5 ft diameter copper rings.

I need to manufacture several rings of 5 feet diameter, in 28 mm copper pipe (domestic plumbing variety). Apart from filling with, sand, heating with a propane torch and bending around a fabricated former, is their an easier way?

Andrew.

You should not need to anneal, fill with sand, etc. But you will need to make a bending form.....

Pete

Possibly a pipe roller with three deep grooved rollers, the middle one being adjustable?

Neil

The best way is like Neil said and use a pipe roller.

.

OK I am curious as to what they are for.?

Anything to do with an antenna.?

Nick

How round do they need to be? can you do them threepenny bit shaped using a pipe bender?

.

Showing your age there Duncan.

We have a modern version these days.

Nick (who also remembers thrupunny bits)

It is for use as a toroid on a large nasty Tesla coil! They normally a have spun aluminium toroid, done in two halves and then tig welded together. The cost of very large toroids becomes astronomic,so a smart Danish guy replaced the toroid with six tubular elements which are spaced in a circular cross section to emulate a toroid, so there are two each of the same diameter.

Aluminium tubing is preferable for weight considerations, but about 3 times more expensive than copper. If you want to see the Tesla in action, we ran it up in a nuclear hardened hangar at the old USAF base at Alconbury. There is a U tube video of it destructing on its final run. We had a nasty strike on the secondary which caused some havoc. Just finished repairing the tube today.

The U tube video is to be found by using the reference **LINK** For some reason I cannot underscore the Bg, on the original link I had, it was underscored and you could click on it to bring up the video.

Well worth the effort to do it manually, it really is amazing! Maybe a computer savvy Moderator could sort it out please?

Andrew.

I think this works

**LINK**

copy and paste the link, don't try typing it in

Edited By duncan webster on 08/09/2017 21:23:03

.

Andrew that's ace.

Nick

Thanks Duncan,

It is indeed the dying throws of the Tesla. I didn't realise that you had to copy and paste a U tube link. You live and learn!

I think we could get away with a three penny bit type of shape. If you look at the "toroid" on the video, it is made up of what we think are some form of air ducting components , That one cost my pal £400 about three years ago from a guy in Switzerland. He said he would not make a crate for it to be transported to UK, so a Polish guy did a round trip (via Poland!) to pick it up with car and trailer and that was another £400. Glad I am not paying for my friends Tesla hobby!

As a matter of interest we were using an 11,000 volt pole transformer. Feeding the 240 volt "secondary" with 260 volt AC (via a huge variac), The Tesla was pulling about 50 amps on the 260 volt AC input to the pole transformer! The whole thing is bloody lethal! I kept well away I can tell you, having earned my keep as a high energy accelerator physicist, I know how to keep clear of high voltages.

The final few frames show the path of a globule of molten copper, as it was ejected from the beautiful secondary coil that I and my friend wound together!

Andrew.

Edited By Andrew Tinsley on 08/09/2017 21:44:28

At 5ft dia. you should be able to bend it with a simple bending spring down the pipe. I've done plumbing bends tighter than that, but the modern pipe is thinner ,and I think, harder. Assuming no great tolerance is needed.

Here's some fun advice on hand-bending from Volume III of the Newnes Complete Engineer, circa 1930:

The period being discussed is about 1900. At that time bending was a speciality of the Coppersmith and the Anglesmith. I wonder if the latter trade still exists?

Anyway, note the requirement for 'highly skilled' work needed to tidy up after the bend is made . That's why the article strongly recommends using a bending machine whenever possible. It prevents kinking and rippling by properly supporting the work. To prevent leakage I think the top load of a Tesla Coil should be as smooth and polished as possible, so a really good job on the toroid should deliver more volts. Quite a challenge to make such a thing, and seriously difficult to do a top-notch job.

Excellent project by the way: but where did the Power Transformer come from? I want one!

Dave

There are plenty dotted about the countryside, anywhere there is an 11,000 volt distribution line, you will find them on the poles feeding maybe a farm or an isolated house!

Seriously they are much rarer than hens teeth in captivity. This one came off Ebay, so at least we didn't pinch it!

Andrew.

Cut a ring of ply & surround it with some wood blocks to hold the pipe in place. Bend the pipe round the ply by hand. If it is underground copper it will bend Ok.

Take it to a local steel playground/street furniture company. They may have a ring bender.

OK, so what is underground copper and why does it bend more easily?

Andrew.

My memory is fading & i am well out of date on codes etc. I left the family building firm in 1980 to form a Joinery Co & although I did have my own building company for 20 years I sold the main operations in 2000. Retirement does not help much.

But here goes:-

There are (or were) 3 grades of copper pipe.

Those were table X,Y & Z. They relate maleability of the pipe .From memory table Z was for pipework underground & was more maleable with thicker walls. I still have a coil of imperial copper underground at the side of my garage.It is 3/4 inch pipe & is coiled in a 2 ft diam coil. that is how they used to supply it as it came in long lengths. X & Y came in 6M lengths. If I knew how to post photos I could post a picture of the coil to prove it

Table x was thinnest & was bad for bending due to thin pipe walls.This was cheaper of course & is probably what one buys from the likes of B & Q these days. One would have to use more fittings in the installation. Table Y could be bent easier & could be formed around obstructions such as piers in walls etc thus saving in fittings & labour soldering or using compression fittings.

Somebody will correct me about the codes , as they have probably changed

Edit

Just looked on Wednesbury's website & 28 mm copper ( Table Y) can be supplied in coils anyway so you can just expand the coil to the size you want

http://www.wednesburytube.com/Size-ranges.cfm

Sorry that should have gone as a "link" not the full URL- that will irritate Vic!!!

Edited By Sam Longley 1 on 09/09/2017 22:21:54

Has your friend been inspired by this - BIGG TESLA COIL OF OKLAHOMA ? (sorry, not sure how to post a link)

Thanks Sam,

Your information is extremely interesting! I never knew about the grade of copper pipe that came in coils. Looks like a good solution!

Anthony,

My friend has been building Teslas for about 10 years. he is very familiar with the big coils in the US, but that wasn't the reason he started building. I think he got fed up with his Wimshurst machine and wanted something more spectacular.

I suspect the coil in the video is probably the largest in Europe. It operates at a 100 BPS (breaks per second) and uses a rotary spark gap to do the switching. The toroid is really too small hence the need for a 5ft replacement. With that, it should be even more spectacular and the larger diameter would help to make strikes on the machine base less likely. As it is the device is really very impressive, but the whole set up is really rather too dangerous for my taste!

Andrew.