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).
The investigation of faults, such as oscillation and noise, in speedometer drive cables.
| Identifier | ExFiles\Box 165\2\ img258 | |
| Date | 6th September 1940 | |
| SPEEDOMETER DRIVES. Since changing over from the large diameter drive to the small one, we have had numerous grumbles due to oscillation of the instrument pointer, the cause of which is lack of torsional rigidity in the drive cable. Another fault with the thinner drive is noise. Complaints re the above were received concerning cars 33.G.VII; 12.B.V; 11.B.V; and 1-R-1. the instruments and drives of which were removed for examination. Bench tests proved the fault to be in the drive. Preliminary tests indicated that eliminating the bends, normal in the drives when fitted to the car, and providing the cable with a thick coating of grease, had little effect in reducing the oscillation. Tests were then carried out with regard to the torsional flexibility of the drive cable. It was found that the amplitude of the oscillation followed, to a great extent, the degree of torsional flexibility in the cable. The Makers agree that the oscillation was due to excessive torsional flexibility and stated that the cause was due to lack of adhesion between the layers of the spiralled wire, owing to some of the strands breaking away from the anchorage at the end. With regard to noise, the standard drive, which has a polished galvanised case, has, on account of the polishing process, to be lined with steel. This makes the case more rigid, also for a given case, the bore is smaller and the drive in consequence, tends to be noisy. The latest experimental drive has an unpolished galvanised steel case and is lined with asbestos like the late standard drive. It should be quieter in operation than the present standard drive. - Continued - | ||