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).
Extract of a letter from General Motors Corporation regarding a valve and slack adjuster mechanism.
| Identifier | ExFiles\Box 158\4\ scan0027 | |
| Date | 9th January 1935 | |
| CONFIDENTIAL. COPY. GENERAL MOTORS CORPORATION. Extract of a letter dated January 9th, 1935. As previously stated, I have had this mechanism in use in my own car and so far as I can see it operates equally as well as the more elaborate mechanism used in my original design. Referring to the attached blueprints (L-2519, Sheets 1 and 2) the centre figure shows an enlargement of the plunger, valve and valve keeper arrangement. To the left of this figures is shown a full-scale of the assembly of the slack adjuster. In this design, a light spherical shell (1) forms the valve body which is arranged to seat in a drilled opening (2) in the slack adjuster plunger. The spherical valve is held close to its seat by a stamped keeper (3). The stamped keeper (3) is of such dimension as to hold the valve a few thousands of an inch off its seat, the keeper being held in position by the return spring (4). An extension (5) - L-2519, Sh. No.2, of the plunger is intended to form a stop in the event that the slack adjuster/cylinder should lose its oil. Valve keeper (3) is a stamping formed with internal ridges which hold the valve away from the surface so as not to prevent free flow of oil through the keeper around the valve and through the plunger opening (2). Assume the system to be at rest. The valve lies upon the stamped ridges within the keeper (3). Oil may, therefore, flow freely through the stamped opening (6) around the valve and out through the opening (2) without restraint. However in operation, the instant the rocker arm acts against the valve spring, the slack adjuster eccentric applies a sudden downward force on the slack adjuster plunger. This movement initiates a high velocity oil flow upwardly through valve keeper opening (6) impinging against the lower part of the spherical valve (1) which is thereby brought against its seat preventing further loss of oil. It will be seen that the system requires a certain oil loss to function but since the space between the valve and its seat need not be greater than .002" - .003", the loss is negligible in terms of the total movement of the slack adjuster plunger. Perhaps the greatest defect of this system is the very rapid response of the valve. It will be found to follow the rapid fluctuations that are set-up due to valve spring surge under which conditions it will continue to feed oil and eventually the engine valve will be held off its seat. However, the rate of response of the proposed hydraulic system may be controlled by varying the oil ject effect against the spherical | ||