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).
Comparison of two plunger mechanism schemes (Hs.1206 & Hs.1210) and test results for self-adjusting tappets.
| Identifier | ExFiles\Box 17\6\ Scan203 | |
| Date | 25th April 1934 | |
| -2- Hs{Lord Ernest Hives - Chair}/SmJ.2/KM.25.4.34. These details are included in two schemes Hs.{Lord Ernest Hives - Chair}1206 & Hs.{Lord Ernest Hives - Chair}1210, the plunger mechanisms being identical. The difference is that in the former, the plunger is housed in the rocker above the push rod, whereas in the latter the plunger is above the valve spring. Of these two schemes, Hs.{Lord Ernest Hives - Chair}1210 is the most satisfactory, noticeably at low speeds where the time limit of load on the plunger is greatest, and the advantage can be attributed to the following reasons :- (1) As the cam starts to lift, the inertia in Hs.{Lord Ernest Hives - Chair}1210 tends to throw the ball on to its seat, other than by the oil pressure in the compression space. Hs.{Lord Ernest Hives - Chair}1206 tends to throw the ball off its seat as the cam starts to lift. (2) At low speeds where cam accelerations can be neglected, the main load on the plunger is exerted by the valve spring. With the radius of the rocker lever being 1.7" on the valve spring and 1.3 on the push rod, the loading on the plunger at the valve spring Hs.{Lord Ernest Hives - Chair}1210 is only 76.5% of the plunger loading at the push rod Hs.{Lord Ernest Hives - Chair}1206. A complete set of Self Adjusting Tappets to Hs.{Lord Ernest Hives - Chair}1210 has been tested both on the Test Bed and in a chassis, with promising results. There is no sign of air locking under any conditions of running and if when stopped the oil is not allowed to drain out of the rocker shafts and oil pipes, the tappets function within 2-3 seconds of starting. If the draining is not prevented it takes 20-30 seconds to operate when cold and 3-5 seconds when hot. Tests are at present being carried out to overcome draining. The standard oil feed arrangement to the rockers is used with a slightly stronger relief valve spring in order to maintain a pressure of not less than 5 lbs/sq.in. with the temperature at 100°C. and slow running. It has been necessary to by-pass the main valve by .062 dia. hole in order to obtain this condition. [Handwritten in left margin]: For previous | ||