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).
Design and material choice for car bonnets, comparing rivetless aluminium and steel options.
| Identifier | ExFiles\Box 119\4\ scan0019 | |
| Date | 8th July 1931 | |
| X385 HS.{Lord Ernest Hives - Chair} FROM DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork} DA{Bernard Day - Chassis Design}/EV{Ivan Evernden - coachwork}1/M8.7.31. C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} BONNETS. X.385 X.7260 X.5260. We have sent to you now two designs for an aluminium bonnet with rivetless hinges. Although these bonnets have been done for P. 2. the design is equally applicable to the 20/25. We would like Works to tell us now whether they still want to us to go on with the development of the steel bonnet. This was suggested by the Economy Committee for J.{Mr Johnson W.M.} 3. and we are now in a position to give you a design for the bonnet in which the hinges are rolled in the strip steel of the bonnet material and sheathed with a chromium strip without the use of rivets. We append herewith a sketch of the top and side joints. Since however we do not believe that we can use steel much thinner than .048 (and might be .064) such a bonnet would be heavier than the aluminium one, and therefore we think it is ruled out definitely for P.2. The other disadvantage had already been put before you, namely, that of being unable to prevent rust on the edges. If a tinned sheet were used as we believe it would have to be then it would need retinning on the edges after the plate has been sheared. Tinning would prevent the use of electric spot welding, but we suggest that the shutters might be sweated on. We would be glad if Derby would go into this question and advise us as to the advisability of progressing with this design. We are inclined to think that the rather complicated rolling of the bonnet hinge would be more costly than using a simple brass strip riveted on. once we return to the rivets we can return to aluminium. DA{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork} | ||