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).
Drawings and design issues for the Phantom Automatic Ignition Advance system.
| Identifier | ExFiles\Box 37\1\ scan 306 | |
| Date | 17th May 1926 | |
| TO BY.{R.W. Bailey - Chief Engineer} FROM E.{Mr Elliott - Chief Engineer} C. to HS.{Lord Ernest Hives - Chair} HS{Lord Ernest Hives - Chair}/RM.{William Robotham - Chief Engineer} N3949 ORIGINAL E1/M17.5.26. PHANTOM AUTOMATIC IGNITION ADVANCE. X8685 We send you herewith drawings LeCs. 2242. & 2244., dealing with the above. The former shews revised instructions regarding the curve of automatic advance. This does not differ very greatly from what we are supposed to have now. Mr. Royce's recent criticisms have arisen from the fact that chassis No.7-EX. was very far from complying with the specification laid down as standard, since the automatic advance did not commence to move at all until 1000 RPM. of the engine, and would not be fully open so far as we could judge by measuring the pull of the governor, until above 2600 RPM. In the diagram on the L.H. corner of LeC.2242. we give the magnitude of the spring torque plus the initial torque due to gravity. We have not gone any further than shewing this in arbitrary units since all the calculations for the governor springs were made in Derby. We should therefore be glad if you would complete this point as before. You may find that the present valve is not sufficiently heavy to give the required initial torque. With regard to the piston shewn on LeC.2242. this is an improved design having a deeper leather. It should not however be tried until it is decided whether LeC.2244. shewing a metal packing ring is a success or not. If the metal rings are not satisfactory we wish to try packing rings of the improved proportions made of cotton and any other materials not likely to deteriorate so much as leather with heat. With regard to the valve this is shewn in the initial position to be flush with the top of the piston. The final adjustment of this valve position is to be obtained by setting the governor lever. It can always be adjudged by noting if the valve is flush with the top of the piston whether the adjustment is as intended. This position gives .1 lap on the valve. We know this is not quite in accordance with the initial advance we specified but this is to the instructions Mr. Royce has given. The servo piston is shewn with a collar turned on the stem immediately below the head to form the limit of its downward movement. The stroke of the servo piston as arranged on this drawing should be adjusted to the movement of the ignition units and control gear by altering the length of the external lever on the servo casing. (1) | ||