Today's Message Index:
----------------------
1. 04:41 AM - Re: Air Compressor (?) Issue (Vic)
2. 05:24 AM - Re: Re: Air Compressor (?) Issue (Jan Mevis)
3. 05:35 AM - Re: Air Compressor (?) Issue (A. Dennis Savarese)
4. 06:31 AM - Re: Air Compressor (?) Issue (Jill Gernetzke)
5. 09:18 AM - Re: Air Compressor (?) Issue (Bitterlich, Mark G CIV NAVAIR, WD)
6. 02:24 PM - Oil Hose (Kelley Monroe)
7. 08:58 PM - Re: Oil Hose (Walter Lannon)
Message 1
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| Subject: | Re: Air Compressor (?) Issue |
........shear pins made from nails should be acceptable, more so than made from
high tensile steel. They should go before more serious damage is done to the
compressor.
Vic
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=410685#410685
Message 2
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| Subject: | Re: Air Compressor (?) Issue |
As you say, they should, but I'd never install them
Jan
On 16/10/13 13:38, "Vic" <vicmolnar@aol.com> wrote:
>
>........shear pins made from nails should be acceptable, more so than
>made from high tensile steel. They should go before more serious damage
>is done to the compressor.
>
> Vic
>
>
>Read this topic online here:
>
>http://forums.matronics.com/viewtopic.php?p=410685#410685
>
>
Message 3
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| Subject: | Re: Air Compressor (?) Issue |
Is it possible when the "Cross" installed on the firewall, which you tested
at the shop, it was disassembled and the check valve coming from the snot
bottle to the cross was reversed?=C2- ie: with the arrow pointing back to
ward the snot bottle line?=C2- This would cause a huge amount of back pre
ssure and no pop off of the pressure relief valve.=0ADennis=0A=0A=0A=0A=0A_
_______________________________=0A From: Jill Gernetzke <jill@m-14p.com>=0A
ject: Yak-List: Air Compressor (?) Issue=0A =0A=0A=0AGroup,=0A=C2-=0AWe h
ave met up with a head scratcher.=C2- I am throwing it out to the group t
o chew on:=0A=C2-=0AThe Yak 52 owner purchased his aircraft on an insuran
ce sale.=C2- The aircraft had been totaled because of an engine fire.=C2
- Attempts to talk to the original owners and learn more about the aircra
ft=99s history have been unsuccessful.=C2- Originally, we were cont
acted because the air system was not building pressure.=C2- A photo sent
by the owner, elicited a remark by me that there seemed to be a lot of oil
in the banjo/outlet valve fitting.=C2- The compressor itself was very dir
ty.=0AThe owner cleaned the outlet valve with no appreciable change in outp
ut.=0AHe then bought a=C2- "NOS" comp from a private party, installed it
and it failed in 2.5 hours.=C2- This compressor had actually been overhau
led by us in 2006.=C2- The nuts stripped off of the 4 studs on the bottom
end of the compressor (green case), allowing the top end off the compresso
r to hammer up and down.=C2- Oil was all over the back end of the engine.
=0A=C2-=0AThe customer then sent his original compressor for overhaul and
run on our test bench.=C2- He installed this overhauled compressor and i
t failed after 40 minutes in flight. This time the 4 studs sheared off of t
he bottom end of the compressor.=C2- =0A=C2-=0AHe sent us both failed c
ompressors, the drive and drive gear, shear coupling,=C2- the FT-1
=9Csnot=9D valve and the pressure relief tee setup.=C2- We built on
e compressor out of the two failed units.=C2- The 4 stripped studs were r
eplaced with new studs and installed with Loctite.=C2- The compressor was
test run and produced 925 psi.=C2- The pressure relief valve tee setup w
as tested =93 it relieved normally -=C2- rebuilt with a new piston,
new seals in the one way checkvalves and the pressure set to 50 atm. (The
pressure relief valve had a Teflon seal which was in very poor condition.)
