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).
Alternative designs and materials, particularly aluminium versus steel, for rivetless bonnets.
| Identifier | Morton\M9\ img030 | |
| Date | 15th July 1931 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey} c. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. EV.{Ivan Evernden - coachwork} ORIGINAL Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey}/AD.15.7.31. RE : RIVETLESS BONNETS. X.7260. X.1085. We have now several alternative designs to work on, and it appears necessary to decide which it will be best to make. The first question is whether aluminium is preferable to steel. If the question of cost is eliminated aluminium is preferable because the difficulty of rusting is entirely eliminated, aluminium will also be lighter and being more ductile will not suffer from irregularities in the flat surface. We do not think we shall be able to overcome the rusting difficulty satisfactorily, even if we do go to the trouble and expense of tinning after the bonnet plates have been fitted, we think the tinning will very soon be rubbed off by the ferodo wearing strip or by contact with the radiator and dashboard, and the rusting process will only be delayed slightly. On the whole we think it more satisfactory to use aluminium. We have two designs for rivetless bonnets in aluminium, one of them (N.Sch.3294) employs rivets but they are hidden from view, the other (N.Sch.3304) is rivetless but has possible disadvantages although less costly. In addition we have in Derby, several schemes on the same lines as N.Sch.3304 all of which may prove to have disadvantages viz. there is a risk of the rolled aluminium straightening out under the tension of the bonnet fasteners and so loosening off the hinge. The best course appears to be to make up one bonnet as N.Sch.3294 (hidden rivets) incorporating thicker gauge aluminium, countersunk rivets for centrally pivoted flip flap shutters and no bonnet stiffeners. In addition we think it worth while to test out the possible disadvantages of N.Sch.3304 as this scheme, if mechanically satisfactory, would appear to be less costly. Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey} | ||