View Full Version : Building a model Gas Tank

brian Rupnow
04-09-2014, 08:32 PM
When I built my Philip Duclos "Odds and Ends" engine a couple of years ago, I never did build a satisfactory gas tank. I have some "down time" now, so thought perhaps I should build a gas tank for it. Since I don't have a separate base that the engine mounts on, I have decided that the gas tank must mount on the engine itself. A hunt through my "bits and pieces" bin yielded a length of galvanized steel tubing 1.165" outer diameter x 1/16" wall thickness. I didn't want to have to deal with the galvanized finish, so I set it up in my lathe and turned the outer diameter to 1.144" diameter, which (I hope) got rid of the galvanizing on the o.d. of the pipe. The piece I turned is 3.48" long. This was a somewhat arbitrary length, but all that matters at the moment is that it be 'long enough". In the picture you can see the unturned length and the turned length setting in front of the engine.
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANK-1001_zps72d24e7b.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANK-1001_zps72d24e7b.jpg.html)

brian Rupnow
04-09-2014, 08:33 PM
I had already modelled the engine before I built it, so today it was simply a matter of bringing up that cad file, and adding in the tank body (in red) and designing a bracket to hold the tank (in dark blue). I have some thoughts as to what the rest of the tank is going to look like, so tomorrow will model them and then setting about building them.
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/ASSEMBLY-ODDSNENDSWITHGASTANK-1_zpsae84ea4e.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/ASSEMBLY-ODDSNENDSWITHGASTANK-1_zpsae84ea4e.jpg.html)

04-09-2014, 08:54 PM
When I made one I used a piece of copper water pipe with two caps. Fitting are then easy to solder too. Fourteen years later, still no leaks. Mike

brian Rupnow
04-09-2014, 09:08 PM
Mike--Most of my gas tanks have been made of brass. I had a halogen floor lamp with a 1" diameter brass tube as its main body. The light burned out, and the body gave its life as a number of highly polished tanks, which were all silver soldered togehter. This build is going to be a bit different, and may end up being made with no soldered joints.

brian Rupnow
04-09-2014, 09:26 PM
I don't expect that anyone is going to build this, however---I have to build it myself, and I need a drawing to do it. It requires no effort for me to post it, and it gives the new guys something to think about. The steel gas tank body will be inserted into the round hole in the bracket and secured there with #638 Loctite. The only thing of importance with this bracket is that the top of the gas tank MUST be 1/2" to 3/4" below the center of the carburetor barrel. The small carburetors on these hit and miss engines have no float and shut off valve, so if the level of fuel is ever higher than the fuel port in the air intake/needle valve assembly in the carburetor they will flood like crazy and fuel will gravity feed from the tank and drip out the air intake side of the carburetor. This makes the engines almost impossible to start and can also be a major fire hazard.
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANKBRACKET_zps57766f91.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANKBRACKET_zps57766f91.jpg.html)

brian Rupnow
04-10-2014, 01:32 PM
This gets rather interesting as the design develops. One picture shows what the finished engine looks like mounted on the engine. The other picture shows a section view through the center of the tank. This is going to be a "no soldering involved" tank, completely assembled with 638 Loctite. The main tube is mild steel, the ends are machined from aluminum, and the filler neck and cap will be machined from purchased brass plumbing fittings. The small tube that runs out to fed the flexible gas line will be machined from mild steel. I'm not 100% sure yet, as to whether I will use 638 Loctite as the bonding agent or J B Weld. They both stand up well to fuel immersion, and they both are super strong when fully cured.
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/ASSEMBLY-ODDSNENDS-FINISHEDGASTANK_zps6ee97a00.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/ASSEMBLY-ODDSNENDS-FINISHEDGASTANK_zps6ee97a00.jpg.html)
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANK-ODDSANDENDSENGINE-SECTIONVIEW_zps9450846a.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANK-ODDSANDENDSENGINE-SECTIONVIEW_zps9450846a.jpg.html)

