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 stroboscopic method of speed measurement with related formulas and a data table.
| Identifier | ExFiles\Box 79\1\ scan0266 | |
| Date | 16th August 1928 | |
| X. 2720. STROBOSCOPIC METHOD OF SPEED MEASUREMENT. Frequency of supply = f No. of views per second = 2f. " " " " minute = 120f. Regular figure of s sides running at speed N R.P.M. recurs sN{Mr Sanderson}/n times per minute, where n is an integer, i.e. 1, 2, 3, etc. If sN{Mr Sanderson}/n = 120f. N = 120 fn/s If f = 50.0 N = 6000 n / s | s | n=1 | n=2 | n=3 | n=4 | n=5 | |---|------|------|------|------|-------| | 3 | 2000 | 4000 | 6000 | 8000 | 10000 | | 4 | 1500 | 3000 | 4500 | 6000 | 7500 | | 5 | 1200 | 2400 | 3600 | 4800 | 6000 | | 6 | 1000 | 2000 | 3000 | 4000 | 5000 | | 7 | 857 | 1714 | 2571 | 3429 | 4286 | | 8 | 750 | 1500 | 2250 | 3000 | 3750 | EFC. | ||