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Author Topic: tank thicness  (Read 1974 times)

Offline Joe Hunt

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tank thicness
« on: September 02, 2019, 06:47:43 AM »
i want to make a 3 oz fuel tank for a model i am building and would like to know what thickness metal is normally used. i have access to .012 brass, will this work?  thanks, joe hunt

Offline Will Hinton

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Re: tank thicness
« Reply #1 on: September 02, 2019, 07:07:28 AM »
Way back before I went exclusively ot plastics I used .010 brass and they were fine.
John 5:24   www.fcmodelers.com

Offline FLOYD CARTER

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Re: tank thicness
« Reply #2 on: September 02, 2019, 09:45:28 AM »
I've made tanks from brass shim stock from auto supply.  They all eventually sprung leaks.  That's because tanks require some very sharp bends in construction.  The brass fractures along the bends, and engine vibration only hastens failure.  K&S tin plate makes the best tanks.  This is a hobby item sometimes available at LHS, but can be ordered from the major model suppliers.
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Online Paul Smith

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Re: tank thicness
« Reply #3 on: September 02, 2019, 10:28:55 AM »
I go down to .007" brass for smaller tanks.  It's strong enough and easier to bend in the smaller sizes.

Yes, brass can fatigue and leak, but I blame that mostly on poor mounting that induces stress cracks.   
Paul Smith

Offline Brett Buck

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Re: tank thicness
« Reply #4 on: September 02, 2019, 10:42:59 AM »
i want to make a 3 oz fuel tank for a model i am building and would like to know what thickness metal is normally used. i have access to .012 brass, will this work?  thanks, joe hunt

   It will work, but as noted, cracking is a serious issue unless you are very careful to radius all the bends. I am not sure how much it work-hardens or if annealing it would help.

    Most people use the .007" K&S "tin" sheet, which tin-plated steel and very tough.
 
   Brett

Offline Joe Hunt

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Re: tank thicness
« Reply #5 on: September 02, 2019, 10:52:30 AM »
this stuff is 1/2 hard and the end die has about a 1/32 radius.   thanks, joe hunt

Offline Brett Buck

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Re: tank thicness
« Reply #6 on: September 02, 2019, 01:06:03 PM »
this stuff is 1/2 hard and the end die has about a 1/32 radius.   thanks, joe hunt

    I haven't experimented enough to tell if 1/32 is adequate or not. But even brass tubing, with a decently thick wall, is prone to cracking after extended exposure to glow fuel (possibly because it leaches out the zinc, I don't know for sure). It will work OK in the short term (a few weeks/months) but I wouldn't trust it for long term use no matter what you do.

     Brett

Offline Joe Hunt

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Re: tank thicness
« Reply #7 on: September 02, 2019, 02:48:56 PM »
thanks, i'll go with tin. hunt

Offline Dan McEntee

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Re: tank thicness
« Reply #8 on: September 02, 2019, 09:35:52 PM »
   Yes, go with the tin and copper tubing. I had read that it's the nitro (Chinese origin and more acidic ) that can get to brass. Jim Lee has a tool for bending tank material that has a nice little radius on it and makes fabricating tanks a bit easier.
    Type at you later,
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Offline Air Ministry .

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Re: tank thicness
« Reply #9 on: September 02, 2019, 11:40:04 PM »
Such Extravagance ! .

Usually cut up empty Thinners Cans . 1 gallon & 1 litre .
Need to be carefull , not to get blood on it . got a few pairs of antigue scissors from the op shop .
Generally a rough cut - roll flat - running a board along it helps . Then cut a straight datum edge .

Thickness is about right . Clean side is inside side .  :-\ Labels throw some thinner on , , or heat .
Bean cans in the youth went ribbed like the modern suckers . I use plubers ( bar ) solder , and acid .
Pre tin in places . Boil in baking soada water , rinse with thinner then fuel , if decadent .

The fuel rinse & you get a good needle setting straight off . Otherwise seems to take a few flights .

Offline Joe Hunt

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Re: tank thicness
« Reply #10 on: September 03, 2019, 04:28:13 AM »
matt, sounds like fun, hunt

Offline FLOYD CARTER

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Re: tank thicness
« Reply #11 on: September 03, 2019, 09:47:00 AM »
Food cans often coated with lacquer.  Hard to solder.  Not a good idea to use acid for soldering.  It will usually cause rusting.  Radio solder (rosin flux) is safe for tanks.
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Offline L0U CRANE

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Re: tank thicness
« Reply #12 on: September 03, 2019, 12:58:42 PM »
Agree. K&S .007 tin plate. This accepts a quite sharp bend. and is easy to form.

