New member, smoke oil system question

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Mjpierce1

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Jul 27, 2022
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Hello, new member refurbishing a Falco, adding a smoke oil system. I have a tank fabricated and would like to ask question on how to plumb it - pick up tube, fill port, breather port, drain port. Anyone wish to look at photo and give advice? Thanks in advance.
 

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Mjpierce1

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Thank you! I’ll do the search. hopefully someone will have the same ports as my tank. I had it fabricated some ten years ago - I don’t remember my logic for all the welded bosses. When I look at those tanks from “smoking airplanes” I don’t see them as complicated as the one I had made. Thanks again.
 

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rv7charlie

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The tank in the Swift I used to own was a 5 gal outboard motor (boat) tank with a Holley fuel pump strapped to the handle. No negative G stuff in a Swift. If you really need it to work inverted, a flop tube would be relatively simple to install.

Filling your tank should be fun. ;-)
 

Mjpierce1

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Flop tube, filler, upright and inverted vents. Combine a drain with a vent, if you like.

Level indication not usually installed.


BJC
1. Flop tube yes, that is the center boss in the end of the tank. I’m unsure how a flop tube can pick up oil when vertical unless the flop tube is a very flexible tube with weighted end (is it. And I see them sold by Aircraft Spruce - you cut to you size.
2) vent. I put it at the top of the tank with a check valve so when inverted no discharge.
3) filler. I put this in the end at the bottom, under the middle flop tube fitting. Filler would be above the tank accessible via battery box some 12 inches above the tank attached to the fuse stringers. Question - should the cap be vented? I think I understand non-vented filler cap works while upright because I have the check-ball vent which would be open. But what about inverted? Both the check-valve vent and the filler neck would be closed so the tank not vented?
4. I do have a welded boss exactly under the center of the tank for which I initially thought I’d use to drain. So would this somehow now be used as the vent while inverted? And if so, does it need a check valve and if so, does it still become a drain port? What plumbing fittings would be used? Or, may I just do away with the drain fitting completely?

Thanks for the thoughts. Truly appreciated! Martin
 

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Mjpierce1

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Couple more facts-
1. Air Vent ball check valve allows air in, but when inverted, plugs the plastic fitting not allowing oil out.
2. With filler cap higher then the air vent, I need to be careful not to fill the tank higher than the air vent check valve, which may be difficult to do as the filler tube and cap are above the tank - and can’t be viewed from the battery box filler access point; so the filler tube would never be “full” as oil would be escaping from the air vent which is lower

Maybe I need to rethink which tank welded bosses are used for different functions. No big deal to have things reworked, but if I don’t have to…

Maybe I need to draw another version to figure it out.
 

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Mjpierce1

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I have inverted fuel, and inverted oil installed so that is why smoke oil needs to work with negative maneuvers.

I’m now thinking my oil filler cap needs to be on the tank (not a remote filler) - so no issue Air vent being below the fill level - which would port fuel overboard if I tried to fill the filler full, above the air vent. To do that, I’ll just have to have access the tank from inside the airplane, which I can do through an access panel behind the luggage shelf behind the seats. I’ll fill the tank so I can see when it is full. Need to add a welded bung for a filler cap on the top of the tank

Am I thinking correctly that when inverted, the pump can pull air through the check ball of the air vent? If so, then all I really need is:
1) filler cap - non-vented (so no oil escapes when inverted
2) air vent with check valve allowing air to enter while positive maneuvers, and no oil out when negative
3) flop tube with very flexible line so as to reach all faces of tank - rear when vertical up, forward when vertical down, and all of the round sides when other maneuvers.
4) no real need to drain it. If need be, I can suck it out of the filler cap opening.

Make sens?
 

Dana

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As long as the pump produces more suction than the pressure from the weight of the oil against the check valve while inverted, you're fine.
 

vhhjr

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For those inspired by this thread to have their own smoke system check out the July 2019 Kitplanes magazine for the article, " How to build a $250 smoke system." It walks the reader through building a smoke system like the one in my Onex. The system is portable and the only connection to the aircraft is the smoke oil injection point and that doesn't even require a hole in your exhaust pipe.

Vince Homer
 

Mjpierce1

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Can anyone add information on the air vent when inverted?

When inverted the normal top vent as gravity pulls the check ball down into the plastic fitting round cavity that stops oil flow out the vent, but… without some other kind of vent, will the pump be able to unseat the ball to pull in air to vent the tank??? And not allow oil to flow out?

I’ve looked at Smoking Airplanes photos of products but can’t envision how the tank vents while inverted? Could there be two vents, with the bottom vent somehow plugged for oil not flowing out the vent when in normal flight attitude, then it opens for inverted?

For whatever reason the solution to inverted venting escapes me!
 

vhhjr

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It doesn't matter that the vent seals when you're upside down unless you intend to be that way for a considerable time. The flow rate out of the tank isn't high enough to immediately cause the pump problems from low suction pressure, especially if the tank is a little flexible. The sytem works upside down for several seconds provided you have a "flop" tube in the tank.

Vince Homer
 

Mjpierce1

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Hi Vince! Thanks for the input. The tank is aluminum, 4.5 gal. I suppose inverted flight will not be excessively long, but who knows. I wonder what is theoretically best plumbing for a smoke oil tank should be - in order to fly at all attitudes. There must be best practices in plumbing somewhere, as many air show airplanes routinely fly with their smoke systems operating during many of their routines. The port for flop tube pick up for pumping the oil seams basic, as does the port opening for filling - but it is the vent plumbing that escapes me. I’m no engineer and can find no schematic to depict it. Thanks again.
 
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