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JOE HOWSE
Joined: 10 Jan 2006
Posts: 140
Location: DUNCAN BC CANADA
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 Posted: Sun Aug 19, 2012 12:44 pm Post subject: obstruction to rotatation |
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yakers
Anyone have experienced a solid mechanical resistance to rotation on M14P, (not hydraulic resistance) when attempting to pull through prior to starting.
Engine has approx. 400hrs since new.
Flown regularly including Oshkosh and return last year.
Parked after last flight with no problems one week ago.
I suspect gear box problem, as very little play at prop.
Any ideas?
Joe
Joe
[quote][b]
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richard.goode(at)russiana
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| Posted: Sun Aug 19, 2012 5:56 pm Post subject: obstruction to rotatation |
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I would be fairly sure that the problem is hydraulic lock.
What often happens is that the weakest point in the cylinder assembly is the connecting rod. It attempts to push the piston down; the piston can't move and so the connecting rod bends. This brings the piston a little closer to the crankshaft, so when the piston next rises (one is of course, typically talking about one of the three bottom pistons), the oil control ring will pop out of the cylinder, preventing the piston going back down, thus jamming the engine.
If the engine continues to run, it will then typically break the piston ring and then continue to work – for a bit!
Richard Goode
Rhodds Farm
Lyonshall
Hereford
HR5 3LW
United Kingdom
Tel: +94 (0) 81 241 5137 (Sri Lanka)
Tel: +44 (0) 1544 340120
Fax: +44 (0) 1544 340129
www.russianaeros.com
I’m currently in Sri Lanka but this Mail is working,and my local phone is +94 779 132 160.
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Joe Howse
Sent: Monday, August 20, 2012 2:12 AM
To: yak-list(at)matronics.com
Subject: obstruction to rotatation
yakers
Anyone have experienced a solid mechanical resistance to rotation on M14P, (not hydraulic resistance) when attempting to pull through prior to starting.
Engine has approx. 400hrs since new.
Flown regularly including Oshkosh and return last year.
Parked after last flight with no problems one week ago.
I suspect gear box problem, as very little play at prop.
Any ideas?
Joe
Joe
| Quote: | | http://www.matronics.com/Navigator?Yak-List |
01234567
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This message has been scanned for viruses and
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[quote][b]
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wlannon(at)shaw.ca
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| Posted: Sun Aug 19, 2012 8:58 pm Post subject: obstruction to rotatation |
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Hi Joe;
Unless you have pulled all lower spark plugs I would not discount hydraulic lock. I have had at least one case that I would have sworn was a “mechanical’ stop but was in fact hydraulic.
Walt
From: Joe Howse (joeh(at)shaw.ca)
Sent: Sunday, August 19, 2012 1:41 PM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: obstruction to rotatation
yakers
Anyone have experienced a solid mechanical resistance to rotation on M14P, (not hydraulic resistance) when attempting to pull through prior to starting.
Engine has approx. 400hrs since new.
Flown regularly including Oshkosh and return last year.
Parked after last flight with no problems one week ago.
I suspect gear box problem, as very little play at prop.
Any ideas?
Joe
Joe
[quote]
href="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/Navigator?Yak-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
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cjpilot710(at)aol.com
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| Posted: Mon Aug 20, 2012 3:35 am Post subject: obstruction to rotatation |
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I believe Richard is mostly right. However I believe he mean the "scraper ring" which is at the bottom of the piston. Being English, he might have different name for it.  . Anyway the effect is the same. The rod may already be bent, shorting it's length, allowing the bottom ring to drop below the cylinder bore, thus preventing the piston from moving back up. There is very little distance between where the scraper ring stops its downward movement and the bottom of the bore. Forcing the engine to turn will most likely break the ring, "freeing" the engine BUT the damage is already done i.e. a bent rod. As was pointed out the engine may run BUT only for a little while.
You can determine which cylinder by removing plugs, and measuring which piston is lowest. Remove that cylinder. That will free up the engine without further damage to the engine, than you can check and maybe replace the rod. Than again it may be something entirely different!
GOD! Don't you just love aviation?
Jim "Pappy" Goolsby
Sent from my iPad from some where on The 3rd rock from the Sun.
On Aug 19, 2012, at 9:53 PM, "Richard Goode" <richard.goode(at)russianaeros.com (richard.goode(at)russianaeros.com)> wrote:
[quote] <![endif]--> <![endif]-->
I would be fairly sure that the problem is hydraulic lock.
What often happens is that the weakest point in the cylinder assembly is the connecting rod. It attempts to push the piston down; the piston can't move and so the connecting rod bends. This brings the piston a little closer to the crankshaft, so when the piston next rises (one is of course, typically talking about one of the three bottom pistons), the oil control ring will pop out of the cylinder, preventing the piston going back down, thus jamming the engine.
If the engine continues to run, it will then typically break the piston ring and then continue to work – for a bit!
Richard Goode
Rhodds Farm
Lyonshall
Hereford
HR5 3LW
United Kingdom
Tel: +94 (0) 81 241 5137 (Sri Lanka)
Tel: +44 (0) 1544 340120
Fax: +44 (0) 1544 340129
www.russianaeros.com
I’m currently in Sri Lanka but this Mail is working,and my local phone is +94 779 132 160.
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Joe Howse
Sent: Monday, August 20, 2012 2:12 AM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: obstruction to rotatation
yakers
Anyone have experienced a solid mechanical resistance to rotation on M14P, (not hydraulic resistance) when attempting to pull through prior to starting.
Engine has approx. 400hrs since new.
Flown regularly including Oshkosh and return last year.
Parked after last flight with no problems one week ago.
I suspect gear box problem, as very little play at prop.
Any ideas?
Joe
Joe
01234567
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This message has been scanned for viruses and
dangerous content by Invictawiz MailScanner, and is
believed to be clean.
8
[b]
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richard.goode(at)russiana
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| Posted: Mon Aug 20, 2012 8:26 am Post subject: obstruction to rotatation |
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Further to my earlier posting on this topic, I would not totally rule out a gearbox problem, but that is almost impossible to occur in a stationary engine!
I have known of two cases of gearbox failure, in both cases satellite years breaking up, and in both cases the gearbox was absolutely locked solid, and no movement at all in the prop. If the prop can move, even a small amount, that is play in the gearbox which means that it is okay and the problem is almost certainly with a piston/cylinder.
Richard Goode
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Joe Howse
Sent: Monday, August 20, 2012 2:12 AM
To: yak-list(at)matronics.com
Subject: obstruction to rotatation
yakers
Anyone have experienced a solid mechanical resistance to rotation on M14P, (not hydraulic resistance) when attempting to pull through prior to starting.
Engine has approx. 400hrs since new.
Flown regularly including Oshkosh and return last year.
Parked after last flight with no problems one week ago.
I suspect gear box problem, as very little play at prop.
Any ideas?
Joe
Joe
| Quote: | | http://www.matronics.com/Navigator?Yak-List |
01234567
--
This message has been scanned for viruses and
dangerous content by Invictawiz MailScanner, and is
believed to be clean.
[quote][b]
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http://www.matronics.com/Navigator?Yak-List |
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