350 Section 4 Nonferrous Metallurgy Loop the other end of the solder around the group of bolts in the same way. Do not stretch the solder. Do not hang these up yet—let them sit on a table with no load until you have all the wires ready. 2. Make up three more groups of bolts, of three, four, and five bolts each. Attach these additional weights to 1′ (30 cm) lengths of solder wire in the same manner as before. 3. When they are all ready, gently lift the coat hanger with wire and weights, and hang it over a hook so that if the wires stretch to twice the original length, the weights will not touch anything. Slide the looped wires sideways until the whole hanger balances horizontally and the bolts do not interfere with each other. With a marker or pen, mark the wires near the top and bottom. Measure the distance between marks for each wire using your standard 1′ (30 cm) ruler. Record the starting length and weight (units of number of bolts is okay) for each length of wire. You should be able to measure a change in length of the wire with the heaviest weight within three minutes. 4. Check and record the lengths of all the wires after five minutes, then every 10 minutes for the next hour. The wire with the heaviest weight will probably break before an hour is up. If you have a magnifying glass, look at the break for a cup-and-cone shape at the point of failure. Save the broken lengths of wire where they will Creep in Solder Equipm ent • A coat hanger with a wood or cardboard horizontal piece, not wire. It will not be damaged. • At least 14 steel bolts, 3/8″ (9.525 mm) diameter and 6″ (150 mm) long. These weigh about 3.5 ounces (100 grams) each. A different-size bolt is fine, if they weigh about 3.5 ounces (100 grams) each. • A hook to hang the coat hanger on, at least 2′ (60 cm) above the floor, and preferably 4′ (120 cm) above the floor. • A length of #18 gage copper wire, or similar-sized wire. • Standard 1′ (30 cm) ruler. • Marker or pen. • Recommended: magnifying glass or low-power microscope (20X magnification). Materials • Solder wire of 0.032″ (0.8 mm) diameter. It may be flux-cored solder. You will need at least 7′ (2.1 m). The solder will still be good for soldering when you are done, but it will be in pieces. Pr ocedure CAUTION Standard electrical solder contains 60% lead. Do not eat food while you are setting up this experiment, and wash your hands thoroughly when you are done. You are not likely to ingest lead by doing this experiment, but washing your hands is a simple precaution to take when handling lead alloys. If you are involved in soldering electronic equipment on a daily basis, then additional precautions are necessary. 1. Wrap the copper wire to hold two of the bolts together in one group. Loop one end of a 1′ (30 cm) piece of solder over the horizontal bar of the coat hanger, then twist the end of the solder wire around itself, as shown in Figure 15-31. The reason for the loop is to avoid making a sharp bend in the solder, where it might crease and fail. SELF-D ISCOVERY Clothes hanger bar Solder wire Goodheart-Willcox Publisher Figure 15-31. This figure illustrates how a length of solder wire is to be attached to a horizontal bar so it can hang freely. Copyright Goodheart-Willcox Co., Inc.