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).
Reduction of dynamo speed on Peregrine and Bensport car engines due to excessive wear at high RPMs.
| Identifier | ExFiles\Box 3\4\ 04-page188 | |
| Date | 8th February 1933 | |
| 4553 To Sg.{Arthur F. Sidgreaves - MD} From Hs.{Lord Ernest Hives - Chair} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} c. to E.{Mr Elliott - Chief Engineer} Ref: Hs.{Lord Ernest Hives - Chair}6/MJ.8.2.33. BENSPORT CAR. You may have noticed from recent memos, that it has been agreed to reduce the dynamo speed on the Peregrine. At the present time the dynamo on the Peregrine runs at one and a half engine speed, which is the same ratio as we have on the 20/25 HP. and Phantom ll. Owing, however, to this engine running faster, it means that at the maximum engine speed the dynamo will have to run at 7500 R.P.M. On the Peregrine car which ran 12,000 miles in France, we found that the brushes were worn out. There is also difficulty with maintaining a reasonable output at this speed. We have looked into the question of what the other makers are doing and S. and Wst. visited Messrs. Lucas and we found that the limit of speed which other people run their dynamos is 5,000 R.P.M. When we go beyond that we are breaking fresh ground with no experience of what the troubles may be. We have also run dynamos on a high speed rig which show that 5,000 R.P.M. is about the maximum we can safely run a dynamo with our present knowledge. R.{Sir Henry Royce} has agreed that the only safe policy to adopt is to reduce the dynamo speed. E.{Mr Elliott - Chief Engineer} has completed a modification to Peregrine incorporating this. It means a modified crankcase. We have accepted that 5,000 revs. is the maximum speed at which we can run a dynamo. This means that the dynamo drive on Bensport engines will have to be altered. If we alter the dynamo ratio we are adopting a safe policy because then the dynamo will not run any faster than on our present cars. The proposal, therefore, is to reduce the dynamo speed on the Bensport engine and at the same time to fit a 40/50 HP. dynamo. This has been suggested many times and we are sure with this type of car the customer will expect powerful lamps and the only hope we have of satisfying him is to fit a Phantom size dynamo. E.{Mr Elliott - Chief Engineer} has practically completed his scheme for this alteration and it will be handed to BY.{R.W. Bailey - Chief Engineer} either tomorrow or Friday. The alteration to the dynamo drive means that we cannot possibly have the stand by magneto. On Bensport it has been agreed to delete this. | ||