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).
Setting difficulties experienced with the Borg & Beck clutch on Bentley & 25/30 HP models.
| Identifier | ExFiles\Box 129\1\ scan0068 | |
| Date | 26th November 1936 | |
| To RH.{R. Hollingworth} from RHC{R. H. Coverley - Production Engineer}/HPS.{Horace Percy Smith - Experimental Factory Mgr} e.c. to DE. (Struck through) c.c. to PH. (Struck through) c. to Rm.{William Robotham - Chief Engineer} Handwritten Note: LE Smith. Would you like to condense this for a depot sheet. 26.11.36. Rm.{William Robotham - Chief Engineer} 1110 BENTLEY & 25/30 HP. BORG & BECK CLUTCH - SETTING DIFFICULTIES. Trouble has been experienced both on Production and in the Expt. Dept. with regard to the "setting" of the above clutches. The withdrawal fingers should be so set that they make contact with the thrust-race of the withdrawal trunnion, but they have been known to be as much as .015" - .020" out of truth, though a limit of ± .005" is called for. We have every reason to believe that they were set correctly by the manufacturers, for we know that by merely putting a clutch down heavily on the bench it may lose its setting. The Expt. Dept. have investigated the trouble, using clutches taken from Production and a cure has been found, approximately three dozen clutches being returned, correct. The following is a brief summary of the work done, and should be read in conjunction with the sketches Ex.I.85/6 supplied herewith. CAUSES OF THE TROUBLE. (1) The nuts, which adjust the clutch fingers by means of the pivoting eye-bolt, (see Draw. Ex.I.85) are spherical, and were supposed to bed on a spherical seating in the clutch-cover. This was not so, as the seating in the cover was only a chamfer which made tangential contact with the sphere of the nut (Fig. 1. Ex.I.85). The cover, not being rigid or hard, was distorted and indented by the nuts at this point when load was applied to the fingers. ".001" difference here makes .005" difference on the fingers. The covers accordingly have had a spherical seating machined at this point, and a better contact-surface is thus obtained. (Fig.2.Ex.I.85). (2) The clutches have hitherto been set without load having been applied to the fingers and this we find gives rise to false readings, for a coating of vaseline and zinc oxide (with which the working parts are smeared) between the finger and the connecting link to the pressure plate, can make a big difference to the setting of the finger. If, however, load is applied to the fingers, any irregularity such as that mentioned above, is obviated, and the fingers settle down into the position they will occupy during ordinary running conditions. A rig has been made (See Ex.I.86) by means of which the continued. | ||