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).
Proposal to standardise a smaller dynamo on the Bentley chassis, detailing performance comparisons and recommendations.
| Identifier | ExFiles\Box 62\3\ scan0458 | |
| Date | 26th October 1934 | |
| K.{Mr Kilner} From Hs{Lord Ernest Hives - Chair}/Wst. c. to Sr. c. to Sor. c. to Dy.{F R Danby} c. to EP.{G. Eric Platford - Chief Quality Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} c. to Su. 86142. Hs{Lord Ernest Hives - Chair}/Wst.5/HA.26.10.34. STANDARDISATION OF SMALLER DYNAMO ON THE BENTLEY CHASSIS. The proposal to fit a smaller dynamo to the Bentley chassis to improve the dynamo charge characteristics on this chassis is due to the fact that we have definitely found on the bench that this smaller dynamo to R.R.Sch.431 has a better high speed performance than the existing larger machine now fitted to the Bentley. For instance at 5,300 R.P.M., it is possible to take 13 amperes from the machine without any appreciable increase in commutator sparking, whereas the large machine when a current of 10.5 amperes is taken through it at the same speed gives excessive commutator sparking. The large machine scores slightly in output for low speed heating, i.e. gives 16 amperes for the same temperature rise that 15 amperes gives on the smaller machine. The difference in cutting in speed as previously reported to you is 100 R.P.M., i.e. the small machine cuts in later than the larger one, but we suggest to counter balance this the speed of the dynamo be increased from 3/4 engine speed to 1 1/4 engine speed in view of its good performance at high speeds. This would make the cutting in speed one mile per hour better than the existing dynamo, i.e. 15 miles per hour compared with 16 miles per hour. The maximum speed would only be 5,625 which we consider is a safe maximum for the smaller machine. The weight of the small machine is 23 lbs. 3 ozs. as compared with 29 lbs. 12 ozs. for the large machine this shows a percentage decrease in weight of 22%. Our recommendation is therefore, at the same time that we fit the small machine to the Bentley chassis we increase the dynamo ratio to 1 1/4:1. Hs{Lord Ernest Hives - Chair}/Wst. | ||