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).
Manufacturing difficulties with car body panels and proposed modifications for spot welding.
| Identifier | ExFiles\Box 26\1\ Scan189 | |
| Date | 8th February 1957 guessed | |
| Sources of Trouble Certain shapes are constant sources of trouble. One example is the Siam roof panel with its built in drip mould and the razor edge line which runs across the roof at the rear. The design of the drip mould is too small to allow the metal to flow freely around the radii and the panel bursts as a result. The razor edge line causes shock waves on either side. The Siam front fender is an expensive piece to make, particularly at the front where the bumper fairing is attached. This panel is annealed and then pressed 3 times, due to the shape being re-entrant and the sharp corners that are required. Operations like this are the reason for tool costs being so high. Another problem is when a boot lid{A. J. Lidsey} panel is made with a rear light fairing pressed into the centre. Unless generous radii are given then the percentage of scrap is high as the flow of the metal is too localised. Also there is a shock wave all around the hump, which can be seen, but cannot be avoided. Curved Z sections on the edges of large flat panels are difficult, because there is so much metal to lose that creasing results all around the edge. Modifications Apart from nuisance value due to altering the tools complications arise due to upsetting the flow of metal. Difficulties were encountered when Humbers modified their boot floor to include two humps to clear shock dampers. This was done at the flangeing stage (to avoid costly changes to the main die) and as the metal is then trapped it is made to stretch locally rather than flow, and again try-out scrap is high. Spot Welding To assemble Siam there are 28 different types of gun used. To assemble a Hillman Minx 4 standard types of gun are used. We should aim to use more simple exposed joints as shown on sketch No. 2806 wherever possible, provided they are not stressed in such a way that they open out under load. Sources of Trouble Whenever possible having to put a spot welding gun through a hole should be avoided. Apart from being unable to see what is going on, this can easily lead to shunting and a poor spot weld results. continued.... | ||