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).
Consultation with Vauxhall regarding issues with Wraith tappets.
| Identifier | ExFiles\Box 10\3\ 03-page023 | |
| Date | 16th June 1937 | |
| B. from Rm.{William Robotham - Chief Engineer} c. Hs.{Lord Ernest Hives - Chair} c. Ry. c. REC. c. HPS.{Horace Percy Smith - Experimental Factory Mgr} 654 Rm{William Robotham - Chief Engineer}4/R.16.6.37. WRAITH TAPPETS. We ran over to Vauxhall's to-day to see Taub about the Wraith tappets. As you know, we got into trouble with these tappets picking up on test even before the engine had run up to speed. We have tried breaking these tappets in on E.P. oil, and the results look promising, but we thought it expedient to get Taub's experience on the subject. Taub gave us the following information:- (1) When they are machining the tappet guides, they raise the front of the block 5/32nds on the Chevrolet and 45 thou. on the Vauxhall, so that the bore of the tappet guides are not machined at right angles to the bore of the camshaft. The camshaft is, of course, machined parallel to the crankshaft. The reason for this is to ensure that the tappets turn round all the time. If they do not turn round trouble occurs. (2) They find it imperative to run the tappets in on an oil having a higher break down characteristic than the ordinary mineral oil. At present they are employing mineral plus 5 to 10% lard oil. (3) Metallurgical properties of the tappet are very important. They find that they get the best chilled cast iron tappets from Smith Bros., Wolverhampton. We are putting some tappets in hand with them immediately. (4) We attach a comparison of the accelerations on our camshafts and those on the Chevrolet camshaft. Taub states that they definitely had to come off maximum acceleration to avoid tappets scuffing. These figures may not agree exactly with the cam drawings we have given you. They were taken from the valve lift curve. | ||