Metal tanks- Boils Law

[John Carrodus]

During open forum last week it was suggested I write this up. My fkying buddy a week or so ago yelled out - "Yer tanks leaking." In a state of denial I removed said tank and tested it. It did not leak. ( Obviously something else - umm still working on that one!) How do I know my metal tanks don't leak? Bear with.......
 I use liquid flux to build tanks. Why? I simply lose the will to breath when I try super polishing the metal clean and dicking about with core solder. ( It kind of works , but I'd rather do something else than struggle with trying to glue bits of metal together with blobs of mercury that don't flow) I have a grunty soldering iron with two settings and never have a problem with the solder freely running into the joints. Most of my joints are folded with ears that wrap over the adjoining face.

However .......The tank MUST be
                         A) Pressure tested. ( especially if buried inside a built up fuse.)
                         B) Flushed thoroughly to remove flux and moisture and treated to prevent rust.
I found a while back , putting the tank in cold water blocking the vents and blowing into it tells you virtually nothing.
Putting it under water just off the boil will reveal all! Even then, some tanks do not leak until 5-10 seconds have passed and pressure has increased.

Most times your tank will pop some bubbles. Seal em and retest until you are 100% sure.

Now the cleaning and treating. Begin with flushing the tank with meths, then some fuel, then some light oil - diesel, kero. The put tank in a warm oven, the window sill in the sun, or even carefully wave over a quiet flame. Flush with some fresh fuel and Bobs your uncle. ( Some guys put after run through their tanks after flying to retard the rust forming.)

Good Luck

[John Carrodus]

I forgot to say. After testing , BOIL the tank in water for 10 minutes, then flush with meths , etc etc.
Cheers again
John C

[Steve Helmick]

The tank not leaking is 1/2 the battle. If you have a commercially made tank, or you used brass tubing, the tubes inside could be porous and cause grief. Especially the uniflow tube, if porous, is no bueno.

When I muck about with a tin tank, I like to put a flat washer at the joint where each tube pierces the tank hull. This reinforces the tube/tank joint, but does add weight. Weight up front...and the added weight is to the front end of the tank...isn't usually a bad thing, and beats heck out of a leaky tank.  Steve

[Brett Buck]

I use liquid flux to build tanks. Why? I simply lose the will to breath when I try super polishing the metal clean and dicking about with core solder. ( It kind of works , but I'd rather do something else than struggle with trying to glue bits of metal together with blobs of mercury that don't flow)

I am not sure what kinds of solder or material you are attempting to use but I have had no problem building 100's of tanks with "core solder" - by which I presume you mean rosin core solder. And I am not sure what you think you need to do extensive surface prep, you basically take the tin out of the package and start soldering. It flows out easily with very little heat and I have and many others have made tanks with as little as a 15-watt uncontrolled  electronics iron, mine acquired from a convenience store and costing about $5 in 1971.

     Additionally, while you might have had some problem with 50/50 solder or RoHS solder (not recommended), it is quite literally impossible to get "blobs of mercury that don't flow" with 63/37, there is no "plastic phase" to speak of, so it can't blob up without a concerted effort.

   There are moderately safe liquid fluxes (i.e. safe from corrosion), they are more-or-less just rosin just like in the core of rosin-core solder. The less-safe versions all have a tendency top corrode the tank, to the point that tanks can simply corrode away even after extensive flushing with water/alcohol/lacquer thinner and glow fuel. I am not sure what "meths" might be, maybe methyl alcohol (methanol). Even something mild like Nokorode should be named soemthing like "less corrode" because while it is about the mildest paste flux you can easily get, it still causes ferrous metal to rust in short order.

    Obviously you can do as you please, but I would very hesitant to recommend almost any liquid or paste flux for tanks, it is just not necessary and more-or-less gaurantees a problem later with corrosion.

     Brett

[Brian Hampton]

I am not sure what "meths" might be, maybe methyl alcohol (methanol).

I'll take a punt he means methylated spirits (or metho) which is what you guys call denatured alcohol.

[John Carrodus]

Brian - you are correct...Hic!

Brett, when I'm ( rarely) messing with or making metal tanks the way I make tanks now - works for me with no corrosion problem, having learned the hard way in my earlier days.  I will probably use brass next time ( if )I make a tank as I now have a sheet of it to play with.

My issue here is BOIL the tank. Unless really pressure tested IMO, it an't 100%.

To be honest I'm now pretty much converted to plastic tanks and inline filters for several reasons- simpler and transparent is 2 of them. 

[Brett Buck]

Brett, when I'm ( rarely) messing with or making metal tanks the way I make tanks now - works for me with no corrosion problem, having learned the hard way in my earlier days.  I will probably use brass next time ( if )I make a tank as I now have a sheet of it to play with.

  What type of flux are you using? What material are you making it from?

    I suggest "tin", as in "tin can", which is really steel with tin plating. .008 is widely available, does not require *any* surface prep, and light enough. Brass is easy to solder and requires no surface prep to speak of, but is highly prone to cracking or corroding. Use 63/37 or 60/40 rosin core solder, and copper - not brass - tubing.

     Brett

[John Carrodus]

Brett Hi
The tin I attempted to use in my earlier day were from bug coffee tins, large fruit tins, baked beans etc. The metal was cruddy and corrosion was a problem.

I then started using good stuff with a good tin coating - as sold in model stores for tanks and other bits.

A flux called Duzzel, magic but very corrosive.