spiral coil in copper tubing

In the ham radio world, we wind big coils, of large diameter wire and small copper tubing, on a form and then let them expand to the desired diameter.. Takes a bit of experimenting to get the correct size form. But, for 5/16 copper tubing, I would suspect the coil form should be close to the desired ID of the coil. You won't get a lot of expansion. As for the spacing, between turns, you can wind a spacing material along with the coil and the remove it after the coil is wound. Since you specify 5/16 tubing and 5/16 spacing, wind two tubes at once.. And, this tubing is stiff enough to enable you to 'adjust' the spacing manually, if required. The technique is fairly simple. Anchor one end of the tubing to the coil form and start winding.. Take your time and you won't kink the tubing. !

Larry Keith KQ4BY

I posted a similar question a while back, no responses :^(. But I'll be watching to see if you get any bites .....

John

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I have seen how red hot steel rods are bent into coil springs. They are made on a spinning horizontal cylinder. I would try something similar to that for your application. You could make one coil out of one continuous piece of copper provided it was long enough.

Find the proper diameter pipe. You can probably find it at a scrap yard. You will have to have someone with welding/cutting equipment. You will have to weld some bars across the ends so that you can mount it on a rod so that it can spin horizontally along the center point. You will have to make a crank on one end. Drill a hole near the crank end of the pipe that is large enough to insert the end of the tubing. Insert end of tubing. Have an assistant turn the crank. The second person feeds the copper tube onto the cylinder, and paces it so that the proper distance between turns is made. You will have some waste by cutting off the inserted part, and the amount left over after the spiral is made. Do your best to make it in one continuous movement without stops and starts.

Like anything else, the more you make, the better you get at it, and the more tricks you learn. First ones would be hard and take a while, but then you could probably make lots of them for fellow 'shiners. ;-)

Good luck

Steve

Naturally a silver plate job takes place after bending...

Martin

Look at this setup;

I'm trying to figure out a way to coil a helix one inside the other. I could just make three or four progressively larger coils and then braze them together but I was trying to figure out how to make it one continuous coil to save on that labor and the possiblility of a leak at one of the joints.

John

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How about sleeving the joints? Swedge the ends to fit inside the next larger diameter tubing. Slip a bit of the next larger tubing over the two ends, apply heat and solder...

No idea if proper diameter tubing is available. Just thinking out loud, so to speak.

Gunner

"At the core of liberalism is the spoiled child - miserable, as all spoiled children are, unsatisfied, demanding, ill-disciplined, despotic and useless. Liberalism is a philosphy of sniveling brats." -- P.J. O'Rourke

No problem. Wind the innermost coil first. When you get to the end, wrap the coil with a spacer material, open out the rolls a bit to get a larger diameter coil and start winding back until you form the second coil over the first. Remove the spacer material. Repeat as needed. All one piece, like fishing line on a reel.

Gary

I think you may have misunderstood me? Each coil, all of the same diameter tubing but coiled in progressively larger diameters, would be swaged at the ends for brazing together. I can do this without a problem, it's just if I can figure out a way to coil three or four coaxial helixes then I can save the step of having to swage and braze each end. BUT, I can't figure out how to do it.

Now what Micheal was thinking of may be easier. Making successive spirals, instead of helixes. The only problem here is how to make a spiral :^). If you use a three roller method to make the curve, the middle roller would have to move away (and towards) from the infeed and outfeed rollers *as* you are rolling the spiral. That shouldn't be too hard, just a gearing problem. Once you've wound a spiral is to the correct number of loops you would just pull it outward, to make room for the next spiral, and reverse the direction of the gear driving the middle roller. For instance, making the first spiral from the center outwards, the second from the outside to the center, the third from the center back outwards again, etc. Pulling the finished spirals out away from the three rollers each time to make room for the next spiral. The thread pitch/gearing ratio of the middle roller would determine the spacing between the tubes in the spiral.

John

Please note that my return address is wrong due to the amount of junk email I get. So please respond to this message through the newsgroup.

I vote for this, and I am sure Harbor Freight's $50 ring roller can do it but only in 1/4 inch tube, not 5/16.

You just adjust and crank, and if possible crank and adjust at the same time.

Take a piece of paper and count crank turns and adjuster knob turns to add OR subtract roughly 5/8 radius on each lap. Then interpolate outward while cranking, while pulling the coil away from the rollers along the axis of the coil. Then interpolate inward while cranking, same way.

You could make a stack of eight if you could find a nice long piece of soft tubing and uncoil it nicely on a stand made for just this job, out of wood.

Yours,

Doug Goncz (at aol dot com) Replikon Research

Replikon Research researches replikons, which are self-reproducing configurations of non-living matter in environments that support replication, analogous to organisms living in ecologies.