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).
Performance analysis and comparison of a faulty Bosch regulated dynamo against a standard model.
| Identifier | WestWitteringFiles\W\September1931-November1931\ Scan097 | |
| Date | 21th November 1931 | |
| -2- The particular Bosch regulated dynamo which we received was found to be faulty in the regulator adjustment. The Bosch people in London admit having hurriedly despatched the machine to us without proper test, and ask us to return it to them. We have, however, in order to save time, adjusted the regulator reasonably well ourselves and have carried out some tests on the bench. This regulator operates by first inserting resistance in the field circuit when the speed has increased sufficiently for the voltage to rise to about 17.0. This action is intermittent as the voltage varies, so that the contacts vibrate. As the speed increases the period of break becomes longer until the resistance is in circuit all the time. With further increase in speed, the moving contact leaves its former companion contact and moves over and commences to make intermittent contact with another contact. This short circuits the field winding in the vibratory manner as before. Attached is a sheet of curves showing the performance of this machine compared with that of our standard 40/50 dynamo under the same conditions. From these curves it will be seen, as stated, that at night time with a big lamp load on, or the battery discharged, we get an output of 17 to 18 amperes as compared with 13 amperes, falling to about 9 amperes from the standard machine. Moreover, this output does not fall at high speeds - if anything it rises. On the other hand, during day running, should the battery become fully charged, the output drops to 5 amperes, rising to 9 amperes at high speeds, as compared with over 12 amperes falling to about 10 amperes. With proper adjustment of the regulator, the output of the Bosch machine could probably be prevented from rising and maintained at 5 amperes. It will also be seen that the cutting in and peak speeds are as follows:- Night Output Cutting in speed, Peak speed. Day Output Cutting in speed, Peak speed. DYNAMO. R.R. 660 RPM. 1520 RPM 760 RPM. 1940 RPM. Bosch 730 " 900 " 790 " 830 " We feel strongly that the principle of this regulated type of dynamo is good, and since we do not doubt the reliability of the generator itself, the job resolves itself into finding out whether the regulator is reliable and has a good life on the car. As regards reliability, it is obvious that Bosch has made drastic alterations from his previous design of the regulator, for the purpose of reducing the cost and in doing so we think he may have made it less reliable. Hs{Lord Ernest Hives - Chair}/C.A.Pignett. | ||