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).
Data log of trials for a speed indicator tester, recording frequency and percentage speed variations over time.
| Identifier | ExFiles\Box 33\5\ Scan082 | |
| Date | 17th May 1926 | |
| TRIALS OF SPEED INDICATOR TESTER. Date. | Approx. time period. | Time under 10 mins. for 3000 counter revs. (Secs). | % fast. | Frequency. -- | --- | --- | --- | --- 17-4-26 | 9-0 to 9-10 | + 2.0 | + .33 | 50.16 19-4-26 | 10-0 to 10-10 | - .2 | - .033 | 49.984 19-4-26 | 3-0 to 3-10 | + 3.0 | + .50 | 50.25 20-4-26 | 11-0 to 11-10 | + 1.8 | + .30 | 50.15 20-4-26 | 4-0 to 4-10 | + 2.0 | + .33 | 50.16 21-4-26 | 12-0 to 12-10 | + .9 | + .15 | 50.07 21-4-26 | 5-0 to 5-10 | + 4.5 | + .75 | 50.34 22-4-26 | 9-0 to 9-10 | + 1.0 | + .17 | 50.08 22-4-26 | 2-0 to 2-10 | + 1.8 | + .30 | 50.15 23-4-26 | 10-0 to 10-10 | + 2.0 | + .33 | 50.16 17.5.26. | ||