Finger strainers, looking for advice

[Guest]

Hi all,

Sadly this is not about a t-craft but my Aeronca. There are some clever and experienced folks here so I figured that I would ask.

My Aeronca has 26 gallons of fuel in 2 wing tanks that are Aeronca tanks. The fuel outlets are 1/4" female pipe thread.

There have been no finger strainers on these and I don't like that.

So I looked for 1/4" male pipe thread finger strainers and found none so I fabricated one.

Its made from a brass AN fitting with one end counter bored to a depth of about .100" and a brass screen rolled, formed, soldered.

The ID of the fitting is not reduced due to the counter bore. It fits thru the 1/4" IPT fitting in the tank.

The finger is 2-5/8" long, longer than the 3/8" ones that suppliers sell.

Anyone know where I might purchase rather than make these?

Anyone have a fuel flow spec to test them too? Its a C90 engine?

Also looking for comments and advice regarding strainers.

Thanks, Dave.

[Garry Crookham]

Re: Finger strainers, looking for advice

Dave

I purchased a couple of finger screens from Aircraft Spruce a few years ago, don't know if they still stock them.

Garry

[Robert Lees]

Re: Finger strainers, looking for advice

Dave, I bought brass finger filters from a supplier here in the UK for my Taylorcraft (admittedly, this was over 10 years ago). See attached photo, but ignore the blue fittings.

Edit: see this link

[Guest]

Re: Finger strainers, looking for advice

Thanks Garry and Rob,

The 3/8" and 1/2" ones seem to be readily available however 1/4" are not so easy to come by.

Dave

[Robert Lees]

Re: Finger strainers, looking for advice

Dave: First & foremost and I should have said on my first reply, you are quite right in being unhappy about the lack of finger strainers in the wing tanks. I would suggest that Aeronca fitted them as original equipment.

Second: correct me where I misunderstand:

1. Aeronca (and Piper and Taylorcraft and others) of that era, 1940's, surely all used NP for National Pipe threads: NPS for straight, NPT for taper.

2. Can you explain MPT? (I assume IPT means "Internal Pipe Taper" but it's not an expression familiar to me)

3. There is a remote possibility there might be some BSPT fittings in Aeroncas (British Standard Pipe Taper) but I don't know for sure. The original English JAP engine that powered the Aeronca C3 was and English engine..perhaps some British thread forms made their way to the airframe, although I find this unlikely.

Third: Fuel flow spec.
An acceptable standard is 50% above the rated fuel consumption of the engine, measured at the carb or injector inlet, at max angle of climb. I can't quote the document that specifies this, because you're in the US and I'm in the UK, but the principles will be the same.

Hope that helps,
Rob

[PA1195]

Re: Finger strainers, looking for advice

Finger strainers have their place providing they're accompanied by periodic draining and flushing of the fuel tank...which I suspect rarely occurs unless one detects debris via a drain valve. If present the strainers can accumulate debris that can't pass the filter's restrictions. That debris can eventually slow or stop the flow especially at low levels of fuel.

Ideally fuel is filtered during filling, but that doesn't eliminate the potential ingestion of contaminants via the tank's breather system, or simple condensation of moisture as temperatures and humidity vary. Ice crystals are a particularly troublesome problem in certain climates when it comes to strainers and filters.

Adding or using a strainer should include periodic inspection and cleaning of the fuel system.

Gary

[Guest]

Re: Finger strainers, looking for advice

Dave: First & foremost and I should have said on my first reply, you are quite right in being unhappy about the lack of finger strainers in the wing tanks. I would suggest that Aeronca fitted them as original equipment.

Second: correct me where I misunderstand:

1. Aeronca (and Piper and Taylorcraft and others) of that era, 1940's, surely all used NP for National Pipe threads: NPS for straight, NPT for taper.

2. Can you explain MPT? (I assume IPT means "Internal Pipe Taper" but it's not an expression familiar to me)

3. There is a remote possibility there might be some BSPT fittings in Aeroncas (British Standard Pipe Taper) but I don't know for sure. The original English JAP engine that powered the Aeronca C3 was and English engine..perhaps some British thread forms made their way to the airframe, although I find this unlikely.

