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).
Extract of a communication regarding the production of lead bronze bearings in the U.S.A.
| Identifier | ExFiles\Box 114\2\ scan0117 | |
| Date | 23th February 1935 guessed | |
| Extract of communication from A.C. Spark Plug Co., Flint, Mich., U.S.A. who produce Lead Bronze Bearings for the Motor Car Manfs. in U.S.A. I am more than glad to know that you have gotten along well with the copper lead bearings; and agreeably surprised to hear that you are using centrifugal cast connecting rod bearings, as in this country more trouble is experienced with them than with main bearings. Just now Allison seem to be having some difficulty in making bearings that will carry the very heavy load imposed by engines such as Pratt-Whitney double row radial and the Curtis double row radial. They are now working on a new furnace in which all the operations of heating, casting, and quenching will be done in an air tight furnace filled with neutral atmosphere. This is the practice we are following here with very satisfactory results. We produce the atmosphere with a General Electric cracker which gives us a neutral gas by partial combustion of the butane gas introduced into the heating cylinder. Unfortunately I do not have a photograph of this unit to send you but I imagine your General Electric branch in London could supply you with information you would need. In connection with the cracking unit, we are using a Frigidaire unit for cooling the gas and dehydrating it so that we have our gas perfectly cold, in fact about 38° when it enters the furnace. It is also perfectly dry. This means that we do not have to use a flux of any kind as the trays come through the furnace when heated to 1950°C. perfectly free from oxide; and when quenched and ejected without the bronze part in them should be just as clean as when they enter the receiving end of the furnace. I am sending you a diagramatic layout of the furnace with a conveyor which is of the walking beam type. The pouring crucible, quench hood, rocking furnace, in which the metal is melted and from which it is transferred into the pouring crucible, and the ejector chute with a water seal at the bottom end of it. One thing we do not show is the suction blower which pulls the steam away from the quenching section and the return of the steam and gas combine to the condensing or refrigerating unit. One of the interesting developments of the last six months has been the determination of oxides in the copper they use to make the bearings. This has been a rather interesting sort of thing as we find no commercial device for determining the oxygen content of metals. It was necessary to construct an outfit of our own. We tried a half a dozen different methods before we found one that would operate in a satisfactory manner. This one proved to be all right for about two weeks, and then we ran into a lot of trouble, and were absolutely at sea as to what was causing the trouble. Then we discovered that the alundum sample boats were of a different grade from what we used at first and contained so much moisture that we were getting far different results than from the original tests. Following some research conducted by Mr. Boegehold of General Motors Research Laboratories we found that a bearing made of oxygen free copper gave very excellent results. In other words, the bearings clamped on a pin in a test fixture with 125 pounds pressure continued. | ||