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).
Comparing the performance of different slipper wheel fitters over mileage.
| Identifier | ExFiles\Box 66\4\ scan0108 | |
| Date | 20th March 1928 guessed | |
| 2. with a slipper wheel fitter of west the cotton duck gave approx 5% better results. This was fitted to 12EX and will be run during the next 10000 miles. The fabric fitter was the 21oz, the 16 1/2oz gave slightly less load. | ||