Author Topic: Tin Tank For 1/2a Build Question (Read 5093 times)

Chancey Chorney · « **on:** November 02, 2015, 08:21:00 PM »

Hi there. I was bored tonight so thought I would try building a tin tank for a Cox engine. The question I have is about tubing installation. I was wondering which way to install tubing is best. The tank is a wedge, and I do already have my fuel line to engine installed straight along the outer wedge with the end filed in a shallow angle. It is the other tubes I have questions about. Do I have to run one up and one down that each end just before bottoming out (as in a Black Widow or Golden Bee style), or could I just run one tube from the top to fill from, stopping before hitting the bottom (kind of like a Babe Bee backplate, just used to fill)? What are the pros and cons of each if they are both feasible? The tank is going to be for use on a couple of planes for just flying in circles, wingovers, and possibly a loop or two, as I have not ever done a loop before, and that is also if it makes the loop before hitting the ground.

Anyways, thank you in advance.

john e. holliday · « **Reply #1 on:** November 02, 2015, 09:28:12 PM »

What plane are you using this on? I have seen tanks with a single fill tube. Hold the plane nose down and fill thru tube until you see fuel coming out of the venturi. This is on engines that have a front intake and not reed valve.

Chancey Chorney · « **Reply #2 on:** November 02, 2015, 09:47:35 PM »

Sorry I forgot to mention that Cox product engine, Sure Start type engine. Planes would be profile type, such as Man-Win trainer, Stunt Chimp, or Osborne Platter. Just for fun flying. Thank you.

john e. holliday · « **Reply #3 on:** November 03, 2015, 04:38:37 PM »

Okay, go with top and bottom vents. File vent openings to face forward.

Chancey Chorney · « **Reply #4 on:** November 03, 2015, 05:07:25 PM »

If I may, I would like to ask a question. Is there any reason that I could not just put a single vent/fill tube out the top side only? I have never used a tin tank before, and thought that it would work. I assume that it has been done before, and probably did not work, but am just curious why? Thank you. Going to make and install my tubes shortly.

john e. holliday · « **Reply #5 on:** November 03, 2015, 05:12:58 PM »

It will work if you can see your fuel while filling and the plane nose down.

Dane Martin · « **Reply #6 on:** November 03, 2015, 05:21:00 PM »

Hey chancey, ditto what John says there. What your describing would functionally be the same as a standard babe bee tank. disassemble the back of a babe bee and something with a stunt tank and study how the fuel flow would operate with that vent system.
if you don't have access or are unsure what I'm talking about, I can post some pictures and drawings

Chancey Chorney · « **Reply #7 on:** November 03, 2015, 06:53:31 PM »

Ok. Thanks. I know how each look like in the back, so I will have to just sit down and figure this one out. Sounds like a good Wednesday evening job for me and maybe a dozen close friends.....

Dane Martin · « **Reply #8 on:** November 03, 2015, 10:23:27 PM »

Heres a pick, and a video is loading. This is a small perfect tank for suction. Will run the same inverted or upright. Sorry its kinda crude

Dane Martin · « **Reply #9 on:** November 03, 2015, 10:46:16 PM »

here's a quick video are some differences in the tanks. hopefully this helps your decision on how to make yours.

Target · « **Reply #10 on:** November 03, 2015, 11:12:48 PM »

Doc/Dane-
Any reason not to make the tank a uni-flow setup?
Regards,
Chris

Dane Martin · « **Reply #11 on:** November 04, 2015, 12:10:15 AM »

Nope, that would be neat. I just wanted to point out how the original cox tanks are set up, so the tank ideas mentioned in the posts above could be visualized. Good call, though. That would be easy enough to incorporate.

john e. holliday · « **Reply #12 on:** November 04, 2015, 12:00:32 PM »

On 1/2A's I just make standard tank as there is only about an ounce of fuel. Now that I think of it, have you considered a balloon tank. The small balloons will hold enough fuel with out putting pressure on the fuel. I think some one has it on here how to do them. I have played with them on the test stand and as long as there are no air bubbles it works great.

