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).
Dynamometer horse power curve data, gear ratios, and ignition specifications.
| Identifier | WestWitteringFiles\K\November1923\ Scan10 | |
| Date | 12th July 1923 | |
| R.R. 403A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. 4609 REF: H.4/4609.11.23. DYNAMOMETER HORSE POWER CURVE. Top gear ratio 3.77 - 1 Second " 6.55 (approx.) Bottom " 11.65 - 1(approx.) Makers tyre size 895 X 135. Effective tyre dia. (80 lbs./sq.in.) - 3 ft. 10 7/16". | R.P.M. | Equiv. M.P.H. | HP. | Comp: pressure. | Vibrations. | |--------|---------------|-------|-----------------|-------------| | 500 | 13.35 | 15.2 | | Bad. | | 750 | 20.0 | 23 | 79 lbs/sq.in. | Bad. | | 1000 | 26.7 | 29.4 | 80.5 " | light. | | 1250 | 33.3 | 36.2 | 82 " | light. | | 1500 | 40.05 | 40.2 | 84 " | Bad. | | 1750 | 46.725 | 44.8 | 84 " | light. | | 2000 | 53.4 | 45.4 | 75 " | Bad. | | 2250 | 60.0 | 46.4 | 74 " | Very bad. | | 2500 | 66.75 | 44.8 | | Very bad. | IGNITION DETAILS. Ignition is by Magneto only - Bosch HL-8 being fitted. For easy starting a vibrator, which is a separate unit, is fitted. This comes into operation when the starter motor button is depressed. The contact breaker is fitted to distributor shaft and is very accessible. Advance is by governor on armature shaft, and also by hand control to contact breaker. Ignition timing is as follows :- Retard - 3° B.T.D.C. Full advance - 22° B.T.D.C. by hand Max. advance hand and automatic - 50° B.T.D.C. Left lock 50° 10" Right lock 51° 2" Firing order - 1. 5. 2. 6. 4. 8. 3. 7. contd:- | ||