Comparison of weight and design for the Phantom III and Wraith bottom tappets, considering strengthening and rod whipping.
| Identifier | ExFiles\Box 96\2\ scan0301 | |
| Date | 1st May 1939 | |
| -2- Rm {William Robotham - Chief Engineer} /Swdl. {Len H. Swindell} 9/WH.1.5.39. lightness of the parts concerned, which are as follows and well worth considering. Ph.III bottom tappet (E.89388) 1.0" dia. in present form weighs 2.5 ozs. and anticipate this will be approx. 3 ozs. after strengthening. This type houses the push rod in the top of the tappet and is an advantage in the reduced length of rod in respect of "whipping". Wraith bottom tappet 1-3/16ths. dia. weighs 3.75 ozs. and houses the push rod in its base, therefore with the equivalent weight of push rod inside the tappet approx. .75 ozs. -2" long, the total effective weight of the tappet becomes 4.5 ozs. or 50% greater than we anticipate the Ph.III tappet will be when satisfactorily strengthened. Rm {William Robotham - Chief Engineer} /Swdl. {Len H. Swindell} | ||
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).