Mike Wills wrote:
>
> For Lynn Hanover,
>
> At 03:08 PM 1/21/2001 -0800, you wrote:
>
> > > > I have had hose failures over the years, but they were all traced
to
the idiot that built the car (me). The point was that Earls and two types
of Aeroquip are not aircraft quality hoses, and are not intended to be.
The reusable aluminum fittings with the nice colors are very good for race
cars. Easy to put together, light weight and available in any race store.
>
> The term "aircraft quality" gets used pretty regularly by many without
really defining what that means. As it applies to hoses/fittings what makes
a hose "aircraft quality"? A milspec number, or simply the fact that a
particular hose is marketed as "aircraft quality", or ??? What is it about
Earls hoses and fittings that makes it not suitable for aircraft use other
than the fact that they don't market it as "aircraft hose"? Or is it simply
the fact that the fittings are user installed and as such prone to
installation errors?
You are correct. It's all of the above.
"Aircraft Quality" means nothing. The hose ends should be identified with an
MS number. That is as depicted on a Military Standard drawing. Available at
big libraries. Just as the various fittings should be AN for Airforce/ Navy
Standard. Later MS, now NAS (National Aerospace Standard) That's now SAE. Its
all very close to the same specs, just different people managing the
drawings. The NAS specs you have to buy from SAE. Didn't see that coming, did
you.
Another thing that makes me crazy is ending a run of solid line to a flex
line with a nonbulkhead fitting. Even solid mounted engines move a bit. Brake
calipers squirm all over the place. It has to have a flex line because it
moves around. When pressurized oil lines become quite stiff. They will
forcefully move the solid line around until it fails if you don't immobilize
it with a bulkhead fitting. In some cases you can see the oil line move when
you rev the engine, (the oil pressure goes up). If it moves some now. wait
until your not looking. There is no burst strength at all to the liner. Pull
out some liner and look at it. See the impression of the braid on the outside
of the liner? Almost all of the burst strength is in the braid. Very little
of the braid need be damaged before the hose fails. Loosing the bearings or
the engine is not the problem. The fire is the problem. The flex line must be
left long enough to flex. If you clamp or strap all of the flex lines
together, they can't flex.
So few lines are involved in the flex mode I think it would be good to build
up all of the installation and get it running well, and when happy with the
installation, remove the firewall to engine lines and have the Aeroquip
dealer make them up in cloth covered and crimped ends.
Last fall I was taking my quick change apart. I hung the RR caliper on a
scrap of coat hanger to avoid stressing the -4 flex line. With all of the
pounding and jerking around I knocked the caliper out of the out of the hook
and it went all the way to the floor. The made up stainless braided line with
the stainless end fittings, meeting several MIL-Fs pulled out of a fitting.
Ouch. Good time for a failure. I should have been able to stand in a loop of
that hose and bounce on it. Before each weekend I get in the car and compress
the brake pedal as far as I can. I have yet to get to burst on a hose (20+
years) but I have made a few connections leak. The crimped end of that hose
did not fail. The end I made up failed. It never leaked a drop before it
failed under just the weight of the caliper. I have yet to have a crimped
connection of any type fail.
At "Sun&Fun" and elsewhere I have seen installations that just take your
breath away. Including pieces of garden hose as a breather line. Another
favorite seems to be the wonderful clear plastic hose from Sears or Home
Depot. For oil I use the same shiny braided Aeroquip everyone else uses but
in locations where the ends don't move relative to each other. Even though my
engine is bolted solid to the chassis, there is some flex and a bit of
movement. The long runs of hose are Aeroquip push on blue kevlar reinforced.
Very light and good for (it says on the box) 200PSI. My fuel line from the
pumps to the fuel pressure regulator is an SAE spec. double stainless braid
cloth covered 5/16" ID.
It passes through the cabin so it meets the rules for that application. You
can beat on it with a hammer and not hurt it. From the regulator to the carb
is another piece of single layer of Teflon lined-4 stainless. When using the
Teflon (or other) lines single layer hoses, note that when abraded or snagged
on a bolt or whatever the little wire braid strands usually fail where the
next set of braid laps over them. When that happens there will be a strand
free between the next lap of strands and the liner. The liner has almost no
resistance to being pierced by this loose strand. If left unattended it will
happen. For fuel and oil, seamless stainless steel tubing with sleeves and
"B" nuts. Then bulkhead fittings to flex lines where required. Flex lines
with cloth covering and the braid encased in a synthetic rubber so that a
braid failure will not penetrate the liner.
From my Earls catalog Perform-O-Flex hose used with their swivel seal
fittings is good to 1000psi (-12 size) and temps from - 40 to +300F.
Which of the Aeroquip hoses types are "aircraft quality" and which are not?
> > I use both the braided stainless with Teflon liner and
> > > the new Aeroquip push on style. The fittings have barbed tubes, and
the
> > hose
> > > is two layers of Kevlar lined hose (blue) in many sizes. Looks good,
very
> > > light. Good for 200 pounds.
> Can you give a part number, style number, or trade name for the hose
your
> talking about here? Doing a little websurfing I see Aeroquip offers a
> "Startlite" style hose using crimped fittings. Is this the hose your
> talking about?
No these just push together. Once on it has to be cut off to reuse the
fitting.
> > For aircraft use the exposed stainless braid is
> > > seldom used. When it is, it is on standoffs in Adel clamps. If it
gets
> > loose
> > > the braid can saw through another hose or airframe aluminum or
electrical
> > > wire. Most aircraft fluids are carried in formed tubing. Otherwise
in
cloth
> > > covered flex hose. The hose liner is selected specifically for the
fluid
> > > being carried.
> I guess most of us are concerned with oil and fuel plumbing. What type
> hose/fittings/liners do you recommend for these applications?
>
> Look in the Aeroquip catalog or visit the dealer. These are not stocked
away from airports. They will have to order the pieces for you. The dealer
will try to sell you SAE hydraulic hose and SAE ends. It will work but it is
heavy as hell. Also there is a little flair angle problem. 37 1/2 degrees
verses 45 degree.
I will gather some more specific data and post it if you like.
Thanks for your input on this subject Lynn.
>
> Mike Wills
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Paul Lamar
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