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).
Further failures of Borg & Beck clutches during high-speed endurance testing, focusing on eyebolt issues and vibratory movements.
| Identifier | ExFiles\Box 129\3\ scan0084 | |
| Date | 5th February 1936 | |
| X1110 To E.{Mr Elliott - Chief Engineer} & By.{R.W. Bailey - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to Da.{Bernard Day - Chassis Design} c. to Hdy.{William Hardy} c. to Mx.{John H Maddocks - Chief Proving Officer} HS{Lord Ernest Hives - Chair}/Smth.10/KW.5.2.36. Borg & Beck Clutches. Further to Hs{Lord Ernest Hives - Chair}/Smth.20/KW.6.1.36. Since issuing the above report we have had two further failures on Borg & Beck clutches on test bed units. In each case the engine has been running under high speed endurance conditions, i.e., 30 mins. at 4,000 r.p.m., 25 mins. at 4,250 r.p.m. and 5 mins. at 4,500 r.p.m. in each hour. A summary of all failures up to date accompanies this n/te, and also a photograph showing typical eyebolt failures. One of the failures occurred on a clutch which had been rebalanced by the latest method, showing that some influence other than the out of balance of the pressure plate was the cause of the trouble. After prolonged running at high speed all eyebolts on clutches which have failed show picking up on the outer side on the bottom end which fits into the hole in the pressure plate, and on the nut where it seats into the cover plate. There is also wear on the outer side of the eye, which receives the fulcrum pin of the release lever. All eyebolt failures have occurred in the threaded portion, and show signs of fatigue commencing from the outer side. We have measured the vibratory movements of the clutch at high speed by measuring the wear of aluminium pointers which were just touching various parts of the clutch at the commencement of a run. We find that at 4,500 r.p.m. there is a flutter of 1/2 amplitude about .006 at the radius of the eyebolts, and a movement parallel to the plane of the flywheel of 1/2 amplitude .010. The bolts appear to move out of the cover by .008 periodically. The total centrifugal loading on the eyebolt at this speed is 600 lbs. The pressure plate and finger assemblies will tend to remain in steady motion as the flywheel vibrates. We have formed the tentative opinion that the failures are due to the shock application of the centrifugal load four times per revolution as the flywheel vibrates. | ||