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HomeTurbineAircraftHelicopterTurbine Helicopters › Syphoning fuel
05-30-2015 02:45 PM  3 years agoPost 1
helihenry

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I have 2 Sigg tanks in parallel with a vent for each.
When I fill the tanks, one fills first and I put a finger over the vent of the first till the second fills.

When both tanks are brim full the fuel syphons out of the last tank to fill and leaves a puddle of fuel till that tank empties out onto the floor down to the bottom of the vent nipple inside the tank. I have been using a pipe to blow back to try and avoid syphoning but not a satisfactory solution.

I could stop refuelling when the first vent starts to overflow but how can I be sure both tanks are full unless I see both overflow?

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05-30-2015 02:54 PM  3 years agoPost 2
modtron

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My immediate guess is that your vent tube is to small in diameter and not letting the air pressure get out quick enough.

Personally, I would connect the tanks in series rather than parallel.
I've never had any issues running them this way on many turbine machine.

modtron
Oxford UK

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05-30-2015 03:14 PM  3 years agoPost 3
helihenry

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Thanks for your reply.
If I made the tanks in series I cannot see how that will help the situation. When the fuel overflows from the vent it would still fill the vent pipe and syphoning would still occur.
I use 3mm Tygon throughout and one of these air traps.
http://www.gbr-jet.com/catalog/prod...4m47025daj6tnu6

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05-30-2015 05:09 PM  3 years agoPost 4
helihenry

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uk

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Raised the vent pipes above the tank outlet and strapped them to the boom. It has stopped the syphoning but does not look as neat as dropping the pipes down below the baseplate.
No fuel mess so that has to be a good thing.
Simon

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05-30-2015 05:47 PM  3 years agoPost 5
modtron

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Oxford. UK

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If I made the tanks in series I cannot see how that will help the situation.
Well, unless ALL of your tubes are exactly the same length, it is always possible for one tank to fill before the other is full.

When in series, you fill into the air trap, when full it then overflows into the first tank, then when thats full, it overflows into the second tank until it starts to exit from the overflow vent tube.
If done at a constant speed without being to fast and a large diameter tube on the overflow, the air can escape easily without building up any back pressure and ALL of the tanks are full to the brim.

modtron
Oxford UK

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05-30-2015 06:03 PM  3 years agoPost 6
helihenry

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uk

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The thing that worries me about series is the fact that the tanks are quite a distance from the frames and 0.6 kg on one side and nought on the other will make for a lop sided heli.

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05-30-2015 06:28 PM  3 years agoPost 7
modtron

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Oxford. UK

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All I can say, is that I have used series tanks in many scale jet heli's and aircraft and it made no difference at all when running with one tank full and one empty.
They would need to be at extream distances apart to make it noticable in flight.

Another issue the keep in mind ...
Assuming that both tanks are not equally filled and are connected in parallel.
The pump will pull fuel equally from each tank, so there is a high chance of one tank emptying before the other.
This now let's air into the fuel line, which is never a good thing at any time.
This can not happen when connected in series.

Just my experiences but others may have different ideas.

modtron
Oxford UK

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05-30-2015 07:00 PM  3 years agoPost 8
helihenry

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uk

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I am just learning so appreciate any ideas and your extensive turbine knowledge is much valued.

I have taken the bottle tops off a few times now after various times of flight to gauge how much flight duration I have, and so far the levels in the tanks have been very even.

I do love that turbine experience though - roll on that big turbine Lama.

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