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).
Analysis and critique of steering gear components, including worm bearings, roller design, and rocker shafts.
| Identifier | ExFiles\Box 173\4\ img141 | |
| Date | 26th November 1935 guessed | |
| -2- They preload the worm bearings to 1 lb. at the rad. of the steering wheel, the remaining 1 to 2 lbs. being tightness in passing over the centre. They say they do not think the shim method of adjustment such as we use is adequate for this preloading and recommend a screw adjustment acting on the outer cones of the bearings. They also do not approve of the method of tightening the roller into the worm by offsetting it .250 as we do because, on account of the angle of the roller to the helix, it cannot tighten both sides equally. they accordingly use a sleeve with an eccentricity of .015 (.030 stroke), in which the worm bearings are carried, this sleeve being rotated by a hexagon on one end and locked in the adjusted position. [Diagram of an eccentric sleeve assembly] LEVER FOR LOCKING SLEEVE ECCENTRIC SLEEVE SCREW ADJUSTMENT (MAY BE LOCKED BY A TANGENT SCREW) They say Timken rollers are not satisfactory in the roller, though all-right on the worm, because they cannot be sufficiently preloaded without risk of bursting the roller. They use and much prefer balls, which they say outlast the rollers with the same load. They had no trouble anywhere. They confirm that any slack, especially in the roller or the worm, causes joggling. The roller is preloaded to a load of 3 lbs. applied on the side of the tooth. They criticise our long rocker shaft for causing joggles. A small point is that when we estimate the angle of the helix, instead of taking the constant lead around the curve of the worm form, we ought to take only that part of the lead which is projected in the plane of the worm axis, at the point of contact, that is [Diagram illustrating the angle of the helix] S If α is the angle of the helix, and β the angle between the true lead at the pitch line and the line parallel to the axis of the worms, instead of α = Helix angle = Tan⁻¹ (lead / circumference.) | ||