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 output and temperature limits of spigot-mounted dynamos, including a table of temperature rises under test conditions.
| Identifier | ExFiles\Box 60\4\ Scan170 | |
| Date | 2nd March 1933 | |
| [Handwritten] WST x6099 To R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} E.L/HP. 2.3.33. c.c. Mr. Cox. FN. Hs.{Lord Ernest Hives - Chair} [Struck through] Hs{Lord Ernest Hives - Chair}/Wst. Dynamo output. Spigot mounted dynamos. Maximum Dynamo output has naturally always been limited by the maximum temperature at which it is safe to operate under actual running conditions, but it is very difficult to determine what this temperature is. The usual method employed in the past has been to attach sentinels to the yoke of the machine which melt on attaining a given temperature, and sentinels of fusing temperatures of 73°, 82° and 90° have been melted on various experimental chassis and two of 100° were fused on a car running in France in Summer time without failure of the dynamo. We do not believe that for cars in normal use the dynamos reach anything like these temperatures and in this connection the figures given by Mr Watson of the Lucas Co. in his paper of January this year are of interest. Table of Temperature Rises. Item. Condition A.{Mr Adams} Condition B. Condition C. Max. output cold...... 11/12 amps. at 13 v.{VIENNA} As A As A.{Mr Adams} Hot output at test.... 8.6 amps at 13 v.{VIENNA} 10.2 amps 14.5 v.{VIENNA} 10.5 amps. 16.7 v.{VIENNA} Temp.rise by thermometer. Yoke.................. 93°C. 32°C. 52°C. Commutator............ 147°C. 78°C. 122°C. | ||