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).
Analysis of spring forces, armature taper, and electrical engagement in a starting mechanism.
| Identifier | WestWitteringFiles\T\November1928\ Scan091 | |
| Date | 17th December 1928 | |
| EFC1/T17.12.28. -3- Contd. There is also the question of the spring being capable of pulling the armature back & up an incline of 1 in 3 which, if we consider the incline to reverse when we wish to reverse the motion, becomes equivalent to a material addition to the friction. In regard to the force of the spring in the other extreme position (fully engaged), we are now approximating to the spring which will be right at this end also, e.g. we had one spring which was too strong in full engagement - not so strong as to prevent engagement but strong enough to allow back and forth oscillation of the pinion when rolling the engine to an extent sufficient in some instances to break the switch contact and let the armature out of gear, even though the push button is not released and the engine not started. In these circumstances a chatter does not take place because the teaser circuit cannot again be made, i.e. once the main switch is broken all current is off except the hold-off current. It certainly appears to have been the case that the amount of armature taper was overdone in the first instance. We now go from 3.100 to 3.000 in a length of 3.500, but from the various results I have sometimes wondered whether, after all, the taper is undesirable. I say 'wonder' because it is still my impression that a small amount of taper is an advantage. We are not up against the stxrxexivex difficulty of failure of complete engagement because the attractive force increases so rapidly with the reduction of the air gap, particularly with a taper such as we have at present. On the other hand, as | ||