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 on a combined roller and ball race for a Bentley.
Identifier | ExFiles\Box 114\2\ scan0054 | |
Date | 26th July 1934 | |
Please forward to GA v3807 M966. Micro-Examination Report. To Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} HL5/AG.26.7.34. Laboratory. Re: Combined Roller and Ball Race - Bentley. This race was made by Hoffmann's. The balls ran in the usual cage, but the rollers were run cageless. The race had been under test on Ransome & Marles rig at high speed under light load. We understand that under these conditions both tracks showed signs of breakdown, the roller race showing "comet" markings and short transverse marks which, it was suggested, were cracks. Further it is understood that Ransome and Marles considered it to be wrong to run a roller-race without a cage, but were surprised at the condition of the ball-track, and were inclined to attribute it to faulty material. We have already tested for you the hardness of all three parts of the race, and some of the rollers. The Rockwell figures obtained were :- Roller track (one part) - C62/3. " " (other " ) - C60. Ball track. - C60 Rollers - C60 These figures were compared with those obtained on a double-ball race which was formerly used and on a Ransome and Marles ball-race both of which gave Rockwell C60. You left with us that part of the race carrying the unrecessed roller track and the unloaded part of the ball-race. The roller track showed the transverse marks referred to above. This part of the race was marked GB.1091. N1421. You also left with us the Ransome and Marles ball-race. Both races were cut up and fractured. The fractures were quite good and together with the hardness figures indicated a satisfactory heat-treatment. This was confirmed by subsequent examination of the micro-structure. Micro-examination showed also that the transverse marks in the Hoffmann race were not cracks but strings of slag which had broken up to some extent leaving a series of shallow elongated pits with the appearance of cracks. The centre part contd. | ||