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).
Design document detailing a special Bibby-type spring coupling for a blower.
| Identifier | ExFiles\Box 140\1\ scan0019 | |
| Date | 24th August 1932 | |
| (2) E.9/HP.24.8.32. Bibby type in accordance with your wishes, but the design is quite special to the requirements of the scheme. Owing to the restrictions as regards length and diameter, we are using the spring blades to drive as cantilevers and not as beams. It is arranged in a very similar manner to a German spring coupling which we noticed in the 'Engineer' of 9/10/31, known as the 'Babba', but instead of continuing the blades through to the outer drum to provide blades stops in double shear, which is arranged by the makers for withstanding unknown loads under all sorts of conditions, we think our blades would be quite capable of acting as stops in single shear. BABBA COUPLING The spring blades when fully loaded are arranged to wrap round the curved faces provided on the inner coupling member, thereby shortening the lever arm, and bending some portion of the springs through a constant radius of curvature. In this way the maximum amount of work is obtained out of the steel and the natural period of vibration of the blower mass relative to the crankshaft would be altered in such a manner as to assist in damping out any occilation from this source; also the way in which the coupling torque increases up to the fully stopped position is favourable to the avoidance of shocks when accelerating. In the design we show, the intention is to provide for a maximum deflection of plus or minus four or five degrees, and we think the proportions are about right for a reasonable stress in bending, and for the normal blower torque to deflect the coupling only part of the way so as to leave the crankshaft some degree of freedom. These proportions we are going into more closely at the moment relative to the blower torque. The construction we have arranged so as to retain the springs in the hub as a unit, and leave the float on the outer driven ends where the loads are lighter to provide for any eccentricity in the drive. The splined shaft engagement of the blower allows for a wide tolerance in respect to the relative positions of | ||