brian Rupnow
04-10-2014, 04:19 PM
While driving around town to buy some material, I got thinking about this tank. It needs one more hole thru the aluminum at the end where the filler cap is, to prevent it "air locking" as it is filled with fuel. Without the hole which I have added, I would have only been able to fill the tank to the top of the center hole thru the aluminum, and then it would have air locked and not taken any more fuel. With the added hole, any trapped air can escape and let me fill the tank almost to the top. I also added a breather hole thru the center of the screw on cap. The threads on the inside of the cap are tapered pipe threads, as are the threads on the fuel filler pipe, and I have found that even though I unscrew the cap a full turn to let air into the tank while the engine is running, the weight of the cap makes it vibrate closed and shuts off the air flow, causing the engine to starve for fuel, again because of an "air lock" situation.
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANK-ODDSANDENDSENGINE-CROSSSECTION-2_zps401ad0c3.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANK-ODDSANDENDSENGINE-CROSSSECTION-2_zps401ad0c3.jpg.html)

brian Rupnow
04-10-2014, 04:34 PM
In the picture you can see the "gas cap" as purchased. It has a rough cast exterior. Beside it you see the same part, after a little cosmetic work in my lathe. (That's the gas cap off my dual opposed piston engine). The pipe nipple which the cap screws onto will have one end cut off and be turned down to match the hole in the aluminum tank end. Also shown in the picture is the "blank" end cap for the far end of the gas tank. There is a small trick to it. It has to intrude into the end of the tank about 1/2" to ensure enough material that the Loctite can get a good leak-proof bond between it and the outer tank shell, but if I didn't but the big counterbore in the end of it, I wouldn't be able to get as much fuel into the tank as I want. This way, the counterbore fills up with fuel too, so I don't lose much tank capacity.
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANKPARTS002_zpsa9856a81.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANKPARTS002_zpsa9856a81.jpg.html)

brian Rupnow
04-11-2014, 05:16 PM
Hey!! I'm starting to like this!!! There is a lot of work in that large aluminum end, but all the parts go together and I think it looks good. I have temporarily ran out of 638 Loctite, so I am going to do all of my assembly with J.B. Weld. I have two tubes of it that may never get used up, so they might as well be used for this.
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANKALMOSTDONE002_zpsca2d5a33.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANKALMOSTDONE002_zpsca2d5a33.jpg.html)
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANKALMOSTDONE003_zps156356ed.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANKALMOSTDONE003_zps156356ed.jpg.html)

brian Rupnow
04-12-2014, 10:59 AM
It doesn't get a whole lot better than this---as far as fit goes, anyways. There is a small bit of deception in the picture, because I haven't completed all of the joints which are being "glued" together with J.B. Weld. I haven't used J.B. Weld in an application like this before, so want it to have a full 24 hours drying time before I put any pressure on it or try to put fuel in the tank. I will finish those joints this afternoon and then wait a couple of days before I test it with fuel in it.
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANKMOUNTED001_zps3f9ef8e3.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANKMOUNTED001_zps3f9ef8e3.jpg.html)
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANKMOUNTED002_zps441c90fc.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANKMOUNTED002_zps441c90fc.jpg.html)
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/GASTANKMOUNTED003_zps140a5b40.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow013/GASTANKMOUNTED003_zps140a5b40.jpg.html)

brian Rupnow
04-13-2014, 10:01 AM
So---Is the forum back to "normal" now?

brian Rupnow
04-13-2014, 10:02 AM
So---Is the forum back to "normal" now?--Guess not.--I'm still getting "Data Base Error".---Brian

Old Hat
04-13-2014, 11:15 AM
Nice work ! Up to the knurl. . . :(
And I'm not being critical, it's just that most of us were taught how to knurl
incorrectly, and your cap has suffered from it.

I'll think out a (how to) that doesn't come accross stuffy
and work up a thread latter.
Love those muti-color schetchs, what generated them?

brian Rupnow
04-13-2014, 02:30 PM
Here is a short video with the new gas tank on the running engine. There is a link to Photobucket, also to Youtube.


http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/th_ODDSANDENDSENGINEWITHNEWGASTANK_zps01af33ad.jpg (http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow013/ODDSANDENDSENGINEWITHNEWGASTANK_zps01af33ad.mp4)