I do tanks a bit differently. The late lamented Kenn Smith(?) developed a square/wedge shape and manufactured them years back. I didn't know that, and also developed the same shape, and at about the same time.

These tanks have a rectangular front end, which changes to a 90° wedge at the rear face. The 'facets' - upper, middle and lower outside surfaces, that do the conversion are all flat triangles before forming. Simple!

I also put the soldered seams inside the shell. This adds two metal thicknesses of volume to the interior. The flat layout was made with a simple, but accurate drawing program (VISIO, f'goodness sake!). Printed it, spray-glued it onto K&S tin that had been painted with DyKem Machinist's Layout Blue. Delicate scribing with a trusty #11 blade does not damage the metal, but leaves bright lines for the bends.

Washed off the paper and spray glue (Ronsonol works well.) Good shears allow cutting ON the perimeter lines. Made all bends as 'outside,' so the interior remained 'clean' metal.  Then washed off the blue (Acetone or dope thinner.)

The only tricky part was cutting the end 'tabs' clearance notches. Used a pliers-type square 'nibbler'...

No form block! All bends were made 'in the air' so that the ends fitted closely, and inside the shell. Completed the shell except for the rear cap, then completed the (uniflow) plumbing, THEN used a scrap of 1/16 iron wire bent to an "L", temporarily soldered on, as a handle to install the rear cap.

Sta-Brite low silver solder, Weller gun. Flushed the interior with baking soda to neutralize the acid flux, first - then water flushed generously, then a spray of WD-40  get under the water, then fuel to coat the inside.

OBTW - pressure-checked every tank as soon as the surface seams were complete...

Sounds like a lot of work, and it takes a bit longer than just whacking K&S tin around a block. The 90° wedge FEEDS! You can design a tank in a dependable form that WILL fit the needed space in your tank bay.

I use the value of 1.80 cu in per 1.0 fl oz. Example, a tank 2" wide and 1" deep calculates to hold 1.06 fl oz of fuel per inch, btw. It does, and looks nice, too.
\BEST\LOU

Offline Joe Hunt

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Re: tank thicness
« Reply #13 on: September 03, 2019, 02:10:57 PM »
lou, any pictures? hunt

Online Ken Culbertson

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Re: tank thicness
« Reply #14 on: September 03, 2019, 05:12:28 PM »
Electric now so I am not in the tank building business any more but when I was I always used used cut up fuel cans and soft Copper.

Ken
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Offline FLOYD CARTER

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Re: tank thicness
« Reply #15 on: September 05, 2019, 11:28:35 AM »
Electric is no excuse to avoid building a tank.  You can always make a nice tank with the battery inside.  In such a case, brass would be acceptable.
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Offline L0U CRANE

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Re: tank thicness
« Reply #16 on: September 05, 2019, 12:59:12 PM »
Joe H. - I'll try to get some pics of finished tanks.

BTW, the last line in the long post refers to the volume resulting in  my tanks. Traditional Froom/VECO tanks claimed 1 fl oz per inch of length.

Also, K&S tin is so easy to work I made up a small "bending brake" from commonly available 1/8" X 1" iron or steel strip.  About 6" long strips are adequate. Clamp the strips together so one edge is as smooth as you can eyeball. Drill two 1/8" holes at different distances from the ends (to maintain alignment.) Solder short lengths of  1/8 dia  to one piece. Clamp together and "draw file" one edge to a fine, smooth common surface.

Often hand clamping is enough to hold the finished edge to the bend line, or use a small vise clamp if you have doubts.

