AN is Air-Force Navy.
>From: Brian Evans <brian@uunet.ca>
>Reply-To: Brian Evans <brian@uunet.ca>
>To: "Mark Palmer" <mgvrmark@hotmail.com>
>CC: vintage-race@autox.team.net
>Subject: Re: More arcane brake fittings stuff
>Date: Fri, 27 Jul 2001 11:48:19 -0400
>
>Blatantly copied from the Dimeband Garage web site:
>
>"The SAE 45 degree double flare usually has a male-threaded tube nut that
>bears directly on the OD of the flared tube- so you need a double flare to
>help control galling that can result in stress cracking right at the flare.
>In short, you need "give" there. Problem is, the deformation that results
>is kind of irreversible, so the next cycle or two will result in your
>having to use astronomical torques to keep the flare from weeping. Worse is
>trying to use a single flare in an SAE flare nut and seat, and worse still
>if the seat is brass- the flared tube is sqaushed from both sides, even as
>it is deformed by the nut galling on it. The brass seat deforms and work
>hardens. It may seal once, with a ton of torque and some luck. It's not
>recommended practice - it's not even a good idea.
>
>Racers (and aircraft, which is where the system originated as the
>"Army-Navy" or AN standard in WWII) use the single 37 degree flare. The AN
>single flare is still a concave flare, but its 37deg angle seals by
>stretching, not squashing. The tube is supported by a separate sleeve that
>the female-threaded tube nut bears upon. This isolates the flare from the
>torques imparted by the nut. So rather than trying to get a seal despite
>the presence of rotating torques and the resulting galling, you press the
>flare between precisely-machined (steel!) seat and precisely-machined
>support sleeve. The sealing area under compression is at least double that
>of the SAE flare. An additional bonus is that the OD of the nut is a lot
>larger than the 3/8" of an SAE nut, which means you won't kill as many
>trying to get the proper sealing torque. (Even so, you should always use a
>proper flare nut wrench on any tube nut.) "
>
>So you're right - the double flare helps reduce the damage caused by
>galling. In the case of Girling "bubble" flares I think that the squashing
>and deformation of the bubble is critical, and you can only squash it once.
>
>brian
>
>At 11:29 AM 7/27/01 -0400, you wrote:
> >Note: normal people can delete this before reading -- abnormally intense
> >brake pipers can read on.
> >
> >>From: Brian Evans <brian@uunet.ca>
> >>What I do now is simply cut off the old girling or SAE flare from
> >>the >bundy tube, and re-flare the existing tube in place
> >
> >Brian,
> >
> >Yes, this seems to be the concensus ... no one (yet) has mentioned a
> >source for Girling-to-AN adapters (or Girling to anything else, for that
> >matter), so the easiest thing to do is cut & re-flare the hard pipe.
> >
> >>One big bennie is that the AN flare is a single flare and almost
> >>foolproof to make.
> >
> >This brings up an interesting question, for which I THINK I know the
> >answer ... have been reading lots of stuff on types of flares for brake
> >pipe, and nearly every "expert" says, somewhere, that one should NEVER
>use
> >a single-thickness flare (i.e. they all recommend a double-thickness
> >flare, like the SAE 45-deg inverted flare). However, obviously the AN
> >system uses a single-thickness flare! And we all know that works.
> >
> >I suspect that the single thickness is OK on the AN system because the AN
> >flare nut has a second piece -- the sleeve -- under the nut, so it
>doesn't
> >transfer the tightening torque to the flare & therefre doesn't gall the
> >flare. Other systems (notably SAE) do not have the sleeve under the nut,
> >so tightening the nut tends to gall the flare, and I guess that's why
>they
> >use a double-thickness flare. Comments?
> >
> >Regards,
> >Mark
> >
> >_________________________________________________________________
> >Get your FREE download of MSN Explorer at
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>
>Brian Evans
>Director, Canada
>MCI Wholesale Internet Services
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