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An900 / ms35769

Grant

Grant

FRIEND
At Work.....
Does anyone have any "approved data" regarding the orientation these crush washers are supposed to be installed. I have plenty of "reference" information and experience to know that I am doing it correctly but I am being questioned by someone who believes I am doing it wrong. I would only like to point him in the direction of something official so he can read for himself.

FYI - I have ALWAYS put the split side toward the fixed surface and the solid side toward the rotating surface. To me the reason is obvious but perhaps I have been doing it wrong for 20 plus years.


military-standard-ms35769-10-copper-asbestos-gasket-11.jpg
 

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I saw that document as well and have looked at several other documents that say exactly the same thing. I wish there was a spec sheet that gave the installation instructions.


Must be somebody important.
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He is a nice guy but very hubris.... Today I had enough of it and just want to defend my maintenance practices and give him an opportunity to learn something without trying to make him look foolish. I don't want to try and embarrass or chastise the guy, but I would like to be able to say "here is the reference..." and then let him decide if he wants to admit that he is not always correct. Or maybe I'm just wasting my time....
 
Grant said:
FYI - I have ALWAYS put the split side toward the fixed surface and the solid side toward the rotating surface. To me the reason is obvious but perhaps I have been doing it wrong for 20 plus years.


View attachment 49481
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That question comes up in my mind every time I use one of those washers. Tell me, how does the washer know which part is turning and which part is not?
 
Found this somewhere

09271A2C-5857-4FE6-8475-EC4473511F90.jpeg
 

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avnxtek said:
Found this somewhere
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Thanks - Thats exactly what I was looking to find. Is that out of the Lycoming or Continental manual?


Tell me, how does the washer know which part is turning and which part is not?
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For example, if the crush washer were to be used on a drain plug, the oil sump would be stationary, where as the drain plug itself would be the rotating part. So, in this case the split side would go toward the sump and the solid side would go toward the plug. Make sense?
 
I have my crush gaskets in a plastic box in the bottom drawer of my tool box with that page from the Lycoming table of limitstaped to the top of it with notes on which gasket for each engine. Saves me having to look it up in the overhaul manual.
 
Grant said:
For example, if the crush washer were to be used on a drain plug, the oil sump would be stationary, where as the drain plug itself would be the rotating part. So, in this case the split side would go toward the sump and the solid side would go toward the plug. Make sense?
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It makes sense to me. However, how does the washer know that it isn't the drain plug which is stationary and that it is not the sump which is rotating? Think about it.
 
Here is what I use out of the Lycoming table of limits.
IMG_20200618_091004.jpg
 

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skywagon8a said:
It makes sense to me. However, how does the washer know that it isn't the drain plug which is stationary and that it is not the sump which is rotating? Think about it.
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I have thought about that same thing. Once the washer is in its final state it does not matter. But when the forces of the rotation are being applied from the rotating plug it is less likely to "Tear" if the surface receiving the rotating force is smooth. Hence my theory on why this is the right way to install. The washer does not turn during the tightening so the washer DOES "know" which side is rotating and which side is fixed. The more "Fragile" side (Split Side) should be against the fixed face, reducing the possibility of damage during installation.

Again, My theory from experience, past instruction, and now by Lycoming documentation.
 
Grant said:
The washer does not turn during the tightening so the washer DOES "know" which side is rotating and which side is fixed.
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Have you actually watched the washer to KNOW that it is not turning? Don't misunderstand me, I'm not on a b--- busting mission. I'm only attempting to get people to put on their thinking caps. I think that the washer does move a little during the first part of the process.
 
The open side should have more friction than the smooth side so it would be less likely to turn against the sump. If you are really worried about it the threads and contact surface of the plug can be lubed before insertion. Yeah I said it.
 
So do we have definitive answer, or just random things in books.... I’m kinda guessing it doesn’t really matter, but I can’t remember what I learned 30 years ago.... might have to dust off a book


Sent from my iPhone using SuperCub.Org
 
The document Steve posted in number 10 from the Lycoming manual tells you everything. It also includes how many degrees turn to set the gasket for Threads per inch.
 
Continental SB96-7 torque Limits pg 7


1.75-16.....Oil Filter Screen....Using new crush gasket ( install with gasket parting line up against screen face).....500-520 in lbs....All Models


 
S2D said:
Continental SB96-7 torque Limits pg 7


1.75-16.....Oil Filter Screen....Using new crush gasket ( install with gasket parting line up against screen face).....500-520 in lbs....All Models
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I'll be damned....

SB96-7D.png

I sent an email to Continental Tech support to see if this is an exception just for this application or if this is the way continental wants you to install all crush gaskets.
 

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:roll:So if you put the drain plug in a vise on the bench and carry the engine over and thread it onto the plug, make sure you put the split side toward the plug because it’s not turning...:roll::roll:
 
ak49flyer said:
:roll:So if you put the drain plug in a vise on the bench and carry the engine over and thread it onto the plug, make sure you put the split side toward the plug because it’s not turning...:roll::roll:
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If you are a downwind turns dont matter kinda guy, this would be right up your alley. How does the gasket know which part is turning ??
 
Has anyone ever had a problem with a split crush gasket leaking? Did you replace it with one turned the other way which solved the problem? Serious question.
 
Steve Pierce said:
I have reused them, seen them turned both ways, over torqued from the spec and never seen one leak.
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Kind of what I thought. I really admire techs who bend over backwards to get information, either for themselves or their customer. But sometimes the energy expended would likely be used better elsewhere. Or, like I used to do when I was in management and one of the pilots asked a question like this I’d say “that’s a great question, why don’t you research it and let us all know what you learn”.
 
Only time I've ever seen them leak is when they were used once too often or a grain of sand got between the gasket and the surface

Sent from my E6910 using Tapatalk
 
I research on my time just because I want to know. It helps too when you are sitting across from the lawyers and you can answer their questions and know more than them. Then they figure out they are gonna have a hard time making you out to be a dumb ass on the stand. ;) 8)
 
Recently replaced a leaky one on a 520 oil pressure relief and front plug. Both overtorqued, squished flat, and a new one cured the leak.
 
I like downwind turn discussions. especially now that I fly much more heavily loaded planes than super tubs nowadays.

As to the AN900 installation:

consider the surfaces that will contact the gasket. I put to “open/asbestos” side toward the best surface since that surface is less likely to “grab” the open gasket edge and deform it. put the “smooth” side of the gasket toward worst surface.

as to torque? the number of degrees of turn required after contacting both surfaces in accordance with the chart and thread pitch of the plug/fitting, etc.

…for a Continental oil screen boss which is 20 threads per inch, that is 135 degrees of turn after contacting both surfaces.
…and generally for an aluminum version, that is twice the degrees of turn than is necessary for the copper gasket.

my feeble two cents. d
 
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