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).
Technical report discussing the performance and testing of a magneto contact breaker.
| Identifier | ExFiles\Box 43\4\ Scan069 | |
| Date | 25th February 1927 | |
| CERTIFICATE OF INSPECTION BY A.I.D. ROLLS-ROYCE ENGINES AND SPARES Contd. -2- EFC2/T25. 2. 27. non-inductive. This explanation however appears to be untenable. It is difficult to give any explanation which is really satisfactory, but it would appear from this that the advantage to be gained from using the very light lever is not really borne out by this test. We suggest for Messrs. Norths consideration that they should perform a test of this nature on this and perhaps other types of contact breaker, as the results are very instructive. The tests do not, of course, indicate the kind of motion actually performed by the contact breaker lever, as an oscilloscope test would give some show of doing, nevertheless in some ways the test is a more reliable one than the oscilloscope test in which it is very difficult sometimes to follow out exactly what is occurring, as in the nature of things observations of the position of the lever at any instant cannot be made. We do feel that the contact breaker should be such that on the test described the make ratio should be well maintained right up to the highest speed desired, even if, after that point, it begins to fall away suddenly. The Watford magneto contact breaker began falling away slowly quite early on, and did not show any sudden decrease after the maximum speed had been reached, as was shown in the case of the B.T.H. As previously stated the exact reason for this is somewhat obscure, but it rather suggests that it may not after all be entirely wrong to utilise a lever with some amount of inertia which may, at its natural periodicity at the nearly highest speed required, assist the spring to maintain contact during the period in which the block is off the cam. Perhaps it should have been remarked that with each of the two types of magneto set to the primary gap of .010" the make ratio of the B.T.H. was considerably greater than the Watford, viz. .65 as against .55. Now referring to our previous note EFC2/T of 21.2.27, copy of which we now attache for the A.I.D., we have recent confirmation from our testers that the performance of this magneto on the engine is as anticipated - unsatisfactory in the advanced position. The magneto has to be retarded a few degrees for satisfactory running to be possible. (Signed) Copy to Mr F.E.C. Copy to R.R. Ltd. Copy to R.R. A.I.D. EFC. (Upside down text) FOR CHIEF INSPECTOR OF ENGINES. AERONAUTICAL INSPECTION DEPT. "AD ASTRA" HOUSE, KINGSWAY, W.C.2 ARRANGEMENTS WITH THE ABOVE. Y.A.H. | ||