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General discussion, chatting and admin contact => General chatting => Topic started by: Downunder35m on August 04, 2018, 06:00:31 AM

Title: Isn't there a better way to make a custom toroid?
Post by: Downunder35m on August 04, 2018, 06:00:31 AM
I looked around for sources of more or less well fabricated toroids.
Nothing in copper of course but at least some are available in aluminium.
But IMHO the prices I have seen do not justify the high price.
Back in my big spark gap days I mainly use tube cages or in some cases stianless steel spheres as a stack.
For a desktop model however this is not to my liking as one day I would like to have something that not just works but also looks nice.
On my tiny lathe I could try to make forms for rolling my own toroids but only to about a diameter of 15cm, thanks to being a tiny lathe...
So what other options for something with a really smooth and nice look are there that can be done on a hobby level?

Ducting, no...
Polystyrene rings, maybe but still a ton of work and definately not easy to get a mirror finnish...
Baking dishes, again maybe but hard to find something that would make a true donut or better still a toroid without major surgery.
And while doing all sorts of weird Ebay searches I found something that might be worth to consider.

What about 180° pipes?
Commonly used for cars and exhaust system in 3 and 4" but certainly also used in oher areas and diameters.
For some configurations it should be possible to get a suitable radius and pipe diameter to make a decent toroid...
But still not really something for a custom creation to fit a specific coil...
Or does anyone happen to know how to get a 60mm copper pipe into a smooth ring?
1.2mm thick walls too LOL

So I thought it should be possible to combine pipe bending with a slightly different cage cage design.
Sure someone has done it before but I could not find any references, so I will try to explain it:
If we take standard copper plumbing tubing then we can use springs or fill it with sand to bend it into any diameter the pipe allows for.
Using a suitable template like a PVC pipe, thick carboard tube or just wooden disks it should easy to create rings that create a donut from several copper rings.
Correct me if I am wrong but the "grooves" between the pipes should not be a problem for arcs as the pointy bit faces inwards?
And yes, I know that such a design would be really heavy but if done well it should look really nice once polished ;)

Last though: Conductive paint and/or electroplating/electrolyse things?
Every time I am welding stuff that needs corrosion protection I use zink or aluminium spray that also allwos to weld through if required later.
At least the aluminium type gives a semi gloss to satin result on smooth surfaces.
The zink based stuff looks more like a surface powdered in grey.
From experiments I know that for copper plating zink I need a cyanide based first plating bath and won't go that route again.
Aluminium should be straight forwards at least in theory.
During my tests I noticed that the aluminium parts often oxidise faster than what I am able to clean and move.
Was a race of often 10 or more rounds until I got an even coating of copper all around bigger parts.
But using aluminium spray as a base for this??
Proper paint that is conductive enough and not carbon based cost a small fortune...
Not to mention the problem of keeping a very light toroid submersed or being able to remove the filling when done without causing damage...

There must be an easy and relatively cheap way to make a proper toroid with a copper finnish that does not involve machining or expensive tools.
So what did I miss?
Would it make a difference if inside the toroid is a solid disk or just wires like on a bicycle wheel?
Title: Re: Isn't there a better way to make a custom toroid?
Post by: Nijin on August 04, 2018, 11:25:14 AM
I recommend you to make a toroid with multiple aluminium pipe. You can design it with JavaTC3D "ring toroid". This type of toroid has a greatter surface, a better look and you can adjust both diameter of the toroid.

I made a 104*28cm toroid with 7x 30mm alumimium pipes and It's the best toroid I've made even if bending 30mm pipe is very difficult. I recommend you to use more pipes with a lower diameter like 6 or 10mm depending the size of your toroid.

If you want more information about this type of toroid, you can check the facebook of Franzoli Electronics.
Title: Re: Isn't there a better way to make a custom toroid?
Post by: Downunder35m on August 04, 2018, 07:16:57 PM
So you are saying that apart from looks there is no realy benefit?
Id a pipe cage performs as good as a real toroid then I might have to reconsider my approach and go for simple instead.
Title: Re: Isn't there a better way to make a custom toroid?
Post by: Nijin on August 04, 2018, 07:22:38 PM
No, the most inportant benefit is the simplicity and the cost to make this kind of toroid. A spun toroid is difficult to find and expensive. With a skeleton toroid, you can adjust the height and the width and this will change electrical properties of the toroid.