Clunk

A weighted fuel pick-up used in a fuel tank to assure the intake line is always in fuel.

The Nitro Fuel Tank Clunk
For those of you in the RC airplane world this is nothing new, but it might be a new term or idea for those of you with nitro RC cars, truck, or boats.

RC aircraft fly in many different attitudes – meaning pointing up, pointing down, on their sides, and upside down... not to mention the high G forces pulling the fuel to one side of the tank or the other.

If the fuel pick up was at a fixed location in the tank – say the lowest part of the tank like in a car – the air craft would only get fuel when it is flying straight and level. Any banking or inverted flying would starve the engine of nitro fuel.

A very simple solution of using a short length of fuel tubing inside the fuel tank with a heavy weight at the end of the tube called a "CLUNK" ensures no fuel starvation. This tube and clunk will simply flop around inside the fuel tank which ever way gravity pulls on it - just like the fuel in the tank. This means no mater what the RC aircraft is doing, the pick up end of the fuel tube in the tank is always submerged in fuel.

This clunk, more specifically the fuel tube it is hooked up to inside the fuel tank should be checked for deterioration every year or so. The tube over the years will get brittle and may crack or come off the supply tube in your fuel tank. This of course means you now have a fixed nitro fuel pick-up and all the benefits of the clunk are lost.