Drop tube pan build

[saekeaton64]

About a month ago I added 80 drop tubes to my 2'x4' flat pan, I wanted to wait and test everything out before posting any pics. The drop tubes have made a great improvement on my evaporation rate.

The tubes are 3/4" x 6" type m copper tubing, I used cutout 2"x4" blocks to hold the section of tubing in a bench vise. Once the tubing was in place I would slide a fender washer and spacer over the end of the tubing. I then used a flaring punch (homemade) to expand the end of the pipe.

[saekeaton64]

Using a 3lb. sledge hammer, I tapped the flaring punch a few times until the end of the tubing looked like the picture below.

[saekeaton64]

Once the end of the tube was flared, I needed to make it flat. I inserted the next tool into the tube and smacked it 3-4 times pretty hard with the 3lb. sledge. The end rolled over nicely.

[saekeaton64]

Once all 80 tubes had the end flared, I made a guide using 1/4" plywood and my plasma cutter to evenly cut all the holes into the bottom of my pan. (Once you make that first cut you really hope it all works out). Using silver solder, I presoldered the flat ends on the tubes and a ring around each hole in the pan. I them dropped the tubes into thier locations and applied heat inside the tube until they sucked down tight to the pan. I was trying to do this on the cheap so I decided to crimp the ends of the tubes instead of using caps. ( Buy the caps - trust me).
Once I though I had everything soldered up I did a test fill to check for leaks (Only had 4, not to bad i think).

I cleaned the pan with a baking soda boil and a good bit of scrubbing, and it works great. I have easily doubled my evaporation rate.

[Waynehere]

Looks great and nice rig you setup for flaring those ends. I did a similar setup on a 2x3 pan for a flu pan. With the setup I now have, I am getting about 35 gph. The AOF really helped though too.

Good luck...

[Mogli]

Did you have to anneal that copper tubing, also is type m the thicker wall?

[RileySugarbush]

Very nicely done!

[saekeaton64]

Type m copper is thin walled, no I didn't anneal the tubing. On the first practice tubes I made I tried to anneal them and the copper would wrinkle when I would try to drive the flaring tool in.

[b116757]

Very impressive work you posess a great deal more patience than I.

[Waynehere]

I did anneal my ends and the first couple squashed from hitting too hard. I will have to try without next time though... Thanks for the tip...

[BobMac]

Would stainless steel tubing work the same as cooper??or is it the cost difference for the cooper??Stainless tubing could be welded to the pans.Maybe cooper transfer heat better too?

[saekeaton64]

There is another drop tube thread on here about someone using stainless tubing. Yes, it can be done but copped tubing is much cheaper and easier to come by. Copper also has a better thermal conductivity than stainless. I think that trying to weld all those tubes on would be a PITA.

[Waynehere]

There is another drop tube thread on here about someone using stainless tubing. Yes, it can be done but copped tubing is much cheaper and easier to come by. Copper also has a better thermal conductivity than stainless. I think that trying to weld all those tubes on would be a PITA.

Man did you hit the nail on the head with trying to weld SS to copper. I was going to simply silver solder my main pan until someone talked my partner into welding them in. Of course I was all for it if it wasn't going to be too much more. But the welder guy wouldn't give me a quote or estimate. Said he would work it out with us. Well, he couldn't get the copper to weld to the 18 gauge bottom, ended up cutting it out and put in 10 gauge without asking me. Then slaps me a bill of over $800!!! Not a happy camper. I could have bought a regular fluted SS pan for what I have into this pan now....

[Mogli]

Trying to solder a cap for a sink drain at the moment. What type of flux did you use to tin around the holes in your pan.

[Waynehere]

I used silver solder with a liquid acid flux. The hard part is getting the metal clean with the flux.

[Mogli]

What type/brand of flux did you use. The oatey paste Im using does not work with stainless now that I looked it up. Sadly doesn't say that on the package.

[b116757]

Go to your local weld shop and ask for Harris Stay Clean tinning flux or if they don't have Stay Clean get whatever tinning flux they have it's the stuff I use to fix radiators on the trucks and tractors when I run a tree branch into them around the farm

[saekeaton64]

I used Oatelys liquid flux, I bought it at Menards. Any plumbing supply or big box store should carry liquid flux. Be very careful when using it and don't breath in the fumes as it contains acid.
When I was tinning my pan; I would heat the area around the hole with a propane torch first then squirt some flux on that spot. I would then reheat the area until the flux turned dark brown, then apply the solder.

[calesdad]

Nice build, that looks great.
Has anyone ever thought of sticking the tubes up into the pan (like a raised flue) rather than below the pan? Would it work?

[Mark]

I have seen the tubes horizontal so the fire passes through the tubes. The pan is dropped down in the middle about the diameter of the tubes.

[saekeaton64]

I don't know if having the tubes sticking up into the pan like a raised flue would work as well. In a raised flue design the heat and flames are forced into the raised channels by the arch, I think that in the tube design the fire and heat would just pass under the tubes because there is nothing to force it up in there. The horizontal design also works very well, similar to a steam boiler, the only down side I think would be trying to clean under the tubes.

[wnybassman]

I don't know if having the tubes sticking up into the pan like a raised flue would work as well. In a raised flue design the heat and flames are forced into the raised channels by the arch, I think that in the tube design the fire and heat would just pass under the tubes because there is nothing to force it up in there. The horizontal design also works very well, similar to a steam boiler, the only down side I think would be trying to clean under the tubes.

Not to mention you would need enough sap depth to cover the tubes. That's a lot of sap.

[Mogli]

I used Oatelys liquid flux, I bought it at Menards. Any plumbing supply or big box store should carry liquid flux. Be very careful when using it and don't breath in the fumes as it contains acid.
When I was tinning my pan; I would heat the area around the hole with a propane torch first then squirt some flux on that spot. I would then reheat the area until the flux turned dark brown, then apply the solder.

That's odd on oatey's site they say not to use it on ss.

[saekeaton64]

I guess I overlooked that when I bought it, I can say that it does work though and I have not noticed any reaction to the areas of the pan that were contacted by the flux.