----- Original Message -----

From: DaveLeonard

To: Rotary motors in aircraft

Sent: Wednesday, August 25, 2004 8:20 PM

Subject: [FlyRotary] Re: more myths questioned!

Kevin, I'm no A&P but I use rigid lines.  Sure does weigh a lot less and puts less stress on the fittings.  Leaks more, and makes me nervous sometimes.  I used a long line for coolant that was poorly supported, and it cracked at about 50 hrs.  Stupid! Stupid!  Have since replaced it, but still use rigid lines for my psru and turbo.

 

Dave Leonard

OK, without stirring up a hornets nest-- could I safely run a rigid oil line to the redrive and back if both ends were rigidly engine mounted?  I would make sure there are bends in it for flex and well supported.  I have rigid brake lines on my -6a, with a 360 degree loop at the end, although admittedly, had one end crack, but I believe that was from a combination of multiple removals and later learning that my hangar partner's flange tool was actually automotive, not aviation. I've had no problems on my Lycoming otherwise with rigid lines.  I know some guys run flex lines everywhere, which seems heavy and expensive.

Kevin Lane  Portland, OR
e-mail-> n3773@comcast.net
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----- Original Message -----

From: paul

To: Rotary motors in aircraft

Sent: Wednesday, August 25, 2004 9:26 AM

Subject: [FlyRotary] Re: Sorry Rusty - no bind

 

----- Original Message -----

From: Russell Duffy

To: Rotary motors in aircraft

Sent: Monday, August 23, 2004 9:31 PM

Subject: [FlyRotary] Re: Sorry Rusty - no bind

please don't take this as being critical, I'm just asking - is it true or not that engine fittings should be steel, not aluminum?  or is that just a myth? does aluminum fatigue faster than steel?  what do certified piston planes use?

Kevin Lane  Portland, OR
 

 

This is sort of a controversial subject.  There is probably an official FAA rule, or at least rule of thumb about only using steel fittings when there's relative motion on the two ends of a hose.  Of course screwing steel fittings, into an aluminum gear drive would also violate some dissimilar metal rules, so damned if you do, damned if you don't. 

 

Since I was schooled at the Van's Aircraft institute, I follow the more common sense rules.  If it's a small fitting, that isn't very strong, it's best to use steel.  If it's a fairly large fitting, then aluminum is plenty strong.  AN-6 is about the dividing line, and it comes down to whether there's much motion.  In the case of the drain fitting you see in the pic, there's no relative motion, so I feel aluminum is fine.  

 

Cheers,

Rusty (not an A&P, and don't even play one on TV)  

 

This topic was recently discussed on the canard aviator's website....seems that Lycoming is sending their brand new engines with aluminum fittings.  I agree, however that there is comfort in using steel for the smaller (-4) sizes.  I have -16 aluminum AN fittings for my radiator hoses, and it would take a sledgehammer to damage one of those aluminum fittings. The general consensus on the canard site was similar....steel for the smaller fittings, but aluminum was fine for -6 sizes and larger.  I guess they figure that if Lycoming can supply a certified engine with aluminum fittings, it's OK on our experimentals.  FWIW.  Paul Conner