A torus is a circular tube. You might want to make one as part of a toy or ornament, for a school science project, or, as in my case, as part of a prototype to test an invention. Bending metal tubing requires a completely different process to bending PVC (plastic) tubing. There are at least three reasons why you would prefer PVC over metal.
There might be easier methods, but the method i'm going to describe worked the best for me. I am using a tube of 25mm outer diameter with 'walls' 2mm thick. The diameter of the torus in relation to the tube diameter is rather small. That is, i need to bend the tube a lot. This caused problems which i had to solve...
Printed on the tube is "25mm".
To make a torus of diameter D, the tube at the end of the whole process will be D times pi. For instance, i want a torus with average diameter 230mm, so the length of the tube (circumference of the torus) will be 230 times 3.1416 = 723mm. So you need a piece of wood (the "mould") at least as thick as your tube diameter (e.g., d = 25mm) and big enough for you to make a hole in it, where the hole is D + d.
The problem is that if you try to bend the whole length of the tube (e.g., L = 723mm) to form the torus in one go, the ends of the tube will probably deform due to the heat (see later), and if you use a piece of tube even slightly too long, you'll have overlap in the mould and the torus will be deformed. The solution: make two crescents. The length of tubing to make the crescents is L/2 + 100mm. L/2 is half the circumference and 100mm is an extra piece which you'll cut off later to get rid of the deformed ends.
You will need
These are the steps:
You'll find that the ends of the crescents are deformed due to handling. From each end, cut off half of what was added (i.e., 100mm/2 = 50mm). Now you should have two half circles. Glue them together with "PVC cement" to get your torus!
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