Fuel Tank System
 

First post!

I needed some advice on a fuel tank system i'm trying to build so I figured this would be the place to ask. I'm running a [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXJDJ6&P=7]Fuji BF-34 gasoline engine[/link] and i'm trying to set up a 100 oz fuel system for it. I've got two 50 oz fuel tanks with clunks/vents installed and i'd like to somehow link them together to feed the engine. My gut instinct was to stack the two fuel tanks, take the fuel line from the upper one and plug it into the external vent of the lower one and connect the lower tank to the engine, but I don't want to risk doing that since the plane is close to impossible to replace and i'm still new to RC planes. I've heard suggestions from some other RC hobbyists to somehow set up a T-fitting between the two tanks so that both tanks are in parallel (simultaneously feeding the engine). Another person who previously owned the plane had some configuration that from what I can tell, somehow linked the two 50 oz tanks together, and connected them to a smaller fuel tank (can't be more than 4 oz by the looks of it) which fed the engine.

Does anyone have insights into the merit of these older designs (or better explanation of how they probably should work)? If someone has an easier idea for how to do this...that'd be even better. Thanks in advance!

RE: Fuel Tank System
 

Your first choice will work well. The two tanks can be side by side or on top of each other. It doesn't matter. This engine has a pump in the carburetor that will suck gasoline out of the first tank no matter where it is. As fuel is sucked out of the first tank it will then create a suction that will pull fuel out of the second tank. Do you know how long this engine will run on 100 oz of fuel? I think about 2 or 3 hours.

RE: Fuel Tank System
 

Thanks for the fast reply, i'll try it out. We've been running fuel efficiency tests and are roughly estimating 10 hours on 100 oz of gas. More flight tests hopefully will confirm our previous static/flight tests.

RE: Fuel Tank System
 

Oh quick follow up on the issue of just hooking the two up with one fuel line going to the external vent of the other. How reliable is that choice because we've found the engine to be a little finnicky at times even with just one fuel supply (the engine sometimes suddenly quits, I have a feeling it may have been a combination of some air bubbles as well as problems with pressurizing/drawing fuel from the tanks).

RE: Fuel Tank System
 

I'm not an expert on that particular engine, but most gassers with a pumper carb will run reliably no matter where the tank is as long as it delivers fuel and not air bubbles. If the tanks are set up properly (clunk not stuck ) the system of two tanks should be very reliable. The "tee" fittting may also work as the engine will pull fuel from both tanks. However, it may not draw fuel evenly, so after a while it may draw all 50 ounces of fuel from one tank and only 30 ounces of fuel from the second tank. As soon as either tank gets empty, the plane engine will quit. That's why I like the idea of two tanks in series.

RE: Fuel Tank System
 

a gas engine doesn't pressurize the tank, it draws fuel from the tank using a small pump in the carb,you need to make sure the tank has a vent to allow the engine to draw the fuel.

a typical vent line wraps around the tank a couple of times then exits the bottom of the fuselage, you give it a couple of loops so fuel doesn't leak out of the line, as long as the tank can draw air to replace the fuel being used,unless there is a inordanate ammount of bubbling of fuel or a air leak in the fuel line than its not going to cause engine stoppage.

most of the time its overheating that causes a gas engine to quit,has it been broken in or is it well used,if the engine is new it needs to be properly broken in just like any engine to seat the moving parts,if its used then there might be a clog in one of the jets or passages in the carb causing the stoppage.

piggy backing tanks is fine just hook up the slave tank supply(the line with the clunk) to a strait pipe entering the primary(the one hooked to the engine, with no bend entering the primary tank,you only need to vent the slave tank as it runs out of fuel its vent allows the fuel to drain from the primary.