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).
Commercial vehicle clutch design, friction materials, and a comparison with Borg & Beck.
| Identifier | ExFiles\Box 179b\2\ img231 | |
| Date | 21th December 1932 | |
| -2- Ha/Aln.1/MA.21.12.32. Cont'd.{John DeLooze - Company Secretary} clutch We were shown a commercial vehicle clutch having the spring type of flexible centre. In this construction short coil springs are inserted with the axes tangential in rectangular which coincide in the two relatively moving plates. They have a small initial compression. Thus it appears t that on a relative movement of the parts in either direction, all the springs compress, the movement beginning as soon as the force exceeds the initial set, i.e. there seems to be a discontinuity in the curve of flexure since there must be a minimum force to begin deflecting either way. We were not told the exact composition of the friction fabric they employ, but were informed that it was a phenol base material. They stated that they commonly obtained coefficients of .3 and more though they only work to .2 in their designs. Values of µ are measured by means of a torque arm attached to an assembled clutch carrying the full spring load. They admitted that the values found are rather indefinite but stated that they do not vary much with pressure but tend to fall slightly with rise of temperature. The clutches however could work satisfactorily up to 400°C. We showed them one of our servo rings in Ferodo RAD.13 material for which we found a µ of .28. They were not familiar with this fabric but did not express much interest in it. We believe all their iron castings both for brakes and clutches are made by Qualcast at Derby. They are endeavouring to get castings sufficiently accurate not to need balancing (for clutch rings). The 18.A1 clutch which we have, has a balancing hole drilled down the centre of one of the spring studs. We conclude that the quantities which we estimate in our clutch designs compare very reasonably with those employed by Borg & Beck. Ha/F.J.Alan. | ||