Third: Fuel flow spec.
An acceptable standard is 50% above the rated fuel consumption of the engine, measured at the carb or injector inlet, at max angle of climb. I can't quote the document that specifies this, because you're in the US and I'm in the UK, but the principles will be the same.

Hope that helps,
Rob

Sorry Rob,

My bad MPT meant male pipe thread. I guess i invented my own acronym.

The threads are standard AN tapered pipe threads (1/4")

Dave

[Robert Lees]

Re: Finger strainers, looking for advice

The threads are standard AN tapered pipe threads (1/4")

Dave

So you mean NPT? (sorry to be a pain, I don't believe there are AN tapered pipe threads, although I'm willing to be educated). To my knowledge I think you mean 1/4 NPT, in which the bore size is 1/4"?

Rob

[Guest]

Re: Finger strainers, looking for advice

So you mean NPT? (sorry to be a pain, I don't believe there are AN tapered pipe threads, although I'm willing to be educated). To my knowledge I think you mean 1/4 NPT, in which the bore size is 1/4"?

Rob

Rob,

You are probably correct. I assumed that all pipe threads are tapered so I may be wrong about that.

Dave

[astjp2]

Re: Finger strainers, looking for advice

Univair should have them in stock for like $15, I would spend 150 in labor to make one...Tim

[Guest]

Re: Finger strainers, looking for advice

Univair should have them in stock for like $15, I would spend 150 in labor to make one...Tim

Thanks Tim,

Found this => http://www.univair.com/ercoupe/view-...tank-strainer/

Should solder to the end of an AN fitting like the one in my pictures.

May go that route.

Dave

[Guest]

Re: Finger strainers, looking for advice

So you mean NPT? (sorry to be a pain, I don't believe there are AN tapered pipe threads, although I'm willing to be educated). To my knowledge I think you mean 1/4 NPT, in which the bore size is 1/4"?

Rob

Just measured a male AN fitting it has about a .030" taper.

Dave

[Guest]

Re: Finger strainers, looking for advice

Finger strainers have their place providing they're accompanied by periodic draining and flushing of the fuel tank...which I suspect rarely occurs unless one detects debris via a drain valve. If present the strainers can accumulate debris that can't pass the filter's restrictions. That debris can eventually slow or stop the flow especially at low levels of fuel.

Ideally fuel is filtered during filling, but that doesn't eliminate the potential ingestion of contaminants via the tank's breather system, or simple condensation of moisture as temperatures and humidity vary. Ice crystals are a particularly troublesome problem in certain climates when it comes to strainers and filters.

Adding or using a strainer should include periodic inspection and cleaning of the fuel system.

Gary

Thanks Gary,

Good point about the inspection of strainers.

There is one in each T-craft tank and they can be seen and inspected thru the filler opening.

I look at mine during the annual.

Dave

[astjp2]

Re: Finger strainers, looking for advice

Just measured a male AN fitting it has about a .030" taper.

Dave

37* to be exact, sae is 45*

[PA1195]

Re: Finger strainers, looking for advice

Thanks Gary,

Good point about the inspection of strainers.

There is one in each T-craft tank and they can be seen and inspected thru the filler opening.

I look at mine during the annual.

Dave

I'd not considered a visual in-tank inspection...a very good suggestion. I'll have a look at mine soon. Maybe a borescope would help.

In the past whenever I (a non-A&P) had troubles getting a quick drain valve to stop I'd suspect debris in the tank. I'd elevate the wing and drain the tank, remove the drain valve, pour fuel in and slosh it around, then drain it again through a filter.

Despite using a chamois (lint side up) or other filtration it seems there's always some way to get debris in the tanks. In winter I now freeze the fuel containers before filling (if not already done so in a bulk tank) before filling to form and filter as many ice crystals as possible. Auto fuel is especially prone to moisture.

I had an O-360 go real quite once from ice crystals so am particularly cautious. It was after a winter annual and because there was nothing in the carb inlet finger screen the inspector assumed there was nothing in the carb bowl. The engine ran lean after T/O and finally quit a half hour later. I cycled the mixture control (thinking the control cable had come loose) which unblocked the main jet inlet and I flew on to my destination. The next day I drained lots of ice crystals from the float bowl.

I don't think I've ever had an inspection where the inspector mentioned this screen inspection process. It must be an on-condition thing if ever done.

Gary