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 for measuring speed, including relevant formulas and a data table.
| Identifier | ExFiles\Box 79\1\ scan0254 | |
| Date | 15th February 1916 | |
| R.R. 235 a (400 T) (S C. 536 15-2-16) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1546. 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 = 120fn/s If f = 41.25 N = 4950 n/s Table of values: s | n=1 | n=2 | n=3 | n=4 | n=5 3 | 1650 | 3300 | 4950 | 6600 | 8250 4 | 1237.5 | 2475 | 3712.5 | 4950 | 6187.5 5 | 990 | 1980 | 2970 | 3960 | 4950 6 | 825 | 1650 | 2475 | 3300 | 4125 7 | 707 | 1414 | 2122 | 2829 | 3536 8 | 619 | 1237.5 | 185.6 | 2475 | 3094 | ||