of cam contour is employed which is stated to give a quiet operation when using the large clearance of .030"; small coil springs are inserted between the rocker arms and a shoulder on the top end of the push rods the object of which is apparently to ensure that the other end of the rocker is always in contact with the valve stem. Several of these little springs appear to have failed which might account for the intermittent tappet noises. Apart from the above and a brush gear noise from the dynamo the engine is mechanically quiet. Detonation is greater than we should tolerate on a new car. Gear Box Noises. All the gears when under load or on the overrun are remarkably quiet. The only time when the gear box noise is objectionable is idling in neutral (idling with any one of the gears engaged and the fluid flywheel slipping is of course dead quiet); under this condition there is a bad uneven dry gear noise. It is questionable whether the gears when under load would be considered quiet enough if used on our standard 20/25 chassis; the general fuss and rumble of the Lanchester may possibly be effective in drowning gear noise which is present but requires concentration to pick out. Rear Axle. The rear axle is very noisy when warmed up, particularly uneven between 25 and 30 m.p.h. forward pulling. An underslung worm drive is employed. Tyres. Buttressed tread Dunlop Tyres are used which are very noisy. Carburetter suction noise is excessive. An S.U. carburetter is employed, fitted with a Smith air filter and silencer; the suction noise is considerably greater than on an S.U. carburetter similarly silenced when fitted to our 20/25 Car. | ||