The K&S tin doesn't need a carefully calculated and formed "bend allowance." It's enough if you can see all of the scribed bend line at the "brake" edge. Aluminum materials need calculated bend allowances forming over the appropriate radius to prevent cracks or breakage - ask an airframe and engine mechanic if you doubt...
\BEST\LOU

Offline Joe Hunt

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Re: tank thicness
« Reply #17 on: September 05, 2019, 02:28:04 PM »
thanks bunch Lou, can't believe all the interest and info this has generating, by the way, I are one, round engines and stearmans mostly.  thanks again, hunt

Online Ken Culbertson

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Re: tank thicness
« Reply #18 on: September 05, 2019, 02:53:29 PM »
Electric is no excuse to avoid building a tank.  You can always make a nice tank with the battery inside.  In such a case, brass would be acceptable.
LL~ LL~ LL~ H^^
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Offline Brett Buck

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Re: tank thicness
« Reply #19 on: September 05, 2019, 10:34:17 PM »
Just to be entirely clear, this is the correct material to get for tanks - K&S #254 "Easy Solder" Tin, .008". It used to be labelled .007, now it's .008 but its the same thing.

   It is NOT actual sheet tin (i.e. the element Tin (Sn) or any alloy of tin). It is mild sheet steel that is plated with tin for easy soldering. The normal sheets you see in a hobby shop are 4"x10", it is also available in 6" x 12" (K&S stock number 16254). The 4x10 will generally require two pieces to make a typical 6-9 ounce tank. I actually prefer making them in two pieces, since it allows you to adjust them so it is exactly square, but you can usually make a 5.9" or so long tank with the 6" material in one piece.

   This material cuts very easily and cleanly with my stainless-steel Fiskars office scissors, with very little distortion compared to tin snips.

  Solder with 60/40 or 63/37 *rosin core* solder, I prefer .040 diameter. If you think you need extra flux, I suggest Nokorode paste flux. I use a 260/220 watt Weller soldering gun, because it can heat up quickly, has very little tip mass, so you can solder one part of it without as much issue with unsoldering it where you don't want it. I have used everything from a 600 watt American Beauty industrial soldering iron to 15 watt pencil iron I got at a convenience store successfully, but the Weller gun is the best overall. The solder needs to be hot to the point of flowing like water, and the resulting hardened solder should form concave fillets. Blobs, balls, etc, are defects and are not acceptable, it doesn't take much solder at all, and putting on more than enough to form tight fillets between the parts is at best pointless, but probably marginally detrimental (since it stiffens up the joint locally, so it is more prone to cracking).

Do NOT use a torch of any type! Yes, it can be done but leaves no room for error.

Do NOT use StaBrite, particularly the flux! The marginal extra strength is not necessary if you get everything else right. If you want something stronger than 60/40, you can get Rosin Core Silver-bearing solder (which is NOT "silver solder") which is actually the same thing as far as solder goes, with a safe flux, and at least that will not corrode everything it touches forever. The StaBrite flux is extremely aggressive, the strongest and most persistent acid flux I have ever seen. This is great to solder difficult materials (like *chrome*) but it will very rapidly corrode anything you might make a tank with, and more-or-less cannot be neutralized. That sort of aggressive cleaning is patently unnecessary. If you have StaBrite solder, you can use that, but use Nokorode flux instead of the StaBrite.

Do NOT "rough up", sand, etc the tin plate on the K&S tin sheets, it is not necessary and will make it harder, not easier, to solder.

Brett


p.s. If you have the StaBrite kit, keep the plastic tube it come in, and keep the cap on it. If you just store the bottle by itself in a metal toolbox, just the fumes will corrode the inside of the toolbox and the tools. It even manages to corrode the solder itself, which is largely silver and tin! Ferrous metal doesn't have a chance. It's great stuff for non-structural connections to difficult materials like stainless steel and chrome (it will even work on nichrome wire, although the melting point is too low for most nichrome applications), but it's far too aggressive for general use.
« Last Edit: September 06, 2019, 10:34:07 AM by Brett Buck »

Offline FLOYD CARTER

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Re: tank thicness
« Reply #20 on: September 06, 2019, 10:12:53 AM »
One final comment:  It is not necessary to allow for bend radius with K&S tin plate.  I clamp the stock in a vise between 2 strips of steel stock (hardware store) and bend using another piece of steel, or a straight file.  The bend is as sharp as the edge of my steel stock.  It does not crack or leak.
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Offline Chuck_Smith

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Re: tank thicness
« Reply #21 on: November 16, 2019, 06:42:54 AM »
You guys using baffles?
AMA 76478

Offline Brett Buck

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Re: tank thicness
« Reply #22 on: November 16, 2019, 09:22:36 AM »
You guys using baffles?

   No, generally.

    Brett


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