Today's Message Index:
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1. 02:22 AM - Re: Re: M14P bent connecting rod (Richard Goode)
2. 03:47 AM - Re: Engine stumble in flight (Vic)
3. 05:41 PM - Re: Re: Engine stumble in flight (Roger Kemp)
4. 06:27 PM - Re: Engine stumble in flight (Looigi)
5. 07:44 PM - Re: CJ6 Gill vanes tend to close at Higher IAS (stephen.hayne)
Message 1
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| Subject: | Re: M14P bent connecting rod |
I have no experience of the Chinese engine, but have seen serious engine
failure quite often with the M 14, and what seems to happen is that the oil
control ring breaks as a consequence of the bent and therefore somewhat
shorter connecting rod; the engine continues to run but with extremely high
oil consumption and after a few hours if no one has had the sense to examine
things, then the connecting rod breaks and causes mayhem. But I've never
seen - or more to the point noticed - damage on the bottom of the piston.
Richard Goode Aerobatics
Rhodds Farm
Lyonshall
Hereford
HR5 3LW
Tel: +44 (0) 1544 340120
Fax: +44 (0) 1544 340129
www.russianaeros.com
-----Original Message-----
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Lancer
Sent: 06 March 2018 06:15
Subject: Yak-List: Re: M14P bent connecting rod
richard.goode(at)russiana wrote:
> What typically happens is that because of the bending, the connecting rod
become shorter and therefore pulls the piston further out of the cylinder.
The oil control ring is close to the bottom of the piston, and will then
jump out of its groove and attempt to prevent the piston going back up.
Inevitably the ring then breaks, and a very obvious sign is high oil
consumption and smoke appearing from that one cylinder; and plug fouling.
With the Housai Engine, when the rod bends to the point where the lower oil
control ring pops out the bottom of the cylinder, the crankshaft
counterweights start milling the bottom off of the piston contaminating the
inside of the engine and the oil system with loads of tiny shards of
aluminum. I'd say the M14 would also do the same.
--------
You can run but you can't hide
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Message 2
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| Subject: | Re: Engine stumble in flight |
In the photo you can see the aluminium foil of the capacitor, the primary windings
are not there, just the HT wires around it.
There are a lot of good ideas in this thread, we certainly know effects from
HT harness and sparkplug troubles. But I can tell you, nothing of that all is
depending on time and temperature like a failed coil cum capacitor. When we had
this stumble first time for real we were thinking along old mogas from last
season that may have gone duff. So we had avgas for next flight - and that took
us some more flights till we realized that time was that matters. It was about
half an hour each time till that stumble showed and could be induced spectacularly
on the ground after landing, setting revs to min. 80 percent: You cannot
fail to notice for sure !! With a cold engine NOTHING showed when doing the
mag test in preflight. So it became crystal clear after realizing the critical
time lapse for the effect that the real problem was the coil. I could demonstrate
that anytime in my oven by watching the spark length with the hot coil
! A cold bad coil produces exactly the same spark like a good one.
Just why the engine misses for a complete second on all cylinders in flight
is not totally logic to me. Burning into the inlet system with an open valve is
hard to imagine. You usually get no ignition without compression in a gasoline
engine. While that effect is not yet well explained I continue to be worried
about a situation when the engine may not pick up again after that stumble !
Vic
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Message 3
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| Subject: | Re: Engine stumble in flight |
The open valve allows the spark from the aberrant discharge to ignite the fuel
mixture in the supercharger. That discharge goes to all 9 cylinders at the same
time.
If you are on the wing when it happens you see a big black belch of smoke from
the carb and the exhaust stacks.
Doc
Sent from my iPad
> On Mar 6, 2018, at 5:46 AM, Vic <vicmolnar@aol.com> wrote:
>
>
> In the photo you can see the aluminium foil of the capacitor, the primary windings
are not there, just the HT wires around it.
> There are a lot of good ideas in this thread, we certainly know effects from
HT harness and sparkplug troubles. But I can tell you, nothing of that all is
depending on time and temperature like a failed coil cum capacitor. When we
had this stumble first time for real we were thinking along old mogas from last
season that may have gone duff. So we had avgas for next flight - and that took
us some more flights till we realized that time was that matters. It was about
half an hour each time till that stumble showed and could be induced spectacularly
on the ground after landing, setting revs to min. 80 percent: You cannot
fail to notice for sure !! With a cold engine NOTHING showed when doing the
mag test in preflight. So it became crystal clear after realizing the critical
time lapse for the effect that the real problem was the coil. I could demonstrate
that anytime in my oven by watching the spark length with the hot coil
! A cold bad coil produces exactly the same spark li!
> ke a good one.
> Just why the engine misses for a complete second on all cylinders in flight
is not totally logic to me. Burning into the inlet system with an open valve
is hard to imagine. You usually get no ignition without compression in a gasoline
engine. While that effect is not yet well explained I continue to be worried
about a situation when the engine may not pick up again after that stumble
!
>
> Vic
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=478418#478418
>
>
>
>
> Attachments:
>
> http://forums.matronics.com//files/p1040303_kk_467.jpg
>
>
>
>
>
>
Message 4
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| Subject: | Re: Engine stumble in flight |
Ok, so I replaced the duff coil and all seems to be happy in the world again.
Ground runs were fine, and we did a proving flight close to the airfield with no
apparent issues. I am calling it fixed.
With regards to the cause of the engine stumble, I am going to exert my feminine
side and change my mind in favour of the other theory put forwards on here.
I still cannot explain how a rogue 'spark' would get to a cylinder with it's
intake valve open without cross firing inside the ignition harness, but on reflection
I agree that it is a more reasonable explanation. The lack of other classic
crossfiring symptoms leads me to still suspect the magneto over the harness.
Many thanks for your input guys. I love this forum for the way we put forward
contrary views and discuss the issue without getting upset or personal, which
is an affliction other forums suffer from.
Cheers
Chris
Oh, and I still haven't got anything from the guy with the Bendix coils in Yak
mags. I will keep chasing him though.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478431#478431
Message 5
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| Subject: | Re: CJ6 Gill vanes tend to close at Higher IAS |
Thanks, Doug - I replaced all the wobblers with new when I OH'd the vanes/gills.
Even without the cable attached, the vanes never seemed to open a full 90 from
closed (on the bench or on the airplane). No kinks or anything in the copper
sheath. I don't worry too much right now, because even in the heat of Colorado
summer, I can mostly keep the CHT under 190.
dougsappllc(at)gmail.com wrote:
> Stephen,Check the wobblers (the little 90 degree arm on each vane). They develop
groves in them which catch on the shank of the bolts they pivot on. This will
cause the vanes to not open or close fully. Another problem may be in the
copper sheath which the control cable runs through. The control cable is made
up of a cable with a piece of stainless rod swaged to each end. If the outer sheath
has a kink or dent in it it may be preventing the shutter control cable
from achieving full movement. Try removing the control from the vane lever and
see if you can close the vanes fully without the cable attached.
>
>
> Doug
>
>
> On Wed, Feb 28, 2018 at 9:05 AM, stephen.hayne wrote:
>
> >
> > My CJ gill vanes seem to be 3/4s open on the ground even after I rebuilt them
to new limits. IMHO, the vanes seem "flimsy" enough that I can easily imagine
how they might close a little at higher airspeeds. I do think that the angle
they "rest" at is nicely aligned with the air coming off the propellor, which
makes me think this angle is by design.
> >
> >
>
--------
-
Dr. Stephen C. Hayne, Professor, CIS, Colorado State University
__!__
_____(_)_____ 666CJ
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