Volunteers wanted for a simple experiment on your old tin/alu rod bearing(s)

The little experiment is simply to rub down a portion of an old shell (or shells) using emery paper or sandpaper until either it returns to a silver colour or you expose the copper (and yes they do have copper! See pics below), if rubbing down exposes the silver colour layer then you can stop there.
Use the most worn shell(s), and rub through the middle of the dark patch. Then post a good quality close up photo of it please (not blurred, off colour, too dark or over exposed! ).

Why do this? Because some of us want to see if any of the Alu/Tin/Copper bearings have actually worn through their babbitt (top) layer.
If they haven't, it'll clean up the Alu/tin layer to return it back to a silver colour, and if it has worn through, you'll clearly see the copper coming through as you rub through the dark patch, the dark patch cleaned off fairly quickly when I did the shell below.

It would also be interesting to see if simply polishing them would remove the dark patch.

On the shell below you can see on the fringes of where I rubbed it down the dark patch has been 'cleaned' off and it's returned to a silver colour. I carried on going to see how obvious the copper is (as you can see, it is very obvious!), any volunteers don't need to go that far (unfortunately I didn't photo the silver only stage).

Thanks to Helmsman for the shell below .







Now don't get me wrong, I'm not saying that a large swath of the Alu/Tin bearings are not significantly worn where they shouldn't be (e.g this recent set of shells at just ~25k miles), they are worn way beyond what they should be. And with a good photo, or a close look, you can clearly see the oil retaining micro-grooves are typically completely worn away where the dark patches are, even when their is still a babbitt layer left.

But in looking through over 500 pictures of shells recently, a mix of lead/copper and Alu/Tin, I've yet to see a single one of the latter worn through to copper. It seems they don't fare as bad as the lead/copper ones.
It would be nice to get some data on that though, hence my request.

Hopefully we'll get some volunteers!
TIA

Thanks to E90M3Ross for this photo - https://drive.google.com/file/d/1T2DhJkhejkaEPPAV43CeNUtE7SbGd2W-/view?usp=sharing

Bump, no one interested?

I forgot , I did get one volunteer , thanks to Fezza for this shot, we can clearly see the left shell still had the babbitt layer left.
Which number shells were they?

Fezza wrote

Assimilator1 did your test on two of my worst LCI shells (59k miles) and it cleaned up to the Tin layer, 2nd shell I went further until Copper showed up

*cough* anyone??

Still seeing photos being posted to the rod bearing thread!

I'll do one when my RB job will be finished and my motor restarted, i think it's an interesting process

Excellent! Thank you, merci even

--Aramis-- wrote

I'll do one when my RB job will be finished and my motor restarted, i think it's an interesting process

Did you get around to doing this?

lots of work, then on holidays I haven't forgotten you, I'll do it when I get back

What are you using to rub down the shell?

I will grab mine when I have a moment and work on one of the bad ones!

For the rubbing down I just used emery paper, sandpaper will do it too (I thought I mentioned that above.....oh, no I didn't, doh! Must've been thinking of a post elsewhere, I'll update the op).

For polishing I was just thinking of car polish, brass polish would probably do it too.

Thanks

Sorry for the late response but here it is :



When i sand it the AluTin layer was quite thick

No worries, thanks for your effort

Although the idea was to sand off in the middle of the shell, in the middle of the wear patch (as per the op) (I know I didn't solely, but I did that before posting this thread).

Nonetheless, it's interesting to see the micro grooves going down to the copper.

Ok i'll do it in the middle and post a picture

Assimilator1 wrote

Although the idea was to sand off in the middle of the shell, in the middle of the wear patch (as per the op) (I know I didn't solely, but I did that before posting this thread).

On the plus side, it shows pretty clearly in one pic the difference between the normal discoloration we see on these bearings (which people had assumed was wear past the top layer) and the actual copper layer.

Assimilator1 wrote

Nonetheless, it's interesting to see the micro grooves going down to the copper.

Makes one wonder whether the "microgrooves are worn away" conclusion on a lot of pics needs to be revisited, eh? Could be an illusion from the lighting and/or resolution in some (if not most or all) cases.

Yea maybe they're not worn away, but (in many cases at least) they are significantly worn down, perhaps flattened off would be a better way to describe the micro grooves wear?

--Aramis-- wrote

Ok I'll do it in the middle and post a picture

Nice one, thank you .
Once part of the dark patch has been rubbed through (to presumably silver), you can stop at that point.

Hey man, any firm conclusions from this experiment yet?

Hardly anyone is responding , so barely any data = no conclusion yet.

But hopefully studntdrivr will be posting some photos soon, and perhaps --Aramis-- could post the extra photo I requested? And SaMaster14 ?

Assimilator1 wrote

Hardly anyone is responding , so barely any data = no conclusion yet.

But hopefully studntdrivr will be posting some photos soon, and perhaps --Aramis-- could post the extra photo I requested? And SaMaster14 ?

Cheers mate. Bumped into your answer by coincident, by using the "quote" button receiver get notified...

Ps. When its not your own thread.

Helmsman wrote

Cheers mate. Bumped into your answer by coincident, by using the "quote" button receiver get notified...

Ps. When its not your own thread.

More than once I told Assimilator1 to use the QUOTE button , and that he is actually speaking in an empty room !

The reply with a "QUOTE" button is not his friend

As I said before M power , the default setting is to be notified of a reply to a thread that one has posted to, therefore they should get notification of my reply, here and elsewhere.
But just in case they've unsub'd or turned off notification, I tagged their names, which you both seemed to have missed , that's what the blue box is around those 3 names.
e.g Helmsman
Hmm, your name ///M-power name seems to stop your name showing in the @ popup list. Maybe manually typing it will work.... ///M Power-Belgium, [edit, yep ].

This should notify both you and Helmsman regardless of your forum sub'd thread notification settings.

Assimilator1 wrote

As I said before M power , the default setting is to be notified of a reply to a thread that one has posted to, therefore they should get notification of my reply, here and elsewhere.
But just in case they've unsub'd or turned off notification, I tagged their names, which you both seemed to have missed , that's what the blue box is around those 3 names.
e.g Helmsman
Hmm, your name ///M-power name seems to stop your name showing in the @ popup list. Maybe manually typing it will work.... ///M Power-Belgium, [edit, yep ].

This should notify both you and Helmsman regardless of your forum sub'd thread notification settings.

I got it , and I can read my username . Well done mate !

But using the Quote Button is much easier...' At least for us .

Lol, well that's good .

But my point is there's no need to use the quotes (aside from picking out a point or a post), most people will get a notification to a thread reply by a simple post . I don't know why you and Helmsman don't, presumably you must have turned it off?

Anyway, let us not sidetrack this thread anymore (aside from my question above).

Assimilator1 wrote

Lol, well that's good .

But my point is there's no need to use the quotes (aside from picking out a point or a post), most people will get a notification to a thread reply by a simple post . I don't know why you and Helmsman don't, presumably you must have turned it off?

Anyway, let us not sidetrack this thread anymore (aside from my question above).

Is it possible to wear down the Ti/Al bearings in a running engine enough to get to this copper layer? Conversely, is there an unwarranted freaking out over what appears to be "worn" bearings (since they don't look like brand new ones) when in fact there is plenty more babbitt to wear away before getting to the final copper layer underneath?