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).
The comparative high and low speed sparking characteristics of a ZR.6 machine compared to a Bosch unit.
| Identifier | WestWitteringFiles\I\July1922\ Scan126 | |
| Date | 31th July 1922 | |
| Contd. -8- EFCL/T31.7.22. * Neither machine would appear from this to be as good as the Bosch when working on leaky plugs. (14) Range for comparative high speed and low speed Sparking Characteristics. For the purpose of this test a range of advance and retard of 34° for the ZR.6 machine was now arrived at in the following manner :- The stop limiting the travel on the contact breaker advance and retard lever was removed (after having made the necessary marks indicating the makers range). The magneto being connected by H.T. leads to the necessary spark gaps set at 5.5 m.m., the machine was in the first instance driven at 3500 R.P.M. and the contact breaker lever advanced until the maximum sparking advance was found, this maximum spark advance being taken to be that advance at which 100 sparks with-out missing are given by the magneto at some time within a period not greater than 5 minutes. A mark was made to indicate this advance after the machine had been stopped. Our range of advance and retard was taken to be a range constituted by 34° back from this mark. Our advance point found in this way agreed with that of the makers, so that as their range is 36°, our retarded position came 2° in advance of theirs. (The reason of finding a range in this way of 34° is in order that a fair comparison of low speed sparking characteristics between the different machines shall be made, utilising in this instance the most advanced obtainable range of Contd. | ||