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).
Micro-examination report detailing hardness tests and failures of cyanide-hardened gears from a Phantom III gearbox.
| Identifier | ExFiles\Box 94\2\ scan0212 | |
| Date | 20th April 1937 | |
| 328 Micro-Examination Report. M.1314. To HPS.{Horace Percy Smith - Experimental Factory Mgr} c. Rm.{William Robotham - Chief Engineer} c. RHC.{R. H. Coverley - Production Engineer} HL.4/AG.20.4.37. Laboratory. PHANTOM III GEARBOX - CYANIDE HARDENED GEARS. The constant mesh gear G.81570 which you handed to us has been examined. The following hardness figures were obtained :- On the case. V.P.N. (10 Kg.) Tops of teeth (ground) 560 - 650 Ends of teeth (not ground) 650 On the core. V.P.N.(30 Kg.) Brinell (2mm/120 Kg.) Centre of teeth 499 470 Ends of teeth 543 - Near splines 499 470 The case on the broken teeth was only .002 to .003" in thickness - See photomicrograph No. A1618. The micro-structure and fracture tests indicated a very brittle core, fairly fine in grain size in the teeth, but coarse in the rest of the gear. The rim of the gear was cracked at the base of two teeth adjacent to, the broken ones, and also on the opposite side of the gear, the cracks running into the sides of the teeth. The central part of the loaded surface on each of the broken teeth was cracked and had disintegrated and broken away. This breakdown of the surface can be seen in a less advanced stage near the end of one of the broken teeth - photomicrograph No.A.1619. We have previously examined one of the Ford gears - Report M.900 - HL1/AG.11.10.33. On that gear the case was .010" thick, the case hardness 740 V.P.N., and the core hardness 514 Brinell. It also was lacking in ductility. Hl. HE Photomicrographs Nos. A1618/9 att. Also specimen. | ||