Finally - a decent coil :)
Posted: Thu Sep 27, 2012 9:22 pmFor my VM build I've been trying to wind coils and despite all the help, ideas and assistance out there (thanks YHB and AM) it just hasn't been working out the way I wanted.
Until today !!
I'd wound two coils and they would work but I wasn't happy with them - and as I had more copper I tried again.
I wound the copper by hand into a 6" coil with the last 12" pointing out from the coil. I picked a 6" coil as that is the max size I can fit in my furnace, heated the ends of the copper tube till they glowed red and immediately quenched them (copper unlike ferrous metals needs a rapid cooling not a slow cooling - thanks YHB), then I heated the remainder of the tube and threw the entire coil in the water bath. I paid specific attention to the ends of the tube as this is the bit that is going to work the hardest in the next section so it needed to be as soft as possible.
I had three bits of coper so I did this three times.
Then I followed the fill with water instructions (fill with water, crimp the tube near the end, solder one end, crimp and fold the other end as per this HD thread http://homedistiller.org/forum/viewtopic.php?f=17&t=28908&p=6983879&hilit=Winding+a+Coil+Condenser#p6983879) except this time I didn't solder the end - I filled the tube with water, crimped them enough to stop the flow, then clamped the entire last 4" of tube in my vice and squeezed it flat, then I folded the end over and around itself until it looks like a snail shell. Then I did the same with the other end.
Total time to anneal the tube, fill it with water and crimp the ends. 30 mins per tube.
I then found a larger mandril - a 20mm steel pipe. This is for a 54mm diameter column so there was plenty of room. I just held the tube across the pipe so the tube hung down across it and turned it round. The water in the tube will stop the tube from compressing (provided the water completely fills the tube)
In the past I'd been trying to keep the pressure on the tube as I wrapped it. This time I didn't. I'd wind a loop, stop, tweak it into the right place with a screwdriver blade and then start again. I got as far down the middle winding as I wanted, slid a short loop of cardboard over the inner loop (so I could still grip the centre copper) and simply started back up with the outer winding. Again stopping as I went to adjust the coils with the screwdriver. When I got to the end of the first piece of cardboard I added another wich cover the complete centre winding
Once I got to the start of the centre wind I bent the tube up to finish it off.
Total time to wind it. About 15 mins
I soaked the cardboard off, cut the ends of the pipe and blew the water out of the tube.
Job done, nice and easy
Key learning points for me.
1. Don't assume that annealed copper tube has been annealed properly. The difference between 'factory annealed' and "annealed by me" was incredible
2. Don't use a small centre mandrel if you don't have to - I could have used 22mm pipe - in fact I might on the next one !
3. Don't worry about stopping - I wound the inner coil and then went out for an hour. The copper didn't seem to mind.
Until today !!
I'd wound two coils and they would work but I wasn't happy with them - and as I had more copper I tried again.
I wound the copper by hand into a 6" coil with the last 12" pointing out from the coil. I picked a 6" coil as that is the max size I can fit in my furnace, heated the ends of the copper tube till they glowed red and immediately quenched them (copper unlike ferrous metals needs a rapid cooling not a slow cooling - thanks YHB), then I heated the remainder of the tube and threw the entire coil in the water bath. I paid specific attention to the ends of the tube as this is the bit that is going to work the hardest in the next section so it needed to be as soft as possible.
I had three bits of coper so I did this three times.
Then I followed the fill with water instructions (fill with water, crimp the tube near the end, solder one end, crimp and fold the other end as per this HD thread http://homedistiller.org/forum/viewtopic.php?f=17&t=28908&p=6983879&hilit=Winding+a+Coil+Condenser#p6983879) except this time I didn't solder the end - I filled the tube with water, crimped them enough to stop the flow, then clamped the entire last 4" of tube in my vice and squeezed it flat, then I folded the end over and around itself until it looks like a snail shell. Then I did the same with the other end.
Total time to anneal the tube, fill it with water and crimp the ends. 30 mins per tube.
I then found a larger mandril - a 20mm steel pipe. This is for a 54mm diameter column so there was plenty of room. I just held the tube across the pipe so the tube hung down across it and turned it round. The water in the tube will stop the tube from compressing (provided the water completely fills the tube)
In the past I'd been trying to keep the pressure on the tube as I wrapped it. This time I didn't. I'd wind a loop, stop, tweak it into the right place with a screwdriver blade and then start again. I got as far down the middle winding as I wanted, slid a short loop of cardboard over the inner loop (so I could still grip the centre copper) and simply started back up with the outer winding. Again stopping as I went to adjust the coils with the screwdriver. When I got to the end of the first piece of cardboard I added another wich cover the complete centre winding
Once I got to the start of the centre wind I bent the tube up to finish it off.
Total time to wind it. About 15 mins
I soaked the cardboard off, cut the ends of the pipe and blew the water out of the tube.
Job done, nice and easy
Key learning points for me.
1. Don't assume that annealed copper tube has been annealed properly. The difference between 'factory annealed' and "annealed by me" was incredible
2. Don't use a small centre mandrel if you don't have to - I could have used 22mm pipe - in fact I might on the next one !
3. Don't worry about stopping - I wound the inner coil and then went out for an hour. The copper didn't seem to mind.
I love it when a plan comes together 
