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).
Letter discussing generator output issues and comparing American and English headlamp specifications.
| Identifier | ExFiles\Box 60\4\ Scan050 | |
| Date | 29th April 1931 guessed | |
| - 2 - definitely at 25 amps. without overheating - in this case the voltage is between 8.5 and 9.0. I am afraid it is rather a difficult matter to compare generator outputs when the conditions of testing may vary so much. Judging from your high ideals, 18 continuous amps. at 18 volts, we are surprised that we have had the trouble we have with English cars as we find with 25 amps. on our machines at 9 volts, we get ample charge. We do not have complaints of generators any more since we adopted our present machine. We have had troubles, such as oil on the commutator, insufficient brush pressure, throwing the armature coils, etc., but these have all been satisfactorily overcome. Perhaps the biggest item in reducing our generated heat was the adoption of .017 thick armature plates A-11377, varnished on both sides, with no paper insulation. With our adjustable third brush we are able to take care of almost any combination of conditions, and complaints have just died down to nothing. Possibly one cause of your trouble is the high load taken by the head lamps. We find that 10 amps. is ample to take care of our lighting load, unless the car is fitted with spotlights and such like gadgets which take a little more. The candlepower of headlamps is limited in all states to a maximum of 32,(and in some to 21) whereas, we know in England you go as high as 50 or more. We would commend to your attention the lenses now used on nearly all American lamps. These have approximately horizontal prisms on the inside which deflect the upper rays down and vertical grooves on the outside which deflect and diffuse the rays sideways, with the result that we are able to get a concentrated illumination just where it is required, but none at all at any point above the height of the center of the lamp. In this connection I would refer you to the "Specifications of Laboratory Tests of Optical Characteristics of Reflex Reflectors for Motor Vehicles" as published by the S.A.E. (see handbook 1931, page 165). We have just tried a set of the new Lucas lamps which we find quite impossible on account of the narrowness of the ray and the glare in the eyes of an oncoming driver when the lamps are set high enough to give light on the road a reasonable distance ahead. This is a complaint which all states are now formulating laws to eliminate. Yours very truly, Robt. B. Burton Robert B. Burton Chief Engineer - Chassis Div. RBB/VB Encl. | ||