[ezetom]

Hi folks,

In reading, I have come across much debate on what material to use for FWF applications of AN fittings,

I have read that EI recommends brass fittings over alum or steel, but Id like to know the reasoning..

Does anyone know the specs (e and yield strength) for AN brass, steel and alum fittings?

thx

Tom

 

[Walt]

Use steel whenever possible, it's stronger and prevents galling when going into aluminum (I will never use aluminum fittings in the engine or oil cooler).

 

[humptybump]

I can only convey the wisdom of the builder of my RV-8 and that of the A&P who does my condition inspection. Both say steel for fuel and oil.

 

[Pat Stewart]

Use steel whenever possible, it's stronger and prevents galling when going into aluminum (I will never use aluminum fittings in the engine or oil cooler).

What he said.

 

[TS Flightlines]

I second Walt-

Steel for FWF applications, and I like stainless hose ends on hose assemblies, especially FWF.
Tom

 

[chaskuss]

Steel is preferred for maximum strength [greatly desired for oil and fuel lines subject to vibration, ie FWF] Aluminum fittings tend to gall when installed into an oil cooler. Brass should be avoided, as when in contact with aluminum, you get a nasty galvanic reaction. See

http://www.eaa1000.av.org/technicl/corrosion/galvanic.htm

Steel fittings are cadmium plated to prevent galvanic issues.

Charlie

 

[ezetom]

Here is what I have..

From the engine driven fuel pump, I have a short hose (about 6") then I have a flow scan fuel flow transducer, from the fuel flow transducer, there is a 1/4" ANPT brass nipple, that threads into the "t" of a brass AN tee. the fuel pressure sensor screws into one side of the tee, and there is a brass AN npt elbow that screws into the bottom of the tee, that has a 1/4" ANPT to #6 AN steel fitting that then connects to the hose that feeds the carb. This arrangement is kind of a "u turn" setup. the tee is secured to the rear cylinder via a couple of adel clamps.

Everything was fine, but I decided to change out the engine driven fuel pump, and all 303 hoses. Im not real fond of the setup, the consensus so far seems to be to change everything out to steel... Why would anyone use brass to start with anyway?

-Tom

 

[airguy]

Why would anyone use brass to start with anyway?


-Tom

Probably because it's cheap and readily available.

So is methamphetamine, and it's not a good idea either.

 

[ezetom]

I cant seem to find the steel tee or elbow..

http://www.aircraftspruce.ca/catalog/hapages/an917.php

http://www.aircraftspruce.ca/catalog/hapages/an914.php

I wonder if thats why it was brass to begin with..

 

[airguy]

Try this site, it's where I get most of my high pressure steel fittings.

http://www.discounthydraulichose.com/Steel_Fittings_Adapters_s/21.htm?Click=2&gclid=CI-7jcG0qq0CFTPktgodtmKZVg

 

[chaskuss]

snipped Why would anyone use brass to start with anyway?

-Tom

Tom,
Brass is also rather heavy. Does that Rube Goldberg plumbing have any support, other than where it mounts onto the transducer? I ask, because if it does not, I would be concerned about the weight/moment arm all those fittings have, and their effect on the transducer where they attach. [future cracking of the female port on the transducer]
While I generally favor steel fittings FWF, if there is no practical way to support some of that weight [or eliminate it with a less complicated design], aluminum fittings may well be a better choice. Just another issue to consider.
Charlie
PS That plumbing reminds me of the joke about the British alloy "Britainium". It's properties are that it's twice as heavy as lead, and half as strong. :