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).
Technical notes on the operation and installation requirements of the Bendix clutch control system.
| Identifier | ExFiles\Box 128\2\ scan0195 | |
| Date | 12th October 1933 guessed | |
| CC.1/1 Before commencing any installation of the Bendix clutch control it is desirable that the simple fundamentals of its operation should be grasped. This device is intended to perform automatically what has hitherto been a foot operation of the clutch pedal when a gear is engaged, during starting, and while changing gear. It also provides a 'free wheel' effect as the clutch is withdrawn every time the accelerator is fully released. This result is obtained by the use of a cylinder, one end of which is connected through two control valves to the induction pipe. The piston working in the cylinder is connected to the clutch withdrawal mechanism. OPERATION REQUIREMENTS. For successful operation it is necessary that: (a) The clutch should be instantly and fully withdrawn when the accelerator pedal is released. (b) The clutch should return to 'cushion point' quickly when the accelerator pedal is depressed. (c) The 'cushion' point should quickly change into 'clutch fully engaged', the rapidity of the change being controlled automatically in conjunction with accelerator pedal movement, so that there is no snatch or excessive slip. The accelerator control valve and automatic pendulum valve do definitely provide the above requirements providing that (a) The cushion point is correctly set. (b) The overlap of valve travel and throttle opening (lost motion) is correctly set. This adjustment allows the engine to accelerate slightly just as the clutch 'cushions' and so prevents stalling of the engine. If too much lost motion is used, the engine may stall - if too little it will race and there will be too much slip on clutch engagement. The actual amount of lost motion is a fixed quantity, i.e. 3/16" at the valve. To compensate for play in carburetter controls etc. a means for limited adjustment has to be provided. After the initial setting has been effected the adjustment must be firmly locked. Before commencing any study of Bendix automatic clutch control it is therefore vitally important that the application of the terms 'cushion point' and 'lost motion' should be clearly understood. There are two applications of the term 'cushion point', one referring to the clutch itself and one to the cylinder, and a satisfactory installation can only be obtained when these two are correctly related. The cushion point of a clutch is the point at which the clutch plates have been brought just so far into engagement that the car will move on a level road, but, if the plates are held from further movement, continual slip will take place. It is the position in which the clutch plates are held by the foot when making a delicate car manoeuvre in a confined space. The cushion point of the cylinder. If when connected to the clutch mechanism the piston is only allowed to travel just far | ||