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barrynorman(at)comcast.ne
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 Posted: Tue Oct 14, 2014 12:45 pm Post subject: Fretting |
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Your right on with the possible causes. My engine was never overheated.
I appreciate your offer to do an analysis but they are aware of the problem. They've just been very quite about it. From what I hear, they have paid for the parts to repair it for some folks depending on how many hours were on it but not everyone. If it's anywhere near TBO, nothing is covered even though the case isn't rebuild-able at that point. I suspect that they will tell me my engine is too old for any reimbursement because that's what they are telling other folks in my situation. The problem production years were 2005-2006. Since it was a problem that slowly occurs over time and hasn't led to a in-flight failure, they probably figured it would be best to let the engines run until symptoms of a problem showed up then deal with each issue. Cheaper for them in the long run because they can pro-rate the amount of compensation based on how much use was provided by the engine. The redesign of the crankcase, fasteners, torque values and stretch techniques is proof they knew there was a problem. As a mater of fact, my engine only had a 1200 hr TBO. The they expanded them to 1500 hr TBO, but the models with the new crankcase, have a 2000 hr TBO and the dealers like Lockwood tell you that once you install the new case, then your engine goes up to the 2000 hr TBO.
I have sent pictures to the folks at Lockwood and they said they'll present my case to Rotax but, I'll be surprised if they offer any relief.
Suggest everyone check the're engines for this periodically.
From: "Bob Hartunian" <bobh5(at)earthlink.net>
To: barrynorman(at)comcast.net
Sent: Tuesday, October 14, 2014 11:56:13 AM
Subject: Fretting
Fretting Barry;
Viewed your pics and was really surprised at the amount of damage, considering the relatively short operating life.
To get fretting, you need relative motion between mating parts and that motion would come from relaxation of the joint clamping pressure. And that means that the bolt preload diminished over time or was too light to start with; i.e, insufficient initial bolt torque.
Was engine ever overheated badly? That would relax bolt preload.
I have never separated case halves so I noticed in your pics that the blind bolt holes had Helicoil inserts. It’s possible that these inserts relaxed slightly, reducing bolt preloads. I prefer Keenserts myself in tension loading because they are steel with large threads into the case. If you want me to write a technical analysis of the probable situation, I can, should you wish to pursue it with Rotax.
Bob H
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rmurrill(at)cox.net
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| Posted: Tue Oct 14, 2014 12:57 pm Post subject: Fretting |
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Is there an accepted range of serial numbers that are at risk posted anywhere?
Bob
From: barrynorman(at)comcast.net (barrynorman(at)comcast.net)
Sent: Tuesday, October 14, 2014 1:43 PM
To: Bob Hartunian (bobh5(at)earthlink.net) ; pulsar-list (pulsar-list(at)matronics.com)
Subject: Re: Fretting
Your right on with the possible causes. My engine was never overheated.
I appreciate your offer to do an analysis but they are aware of the problem. They've just been very quite about it. From what I hear, they have paid for the parts to repair it for some folks depending on how many hours were on it but not everyone. If it's anywhere near TBO, nothing is covered even though the case isn't rebuild-able at that point. I suspect that they will tell me my engine is too old for any reimbursement because that's what they are telling other folks in my situation. The problem production years were 2005-2006. Since it was a problem that slowly occurs over time and hasn't led to a in-flight failure, they probably figured it would be best to let the engines run until symptoms of a problem showed up then deal with each issue. Cheaper for them in the long run because they can pro-rate the amount of compensation based on how much use was provided by the engine. The redesign of the crankcase, fasteners, torque values and stretch techniques is proof they knew there was a problem. As a mater of fact, my engine only had a 1200 hr TBO. The they expanded them to 1500 hr TBO, but the models with the new crankcase, have a 2000 hr TBO and the dealers like Lockwood tell you that once you install the new case, then your engine goes up to the 2000 hr TBO.
I have sent pictures to the folks at Lockwood and they said they'll present my case to Rotax but, I'll be surprised if they offer any relief.
Suggest everyone check the're engines for this periodically.
From: "Bob Hartunian" <bobh5(at)earthlink.net>
To: barrynorman(at)comcast.net
Sent: Tuesday, October 14, 2014 11:56:13 AM
Subject: Fretting
Barry;
Viewed your pics and was really surprised at the amount of damage, considering the relatively short operating life.
To get fretting, you need relative motion between mating parts and that motion would come from relaxation of the joint clamping pressure. And that means that the bolt preload diminished over time or was too light to start with; i.e, insufficient initial bolt torque.
Was engine ever overheated badly? That would relax bolt preload.
I have never separated case halves so I noticed in your pics that the blind bolt holes had Helicoil inserts. It’s possible that these inserts relaxed slightly, reducing bolt preloads. I prefer Keenserts myself in tension loading because they are steel with large threads into the case. If you want me to write a technical analysis of the probable situation, I can, should you wish to pursue it with Rotax.
Bob H
[quote]
href="http://www.matronics.com/Navigator?Pulsar-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
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freedom4life(at)xtra.co.n
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| Posted: Tue Oct 14, 2014 1:15 pm Post subject: Fretting |
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I believe the fretting problems were mostly related to the 912S 100 HP engines. I have the 80 HP which would have been produced in about 1995. It has now done 2,100 hours and has never had a problem. It is still not using oil and I suspect I should get about 4,000 hours from it before overhaul. I have run a product called Power Up in it since almost new which I know has helped cut wear to a minimum.
Cliff
Your right on with the possible causes. My engine was never overheated.
I appreciate your offer to do an analysis but they are aware of the problem. They've just been very quite about it. From what I hear, they have paid for the parts to repair it for some folks depending on how many hours were on it but not everyone. If it's anywhere near TBO, nothing is covered even though the case isn't rebuild-able at that point. I suspect that they will tell me my engine is too old for any reimbursement because that's what they are telling other folks in my situation. The problem production years were 2005-2006. Since it was a problem that slowly occurs over time and hasn't led to a in-flight failure, they probably figured it would be best to let the engines run until symptoms of a problem showed up then deal with each issue. Cheaper for them in the long run because they can pro-rate the amount of compensation based on how much use was provided by the engine. The redesign of the crankcase, fasteners, torque values and stretch techniques is proof they knew there was a problem. As a mater of fact, my engine only had a 1200 hr TBO. The they expanded them to 1500 hr TBO, but the models with the new crankcase, have a 2000 hr TBO and the dealers like Lockwood tell you that once you install the new case, then your engine goes up to the 2000 hr TBO.
I have sent pictures to the folks at Lockwood and they said they'll present my case to Rotax but, I'll be surprised if they offer any relief.
Suggest everyone check the're engines for this periodically.
From: "Bob Hartunian" <bobh5(at)earthlink.net>
To: barrynorman(at)comcast.net
Sent: Tuesday, October 14, 2014 11:56:13 AM
Subject: Fretting
Barry;
Viewed your pics and was really surprised at the amount of damage, considering the relatively short operating life.
To get fretting, you need relative motion between mating parts and that motion would come from relaxation of the joint clamping pressure. And that means that the bolt preload diminished over time or was too light to start with; i.e, insufficient initial bolt torque.
Was engine ever overheated badly? That would relax bolt preload.
I have never separated case halves so I noticed in your pics that the blind bolt holes had Helicoil inserts. It’s possible that these inserts relaxed slightly, reducing bolt preloads. I prefer Keenserts myself in tension loading because they are steel with large threads into the case. If you want me to write a technical analysis of the probable situation, I can, should you wish to pursue it with Rotax.
Bob H
[quote]
href="http://www.matronics.com/Navigator?Pulsar-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
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