How to Make a Spring Scale
A spring scale is a low-tech way to measure weight and is easy to make with the right materials. You'll need a set of standard weights or a kitchen scale to calibrate the spring scale before use. Once made, the spring scale will be accurate and easy to take into the field. Homemade spring scales are used in rural areas of sub-Saharan Africa to measure babies.
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Things You'll Need
- Sturdy spring --the longer the spring, the more weight you can measure 2 pieces of 2-inch-square 1-inch pine board 2 metal screw-in cup hooks 1 metal clip 2-inch-wide piece of cardboard twice the length of the spring Permanent black marker Kitchen scale Ziploc baggies Water Wood or super glue Hammer Nail 1 bread tie
Instructions
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Decide whether your spring scale will be used for larger or smaller weights before you select the spring. The longer the spring, the more weight it will be able to support, without losing its ability to regain its shape once the weight is removed. Pull on the springs to make sure that the one you choose will be strong enough to do what you want.
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Hammer a nail into the center of each 2-inch-square piece of wood. Pull the nails out and then screw in one of the hooks using the hole made by each nail. Glue the pieces of wood so that one hook faces up and the other faces down. Let the glue dry to make a strong bond.
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Glue the cardboard to the back of the wood block so that the cardboard extends down from the wood. Make the top of the cardboard even with the top of the wood block. After you calibrate the spring scale you will mark the cardboard to show the weight.
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Hang the long spring from the bottom hook. Place the metal clip securely on the bottom of the spring using the bread tie or a short length of wire if necessary. Whatever you weigh will be held in place by the clip.
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Calibrate the spring scale. Put water in a Ziploc closing plastic bag. Weigh it on a kitchen scale. Start with 1/4 pound of water. Clip the baggie to the bottom of the spring scale. Hang the spring scale from the top hook. Mark the point on the cardboard where the 1/4-pound pulls the bottom of the spring with a short black horizontal line. Write 1/4 next to the line. Measure 1/3 pound of water. Mark where it pulls the bottom of the spring. Then measure 1/2 pound, 2/3 pound, and 3/4 pound of water. Finally measure one pound. If your spring scale is for measuring lighter weights, start with grams. Use pennies or jelly beans to calibrate a smaller spring scale instead of water.
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