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).
Engine lubrication tests, focusing on the big end bearing and gudgeon pin oil supply under various conditions.
| Identifier | ExFiles\Box 132\4\ scan0008 | |
| Date | 2nd November 1934 | |
| -2- We then cut a groove in the big end bearing (see D.V.62) in order that a more consistent supply of oil could be obtained and with this modification and having a .031" diameter jet in the side of the rod we managed to get good results. In order to reproduce the conditions as near as possible of an engine in a cold climate we used Amber "A" gear oil instead of the normal engine lubricating oil. A good jet of oil was thrown on to the bore at first giving adequate lubrication, but as the oil warmed up and the pressure fell the oil jet failed to reach the cylinder wall directly but instead ran down the connecting rod and was thrown by the big end on to the outside of the cylinder wall and then ran down and was picked up by the piston skirt. As the oil got hotter the jet was reduced considerably until under normal working temperatures the jet ceased to function, for this reason, that with the oil thoroughly hot practically the whole of the oil is lost through the big end bearing clearance. In fact, from our experience during these experiments we should say that practically no oil goes up to the gudgeon pin by way of the oil passage provided and that the gudgeon pin relies entirely on the oil mist in the crankcase for lubrication purposes; this of course is only the case when the lubricating oil is hot under working conditions and does not apply when the oil is cold. In that case we should say that an adequate amount is provided. With the standard scheme of big end lubrication in which there is no groove in the big end and the supply to the gudgeon pin relies upon the registering of the oil hole in the crankpin with the two holes in the bearing shell, we think that the supply to the gudgeon with the oil hot, is, for all practical purposes, negligible. These tests were of course carried out on only one rod, and we have since built the unit with all the rods modified to this scheme to verify our theory that with the oil under normal working conditions no extra oil is supplied and that the oil consumption with this scheme incorporated is no worse than standard. | ||