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 letter providing a detailed troubleshooting guide for resolving booming and vibration issues on a car.
| Identifier | ExFiles\Box 27a\1\ Scan223 | |
| Date | 25th January 1935 | |
| To Sr/VA - Levallois. Re your Sr/VA5/ET. 22.1.35. Sorry to hear that the old owner of 24-EX is not pleased with his new car. I remember tapping the panels of this car before it went back to the Coachbuilders for padding. It certainly seemed an excellent sound-box for a moving coil speaker rather than a silent luxury carriage. However, here is a little information on booming. It is rather old as we don't have much trouble nowadays. From the chassis. The only two causes are the exhaust system or the engine vibration. The exhaust system generally means that some suspension brackets are doing unnecessary work in the wrong direction. Bits of string and rope act as splendid temporary supports for the exhaust system. Engine vibration. In order to get the best results from the engine mounting, try the car with the engine really floppy. That is, loosen the torque reaction dampers in front of the engine, remove the rubbers in the front engine feet, and ensure bags of clearance between the alum castings and the rubbers in the frame underneath the dashboard. In fact, try to get the engine sufficiently sloppy to rotate about its fore and aft pivots during snap openings of the throttle. When the best result has been reached, then of course the front engine rubbers must go back. However, care should be taken to ensure no load on the rubbers. The torque reaction dampers can be left as loose as you like. They only need to have a very little poundage to overcome torque reaction at 10 m.p.h. top gear. The large load at which they are set is in order to reduce the front wing flap and improve the controllability of the car for fast cornering. There are then things like scuttle isolation bolts. If the dashboard has too solid a connection to the body, booms are made more pronounced. Try slackening the scuttle bolts. Bad booms have been overcome by the most simple thing on occasions. Floorboards which the change speed mechanism touches when over-running are quite common. Sometimes the draught-proof scheme round the change speed mechanism has direct contact. | ||