Car Parts and Accessories

All the methods of repair discussed so far can be used where normal strength is required, such as door and general bodywork panels, but they are not suitable for points of high stress such as rotted chassis members or areas of pressed bodywork which bear the full weight of suspension units. But no matter what steps are taken to ensure a good bond between metal and glass fibre, it can never have the strength of the original sheet metal bodywork as far as stress is concerned. Where a section of metal which normally has to stand high stresses has corroded, the only safe method of repair is to replace it with a similar piece of metal with similar characteristics. These characteristics not only need to extend to the replaced piece of metal but also to any methods of joining used. For example, were you to replace 22 S.W.G. steel with a similar section and then try to fasten the two together with body filler, the body filler would obviously fail very rapidly.

The strongest method of repair in this case is welding. The idea of welding is that the two pieces of metal to be joined are placed together and heated to such a temperature that the edges of both metals melt and fuse into each other forming one piece of metal. The principle is the same for various methods of welding, the only variation being in how to obtain the heat to fuse pieces of metal together.

Gas welding

In the small or medium sized garage, for instance, the normal method of welding is that known as gas welding. Two gases, oxygen and acetylene, are mixed together in the correct proportions and then ignited. The flame they produce has an extremely high temperature and is used to heat the metals until they melt. But the equipment required for this is quite expensive, sometimes costing up to £100, and obviously beyond the range of the ‘Do It Yourself’ man.

Arc welding

Another method of welding is arc welding. This relies on the fact that if a heavy electrical current passes across a very small gap or arc (which is in effect a continuous sort of spark), then a great deal of heat is generated. Using the normal type of equipment for arc welding requires an extremely high current and this can only be obtained from expensive transformers which are once again too costly for the ‘Do It Yourself’ motorist.

In recent years, however, various types of carbon arc- welder have come on to the market. These welders, costing around £5 or £6 each, complete with the necessary accessories, will run off a normal car battery. The current consumption when running is high but the average car battery will last for about one hour and in one hour a great deal of welding can be done.

The carbon arc welder

Basically, the carbon arc welder consists of a piece of copper plated carbon rod, set into a handle, with a lead and crocodile clip on the end. The clip is attached to the battery terminal which does not go to the chassis of the car. If the battery has a positive earth, then the clip is fastened on to the negative terminal and vice versa. When the tip of the carbon rod comes into contact with any part of the car’s bodywork, a high current flows through the tip of the carbon.

If the tip is left in contact with the bodywork it will heat up rapidly. However, if the tip is drawn away from the bodywork by approximately is the heat will intensify tremendously and what is known as an arc will be struck. This is a white hot ridge between the tip of the carbon and the bodywork which is perfectly capable of melting the metal used on motor cars.

This is the principle on which the welder works. Of course, in practice it is not quite this simple, and various other accessories are required, such as cleaning fluid to remove any grease etc., from the work, fluxes and filler metals for filling in the parts to be welded or for building up worn areas etc. All of these items, together with a pair of protective goggles (to protect your eyes from the intense white light of the welding process), will be included if you purchase a small battery operated welding kit.

Before welding, the two pieces of metal must be free from paint and rust and any traces of oil or grease. Emery paper should not be used as small pieces of emery can become embedded in the work. The initial cleaning is best carried out with a metal wire or brass bristled brush. This should then be followed by degreasing the edges to be melted in special cleaning fluid.

The piece of metal to be welded to the car bodywork is held in place and welding flux is sprinkled along the edges to be welded.

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