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).
Specifications for the adjustment and testing of speed indicating instruments.
| Identifier | ExFiles\Box 59\2\ Scan119 | |
| Date | 24th March 1931 | |
| EFC1/AD24.3.31 contd. -4- (3) In addition to the above the makers must be instructed to adjust the speed indicating portion of the instrument until, when the instrument is at 35°C. and it is driven at exactly 612 (i.e. 45/60 x 816) R.P.M. of its driving spindle, the speed indicated is exactly 45 miles per hour. It is definitely unnecessary to give the makers of the instruments any particulars of tyre sizes and drive gear ratios, --- the information in (1) (2) and (3) above comprises all that they need to know. It may, however, be explained to them that what we are asking them to do depends upon well considered principles arising out of the known effect on road wheel revolutions per mile of the alteration of effective tyre diameters with speed, and will result in a superior general correctness than at present. It will be understood that owing to the principles on which these instruments work, the speed indications at various speeds and the counter mile indications at all speeds will, on an instrument arranged in accordance with the above specification, be substantially as described in our notes. One or two instruments arranged to this specification should be ordered for experimental test. We can readily provide, when standardisation is effected, a specification of production acceptance for these instruments which can be carried out by the Test Dept. and thus enable the whole matter to be put on a better footing. Further to the above we can provide a similar specification for the 20/25 H.P. requirements as soon as this is considered desirable. EFC. Attached. | ||