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 from a letter to Mr. Rod Banks detailing the process and benefits of lead-plating copper bearings.
| Identifier | ExFiles\Box 115\2\ scan0536 | |
| Date | 14th December 1939 | |
| EXTRACT FROM A LETTER DATED DECEMBER 14th. 1939. to Mr. ROD BANKS. I am highly in favour of your lead-plated copper lead bearings. But why only .0005 of lead? We use up to .002 of lead with great success: roughly 7,500 lbs. per sq. in. bearing load in the test rig against about 3,100 to 3,300 lbs. per sq. in. for copper lead without plating. The lead stays on almost indefinitely if we guard against removal by acid oil, which I'll mention later on. The bearing metal backing is simply good insurance against a catastrophe in case the lead should be removed, and in that event I think you are better off with copper lead than we are. Here's the story. We sand blast the bearing surface to clean it before lead plating, as follows:- The bearings are cleaned of oil by degreasing in a solvent cleaner. They are then dipped in an alkali cleaner and rinsed in cold water and dried. A fixture is used to prevent sand blasting the mating surfaces, etc., and the bearings lightly and uniformly blasted at 8. lbs. per sq. in. I'm omitting the quotation marks. We use a rather elaborate system of masking with wax and tape to prevent plating where it is not desired. I won't try to describe it because probably several dozen other methods would do as well. A fixture is used to centre the anode. The surface of the bearing is prepared for plating by swabbing with alkali, rinsing in cold water and scrubbing with pumice. After rinsing in cold water the bearing is made anodic in a 5% sodium cyanide solution for 15 seconds. After rinsing again in cold water the anode is assembled and the bearing plated. The lead anodes are made of extruded grade 1 or 3 ASTM. lead 3/8" in diameter. The anode is taped with rubber tape so that it's effective length is the same | ||