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).
Hand-drawn graph of efficiency versus helix angle for different coefficients of friction, titled 'Joggles' and 'Parking'.
| Identifier | ExFiles\Box 67\4\ scan0336 | |
| Date | 13th July 1927 guessed | |
| JOGGLES FIG I PARKING. EFFICIENCY % HELIX ANGLE θ μ = .050 μ = .100 μ = .150 100 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 80 90 | ||