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).
Failure of a crankshaft damper disc and proposing design modifications for the low inertia slipper wheel.
| Identifier | ExFiles\Box 137\4\ scan0186 | |
| Date | 28th January 1931 | |
| R.{Sir Henry Royce} FROM E.{Mr Elliott - Chief Engineer} X634 E1/M28.1.31. C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} C. to HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} P. 2. LOW INERTIA SLIPPER WHEEL. We send you herewith the broken crankshaft damper disc mentioned in HS{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}1/KT21131., which memo. states that a failure has occurred on production as well as on 19-EX. Enclosed also is a tracing of E79915. shewing the standard arrangement of this wheel. There appears to be no very satisfactory and obvious theory to account for this breakage since the wheel is mounted on bearings wide apart on the shaft, but the nature of the fracture certainly indicates side load. The wagging of the crankshaft on its resonant periods might result in end loads or the deflection of the small part of the shaft within the wheel may be a source of stress in the disc. In any case the disc is not well fitted to bear loads of this description owing to the rapid change of section due to the spokes and hub, and it may be wise to strengthen it up in this respect as soon as possible. Three methods of doing this are suggested: (1) Increase the thickness all over from .075 to .125 and thereby reduce the present stress to about one third. (2) Alternatively increase the thickness of the spokes and all metal within a dia. of 4.5" leaving the part carrying the friction surface unaltered. This is more difficult to produce than (1) but has the merit of not increasing the inertia and the increase in thickness could be more, say up to .175". (3) Use some good alloy steel such as nickel chrome or chrome vanadium to resist fatigue. Present material is .5% carbon. (4) Extend the clamping effect of the hub to a diameter nearer the friction surface cutting away the metal of the wheel unit where required for clearance. E.{Mr Elliott - Chief Engineer} | ||