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).
Failure analysis report on the Phantom III's front brake dumb bell, detailing seven contributing design issues.
| Identifier | ExFiles\Box 92\4\ scan0357 | |
| Date | 25th August 1937 | |
| To Hs.{Lord Ernest Hives - Chair} from Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} c. to Ey. c. to Rm.{William Robotham - Chief Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} 306 Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux}3/N.25.8.37. Phantom III - Front Brake Dumb Bell Failure. -------------------------- The recent failure of the Phantom III Front Brake Dumb Bell is due to several features. The design is such that accurate setting of the levers is necessary. (1) To give the least amount of misalignment of the dumb bell. (2) The brake stop is not sufficiently robust and is not adjustable to allow for resetting after wear in the spherical cups has taken place. (3) The operating lever inside the brake is too near the brake shoe and will not allow any misalignment. (4) The countersunk of the outside operating lever G.84118 does not give sufficient clearance in the angle to the spindle of the dumb bell. (5) The spherical balls of the dumb bell are too small in dia. to allow for the angles the dumb bell has to operate through. The dia. should be increased to at least .750" (6) With wear in the spherical seatings of the operating levers, the angle through which the Dumb Bell has to operate is increased, which makes a foul still more. (7) The incorrect setting of the inside operating lever allows the lever to foul the auxiliary shoe of the front brake shoe. This forces the lever over and places a strain on the neck of the dumb bell. Cont'd.{John DeLooze - Company Secretary} | ||