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Lotus Service Notes
Section FJ C64 Gear Clusters (other variants similar) The input shaft includes integral drive pinions for 1st, 2nd and reverse gears, and carries the clutch driven plate, the 3rd/4th synchroniser and the 5th/6th synchroniser. The output shaft features an integral final drive gear, spline fixed 3rd/4th/5th/6th driven pinions, and carries the 1st/2nd gear synchroniser. All forward gears are constant mesh with inertia lock type synchromesh, with reverse gear attained by sliding a spur idler pinion into engagement with both a gear on the periphery of the 1st/2nd synchroniser and a drive gear integral with the input shaft. All gears, with the exception of reverse, use a helical tooth form for quiet running. Sychromesh: For each gear ratio, one of the shafts has a fixed gear, and meshes with a freely revolving pinion on the other shaft. To engage a particular gear, the freely revolving pinion must be connected to its shaft via the sychroniser hub. This connection is made by sliding a sleeve splined to the outside of the synchroniser hub, to engage the sleeve's internal teeth with a ring of external teeth integral with the adjacent drive pinion. As an example, third gear selection operates as follows: Under normal road driving, when the clutch is depressed as a precurser to a gear change, the input shaft with the third gear synchroniser are de-coupled from the engine, but will continue to turn under decaying inertia, clutch windage, and oil drag from the drive pinions (which are being driven from the roadwheels via the output shaft). Before the outer sleeve of the synchroniser may be slid on its axial splines to engage with the spline ring integral with 3rd drive gear, the speeds of the two parts must be commonised. For this purpose, a baulk (or synchroniser) ring is fitted between the two parts, being rotationally driven by the synchroniser hub, and equipped with a female conical surface to mate with a male cone integral with the gear. Teeth on the outside of the baulk ring, over which the synchro sleeve must slide before engaging the third gear splines, perform a baulking function described below: When the gear lever is operated, the outer sleeve of the synchroniser is moved towards third gear, and pushes three spring detent plates which press the baulk ring onto the gear cone. As the input shaft train is turning faster than third gear, the baulk ring is dragged to one end of its rotational constraint slots in the syn- chroniser hub, in which position the internal spline teeth of the synchroniser sleeve are mis-aligned with the teeth on the baulk ring. When further pressure is applied via the gearlever, the detent plates are overidden, and the synchroniser sleeve splines are pressed against the ends of the baulk ring teeth, increasing the pressure on the conical surfaces. The bevelled ends of the sleeve splines and baulk ring teeth tend to turn the ring into alignment, but whilst a speed differential between the ring and the gear remains, the cone drag force (caused 6th gear 5th gear 4th gear 3rd gear
2nd gear 1st gear Reverse Input shaft
f130 Output shaft Double cone 2nd Final drive gear gear synchromesh |