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).
Design history and production modifications of M.40 and B.60 tappets.
| Identifier | ExFiles\Box 109\3\ scan0184 | |
| Date | 19th July 1941 | |
| To TB/KNG. from Rm{William Robotham - Chief Engineer}/HH. c. to Rm.{William Robotham - Chief Engineer} c. to Jnr.{Charles L. Jenner} 700 Rm{William Robotham - Chief Engineer}/HH.3/SW.19.7.41. M.40 Test Rig Tappets. We have completed the modifications requested by yourself, to the above tappets and, after consideration, are concerned as to how you intend casting these pieces. It is difficult to conceive a convenient method of splitting the mould (and building the core) which is readily acceptable to both the windows and the small cast hole. For your information, we offer a brief history of this aspect of tappet production. B.60 Tappets - EB.3855/6. These pieces have spiral slots with 45° angle sides cast on a 20° Helise angle. They originally had a .187 dia. drilled hole in the side of the tappet until, under instructions from Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner} this was replaced by a .200 dia. cast hole which was moved round so as to appear between two of the slots (Ref: Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner}15/W.15.7.38). Some months later, trouble was experienced through cracks appearing on the base face of the tappet which on occasions ran up to the hole in the side of the tappet. In consequence Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner} issued PD.324, which showed the base thickened up and the hole deleted. This is how the B.60 tappets stand at present. M.40 Tappets - RE.1881-2. These tappets were originally drawn with spiral grooves but, at the Works request (Mr.Vickers) these were deleted, and replaced by a series of eight holes in two rows of four holes with 45° angular sides. This brings us to the present position with which you are fully acquainted. Attached we show sketches of the straight slots (a) with parallel sides and (b) with 45° angular sides, and we would be appreciative of your observations regarding this and also the relative position of the small cast hole. Rm{William Robotham - Chief Engineer}/HH. | ||