Originally posted by p75213
View Post
As far as a practical answer to your build question, the simplest way is to use a cylindrical coil form big enough to fit around all the secondaries. PVC works but is harder to find in larger sizes. I have used the cardboard tubes that are sold for use as concrete forms (for pouring piers and bases for things like lamp posts and street signs). These work, although I learned from my SSTC that the black writing on the outside of the tube has enough carbon content in the ink to be CONDUCTIVE. I didn't know this until my tube started smoking and actually burning around the writing. Thankfully it was just smoldering and it went out on its own when I cut the power off. It ruined my secondary by shorting some turns though, so I had to wind another one. This time I peeled the outer paper layer off and sanded any remaining bits of writing until it was clean enough.
For holding the turns in place, obviously the easiest idea is the one you're already using: just drill two holes. However, if you have tubes in a number of different sizes and your wire is rigid enough, you can wind the right amount of wire on a smaller diameter tube, coiling it tightly enough so the wire yields and conforms. Then slide it off that form and work it progressively around your bigger form without uncoiling it, and it will have some tension. This can be a bit tricky depending on how much wire you're working with, it's like holding one of the "slinky" spring toys.
Leave a comment: