First post...stupid questions about hoses and fittings

The place to raise issues, ask questions, swap ideas and discuss anything related to aircraft engineering, maintenance and building.
NB Any opinions expressed in this forum are not necessarily those of LAA Engineering

Moderators: John Dean, Moderator

Post Reply
TaylorMono12
Posts: 11
Joined: Fri Aug 02, 2024 9:22 am

First post...stupid questions about hoses and fittings

Post by TaylorMono12 » Fri Aug 02, 2024 9:55 am

Hello,

This is my first post on these forums - I am a younger LAA member, very much on the greener side in terms of engineering experience - so please be gentle!

I am currently restoring a Taylor Mono under the supervision of my inspector, which has included fully rebuilding the engine. I am very nearly there now - hopefully a matter of weeks before starting the engine for the first time in 10 years. It's a VW1600 - we've replaced the mags with Leburg and tidied up what was previously a bit of a hornet's nest.

I do have lots of questions that are probably very much beginners' questions, but please would you kindly indulge my ignorance and help me - I'd rather try and find answers to my problems before I bother my inspector. I'll post them on separate threads to avoid confusion but here's my first one:

I am struggling to get my head around the plethora of options for a) oil lines, and b) fittings. I'll ask about the oil lines first, but the two go hand-in-hand.

I have removed a remote oil filter head (in lieu of more frequent oil changes), which was previously fed by a braided PTFE oil line up and down - by my measurements it's 5/8 hosing.

Instead of an oil filter, we plan to route the oil lines to the intake manifold to pass warm oil through the shrouding, which is how it would have been originally.

My question is actually quite simple really: what sort of lines should be used? When is it appropriate to use braided PTFE vs medium pressure 303 hosing?

Onto my next question: fittings. I am tying myself in knots getting confused between UNF, UNC, AN...and trying to source the adaptor I need.

On the intake manifold, we've got 2 x AN4 male fittings welded (one for the oil intake into the shrouding, one for the oil returning back to the case), shown below:

Image

But the lines that will feed these are 5/8 (by my measurements - which may not be 100% precise - 16mm diameter for the PTFE tubing without the braid).

The oil lines originate and connect to a plate with two male 'quick connect' fittings, secured by a hose clamp, shown below:

Image

What I am therefore trying to find is a fitting / adaptor to fit a 5/8 hose (AN10 size?) that offers a female concave connection to an AN4 male fitting - see below:

Image

OR, to understand if I really do need to retain the 5/8 (or AN10?) oil line and whether I could replace it with something of smaller diameter (in which case, I then need to source an adaptor at the other end to fit the block into which the lines originate.

Hopefully I haven't bewildered you too much with my question...any help would be gratefully received!

tnowak
Posts: 530
Joined: Wed Jan 02, 2008 11:00 am

Re: First post...stupid questions about hoses and fittings

Post by tnowak » Mon Aug 05, 2024 8:24 am

Hello TaylorMono12,

Welcome to the world of aircraft maintenance and hose fittings!
My own experience with hose fittings is that nothing seems to be standard…….
It really is a case of doing careful research and looking at on-line at catalogues or speaking with established hose assembly companies.
Try these resources:
https://www.lasaero.com/products/article/L01ARUUSP
https://www.aircraftspruce.com/catalog/ ... ey=3032831
https://www.saywell.co.uk/products/hose-shop/

I found Saywell particularly helpful when I needed to get a new fuel hose for my Cont. A65 engine.

Regarding the selection of hoses for your engine, my suggestion would be to stick with “familiar” aviation hose, unless you do very careful research.
Aeroquip 303 hose is a very common aviation hose and you can find full specifications on-line.
If you select an alternative “braided PTFE” hose then you will need to do careful research to see if it is suitable with regards to operating pressure, temperature range, fluid (oil) compatibility etc. etc.

Regarding adapters (for my vintage Piper brake lines), I managed to find one at a company that deals with racing car hose and brake lines.
Of course, you will need to liaise with your LAA inspector to ensure he is happy with your decisions and parts selection.

Hope this helps

Tony
Tony Nowak
008249

mikeblyth
Posts: 157
Joined: Tue Mar 18, 2008 8:24 am
Location: Bedford UK

Re: First post...stupid questions about hoses and fittings

Post by mikeblyth » Tue Aug 06, 2024 9:46 am

What size engine?
Mike Blyth
005633

TaylorMono12
Posts: 11
Joined: Fri Aug 02, 2024 9:22 am

Re: First post...stupid questions about hoses and fittings

Post by TaylorMono12 » Tue Aug 06, 2024 10:28 am

Slightly over 1600cc.

TaylorMono12
Posts: 11
Joined: Fri Aug 02, 2024 9:22 am

Re: First post...stupid questions about hoses and fittings

Post by TaylorMono12 » Tue Aug 06, 2024 10:29 am

Thanks Tony and others for replies.

Previously, the engine had braided PTFE lines on it, not 303. I'm not all that clear as to what advantages the braided hose gives in an engine like the VW - seems like added weight? I was going to replace with 303 so your replies give me confidence in my decision!

Nick Allen
Posts: 458
Joined: Wed Jan 02, 2008 11:00 am
Location: Oxford
Contact:

Re: First post...stupid questions about hoses and fittings

Post by Nick Allen » Tue Aug 13, 2024 12:03 pm

On the recommendation of our inspector (who's both an LAA and BGA inspector), we've replaced fuel lines with PTFE hoses on our motorgliders on the grounds of longevity (i.e. they are no longer "lifed" as such). Obviously, as noted, oil lines have different temperature/pressure requirements, but should be simple enough to check. We got hoses made up by a local specialist, who manufacture for various motorsport outfits, including F1 teams -- one advantage of living near Silverstone!

Post Reply