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Engine basics => Engine set up tips => Topic started by: Paul Allen on July 19, 2009, 03:21:48 PM
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Guy's
Whats the purpose of a restrictor in the vent line/uniflow vent of a tank?
What is the affect on the engine run?
Thanks
Paul Allen
Australia ???
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G'Day Paul,
Your question is a bit open - several possible approaches to answer it, or try to...
I often sweat in a smaller ID tube in the forward facing vent, to reduce the effect of ram air as the model comes into, or turns away from dead headwind location on the circle. That is a restrictor....
Others have joined a piece of smaller ID tube ahead of the vent tube opening, holding both with fuel line. To test to see whethere more or less restriction helps, the smaller tube can be crushed in pliers. Easy and inexpensive to replace if "adjusted" too far...
I don't know of other "restrictor" approaches. So long as the open end of the uniflow vent is inboard of and "above" the tank, particularly in regard to the angle of the combined loads of gravity and circular flight, there should be no fuel siphoning.
Is this any help?
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If you want to experiment, take one of those little yellow caps that came with a new Brodak tank and just use a hot pin to melt a small hole in it and put it on the uniflo vent.
Phil
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The point of a uniflow is to provide uniform flow of fuel to the engine. I use a one way valve on the uniflow to "protect" the fuel tank from the effects of varying air pressure on the vent. Also, it is possible for a uniflow to siphon fuel out of the tank. I've also used a restricted tube. The hole in my KK one way valves is probably a #80.
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A simpler method of minimizing the effects of ram air is to place the uniflow in a "dead" airspace, such as the backplate of the engine.