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Tuesday, 8 May 2012

A home-made rain gauge

Once you start looking at weather, you may want a rain gauge. You can buy one, of course, but you can also make one from scrap materials.

The last thing you want with an evaporation pan (I'll come to that later) is rain water falling in it, the last thing you want in a rain gauge is evaporation, so it needs a bit of design to control for that and to stop rain splashing out.

This entry is essentially a set of partly-baked ideas, because before I got too far, I dropped this one from the book: that's why this entry is a bit deficient in photos.  Grab the idea and run with it, changing it as you go.

For my model, I decided to take a 1-litre milk bottle and lop the top off to make a funnel that would catch the rain and lead it in, and at the same time, stop too much loss by evaporation.

To make the base more stable and also to make the bottom level, I filled the bottom with water, added plaster.

Note well: you need to put down newspaper to work on before you use plaster, and you should clean up any spilled plaster with a vacuum cleaner.

If you have excess water in a container, the plaster powder settles down to a nice flat surface and it still sets, so use a spatula to add plaster powder to an excess of water.  Bounce the container up and down to flatten the plaster.

Then let the plaster set for an hour (20 minutes is enough, but it does no harm to be patient) and pour off the excess water.

On testing, I found that a bit of the water soaked into the plaster, so if I do this again, I will add water-based paint to seal the plaster. Also, if I did this again, I might use cement.

My first tests revealed that the rain gauge still blew over, so I made a stand for it from scrap timber. The second and third pictures show the basic design, near enough for you to make your own.

The wire came from a coat hanger, but note the spiral on the dowel. This is a special feature, because when you hold it, the spiral will slide up and down the dowel stick easily enough.

When you let go and it is hanging under its own weight, it clings.  You can see this in the second photograph.

I used this design feature later when I was rigging home-made stands for lights than I use for close-up and micro-photography—I'll talk about those some other time.

To finish it off, I suggest adding a scale up the side.

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This blog covers quite a few different things, so I tag each post. I also blog about history, and I am currently writing a series of books called Not your usual... and the first two have been accepted by Five Mile Press, The offcuts appear here with the tag Not Your Usual... . For a taste of Australian tall tales, try the tags Speewah or Crooked Mick.   For a miscellany of oddities, try the tag temporary obsessions. And language us covered under the tags Descants and Curiosities, while stuff about small life is under Wee beasties.

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