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  #1  
Old 03-18-2020, 05:46 PM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
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Question Need Crank - Reman or New?

My 540 suffered a significant overspeed last summer and it's just now working through the shop. Long story short, the overspeed event cracked one of the counterweight ears. Shop is giving me the option of an overhauled or new crankshaft - the latter at a substantial price premium.

The price difference is not a major problem, but certainly worthy of consideration. The main issue I'm now struggling with is whether the extra cash actually buys me any benefit. It seems obvious to go with new, but I've been bitten by the "improperly manufactured" crank AD once before, and there's a NEW one out currently. OTOH, a properly overhauled and inspected used crank has lived through the gamut of AD's and is likely to simply keep on truckin' until fatigue or wear finally takes it out of service.

Has anyone faced a similar choice or have any opinions that favors one or the other?
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  #2  
Old 03-18-2020, 06:17 PM
David Paule David Paule is offline
 
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With the various shut-downs I've been hearing about, perhaps the one most quickly-obtained would be the way to go.

I wouldn't hesitate with the reman, assuming it was done correctly by a reputable shop. Caveat, I'm not an engine guy, just an old stress engineer.

Dave
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  #3  
Old 03-18-2020, 06:17 PM
BobTurner BobTurner is offline
 
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Location: Livermore, CA
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Only thing I can think of is a potential issue at TBO. If the overhauled crank has been turned down a few times already, it may be at its limits -can't be turned down again. Can you find out the current dimensions of the used crank bearings?
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  #4  
Old 03-18-2020, 06:51 PM
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Toobuilder Toobuilder is offline
 
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Any crank that goes back in the engine will be within "new" standard tolerance - just like the "AD" crank that came out, and the reman that went in 3.7 hours ago to replace it (now cracked).
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
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1984 L39C

Last edited by Toobuilder : 03-18-2020 at 06:53 PM.
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  #5  
Old 03-18-2020, 09:23 PM
RV7 To Go RV7 To Go is offline
 
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Certainly no expert here but I wouldn't have an issue either way. Running an overhauled crank in my 360. So far 370 hrs with no issues. The club uses reman cranks in their rebuilds and they go over 3000 hrs consistently. As long as it is done by a reputable shop should not be an issue. Haven't really heard about engines failing due to broken cranks unless they have been abused or have a manufacturing defect...ie. overspeed or prop strike with no bulk inspection after or an AD issue....

Used both new and overhauled in my hot rod days. Never had a crank fail...threw a couple rods though.... FWIW.
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  #6  
Old 03-18-2020, 10:38 PM
Flybipe Flybipe is offline
 
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Default I went new...

My builder went with a new one, and I asked him to have it cryo-treated.

https://www.kitplanes.com/coming-into-the-cold/
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  #7  
Old 03-19-2020, 07:04 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Toobuilder View Post
It seems obvious to go with new, but I've been bitten by the "improperly manufactured" crank AD once before, and there's a NEW one out currently. OTOH, a properly overhauled and inspected used crank has lived through the gamut of AD's and is likely to simply keep on truckin' until fatigue or wear finally takes it out of service.
This is my current thinking. No current evidence to suggest age has any impact on potential crank failure, assuming positive NDT results. On the flip side, it seems many cranks produced in the last 10 years are suffering from failures due to manufacturing issues.

Seems there is little to no evidence to support the logic that new is better and some evidence to imply old, used is better. Your stated experience would seem to back that up.

Larry
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Last edited by Mike S : 03-19-2020 at 12:05 PM.
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  #8  
Old 03-19-2020, 10:01 AM
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skylor skylor is offline
 
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Default Lycoming

[quote=lr172;1415741]
Quote:
Originally Posted by Toobuilder View Post
It seems obvious to go with new, but I've been bitten by the "improperly manufactured" crank AD once before, and there's a NEW one out currently. OTOH, a properly overhauled and inspected used crank has lived through the gamut of AD's and is likely to simply keep on truckin' until fatigue or wear finally takes it out of service.
/QUOTE]

This is my current thinking. No current evidence to suggest age has any impact on potential crank failure, assuming positive NDT results. On the flip side, it seems many cranks produced in the last 10 years are suffering from failures due to manufacturing issues.

Seems there is little to no evidence to support the logic that new is better and some evidence to imply old, used is better. Your stated experience would seem to back that up.

Larry
I don't think factory Lycoming cranks manufactured since about July, 2005 have any known issues, service bulletins or AD's against them. The current issues seem to be with aftermarket crankshafts.

Skylor
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  #9  
Old 03-19-2020, 10:31 AM
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rv6ejguy rv6ejguy is offline
 
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I think it was early 2006 when the last crank SB was issued from Lycoming so you should be safe getting one that was made after that.
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  #10  
Old 03-19-2020, 10:36 AM
Jpm757 Jpm757 is offline
 
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Unfortunately Lycoming SB 505B (corrosion inside hub) has taken a lot of otherwise good cranks out of service (one of mine included). The price of O/H crankshaft remains at a premium. Sold mine to the airboat guys for $500.
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