Model Engine Gas Tanks and Caps

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Brian Rupnow

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This is something that I don't see much about, but it is integral to almost every model internal combustion engine. I build my own gas tanks, generally from 1 1/2" schedule 40 steel pipe. a clean-up pass on the outer diameter, and ends either from steel silver soldered into place, or from aluminum attached with J.B.Weld. (No, Naptha gas doesn't soften J.B.Weld) I use a 1/2" schedule 40 pipe nipple silver soldered into place as a tank filler neck. This filler neck is approximately 1/2" inside diameter, and it lets me see how much gas I'm putting into the tank without messy and dangerous overflows.--I buy a standard 1/2" pipe cap and modify it slightly by machining the outside diameter and drilling a 1 mm "breather hole" in it for use as a gas cap. These caps are uglier than sin in their "as cast" original shape. Turning the outer diameter and sometimes knurling it improves the look, but not much. Today I took one of these "modified" gas caps and modified it even more by turning the outer diameter to as much smaller as I could get without breaking thru the internal threads, turning off the raised section, and knurling the outer diameter. It improves the look. All my previous gas tanks had a lot more of the filler neck stuck up above the tank than was necessary. Tomorrow I will finish the gas tank on my current vertical i.c. engine project. I will have less exposed filler neck, and use the new style cap as seen in the picture. The second picture shows an existing gas tank with the "new style" gas cap on it.

 

Brian Rupnow

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Jeez--we might be twin sons of different mothers!!! Your pipe looks a bit smaller than what I'm using. Is it?
 

scottyp

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Yea, it is 3/8" I believe. Since I don't yet cut threads, I thought that it would be a good solution and since I don't knurl yet, that is what I ended up with. I do have a tiny vent hole and it works pretty well, overall. Say hi to pa! :0
 

DLM

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I like to use thin wall brass tubing 1 1/2 in. od. x .032 wall thickness and use a Dorman # 565-095 brass freeze plug for the ends works well for gas tanks.

Or if you want a little bigger tank use 2 in brass x .045 wall and Dorman
# 565-049 brass freeze plugs.

I have used both size and they work well

Thanks Don
 

perko7

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I used 65dia thin-wall steel tube (auto exhaust pipe to be exact) with 1.5mm thick end silver-soldered in place and like Brian a brass plumbing fitting with end cap as a lid. My tank is vertical so for the top I used the top of a pressure-pack can (WD40 I think) soldered in with the brass pipe fitting soldered to the top of that.
 

werowance

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if it helps, i found chrome plated sink drain pipe cheap at the hardware store. its thin walled brass once you sand off the chrome plate. solders easily.

1613584571220.png
 

werowance

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i used it on my last engine. one thing is dont try to do a side fill tank like i did last time. where the filler is a 90 degree into the top edge of the end plate. aweful experience on that. drill it like Brian shows on his pic, or move it to the left or right but dont drill it on the end plates. it vapor locks trying to fill it. tank before last was similar to brians and it fills easily that 90 on the side fill just makes it hard
 

rklopp

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Here's the tanks that I made for my six Upshur Twin riffs:
P9091935.jpg
P9091953.jpg

P9091957.jpg
P9091958.jpg
 

Olli-Matti

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Beautiful tanks! Definately going to give tank making a try. Little hard to find thin walled brass tuging. I did order from china 30mm tube with 1mm wall but it will take some time to arrive again... I found one local supplier that has 30mm tube with 1,5mm wall, guess I could thin that out on a lathe 🤔
 

bluejets

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Rivierra boat tank, all hand made flat brass sheet, approx. 400cc.
Has anti-surge panels fitted and roll over venting to avoid any spills.
Use screw cap fittings from rac charge lines.
Caps may be too small for some but I have fitted a level tube on the exterior for fill reference.
Also low level probe and currently modifying to install a miniature laser ($5) for a tank guage via Arduino.
On board cameras (2 via a switcher) relay info back to shore via FPV video link.
Looking a bit grubby at the moment , will clean up after latest mods complete.
 

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bluejets

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Exhaust shops usually carry many sizes of thin wall stainless steel tubing which can be silver soldered together.
 

Jasonb

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Or you can use a slightly thicker walled aluminium and cut a fine thread to take screw in end caps sealed with a thin section O ring. I also like the mini jam jars - if it was good enough for Maytag.




 

el gringo

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I normally hide the gas tanks inside the frame somewhere such as these Shores engines...
BOB_SHO2.JPG


On a recent build I decided on a exterior tank of a 'tulip shape' carved out of a piece of 6061 with an internal float level indicator
P1020544_Moment.jpg
 

Brian Rupnow

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El Gringo---I like your fuel level indicator. I can't count the number of times that I've tried to start an engine with no success, only to find out eventually that the gas tank was empty.---Brian
 

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