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).
Difficulties with keeping plates tight on splines and the effectiveness of a damper system.
| Identifier | ExFiles\Box 25\3\ Scan277 | |
| Date | 22th April 1927 | |
| contd :- We have not yet hit on the explanation of the periods being as they are and not in harmonical progression as with the standard drive. The most interesting difficulty we have so far encountered is that of keeping the plates tight on their splines particularly the inner ones. Owing to the shortage of space these splines have been made rather small. A total of .005" clearance in the splines is sufficient to give .1 of an inch movement on the end of an 18" lever and is equivalent to 3° 12' of free crankshaft movement. With reference to the curve of amplitudes for the various periods given in Hs{Lord Ernest Hives - Chair}/ACL1/LG22.4.27., shews that the damper will then be unable to reduce any of the lower periods at all. This has been borne out in practice - as soon as any slack appears in the splines, the damper becomes ineffective. With a set of well fitted plates it is possible to abolish the lower periods with this spring drive and by the use of a very heavy flywheel (.0384 slugs ft²) and heavy damping (15 to 18 lbs.ft.) the severity of the master period (3650 r.p.m.) can be very considerably reduced. The master period, however in this case, extends some 350 r.p.m. either side of the critical speed. Thus from 43 m.p.h. upward on 3rd. gear in this condition the engine roughness is such as could not be tolerated. The lower periods can also be dealt with effectively with the lighter flywheel (.0192 slugs ft²) and less damping (9 lbs.ft.) At the moment therefore we do not see much virtue in the larger inertia element. We enclose a drg. which shews the type contd :- | ||