StillSmart

whats the best and workable size of copper for making a
coil,8mm,6mm or 3/16

This is mine...

and...


...I made this one out of 6mm tubing and it is the perfect size for a 2" or 54mm column.

Winding was relatively easy after I read this...
Good luck with it

AM

I also used 6mm, mine is just a single coil not a double like Adian's. I stuffed a scrubber in mine for a bit of turbulence since it was only a single winding.

Really nice, Ive had a go twice before but wasnt very successful. I always seem to get the inner coil way too flat or of course kink it. Do you pump through it or use mains

I'm on mains, but I doubt I'd have any issue if on a pump, it's free flowing.

I used a solid stainless steel rod as a mandrel for the inner coil and used gardening gloves, the kind with the rubber coating on the palms and fingers, to keep a good grip on the tubing. I think the secret is to keep good pressure on the copper tube as you use your thumbs to shape it onto the mandrel.

AM

Re-reading these posts its just occured to me that when I tried it my tube was 8mm. I can see that smaller tube should be easier to work with but do you not get problems with flow resistance

My 6mm coil, pictured below, runs silent and completely knocks down the vapours from my 2" column of my 50l boiler at full flow.

I've never had any 'flow resistence' problem and I think that would only occur if your coil was being fed from a pump with a fixed pressure that was too high for the coil. However, once your cooling water is coming from a tap you can control the pressure to the coil.

I reckon if my coil was half the size it is it would still knock down all the vapour in my VM column during full reflux.

I used 6mm tube because I wanted a twin coil to fit inside a 2" column. If you use 8mm tube you would only be able to fit a single coil, maybe with a cold finger, into a 2" column

AM

My coil is a bit ugly, but it is 6 mm too. I took a slightly different approach and used two 6mm T's so I have a centre feed (straight bit of 6 mm) going into 2 parallel 6 mm coils.

Mine was salt filled and the inner coil was wrapped around a 15 mm tube, the outer was wrapped around a 35 mm tube. In the long run it is better to improvise a mandrel and just wind a double coil, then use paper to create the gap before winding the outer coil.

I have also made them in 1/4" brake tube which is easy to wind empty. You can do it in 8 mm, but it is harder to do.