The mixer creates the correct fuel-air mixture by means of a needle valve attached to a weighted or spring-loaded piston usually in conjunction with an oil-damped dashpot.
32.
While not completely solving the problem, the restrictor, along with modifications to the needle valve, permitted pilots to perform quick negative G manoeuvres without loss of engine power.
33.
This attachment typically has a pressure regulator with upstream ( inlet ) and downstream ( outlet ) pressure gauges and a further downstream needle valve and outlet connection.
34.
The engine can be run over a very wide range of mixtures and adjusting the needle valve can be used to adjust the engine speed over a small range.
35.
The virtue of the "'needle valve "'is from the vernier effect of the ratio between the needle's length and its diameter, or the difference in diameter between needle and seat.
36.
Since the orifice is small and the force advantage of the fine-threaded stem is high, needle valves are usually easy to shut off completely, with merely " finger-tight " pressure.
37.
The needle valve and carburettor are behind the cylinder where they are protected, and the crank case, cylinder and fuel tank are all machined from forgings, rather than weaker castings.
38.
As the balloon reaches the correct size the inflation nozzle will begin to lift . At this point the needle valve is closed along with the regulator valve and cylinder vale.
39.
:Note that the float valve of a carburetor ( controlling the fuel level within the carburetor ) is " not " a needle valve, although it is commonly described as one.
40.
The scheme was extended in 1984 with the addition of the Drumjohn power station which made use of the existing needle valve where the water from Loch Doon and the Deuch feed into the Dee.
