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).
Method of conducting car performance tests using a three-pen chronograph.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan129 | |
| Date | 25th August 1925 | |
| R.R. 493A (50H) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. Expl. No. REF. Hs{Lord Ernest Hives - Chair}2/LG25. 8. 25. X1725 XL630 To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c. to CJ. BJ. c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} EY. c. to Wor.{Arthur Wormald - General Works Manager} ORIGINAL METHOD OF CONDUCTING CAR PERFORMANCE TESTS BY MEANS OF THE CHRONOGRAPH. For some time we have been endeavouring to obtain an instrument for measuring car performance which would be independent of the speedometer and eliminate the personal factor of the operator. We have finally adapted a three-pen Chronograph for our purpose made by The Cambridge Scientific Instrument Co., Cambridge. For acceleration and tractive resistance readings a contact piece is fitted to one front wheel which completes an electrical circuit once per revolution. This actuates one pen on the Chronograph. A second pen on the Chronograph is connected to a time recording element and marks 1/10th. seconds. The third pen is operated by closing an electrical circuit manually and indicates the commencement and finish of each test. The records are therefore obtained in the form of a space time graph. The record can be read with great accuracy if desired as the paper speed permits 1/10 secs. to be represented by .400" on the space time strip. This enables analysis to be carried to .001 secs. The instrument has been checked as far as possible here, without a detection of error. In any case, as it will be used for all future tests, it should be a reliable basis of comparison between different cars. Precautions have been taken to prevent the effective tyre diameter altering with speed. | ||