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).
From the research department reporting on a test of a C.C. type car heater and rheostat.
| Identifier | ExFiles\Box 137\2\ scan0018 | |
| Date | 7th February 1938 | |
| 12-7 EWS/IMS. MEMORANDUM 7th. February, 1938. From RESEARCH DEPT. To L.667 REPORT ON TEST OF C.C. TYPE CAR HEATER NO.A.75 AND RHEOSTAT CT.776/2 AS RETURNED FROM ROLLS ROYCE LTD. The motor in the heater when received in the Research Dept. was a Klaxon ECM. 12 volt No. 11191 and during the test it was found to be faulty since upon applying an end-wise pressure on the spindle the motor speeded up consider-ably. The motor was dismantled and the commutator found to be in a dirty condition although the brush faces were in perfect condition. With this motor on the heater the fan would not commence to rotate until the rheostat was on stud 4, the studs being measured from the off position and the motor being tested without any previous warming up. A fresh motor was put in the heater Klaxon ECM 12 volt No. 11213 and it commenced to rotate on the 3rd. stud when tested in the cold condition. It was allowed to run for three hours then tested again and found to rotate when placed on the first stud but the speed fell off progressively and when the revs had fallen from 910 to 150 it failed to start when placed on the 1st. stud due no doubt to the cooling off of the motor. The tabulated results are shown on sheet 1. The motor was again tested, the next morning and found to rotate on stud 1 when tested cold; the results being shown on sheet 2. The resistance of the rheostat for the various studs was found to be as follows:- | Stud No. | 1 | 2 | 3 | 4 | 5 | |-----------------|-----|-----|---|-----|------| | Resistance OHMS.| 7.9 | 6.3 | 5 | 3.5 | 2.05 | | ||