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 performance and wear of electrical components, specifically addressing issues with dynamo commutators and brush materials.
| Identifier | ExFiles\Box 180\M1\2\ img005 | |
| Date | 12th May 1922 guessed | |
| contd:- -2- slightly greater proportionately than the loss of metal at the points, though the amount of wear for the amount of running is not considered at all excessive. It should be mentioned that the cam may not have been greased for the first 1000 miles or so. Apparently some slight wear had taken place on the contact lever pivot, as the points had not continued to close in exact opposition. The high tension rotor was in good condition and indicates that the spark was taking place at the correct instant in relation to it. The nickel revolving and stationary points have not burst away to any appreciable extent. Generally speaking, the battery ignition on all the Coshawks have done very well, the most general complaint being the wear on the rubbing block. The LeC. scheme of lubrication to minimise this is well in hand. DISTRIBUTION BOARD AND CUT-OUT. This unit appears to have functioned perfectly correctly all the time; all the cut-outs have certainly behaved remarkably well both on the bench and on the various cars, and we have no hesitation in saying that this is easily the best automatic cut-out of which we have had experience. The only point is that perhaps the contact points were somewhat discoloured, though this did not affect the operation. DYNAMO. The serious matter in connection with the dynamos is the bursting of two commutators, though on the bench we have not succeeded in bursting one of these by running at a very high speed 6000 R.P.M. for several minutes when in a fully hot condition after prolonged running. Alterations in the commutator construction intended to overcome this trouble are in hand and also trials of different moulding materials will be made. We have, for instance, at the present time, two commutators made up with Elo material reinforced with asbestos fibre. These two commutators are at present with the whole of the copper previous to turning, and it is considered that if they will stand running with this extra mass of copper at 6000 R.P.M. at about 100°C, there is little likelihood of them bursting under running conditions, so arrangements are being made for this test to be carried out by arranging the commutator in place of an armature in an old starter motor casing. The fact of one only of the dynamos being fitted with brushes of copper morganite composition was the result of a combination of circumstances, among which were - (1) Unsatisfactory pigtail connections on LeC. brushes (a number of these connections have parted from their brushes with quite a small applied tension) (2) Some considerable delay in further delivery on the part of Le Carbone, resulting in there being insufficient Le Carbone brushes to go round. The CM3. brushes fitted were some of those recommended by Morganite as suitable and having given excellent results on tests on the bench as previously reported. We considered these the most satisfactory alternative. contd:- | ||