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).
The layout and function of accelerator controls, including lost motion and travel adjustments.
| Identifier | ExFiles\Box 128\2\ scan0200 | |
| Date | 12th October 1933 guessed | |
| CC.1/6 -6- LAYOUT OF CONTROLS. LOST MOTION INCREASED ACCELERATOR TRAVEL The first movement of the accelerator control valve plunger cuts off the working cylinder from vacuum and allows air to enter the cylinder, thus allowing the piston to come up to cushion point. As this movement must take place before the throttle opens, it is essential that the initial movement of the valve plunger should be independent of the throttle opening. This is arranged by connecting the control valve plunger direct to the accelerator pedal, and operating the throttle by a separate control which is "picked up" by the plunger controls. The amount of plunger movement which takes place before the throttle is "picked up" or starts to move is called "lost motion", and should be adjustable within narrow limits. Thus it is necessary to provide sufficient accelerator pedal travel to give a movement equivalent to full throttle movement from open to closed, plus an amount equivalent to the initial control valve plunger movement i.e. lost motion, usually 3/16". Short travel valves have 1/8" plunger movement. Long " " have 1" " " The short travel valve is only used with A.{Mr Adams} and B. size cylinders. the long travel valve is always used with C. size cylinders and should preferably be used with B. size cylinders. When working out pedal travel remember that a small initial portion of the accelerator pedal travel is utilized solely to operate the accelerator valve plunger through the "lost motion" period, the remaining portion operating both the accelerator valve plunger and the throttle valve. In order to get smooth control it is essential that the initial opening of the throttle valve on the carburetter should be fairly slow and progressive, while the movement of the control valve plunger should by comparison be fairly rapid. This object can be attained by paying strict attention to the angle at which control levers meet their rods, as shown in the sketches. RULE. Driven levers (to carburetter) should start near normal. Driving levers should start beyond normal and finish near normal. The importance of this cannot be stressed too much - remember, if the throttle movement is too rapid it is impossible to get full control of clutch operation under all conditions. Also, as the "lost motion" is a definite adjustment, it is also essential that control levers, bell cranks, etc. should be rigid and be free from play. Also, when ball joints are used, a type should be selected which gives a positive movement in either direction, i.e. opening or closing. | ||