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).
Log of trials for a speed indicator tester, showing results from April 1926.
| Identifier | ExFiles\Box 33\5\ Scan083 | |
| Date | 17th May 1926 | |
| TRIALS OF SPEED INDICATOR TESTER. Date. | Approx. time period. | Time under 10 mins. for 30000 counter revs. (secs). | % fast. | Frequency. --- 23-4-26 | 3-0 to 3-10 | + 1.5 | + .25 | 50.12 24-4-26 | 11-0 to 11-10 | + 3.0 | + .50 | 50.25 26-4-26 | 12-0 to 12-10 | + 1.5 | + .25 | 50.12 26-4-26 | 5-0 to 5-10 | + .8 | + .13 | 50.06 27-4-26 | 9-0 to 9-10 | - .4 | - .12 | 49.94 27-4-26 | 2-0 to 2-10 | + 1.0 | + .17 | 50.08 28-4-26 | 10-0 to 10-10 | + 3.0 | + .50 | 50.25 28-4-26 | 3-0 to 3-10 | + 1.0 | + .17 | 50.08 29-4-26 | 11-0 to 11-10 | + 1.3 | + .22 | 50.11 29-4-26 | 4-0 to 4-10 | - .8 | - .13 | 49.94 17.5.26. | ||