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).
Operation and adjustment instructions for a Stromberg carburetor switch.
| Identifier | ExFiles\Box 122\3\ scan0213 | |
| Date | 11th September 1939 guessed | |
| STROMBERG CARBURETOR OPERATION AND ADJUSTMENTS Closed Throttle—Engine Not Running—Fig. 1 When the ignition is turned off and the throttle is allowed to close, the insulated high side of the rotor (A) moves the lock-out lever away from the guide pin and allows the diaphragm return spring (D) to move guide pin (C) to its “down” position. This keeps the electrical circuit open. FIG. 1 UNLATCHED POSITION WITH CLOSED THROTTLE (ENGINE NOT RUNNING) Labels: LOCK OUT-LEVER (B), DIAPHRAGM RETURN SPRING (D), GUIDE PIN (C), CONTACT ROTOR (A) Open Throttle—Cranking Position—Fig. 2 As the accelerator pedal is depressed to crank the engine, the insulated high side of the cam is rotated and allows the lock-out lever to bear on the brass contact surface of the rotor and completes the starting motor circuit. In the same operation, the end of the lock-out lever positions itself ahead of the guide pin (C) so that the guide pin cannot be pulled upward. The entire mechanism remains in this position during the cranking period. FIG. 2 CRANKING POSITION WITH OPEN THROTTLE Labels: DIAPHRAGM, DIAPHRAGM RETURN SPRING, SPRING CUP, GUIDE PIN & LOCKOUT(c), SWITCH HOUSING, ROTOR (CONTACT)(A), CONTACT SPRING, BATTERY TERMINAL, LOCKOUT LEVER & CONTACT (B), RELAY TERMINAL, TIMING WASHER, VACUUM PASSAGE (DOTTED) Closed Throttle—Engine Running—Fig. 3 As soon as the engine fires and the throttle is allowed to close, the insulated high side of the rotor makes contact with the lock-out lever (B) and thereby opens the circuit. During this operation the end of the lock-out lever is moved away from the guide pin and allows the manifold vacuum to lift the diaphragm and the guide pin to their “up” positions. FIG. 3 ENGINE RUNNING THROTTLE CLOSED Labels: DIAPHRAGM, VACUUM PASSAGE, LOCK OUT LEVER (B), INSULATED SECTION OF ROTOR(A), GUIDE PIN, ROTOR CONTACT(A) Partially Opened Throttle—Engine Running—Fig. 4 With the engine running and the throttle partially opened, the end of the lock-out lever comes to rest on the guide pin preventing the lever from making contact with the brass surface of the rotor and keeping the circuit open. FIG. 4 RUNNING POSITION PART THROTTLE Labels: LOCK OUT-LEVER (B), CONTACT LOCKED OUT TIMING THE SWITCH The switch is properly timed when it is originally assembled onto the carburetor. If any parts of the switch, rotor or throttle shaft assembly require replacing or if the entire switch is assembled onto another carburetor, it is necessary to check the timing. The rotor is a slip fit on the throttle shaft and is held in position by the lug on the timing washer. The timing washer is directly connected to the end of the throttle shaft and positions the rotor in relation to the throttle valve. The washers are numbered with each number representing a difference of three angular degrees in throttle shaft rotation. The number is stamped on the face of the washer. The smaller the number, the less the angular degree; the higher, the greater number of degrees. When checking the timing, it may be necessary to use a washer of another number in order to obtain the limits shown in Figures 5 and 6. FIG. 5 UNLATCHING POSITION Labels: 3/64" TO 3/32" CLEARANCE WITH 8 M.P.H. HOT IDLE, LOCK OUT LEVER SHOULD CLEAR PISTON SO IT CAN MOVE DOWN, TIMING WASHER, LOCATING LUG, TIMING WASHER, IDENTIFICATION NUMBER STAMPED ON OPPOSITE SIDE CHECKING SWITCH TIMING 1. Set throttle stop screw for 8 M.P.H. (HOT IDLE) THIS IS VERY IMPORTANT. 2. Remove switch cover plate and gasket. Place mirror so that guide pin and lock-out is visible from left side of car. 3. Leave ignition off. Open the throttle approximately 1/4” by hand and with a short piece of wire or a small drill, move the guide pin to its “up” position so that it is held by the lock-out lever. The switch will then be in the same position as shown in FIG. 4. (Disconnecting the throttle rod from the throttle lever to eliminate the throttle return spring tension will be of help when going through this operation.) 4. Slowly close throttle until guide pin releases. This can be seen in mirror, or usually the “click” which results when the guide pin drops down on the rotor is loud enough to be readily heard without difficulty. 5. With the throttle in this position, measure the clearance between the idle screw and the cold idle cam when the cam is held in fast idle position. This clearance should be not less than 3/64” or more than 3/32”. If the clearance is less than 3/64”, replace timing washer with a higher numbered washer. If more than 3/32”, replace washer with one hav- FIG. 6 Label: 3/64" TO 3/32" CLEARANCE Page 6 Form 10C-635 Form 10C-635 Page 7 | ||