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).
Examination report on a faulty distribution box from chassis 29-MC.
| Identifier | ExFiles\Box 70\3\ scan0196 | |
| Date | 25th March 1926 | |
| EFC. AC.71. 25th March, 1926. DISTRIBUTION BOX AP.15 FROM CHASSIS 29-MC. This box has been returned for examination owing to failure of the cutout. On inspection it is found that :- The flexible point support is very loosely attached to the base. The shunt lead connected to it (negative) is burnt and the whole support has been very hot, burning the sheet bakelite on which it is mounted and the surrounding moulded bakelite, and melting the solder below it on the underside of the board. The contact point surfaces are badly affected, apparently due to arcing. The moving point spring blade has been interfered with as its tip is fitted under the end of the armature instead of over it. One of the blade fixing screws is loose. The riveting of the points appears to have remained quite sound. The windings do not appear to have been overheated except locally on the shunt coil close to the fixed point support. The field fuse (cartridge type) has blown apparently in the normal way, i.e. due to over excited dynamo, judging from the signs of arcing contained in it, i.e. not due to an earth on the dynamo field wire or terminal. The main fuse (8) has been removed. It is also noted that one end of the box cover is broken out and that one of the scews in the fuse clip (5) (side and tail lamp) has not been gripping (i.e. not capable of gripping) the wire properly with the result that the clip and the wire have scorched. We have known two cases of this previously and, so it is a point worth watching. It appears probable that the failure of this cutout was due to an imperfect contact at the base of the fixed contact point support, which set up a resistance at this point causing heating and over-excitation of the dynamo. Bad contact at the silver points might also result from the same cause. Such a fault would, as it was, eventually be shown up by blowing of the dynamo field fuse. EFC/FJA. | ||