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 the operation of a starter motor engagement mechanism.
| Identifier | ExFiles\Box 40\5\ Scan069 | |
| Date | 16th December 1921 guessed | |
| -2- OPERATION. The device is operated simply by closing the starting switch. This causes the starter shaft 1 with its threaded sleeve 2 to rotate rapidly within the flanged nut 9, the inertia of which establishes a speed difference between it and the shaft. The nut will thus travel longitudinally along the threaded shaft, pushing ahead of itself the entire barrel and pinion assembly through the spring 7. The pinion 4 enters then into mesh with the flywheel gear ring. The longitudinal motion of the device stops when the plate 6 meets the stop shoulder "B" of the threaded sleeve 2, fitted with two washers 12 and 13. The entire system is then in the position shown in Sketch No.2. With the nut 9 stopped in its longitudinal motion and the pinion engaged with the flywheel gear as shown in Sketch 2, the continued rotation of the starter shaft tightens the nut 9 against the clutch assembly 8-6, and the axial pressure on the clutch face rises considerably. In other words, the clutch becomes self-tightening to meet the load of starting. The starting torque is thus transmitted from the starter shaft 1 and threaded sleeve 2 to the flanged nut 9, friction clutch 8-6, barrel 5, pinion 4 and flywheel gear ring, and normal cranking takes place. It will be noted in the above operation that the spring 7 does not enter into play to any great extent, and that it does not carry any torque whatever. It may also be mentioned that the automatic tightening of the friction clutch in proportion to the cranking load throws this load on the starter gradually, and very effectively absorbs the shock of starting. Of course, this entire operation requires but a fraction of a second. After normal cranking has taken place as just described and the engine is running under its own power, disengaging or coming out of mesh of the device is caused by the over-riding speed of the pinion, barrel and nut with respect to the starter shaft, the device being then thrown back in its original position. The purpose of the small spring 14 is merely to prevent the device from coming into contact with the flywheel of its own accord, especially when the car is running down hill. The engagement of the automatic meshing device does not always take place in the simple manner described above. It may happen, when the pinion is pushed forward into mesh with the flywheel gear ring, that a tooth of the pinion strikes the extremity of a flywheel tooth and "butts" against it. This prevents the normal entrance or meshing of the pinion, since it stops its forward motion. Under these conditions, the device as represented in Sketch No.1 will advance the short distance contd:- | ||