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).
Dynamos, starter motors, and car weights, with comparisons to American automotive practices.
| Identifier | ExFiles\Box 178\2\ img133 | |
| Date | 4th April 1934 | |
| -10- Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}5/KW.4.4.34. DYNAMOS. It will be recollected that on the Bentley we reduced the speed and increased the size of the generator because we were afraid of running this machine at 7500 R.P.M. Had we known of current American practice this could have been avoided as they are running their dynamos up to 8000 R.P.M. without trouble. They have also stepped up their outputs considerably by air cooling them. Two methods are employed; on the Cadillac an air scoop which collects its draught from the forward speed of the car, on the La{L. A. Archer} Salle cold air is forced through the generator by fan blades cast in the driving pulley. By adopting one or other of these devices we should be able to improve the efficiency of our own machines. The objection of dirt entering the machine does not seem serious as the forward scoop has been in use for over two years. STARTER MOTORS. The accelerator starter control has gained popularity and is now utilised quite generally. The alternative is a solenoid mounted on the dynamo with a push button on the dash. This is fitted to the Cadillac. A lower ratio has been obtained without going to a geared motor by employing a finer tooth pitch on the flywheel ring. This we believe is something that we want very badly. They have been using it for almost two years in the U.S.A. For the big engines, geared starter motors are employed with ratios of about 25-1. We have samples of the Cadillac. The fact that they use thin oils and low ratios explains how the Americans succeed in starting in cold weather. CAR WEIGHTS. The Americans, in spite of using cast iron where we use cast aluminium, and sheet steel wings and body panels where we use sheet aluminium, are at present achieving some remarkable overall car weights. We succeeded in getting a complete analysis of the 1934 Pontiac four-door saloon car, the curb weight (i.e., petrol, oil, water etc. included) of which is 3474 lbs. or 31 cwts. | ||