The snot valve was tested, flushed and retested.=C2- The compressor, gask
ets and drive unit were secured to one another in the proper alignment for
the reinstall.=0A=C2-=0AThe air compressor was returned to the customer a
nd it was reinstalled without attaching the steel air line. Everything was
normal for about 1.5 hours of ground runs.=C2-=0A=C2-=0AA flight was co
mpleted with the steel coiled air line still not attached.=C2- The flight
was normal.=0A=C2-=0AThe steel line was reattached and 90 minutes of gro
und run time.=C2- He noticed that pressure was not building as it should
and opened the cowling=C2- to find one of the 4 hold-down nuts backing of
f. He also reported that the other 3 nuts were not tight.=C2- The owner d
rilled and safety wired the nuts.=0A=C2-=0A(Note:=C2- There is a CRITIC
AL clearance that is set between the bottom of the Stage I piston and the t
op of the Stage II cylinder.=C2- Over-tightening these nuts will cause th
e top of the piston to hit the top of the Stage II cylinder.=C2- Too much
clearance and it bottoms out on the other end.)=0A=C2-=0AWe received the
compressor and installed new studs and steel locknuts with Loctite.=C2-
The compressor has been returned but not run, yet.=0A=C2-=0AHere is what
we know:=0A1.=C2-=C2-=C2-=C2-=C2-=C2- The FT-1 Snot valve is wa
s flushed and functioning properly.=0A2.=C2-=C2-=C2-=C2-=C2-=C2
- The pressure relief valve tee and checkvalves were all tested and the s
ystem functioned normally on a bench test, with the pressure relief valve p
opping off at 750 psi. =0A3.=C2-=C2-=C2-=C2-=C2-=C2- A new stee
l line was provided to the customer, but I do not know if this was installe
d.=0A4.=C2-=C2-=C2-=C2-=C2-=C2- On the 4th installation of the
compressor, we returned the compressor, shear coupling, drive pad and gear
tie-wrapped as a unit for correct clocking.=C2- We received photo verific
ation that the compressor drive was installed correctly.=0A5.=C2-=C2-
=C2-=C2-=C2-=C2- The compressor operated normally on the last run u
ntil the steel line was attached to it.=C2- Then, 1 nut backed off and th
e other 3 were reported loose. =C2-Hence, we replaced the hex nuts/lockwa
shers with steel locknuts in case the lockwashers had failed and that was t
he only problem on the last run.=0A6.=C2-=C2-=C2-=C2-=C2-=C2- T
he force to shear the compressor studs is in excess of 22,000 lbs.=C2-
=0A7.=C2-=C2-=C2-=C2-=C2-=C2- The shear coupling appears to be
a factory unit.=C2- A new one was sent to the customer, but returned back
to me.=0A8.=C2-=C2-=C2-=C2-=C2-=C2- The oil return holes in th
e accessory case are large and not plugged.=0A=C2-=0AIn the 20+ years tha
t we have been overhauling air compressors, we have never encountered this
problem.=C2- Please use this problem as your own theoretical and reasonin
g challenge to put forth real possibilities =93grasping at unicorns,
rainbows or butterflies not allowed. =C2-: =C2-)=0A=C2-=0AJill=0AM-14
=========================0A
=======================
Message 4
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| Subject: | Re: Air Compressor (?) Issue |
Group,
Replies to issues brought up in your posts:
1. None of the pistons were seized. In fact, they were all oily.
2. The original steel line, as reported by the owner, was free of
restrictions. I sent him a new one because he said the outlet valve/banjo
departed the aircraft on the first failure. (That is another head
scratcher.) I don't know if the new line is installed or not.
3. Again, we tested the snot valve and the pressure relief valve tee
was sent back to him as a unit - ready to bolt back on the aircraft.
4. I sent the customer a new shear coupling and it was returned to me.
The old coupling looked like a factory unit, but as we know, there was a
batch of Yaks that went out the door with shear pins that were too hard.
Years ago, we had a metallurgist analyze the hardness of the rivets for the
"before driven" value and we have machined our own rivets for the shear
couplings. We know our rivets are the correct hardness...anything else you
are putting in from ACE hardware, etc. is a game of roulette unless you have
the hardness value before and after driving the rivets. We will repin your
shear coupling, we do not sell the pins.
Never thought that MMO might be the solution and magic elixir! ; )
Jill
Message 5
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| Subject: | Air Compressor (?) Issue |
Jill, some suggestions if I may.
Step number one:
Have the owner disconnect the steel air line that goes from the compressor to the
snot valve (at the compressor side). Loan him an adapter fitting so that he
can go from that line to an AN fitting.
Then with a regulated air supply (from a bottle), have him apply air to the airplane
(through the steel line). I.E. The air bottle will now act as the source
of air, as the compressor normally would. Check to see that the aircraft bottles
pressurize normally. Increase pressure to 735 PSI and insure the pop-off
valve functions normally.
Close off the air bottle but do not release pressure.
Now open the snot valve and insure air is released AND THERE IS NO FLUID IN IT
WHAT-SO-EVER! If OIL comes out, we really want to know that!
This test takes all conjecture and guess work out of the: "Is something wrong with
the airplane?" question, and this test can still be done now. I suspect
it will check good, but you never know... in any case, if there is anything wrong,
or leaks, or whatever, this test will find it. I have done it myself.
Moving on, the short version of your story is that he lost the ability to pressurize
his tanks, changed the compressor and things got worse from there.
I have to tell you that I find it hard to imagine that air pressure could cause
the kind of damage to the compressor studs and nuts that you have described.
If a compressor is working against head pressure (AIR), it usually just eventually
stops making more pressure and does not beat itself to death and blow the
head off. Anyway, not one this small with this low of a volume. Of course
I could be wrong.... but......moving on.......
That said, if the first test above does not find anything wrong... And I repeat
ONLY if the above test was done and again I repeat... checked good, then my focus
would go back to the compressor and drive assembly itself.
