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  #1  
Old 07-01-2021, 04:44 AM
thiggins thiggins is offline
 
Join Date: Mar 2020
Location: Saluda,NC
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Default Engine mount crack?

In helping a friend complete his annual condition inspection we found what looks and feels like a tiny crack on the bottom port side of the engine mount.
I can catch it with my fingernail (barely). Hopefully the quality is good enough. The “crack” is by the weld, the streak higher on the tube is dirt.

Could this just be the powder coat?

What do we think?
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  #2  
Old 07-01-2021, 05:30 AM
pat76cj pat76cj is offline
 
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suggest you remove the paint and see what's underneath
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  #3  
Old 07-01-2021, 06:58 AM
bobg56 bobg56 is offline
 
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If you remove the paint use paint stripper sparingly, if you sand the paint you may fill in the crack and obscure it, then get dye penetrate and developer, and apply per instructions, from what I see it very well could be a crack, especially in the weld area...
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  #4  
Old 07-01-2021, 08:04 AM
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Piper J3 Piper J3 is offline
 
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Looks like a crack to me. Everything nice and clean - how many hours on airplane?
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Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 735

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  #5  
Old 07-01-2021, 08:18 AM
lr172 lr172 is offline
 
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I would scrape off the paint with a knife or razor blade to check. Not a logical place for a crack. The most likely place for a crack in that area would be in the HAZ (heat affected zone) that would extend about 1/4 - 3/8" from the weld. If something in that area were to crack, it is most likely in the HAZ, as that area is more brittle. That said, a defect in the tube would also support a crack.

My money is on just the paint that cracked. Powder coat has much less elasticity than paint.

EDIT: My apologies, I was looking at the long crack that I now see you said was dirt. The small crack by the weld is exactly the spot that is most vulnerable (intersection of weld deposit and HAZ). It is likely that is a crack in the steel and not just the paint. While I don't know the 12, that area appears to be in compression and that causes the most stress on welded joints; Just like we see in the side by side, steps at the lower weld.

Larry
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Last edited by lr172 : 07-01-2021 at 08:31 AM.
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  #6  
Old 07-01-2021, 09:33 AM
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Piper J3 Piper J3 is offline
 
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Cracks can, and do, happen outside Heat Affected Zone.

I have proof...
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Jim Stricker - EAA #499867
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80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 735

LSRM-A Certificate 2016 for RV-12 N633CM
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  #7  
Old 07-01-2021, 10:17 AM
DennisRhodes DennisRhodes is offline
 
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The indication im looking at does appear to be in the HAZ ( heat affected zone) of that weld I would clean up powder coat and dye penetrate test. Very Common place for weld cracks under load.
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  #8  
Old 07-01-2021, 10:36 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Piper J3 View Post
Cracks can, and do, happen outside Heat Affected Zone.

I have proof...
-
I didn't state that they didn't; Only that they are much more common in the HAZ than an inch or two away from it.
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  #9  
Old 07-01-2021, 10:24 PM
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rv6n6r rv6n6r is offline
 
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Just a voice of support if you have a crack... I had cracks in my RV-6 engine mount after 1400 hrs some of it on pretty rough "landing areas". Removal, stripping, welding (including reinforcing gussets from Vans), re-powder coating and engine back on the plane was not an easy task but I did it and flying and hardly remember the pain of all that. Be VERY clear with whoever strips & re-coats it, not to bead blast or paint inside any tubes where bolts / landing gear / etc. go.
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  #10  
Old 07-02-2021, 06:13 AM
thiggins thiggins is offline
 
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Quote:
Originally Posted by Piper J3 View Post
Looks like a crack to me. Everything nice and clean - how many hours on airplane?
It has 570 hours on it, very clean and in a hangar. It belongs to a CFI that built it and babies it…. oh boy.



Has anyone elected to replace the mount with new (and improved) engine mount offered by Vans @ approx $350 for the mount plus 7 or 8 hours labor to change it out?
(Or is that a new nose gear leg?)

Is this a good option?

Thanks.
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Last edited by thiggins : 07-02-2021 at 06:52 AM.
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