The temperature of the different parts of the flame varies considerably, the hottest part being just beyond the end of the inner cone. Experience with the particular welding outfit used will soon show how far the tip of the torch should be held from the lead to be melted.
Cleanliness. Lead surfaces which are to be welded together must be absolutely free from dirt. Lead and dirt will not mix, and the dirt will float on top of the lead. Therefore, before trying to do any lead welding, clean the surfaces which are to be joined. The upper ends of plate lugs may be cleaned with a flat file, knife., or wire brush. The posts and inter-cell connectors should be cleaned with a knife, steel wire brush, or triangular scraper. Do not clean the surfaces and then wait a long time before doing the lead burning. The lead may begin to oxidize if this is done and make it difficult to do a good job.
The surfaces which are to be welded together should also be dry. If there is a small hole in the top of a post which is to be welded to a connector or terminal, and this hole contains acid, a shower of hot lead may be thrown up by the acid, with possible injury to the operator.
Do not try to save time by attempting to weld dirty or wet lead surfaces, because time cannot be saved by doing so, and you run the risk of being injured if hot lead is thrown into your face. Remove absolutely every speck of dirt — you will soon learn that it is the only way to do a good job.
Safety Precautions. Remove the vent plugs and blow down through the vent holes to remove any gases which may have collected above the surface of the electrolyte. An explosion may result if this is not done. To protect the rubber covers, you may cover the whole top of the battery except the part at which the welding is to be done, with a large piece of burlap or a towel which has been soaked in water. The parts covered by the cloth must be dried thoroughly if any welding on them. Instead of using a wet cloth, a strip of asbestos may be laid over the vent holes, or a small square of asbestos may be laid over each vent hole.
Burning on the Cell Connectors and Terminals
Have the posts perfectly clean and free from acid. Clean the tops, bottoms and sides of the connectors with a wire brush, Figure 143. Finish the top surfaces with a coarse file, Figure 144. With a pocket knife clean the inside surfaces of the connector holes. Place the connectors and terminals in their proper positions on the posts, and with a short length of a two by two, two by one, or two by four wood pound them snugly in position, Figure 145. Be sure that the connectors are perfectly level and that the connectors are in the correct position as required on the car on which the battery is to be used. The top of the post should not come flush with the top of the connector. Note, from Figure 146, that the connector has a double taper, and that the lower tapered surface is not welded to the post. If the post has been built up too high it should be cut down with a pair of end cutting nippers so that the entire length of the upper taper in the connector is in plain sight when the connector is put in position on the post. This is shown in Figure 146. With the connectors in place, and before welding them to the posts, measure the voltage of the whole battery to be sure that the cells are properly connected, as shown by the voltage reading being equal to two times the number of cells. If one cell has been reversed, as shown by a lower voltage reading now is the time to correct the mistake.
The connectors and terminals are now ready to be welded to the posts. Before bringing any flame near the battery be sure that you have blown out any gas which may have collected under the covers. Then cover the vents with asbestos or a wet cloth as already described. You will need strips of burning lead, such as those made in the burning lead mould described on page 164.