Fredvon4 · « **Reply #13 on:** November 04, 2015, 12:43:46 PM »

I gave up on hard tanks for 1/2A decades ago for pressure or balloon.... nearly impossible to open a 3/8 to 1 oz Perfect tank to fix it and get it all air tight ....Grrrr

Bladder is exceeding easy if the engine has a fine thread needle, for normal NVA a Party Balloon in a film canister fits in most wings and is idiot proof as long as you suck air out and put 3/4 to 1 oz in..... on suction the balloon tank works equally well upright or inverted

I know the OP is BUILDING a tank---- and if stuck on this cuz building is fun, and I agree

I recommend emulating a standard vent with top and bottom vents and pickup close to outside center rear, similar to reed valve stunt tank.....uniflo just complicates it and offers another area to leak in this small form factor

BTW.... with a vent on top and on bottom you can add short fuel line to both vents and cut a "V" notch in the middle and have a semi poor man uniflo...I have done this with lil Satan and Black Widow and the engine run was full rpm until it just quit when out of fuel

Chancey Chorney · « **Reply #14 on:** November 04, 2015, 05:28:28 PM »

Firstly to clear the air. Yes, I am building this just for fun. Never built one before and seen how many of the modelers used to build them, I wanted a try at it. Also, one of my next builds, Pinto, requires to build a tank to fit, so I wanted a bit of practice for that one as it will be enclosed, and not accessible later.

Secondly, thank you for the balloon idea. I had stumbled across this earlier this year and have built and used them already, only a couple of times, but think I have the hang of them. They are quick, easy, and light.

Lastly, without further ado.....

Chancey Chorney · « **Reply #15 on:** November 04, 2015, 05:29:44 PM »

And a couple more.

Chancey Chorney · « **Reply #16 on:** November 04, 2015, 05:32:55 PM »

And I forgot to add that the final AUW is at .56 oz. It still has to be cleaned and leak tested, but am confident in it. I hooked up a line to go from vent to vent, and blew on another attached to the fuel line and my cheeks puffed up like a squirrel, and had no leaks visible or audible. But, with that said, I will submerge it in water and test it carefully then flush it out with something else.

Dane Martin · « **Reply #17 on:** November 04, 2015, 05:54:33 PM »

Looks awesome! That should work real nice!

Target · « **Reply #18 on:** November 04, 2015, 07:30:01 PM »

That does look very good indeed. Nice job.
I'm going to making mine in the uniflow configuration though. I have read one key to Norvel smooth running for 1/2A stunt planes is a uniflow setup. Since it works so perfectly on my .40 size stunter, why not stick with it, I'm thinking.
Might be good on the pinto as well.
Please report on how the tank works for you after the plane is flying. Maybe I'll shift gears based on your experience, but I'm pretty certain I can get the steadiest run on the stock venturi/NVA with a uniflow arrangement. And if I'm building a tank to fit anyway, its not to hard to make it that way.
What size sheet did you use?

Chancey Chorney · « **Reply #19 on:** November 04, 2015, 08:03:57 PM »

Thanks for the compliments. As for what size sheet I used, I cannot tell you. No, really, I cannot. I am honestly not sure the thickness, as I had read somewhere online and went to a bodyshop and they gave me an empty clearcoat gallon container (tall and rectangular). I had cut off the top and bottom of it and used a piece from a flat area.

Chancey Chorney · « **Reply #20 on:** November 04, 2015, 08:13:09 PM »

Ok. I had a brainwave. I went out to the garage and using my cheap digital calipers, I came to around .010 - .012 ish. The reason for change is the edges are slightly ridged from my tinsnips. So I took a spot and hammered it lightly down then took the measurement. Hope this help a little.

Target · « **Reply #21 on:** November 04, 2015, 09:15:49 PM »

Cool, thanks. No need to go out of your way, most folks here on this forum can answer questions like that so there is always a good source of info on tap.
But I'll take note that you seem to have successfully used .010" thick material.
I think for a 1/2A tank, the material might be able to be thinner if it's still workable, since the dimensions are less and the weight held less. Of course, making one that is from "too light" a material and having a leak later is bad.
One of my buddies with some experience said to not worry about weight and just use whatever the standard material is. Seems like safe advice.

I also have considered a composite tank as a possible solution. Although some knowledgeable gents said that a specific brand and formulation of resin needs to be used.

I'll consider the metal uniflow tank as my first choice.

Thanks for the info!