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).
Brief description of the STRAT GEAR mechanism and its principles of operation.
| Identifier | ExFiles\Box 136\4\ scan0024 | |
| Date | 7th October 1925 guessed | |
| 3 Brief description of STRAT GEAR. The action of this Gear depends mainly on the hypocyclic motion of a wheel rolling upon the inner surface of a cylinder or track of variable internal diameter. This is shown in its simplest form in Fig.1. which is merely a diagram. The expansible track consists of a number of segments of a circle the radial movement of which controls the gear ratio. Concentric with the track is a crankshaft which if revolved imparts two motions to the wheel. (1) Planetary motion due to its excentricity. (2) Hypocyclic motion due to its frictional contact with the track. Disregarding motion (1) the driven member will transmit the rotation of the driving shaft at a reduced speed and in the opposite direction (4-1 with the relative dimentions given in the Fig.) Contraction of the track results in the gear ratio falling until the position of Fig. II is reached where the effective diameter of the track is reduced to the diameter of the wheel and rotation of the crankshaft produces no motion in the wheel or driven member this giving neutral drive or a gear ratio of infinity to 0. It will be observed that the planetary motion (1) referred to above must be eliminated to produce a practical drive. This may be carried out by connecting the outer member of the wheel to a driven shaft running upon the crankshaft by means of an Oldham or similar Coupling, but in a superior alternative the member is connected to the driven shaft by spur gearing as follows:- A pinion mounted upon the crank engages with two internally (1) | ||