My suspicion at this point would be that there is some kind of internal crack in
the drive assembly (or something else internal) that is allowing oil into the
compression path. If you get a FLUID into a compressor like this, well... FLUIDS
(like oil) do not compress like air does, and you get the exact duplicate
of a hydraulic lock in our M-14 engines. A situation I am sure you are an expert
at. A fluid in ANY kind of compressor, whether it be an air compressor
or an engine cylinder and piston is disastrous and SOMETHING HAS TO GIVE. Something
mechanical. In this case, I believe that is what is blowing your compressor
right off the top of the drive assembly. You would have to tell me if
the same drive assembly was used both times. However, this would also explain
the amount of oil he is seeing in the outlet.
All guesswork, but logical anyway.
Mark Bitterlich
-----Original Message-----
From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of Jill Gernetzke
Sent: Tuesday, October 15, 2013 17:10
Subject: Yak-List: Air Compressor (?) Issue
Group,
We have met up with a head scratcher. I am throwing it out to the group to chew
on:
The Yak 52 owner purchased his aircraft on an insurance sale. The aircraft had
been totaled because of an engine fire. Attempts to talk to the original owners
and learn more about the aircraft's history have been unsuccessful. Originally,
we were contacted because the air system was not building pressure. A
photo sent by the owner, elicited a remark by me that there seemed to be a lot
of oil in the banjo/outlet valve fitting. The compressor itself was very dirty.
The owner cleaned the outlet valve with no appreciable change in output.
He then bought a "NOS" comp from a private party, installed it and it failed in
2.5 hours. This compressor had actually been overhauled by us in 2006. The
nuts stripped off of the 4 studs on the bottom end of the compressor (green case),
allowing the top end off the compressor to hammer up and down. Oil was
all over the back end of the engine.
The customer then sent his original compressor for overhaul and run on our test
bench. He installed this overhauled compressor and it failed after 40 minutes
in flight. This time the 4 studs sheared off of the bottom end of the compressor.
He sent us both failed compressors, the drive and drive gear, shear coupling,
the FT-1 "snot" valve and the pressure relief tee setup. We built one compressor
out of the two failed units. The 4 stripped studs were replaced with new
studs and installed with Loctite. The compressor was test run and produced 925
psi. The pressure relief valve tee setup was tested - it relieved normally
- rebuilt with a new piston, new seals in the one way checkvalves and the pressure
set to 50 atm. (The pressure relief valve had a Teflon seal which was in
very poor condition.) The snot valve was tested, flushed and retested. The compressor,
gaskets and drive unit were secured to one another in the proper alignment
for the reinstall.
The air compressor was returned to the customer and it was reinstalled without
attaching the steel air line. Everything was normal for about 1.5 hours of ground
runs.
A flight was completed with the steel coiled air line still not attached. The
flight was normal.
The steel line was reattached and 90 minutes of ground run time. He noticed that
pressure was not building as it should and opened the cowling to find one
of the 4 hold-down nuts backing off. He also reported that the other 3 nuts were
not tight. The owner drilled and safety wired the nuts.
(Note: There is a CRITICAL clearance that is set between the bottom of the Stage
I piston and the top of the Stage II cylinder. Over-tightening these nuts
will cause the top of the piston to hit the top of the Stage II cylinder. Too
much clearance and it bottoms out on the other end.)
We received the compressor and installed new studs and steel locknuts with Loctite.
The compressor has been returned but not run, yet.
Here is what we know:
1. The FT-1 Snot valve is was flushed and functioning properly.
2. The pressure relief valve tee and checkvalves were all tested and the
system functioned normally on a bench test, with the pressure relief valve popping
off at 750 psi.
3. A new steel line was provided to the customer, but I do not know if this
was installed.
4. On the 4th installation of the compressor, we returned the compressor,
shear coupling, drive pad and gear tie-wrapped as a unit for correct clocking.
We received photo verification that the compressor drive was installed correctly.
5. The compressor operated normally on the last run until the steel line
was attached to it. Then, 1 nut backed off and the other 3 were reported loose.
Hence, we replaced the hex nuts/lockwashers with steel locknuts in case the
lockwashers had failed and that was the only problem on the last run.
6. The force to shear the compressor studs is in excess of 22,000 lbs.
7. The shear coupling appears to be a factory unit. A new one was sent to
the customer, but returned back to me.
8. The oil return holes in the accessory case are large and not plugged.
In the 20+ years that we have been overhauling air compressors, we have never encountered
this problem. Please use this problem as your own theoretical and
reasoning challenge to put forth real possibilities -grasping at unicorns, rainbows
or butterflies not allowed. : )
Jill
M-14P, Inc.
Message 6
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I am looking for oil hoses to replace the hoses on my CJ from the cooler
to the engine. Doug is out of stock on both the assemblies and bulk.
Thanks Kelley Monroe
Message 7
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Kelley;
Aeroquip 303-12 or Stratoflex 111-12.
Walt
From: Kelley Monroe
Sent: Wednesday, October 16, 2013 2:19 PM
Subject: Yak-List: Oil Hose
I am looking for oil hoses to replace the hoses on my CJ from the cooler
to the engine. Doug is out of stock on both the assemblies and bulk.
Thanks Kelley Monroe
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