Fuel Tanks

The following descriptions are in general. There are four basic designs that are used by most modelers. There are others such as balloon tanks, baffled

tanks, etc. As you will see in this website, the designs of the tanks will fill almost all needs in design. However, if a custom design is desired, contact BJM

using the info on the right. Most designs can be built for no increase or a small nominal increase in price.




The front or Pick-up tube is the engine fuel feed tube. This is connected to the needle-valve on the engine.

The bottom tube is the Overflow. When filling the tank, the fuel will overflow out this tube when the tank is full.

The top tube is the fuel Fill tube. This is the tube into which you put the fuel awaiting the overflow from the Overflow tube.




This tank is actually a pressure tank. The idea is to have air forced into the Fill (or Uniflow) tube so the tank has positive pressure inside.

This forced air can be the air directly from the prop wash or can come directly from the muffler.

The front or Pick-up tube is the standard engine fuel feed tube. This is connected to the needle-valve on the engine.

The bottom tube is the overflow. When filling the tank, the fuel will overflow out this tube when the tank is full.

THIS IS VERY IMPORTANT!! After filling the tank, the overflow tube is capped so no air can get in. Of course, this cap is removed when filling

the tank. The cap prevents air pressure from escaping from the inside of the tank as the tank is being pressurized by the air coming in the

Uniflow tube.




 This type fuel tank can be either the standard or the uniflow type design. There is only one construction difference that should be noted. It has, what one

might call, a reservoir on the outer edge of the tank. The tubes are positioned similarly in the chicken-hopper. The differences are the fill or uniflow tube and

the pick-up tube end in the inside, back corner of the reservoir. See the picture to understand the reservoir and tubing positioning. The primary purpose for

a chicken-hopper tank is to have more fuel in a smaller space.




The plastic tanks can be used for all models (control line and radio control). It is unique in design. These come is many shapes (round, cylindrical, rectangular,

square, oval, even flexible walls) and sizes. However,  they all work, in principle, the same. By observing the picture, the items A are pick-ups for fuel, usually

filters. They connect to B, very flexible plastic tubing. It looks like there are two tubes in the figure. The figure is drawn with the two tubings and the curved

double arrows to show the A termination is loose or floppy in the tank. That is why these tanks are also called "clunkers". The end of the pick-up "clunks"

against the sides of the plastic tank. The length of the flexible tubing is just right to not get hung-up on the sides or corners of the plastic tank. The flexible

tubing is connected to copper tubing which go through a rubber grommet to the outside of the tank. The "clunker" is the fuel pick-up which feeds the motor

venturi. The item C is the overflow. It is rigid copper tubing which is bent to the inside top of the tank. As the fuel rises in the tank when the tank is being filled,

it eventually flows outside the tank. These tanks can be "standard" or "uniflow" designs, as explained in the above examples. The uniflow is different because

it has two flexible tubes. They connect together inside so they move (clunk) together. In the design principle, they are the same.