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).
Notes and a graph analyzing engine timing advance characteristics against engine revolutions.
| Identifier | ExFiles\Box 65\1\ scan0154 | |
| Date | 1st May 1926 | |
| -4- Max. for full power. Minimum. Gov. wide open full advance motor piston at top of its 1/2" stroke. Feeble spring no initial set so that from 500 to 1500 rate of advance very great. Governor insufficiently fast to open. Anticipating detonations at slow speeds, and weak mixtures at high speeds. [Graph Labels] ADVANCE ENGINE REVS HAND CONTROL .47" SERVO PISTON STROKE Oil pressure advance say .050 [Main Body Text] From 500 to 1500 auto advance is 80%, from 1500 to 2000 only 20%. 10% is oil pressure advance. The stiffer the governor springs the flatter the advance; we want it to start at 500 and be slightly quicker than graph 1. Auto advance on 7-EX did not start until 1000 engine revs. and at 1500 advance = 11° approx. (no initial lift). Graph 1. shews advance starting 2 or 3° initial, then by governor = 5°, total 8° at 1000, and at 1500 by governor 18° plus 3° initial = 21°. SCALE OF CRANKSHAFT DEGREES AND REVS. Magneto total 38° = 6° per hand, 2° initial (servo without governor) 30° per gov. i.e. automatic advance) Full auto advance must take place between 500 and 2000 & 80% of it between 500 and 1500. Contd. | ||