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).
Various breather pipe modifications and their effect on crankcase pressure.
| Identifier | ExFiles\Box 132\3\ scan0109 | |
| Date | 14th September 1938 | |
| -2- We first fitted to the end of the existing pipe and well down into the air stream, a copy of the breather fitted to the Bedford lorry. This showed a slight improvement over the standard pipe. We then tried in the same position i.e. at the end of the standard pipe, a breather which we made ourselves (sketch attached). This gave a negative pressure of 1.500" of water as against .300 standard (gauge fitted into top of breather pipe by oil filler). It has also the advantage of commencing to work at 20 M.P.H. as against 40 m.p.h. standard. We found it impossible to fit this underneath the car, as we are already tight for ground clearance. Several positions were tried underneath the wings in the undershield etc. but in each case the air flow was not sufficient to give a reasonable figure. Lastly we tried it fitted to the front bumper bracket, where it gave a 1.00" max. negative pressure. This breather could be fitted hereabouts, but would mean a modification, as the connecting pipe would have to be fitted to the front end of the crankcase. As a final effort we fitted a small shield which cowls the front of the existing breather pipe but which is open at the rear, this tends to increase the vacuum in the pipe. Results showed a 100% increase over the standard pipe. It is also easy to fit. An inlet with an air cleaner could be fitted, but the depression created by the breather would lose its beneficial effect on crankcase leaks. Figures showing the effect of the breathers and the various positions, attached. Rm{William Robotham - Chief Engineer}/Brazier. Rm{William Robotham - Chief Engineer}/G.H. Hyman. | ||