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).
Description of a combined electric starter and lighter, detailing its patented internal epicyclic change speed gear and operational principles.
| Identifier | ExFiles\Box 48\3\ Scan310 | |
| Date | 18th November 1920 | |
| X 4216 (crossed out) X4216 (filed 18.11.20) X.294 Combined Electric Starter & Lighter, patents Nos. 19108/19 & 161/20. This machine has an internal change speed gear, which provides that when Electricity is applied to it from a suitable Accumulator; that the Armature shall revolve at a speed greater than it's shaft; also that when mechanical power is applied to it's shaft the Armature immediately revolves at the same speed as that of it's shaft --- to state a case:- the test machine was made up with a gear reduction of 3 to 1; it was fitted to a car with a further reduction of 1.7 to 1, from the pinion to the Engine; so that on applying power from the battery to the machine the Armature revolved at 5.1 to 1 of the Engine; immediately the speed of the Engine rises above a certain point the internal reduction gear is out of action, so that the machine is then being driven at 1.7 times the speed of the Engine. Many attempts have been made to design satisfactorily combined machines, but it has been found that unless very large machines are used there is not sufficient margin of power to start up a Motor Car Engine when cold; or when very "sticky"; in some cases, to get over the trouble, these machines have been fitted with gear ratio of 3, or even 3½, times Engine speed; this sometimes enables the machines to start up the Engine but has the disadvantage of having the machines rotating at excessive speeds when the Engine is running; 2,000 r.p.m. on the Engine of course means 6,000 to 7,000 r.p.m. of the machines; with great strain on the driving chains, wear on the commutators, ball bearings etc. With the patented gear; a ratio can be chosen that makes starting up certain under all ordinary conditions; and when running as a dynamo, a reasonable speed of rotation assured. The change speed is effected by fitting in the machine an epicyclic gear, mounted on a shaft, around which the Armature revolves; the small pinions of the gear are mounted on a spider which is threaded internally and screwed on to a threaded portion at the end of the shaft; the spider has a tooth or teeth projecting from the pinion end which engage, when screwed up, with a nut having teeth thereon; which nut is fixed on the shaft; the outer gear wheel; having internal cogs to engage small pinions on spider is arranged with a free wheel device so that it can only revolve in one direction; the Armature has a pinion attached to it which engages with the small pinions on the spider, the spider is fitted so that there is a small movement on the shaft; by reference to the blue print it will be seen that if the main shaft is held; and the Armature turned a small amount the spider will attempt to revolve the outer gear wheel in reverse direction; but as this latter is held by the free wheel; the spider is screwed along the shaft until it engages the teeth on the nut mounted on the shaft; continuing to turn the Armature it is found that it then revolved 3 times to one revolution of the shaft. (Over). | ||