Quick and Easy Homestead Scales
(Page 2 of 2)
March/April 1976
By Gordon Solberg
I should probably point out that the accuracy of this kind of scale is limited by the stretchiness of its main working component. A loose, very elastic spring can measure small weights quite precisely . . . as long as you don't put enough weight on it to permanently deform or "set" the spring. On the other hand, a large, stiff coil can measure heavier weights but its accuracy is limited by the fact that it doesn't stretch much per pound of additional load. So, you have to play one against the other.
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Since I wanted to weigh rabbits from birth until selling age, I looked for a spring that'd stretch at least an inch per pound. With this in mind, I came up with the best "weighin' coil" I could find: the throttle spring from an old car (which, it turned out, enabled me to check the poundage of every bunny on the farm from the youngest to the oldest with a total error of only about four ounces). I nailed the spring to a scrap piece of 2 X 4, glued a cardboard pointer right to the end of the coil, thumb tacked a piece of white cardboard next to the pointer, and—presto!—l had my scale.
To calibrate the measuring device, I hung a burlap sack-the one I would be using to hold rabbits-on the spring and marked the zero point. I next replaced the sack with the old paint bucket from my first scale. The bucket weighed a bit more, so I marked the extra deflection on the cardboard and remembered to subtract it throughout the calibration procedure. Then I simply poured exactly one pound of water into the bucket, marked the deflection on the cardboard, added another pound of water, marked the deflection, and so on (Photo 2).
If you're really interested in accuracy, it's best to pour the water out each time and remeasure rather than to just add one-pound increments. This is because if you systematically over or under estimate the amount of water each time you add a pound, the errors will add up as you go along . . . whereas if you measure the total amount of water each time, the errors at least will not be cumulative.
My spring scale took ten minutes to build and maybe half an hour to calibrate. It's not the prettiest piece of weighing equipment in the world, nor the most accurate. But at a cost of nothing but a little time and a few "junk" odds and ends, its price is certainly hard to beat!
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